Category: Dermatology

A 22-year-old male presents with a one-week history of a lesion on his index finger after working at his uncle’s sheep ranch two weeks earlier. When he first noticed the lesion, it was a small firm papule and accompanied by a low grade fever. Examination now reveals a targetoid lesion on his right index finger

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Patients who may be reluctant to start using an injectable medication warm to the idea when they are first offered a once-daily shot, then presented with the alternative of a once-monthly shot, a small study finds.
Reuters Health Information

An 80-year-old female with a history of arthritis and high blood pressure presents with recurrent lesions and erythema on the palms of her hands and the soles of her feet. On examination, hyperkeratosis, brown macules, and discrete pustules are seen on her palmoplantar surfaces. A fungal culture and serologic tests are unremarkable. Which of the

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Photoallergic reactions to suncreens can come out of the blue. A dermatologist at the Cleveland Clinic offers advice on how to avoid them.
WebMD Health News
The first guidelines on comorbidity screening in children with psoriasis have been published; the recommendations focus on routine screening and early intervention to minimize health complications.
Medscape Medical News
Consumer Reports magazine tested 58 suncreen products and has made recommendations, following FDA recommendations.
WebMD Health News
The EMA's CHMP has recommended granting marketing authorization for brodalumab (Kyntheum, LEO Pharma, A/S) for the treatment of adults with moderate to severe plaque psoriasis.
International Approvals

Sandra Koch, DVM, MS, DACVD
College of Veterinary Medicine, University of Minnesota

For more information on diagnosis and treatment of chronic otitis, see the May/June 2017 article “The Challenge of Chronic Otitis in Dogs—From Diagnosis to Treatment.”

Deep ear flushing is very helpful not only as a diagnostic tool in assessing chronic otitis but also as part of the treatment plan.1 A short course (2 to 3 weeks) of an anti-inflammatory dose of oral and/or topical glucocorticoids may be needed before deep ear flushing in order to decrease inflammation and stenosis of the ear canals.

The deep ear flush procedure should be performed with the patient under general anesthesia so that the ear can be completely cleaned and the ear canal and tympanic membrane examined. Anesthesia also allows the placement of an endotracheal tube, which precludes the aspiration of fluids that may pass through the middle ear into the auditory tube and then into the posterior pharynx. Ideally, computed tomography of the tympanic bulla should be performed before the flush to stage ear disease and help make the decision to perform myringotomy if otitis media is present. Make sure to collect samples for cytology and bacterial culture and sensitivity testing (C/S) before flushing.

Several techniques to clean and flush the ears exist1; below is the method I use in practice.

Procedure

  1. Evaluate the canal to determine the severity of disease, the type and amount of debris in the canal, and the best initial approach for removing the debris.
  2. After examination, if the debris is waxy, soak the external ear canal for 5 to 10 minutes with a ceruminolytic ear cleaner.
  3. Flush the ear with warm sterile isotonic saline. A video-otoscope is ideal for this procedure because of its superior magnification and flushing equipment; however, a bulb syringe or an 8-French polypropylene urinary catheter attached to a 12 mL syringe passed through an otoscopic cone can be used. Alligator forceps and ear curettes can be used to remove larger debris.
  4. Once the ear is clean, evaluate the tympanic membrane.
  5. If the tympanic membrane is not intact, obtain samples from the middle ear cavity for cytology and C/S.

o   If using a handheld otoscope:

  • Insert a sterile otoscopic cone into the horizontal ear canal and pass a sterile pediatric-size needle into the middle ear cavity to obtain samples for cytology and C/S.

o   If using a video-otoscope:

  • Place an open-end 3½-French tomcat catheter attached to a 12 mL syringe through the port of the otoendoscope.
  • Obtain two samples. For each sample, flush a small amount of saline into the middle ear cavity and aspirate it back. The first sample is for culture, and the second sample is for cytology.
  • The video-otoscope channel can also be used for passing instruments to obtain biopsy specimens or collecting samples.
  1. If the tympanic membrane is intact and appears abnormal, and otitis media is suspected or confirmed with imaging, perform myringotomy to obtain samples for cytology and bacterial C/S and to flush the middle ear cavity. In dogs, an intact tympanic membrane does not rule out the possibility of otitis media.

o   If using a handheld otoscope:

  • Insert a sterile otoscopic cone into the horizontal ear canal and visualize the tympanic membrane.
  • Using a spinal needle, a special myringotomy knife, make an incision into the caudoventral quadrant of the tympanic membrane, specifically the pars tensa.
  • Collect 2 consecutive samples by passing sterile pediatric-size needles through the incision. The first sample collected is submitted for bacterial C/S and the second for cytologic analysis.

o   If using a video-otoscope:

  • Place an open-end 3½-French tomcat catheter through the port of the otoendoscope and use the catheter to make the incision.
  • Flush saline into the middle ear cavity and aspirate it back using a 12 mL syringe attached to the tomcat catheter. Submit the first sample for C/S and the second for cytology.

Postprocedure Management

A normal tympanum usually heals in 21 to 35 days. Therefore, if the ear is kept free of infection after myringotomy, the tympanic membrane should heal within 5 weeks.

Non-ototoxic antibiotic and steroids may be infused inside the middle ear and external ear canal after the ear flushing, if necessary. The patient may also be sent home on empiric topical and systemic therapy according to cytology results, and treatment may be modified once C/S results are available. The ototoxicity of most topical otic medications is not known, so if a myringotomy is performed, owners should be instructed to watch for signs of ototoxicity and discontinue the otic medications if they occur. Signs of ototoxicity include the following:

  • Horner syndrome
  • Facial nerve paralysis
  • Vestibular disturbances
  • Deafness

Owners should be made aware of these potential complications and sign a consent form before deep ear flush and myringotomy are performed.

A short course of oral glucocorticoids and pain medication may be sent home with the patient to reduce discomfort and inflammation associated with the procedure, particularly if trauma to the ear canal occurs or myringotomy is necessary.

Recheck the patient 2 to 4 weeks after the ear flush to monitor the response to otic treatments and evaluate the status of the tympanic membrane, particularly if myringotomy was performed.

Reference

  1. Patterson S, Tobias KM. Atlas of Ear Diseases of the Dog and Cat. Ames, IA: Wiley-Blackwell; 2012.

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Prices for generic topical steroids to treat skin conditions like eczema and psoriasis are on the rise, and many seniors may pay more for generic medications than the brand-name versions, a U.S. study finds.
Reuters Health Information

Sandra Koch, DVM, MS, DACVD
College of Veterinary Medicine, University of Minnesota

Canine chronic and recurrent otitis externa can be extremely challenging to treat and require multifactorial, step-by-step strategic plans. Understanding otitis and its associated causes and contributing factors is an important initial step toward successful diagnosis and treatment.

UNDERSTANDING OTITIS: CAUSE AND PATHOGENESIS

Understanding the multifactorial nature of otitis and paying attention to the different causes and contributing factors, not just the infection, is critical because the infection is usually only part of the problem (Figure 1). The most recently proposed classification for otitis includes primary and secondary causes and predisposing and perpetuating factors (Table 1).1–3

FIGURE 1. Pathologic cycle for chronic otitis externa.

Primary Causes

Primary disorders initiate the inflammatory process within the ear canal and alter the aural environment, allowing secondary complicating factors, such as infections, to develop. The primary cause may be very subtle and often is unrecognized by the owner or even the veterinarian until a secondary complicating factor arises. Most cases have a primary cause. In a retrospective study3 of 100 dogs with acute (37%) and chronic-recurrent (63%) otitis externa, the most common primary cause of otitis was allergic dermatitis (43/100 dogs; Figure 2), followed by grass awns (12/100) and otoacariasis (7/100). No primary factor could be identified in 32 of 100 cases. Allergic and hormonal diseases can be associated with unilateral or bilateral otitis, but bilateral otitis is more common. Foreign bodies, neoplasia, and polyps are usually associated with unilateral otitis; however, bilateral problems have been reported.3

FIGURE 2. Otitis externa secondary to allergies.

Secondary Causes

Secondary causes occur in combination with primary causes or predisposing factors. The most common secondary causes are infections.1–3 Generally, secondary causes of otitis externa are easy to eliminate once identified. When they are chronic and difficult to treat, it is usually because primary causes or perpetuating factors have not been adequately addressed.

Predisposing Factors

Predisposing factors alone do not cause otitis externa, but they facilitate inflammation by permitting the external ear canal microenvironment to be altered, thereby allowing pathogenic or opportunistic bacteria or yeast to become established.1,2 In conjunction with primary or secondary causes, these factors become a significant problem. It is important to eliminate as many of these factors as possible while realizing that some, such as ear conformation, cannot be changed.

Perpetuating Factors

Perpetuating factors sustain and aggravate the inflammatory process and prevent resolution of, or worsen existing, otitis externa.1,2 Once present, they accentuate or permit the development of secondary causes, such as infection, by providing favorable environments and microscopic niches. In many cases, perpetuating factors prevent the resolution of otitis externa when treatments are directed only at primary and secondary causes. These factors may be subtle at first but can develop into the most severe component of chronic ear disease. They are not disease specific and are most commonly seen in chronic cases. Perpetuating factors are the most common reasons for surgical intervention.

IMPORTANT DIAGNOSTIC STEPS

History

A detailed and complete history is essential to help investigate the underlying cause and associated factors.

Otic Examination

The ear examination allows the clinician to evaluate the amount and type of exudate in the ear canals; estimate the amount of otic inflammation; identify hyperplasia (along with palpation of the horizontal and vertical ear canals), masses, and foreign bodies; and determine the status of the tympanic membrane (eg, changes in structure or rupture). These findings help in determining whether medical management or surgery (total ear canal ablation with or without bulla osteotomy) is the best treatment. If the patient’s ears are painful, sedation or general anesthesia may be necessary before otoscopic examination.

Regular (ie, handheld) otoscopes should have a strong light and power source. If available, fiberoptic video-enhanced otoscopy (eg, video-otoscope [Figure 3]) is extremely helpful in improving diagnosis and therapy because it not only allows visualization of fine details that may not be seen with regular otoscopes but also facilitates proper flushing of the ears, determination of disease extent, and discovery of indications for additional diagnostics and treatment (eg, myringotomy, otitis media). However, because of the expense to purchase and maintain this equipment, referral to a dermatologist may be necessary

FIGURE 3. Video otoscopic examination.

Physical Examination

Performing a complete physical examination, including a detailed dermatologic examination, can help in identifying an underlying or primary cause. In patients with otitis media and/or otitis interna, concurrent neurologic abnormalities (eg, facial paralysis, nystagmus, ataxia, head tilt) may be present; therefore, a detailed neurologic examination is indicated.

Otic Cytology

Otic cytology establishes whether an infection is present in the ears and assists with the selection of topical therapy. Cytologic samples should be collected gently from the horizontal canal. Exudate samples can be smeared onto a slide with mineral oil to look for mites. The most common type of coccoid bacteria found in the ears of dogs with otitis externa is Staphylococcus pseudintermedius, and the most common type of rod bacteria is Pseudomonas aeruginosa.1–6 Malassezia species are also common organisms1–5 (Figure 4).

It is important to describe the presence of any inflammatory or neoplastic cells as well as quantify each type of bacteria and yeast per oil immersion field (100×) to establish severity and allow monitoring at future visits. In one study, mean bacterial counts per high-power dry field of ≥25 and mean Malassezia counts per high-power dry field of ≥5 were considered abnormal in the external ear canals of dogs.5 Leukocytes are always abnormal, and bacteria in the presence of leukocytes signal infection.

FIGURE 4. Cytologic appearance of Malassezia species (high-power oil immersion field 100× objective).

Bacterial Culture and Sensitivity

Culture and sensitivity (C/S) may be useful in identifying specific otic pathogens and assisting with treatment decisions; however, a limitation is that antibiotic sensitivity data reflect the serum level needed systemically and may not predict true susceptibility of otic topical antibiotics.

Typical indications for bacterial C/S include the following1–4:

  • —Chronic otitis associated with bacteria (cocci [Figure 5] and/or rods) seen on cytology
  • — Rods seen on cytology (Figure 6)
  • — Suspected or confirmed cases of otitis media (systemic therapy may be indicated)
  • — History of multidrug-resistant bacteria
  • — History of long-term oral or topical antibiotic therapy
  • — Bacteria persisting on cytology despite apparently appropriate therapy

FIGURE 5. Cytologic appearance of degenerate neutrophils and cocci (high-power oil immersion field 100× objective).

FIGURE 6. Cytologic appearance of degenerate neutrophils and rods (high-power oil immersion field 100× objective).

Cytology should always be performed before aerobic C/S to assist with interpretation of results and identification of concurrent problems. In one study,7 however, cytologic results agreed with culture results only 68% of the time. The same study7 showed that different bacterial organisms were isolated from the same ear in 20% of the cases; therefore, it is important to remember that ear cytology or a single swab submitted for C/S may not reveal the total population of organisms truly present in the ear canal. This might explain why, in some cases, sensitivity results (in vitro) and response to topical therapy (in vivo) do not always correlate. This study poses questions regarding the true benefit of C/S for selecting antimicrobials for otic infections; therefore, clinicians should be careful and critical when interpreting otic cytologic and culture results.

Clinicians should sample the middle ear separately if otitis media is confirmed when the tympanic membrane is intact. The types and sensitivity pattern of bacteria isolated from the middle ear may differ from those of bacteria isolated from the external canal.8 In one study, different organisms were cultured from the middle and external ear, and even when Pseudomonas species were cultured twice from the same ear, different strains were suspected on the basis of the sensitivity pattern exhibited.8 Culture results should be interpreted with caution because mixed bacterial flora and light commensal and contaminant bacteria might be present and may not be relevant as pathogens.

Diagnostic Imaging Techniques

Dogs with chronic, recurrent, and severe otitis and those with neurologic signs (eg, vestibular signs or facial nerve paralysis), para-aural swelling, or pain on opening the mouth usually require diagnostic imaging to help identify contributing problems, such as middle ear disease (eg, otitis media, neoplasia) and otitis interna, that cannot be identified with regular otoscopy (Table 2). Patients with an apparently normal tympanic membrane may also have otitis media. Although otitis interna is uncommon in dogs with chronic otitis externa, otitis media is common, with a reported incidence of 50% to 88.9%.8 In dogs with recurrent ear infections of 6 months or longer, up to 89% may have concurrent otitis media; about 70% have an intact but abnormal tympanic membrane.8

Deep Ear Flushing

This procedure is very helpful not only as a diagnostic tool but also as part of the treatment plan.9 A short course (2 to 3 weeks) of an anti-inflammatory dose of oral and/or topical glucocorticoids may be needed before deep ear flush in order to decrease inflammation and stenosis of the ear canals. This procedure should be performed under general anesthesia so that the ear can be completely cleaned and the ear canal and tympanic membrane examined. Anesthesia also allows the placement of an endotracheal tube, which precludes the aspiration of fluids that may pass through the middle ear into the auditory tube and then into the posterior pharynx. Ideally, computed tomography of the tympanic bulla should be performed before the flush to stage ear disease and help make the decision to perform myringotomy if otitis media is present.

Several techniques to clean and flush the ears exist.9 Follow-up visits after flushing are very important to monitor response to therapy and evaluate the status of the tympanic membrane. If myringotomy is performed, the tympanic membrane usually heals within 30 days after the procedure. Deep ear flush and myringotomy are best performed by experienced practitioners with a video-otoscope; therefore, referral to a dermatologist might be ideal.

TREATMENT

There are 5 general goals of otitis externa treatment:

  1. Resolve discomfort and pain.
  2. Remove debris and discharge.
  3. Eliminate infection from the external and middle ears.
  4. Reverse chronic pathologic changes, when possible.
  5. Identify and treat the primary cause of the otitis.

Topical Therapy

In most cases of otitis externa, topical therapy alone is sufficient and is preferred when possible. In contrast, chronic, severe cases of otitis externa and otitis media often require additional systemic therapy. The amount of medication applied is important. Generally, the recommendation is to use about 0.5 to 1 mL (10 to 20 drops) per ear, depending on the size of the dog.

Ear Cleaners

Ear cleaners should be used at home as part of most treatment protocols initially (once daily to twice weekly depending on the severity of the otitis and amount of discharge present) and as maintenance therapy (usually once to twice weekly) to help prevent future infections once the otitis and infection are resolved.10–13 Removal of debris and purulent material greatly improves the efficacy of topical antimicrobials, especially aminoglycosides and polymyxin B. However, overcleaning should be avoided because it can contribute to maceration and ear disease. Clients should be educated on the proper technique to clean the ears and to avoid using cotton balls and cotton swabs inside the ears. Available ear cleaners include drying agents, antiseptics, ceruminolytics, and combination products.

Acaricidals

Many different acaricidal products may be used to treat infections caused by Otodectes cynotis (ear mites) and, less commonly, Demodex species.10–13 Veterinary acaricidal products for label and extralabel use include ivermectin, milbemycin, selamectin, fipronil, monosulfiram, permethrin, piperonyl butoxide, pyrethrins, thiabendazole, and rotenone.1

Antimicrobials

It is important to always use higher volumes or concentrations of topical antibiotics because they may prove efficacious, even when resistance has been suggested on a susceptibility panel. With topical drugs, concentrations 100 to 1000 times superior to the minimum inhibitory concentration may be reached.13 Antimicrobials should be used until 1 week past negative cytologic results for most bacterial and/or yeast otic infections.10-13 Twice-daily applications are usually recommended. For Pseudomonas (Figure 7) and multidrug-resistant infections, I recommend treating the patient until 1 week past negative cytologic and culture results.

Antibacterial agents: These products are indicated when infection is present and cleansing solutions are insufficient. Most topical antibacterial products also contain glucocorticoids and antifungals.

  • —First-line antibiotics most commonly used include products containing neomycin alone or in combination with other agents (Tresaderm, us.merial.com) and gentamicin (Gentocin Otic; Otomax, merck-animal-health-usa.com; Mometamax, merck-animal-health-usa.com). Ototoxicity is reported with all gentamicin topicals. However, as with chlorhexidine, this concern may be overstated. One study showed no vestibulotoxic or ototoxic effects from 21 days of otic gentamicin applied q12h to ears with ruptured tympanic membranes.13,14 Polymyxin B (Surolan, elanco.com) can also be a highly effective topical antibiotic and often is effective in many Pseudomonas infections; however, polymyxin can be inactivated by purulent exudates.
  • —Second-line antibiotics include tobramycin (Tobrex ophthalmic solution, alcon.com), injectable amikacin mixed with saline at a final concentration of 25 mg/mL, and ticarcillin–clavulanate potassium, which may be ordered at compounding pharmacies. Care needs to be used with certain topical aminoglycosides because ototoxicity, based on brainstem auditory evoked response testing, was recently seen to occur more commonly in dogs treated with amikacin- and tobramycin-based topicals.13,14
  • —Third-line antibiotics include mupirocin and fluoroquinolones, ideally based on C/S. Mupirocin should be saved for multidrug- and methicillin-resistant Staphylococcus infections; the product is mixed as 1 tube of product (30 g) to 30 mL of sterile saline. Enrofloxacin and silver sulfadiazine (Baytril Otic, bayerdvm.com) is often ineffective in chronic severe cases. Injectable formulations of enrofloxacin (Baytril injectable) are preferable in many different extralabel recipes, such as a 25% mixture of injectable enrofloxacin (22.7 mg/mL diluted with water, saline, or other active agents with variable concentrations of dexamethasone, not exceeding 0.1% to 1%). Posatex (merck-animal-health-usa.com) contains orbifloxacin, posaconazole, and prednisone and may be used against multidrug-resistant infections, such as Staphylococcus and Pseudomonas infections.
  • —Antifungal agents: These may be used in any otitis case associated with yeasts, such as Malassezia or Candida species.10–13 Many available products contain glucocorticoids and antibiotics; however, products containing only antifungals can be found. Usually effective antifungals include clotrimazole (Otomax, Mometamax), miconazole (Conofite, merck-animal-health-usa.com), thiabendazole (Tresaderm), acetic acid (MalAcetic Otic, dechra-us.com), and TrizEDTA and ketoconazole flush (TrizUltra+Keto, dechra-us.com).

FIGURE 7. Chronic Pseudomonas otitis.

Glucocorticoids

Numerous topical preparations of variable potencies are available for use in the external ear canal.10–13 The frequency of use varies from q6h to q24h, depending on the product and the severity of the otitis. Most cases of chronic otitis externa benefit from topical glucocorticoids. Glucocorticoids have antipruritic, anti-inflammatory effects and decrease exudation and swelling, thereby helping to reduce pain and discomfort. In addition, they cause sebaceous atrophy and decrease glandular secretions. Glucocorticoids may reduce scar tissue and proliferative changes, which helps to promote drainage and ventilation. Most ear products contain various combinations of glucocorticoids, antibiotics, antifungals, and parasiticides.

  • Otic products containing betamethasone (Otomax) and dexamethasone (Tresaderm) are usually effective but can be absorbed systemically and cause adrenal suppression with long-term use, so they should be used cautiously. In one study, a more potent yet “soft” glucocorticoid, mometasone (Mometamax), showed no adrenal suppression after 1 week of therapy.12 In cases of allergic otitis externa, long-term topical glucocorticoids may be required with careful monitoring for adrenal suppression or local side effects, such as pinnae hair loss. Products with weaker-strength glucocorticoids should be used in these situations, such as those containing 1.0% or 0.5% hydrocortisone (Zymox HC, zymox.com). I often recommend fluocinolone and dimethyl sulfoxide (Synotic, zoetisus.com), with great results for many chronic, hyperplastic, and stenotic otitis cases.

New Food and Drug Administration–Approved Single-Dose Antimicrobial and Steroid Otic Solutions

Two new veterinarian-administered products containing florfenicol, terbinafine, and mometasone furoate (Claro, bayerdvm.com) and florfenicol, terbinafine, and betamethasone acetate (Osurnia, osurnia.com) are indicated as single-dose treatments for canine otitis externa associated with susceptible strains of yeast (Malassezia pachydermatis) and bacteria (S pseudintermedius). The duration of effect is 30 days for Claro and 7 days for Osurnia. Ears should not be cleaned at home after application. The recommendation is for use in the clinic after ear cleaning, and only with intact tympanic membranes. These are great options for patients that do not allow topical therapy at home and to improve compliance, with potential benefit for acute or mild otitis cases. Their use in chronic severe otitis cases is limited because severe hyperplasia and stenosis preclude ear cleaning and evaluation of the tympanic membrane.

Systemic Therapy

Indications for systemic therapy include the following:

  • —Otitis externa that is severe and unresponsive to topical therapy alone
  • —Concurrent otitis media
  • —Owner unable to medicate with topical therapy
  • —Topical therapy precluded by adverse reactions
  • —Marked proliferative chronic changes

Antibiotics

These drugs may be used in animals with otitis media, moderate or marked proliferative changes with suspected otitis media, or no response to appropriate topical therapy and cleansing. I usually recommend C/S before a systemic antibiotic is selected. Usually, higher doses are recommended to achieve good penetration in the middle ear. Treatment duration may vary; however, I usually treat for 1 month after resolution of clinical signs and healing of the tympanic membrane (from spontaneous perforation or myringotomy). Fluoroquinolones may be prescribed when Pseudomonas species, other relevant gram-negative organisms, or very resistant gram-positive bacteria are isolated and susceptibility is confirmed after culture. Higher doses than usually recommended may be needed.

Oral fluoroquinolones that may be used include enrofloxacin (Baytril) at 10 to 20 mg/kg q24h, marbofloxacin (Zeniquin, zoetisus.com) at 5 to 10 mg/kg q24h, or orbifloxacin (Orbax, merck-animal-health-usa.com) at 10 mg/kg q24h. Ciprofloxacin should be avoided in dogs because oral absorption is inconsistent and low (58.4%) with oral tablets,15 potentially leading to inefficacy and bacterial resistance. In rare cases, injectable antimicrobials, such as aminoglycosides, carbapenems, and ceftazidime sodium, may be required to treat multidrug-resistant otitis cases. Potential side effects with these therapies need to be considered. Referral of these cases to a dermatologist should be considered, particularly when treatment options are limited.

Antifungals

Antifungal agents can sometimes be used in severe cases of Malassezia otitis or cases with poor response to topical agents alone. Oral antifungals commonly used include ketoconazole (Nizoral, nizoral.com), fluconazole (Diflucan, pfizer.com), and itraconazole (Sporanox, janssen.com). All are dosed at 5 to 10 mg/kg q24h or q12h (divided). Terbinafine (Lamisil, lamisilat.com) may also be used at 30 mg/kg q24h.

Glucocorticoids

Glucocorticoids are usually indicated in cases of markedly inflamed and painful otitis with chronic pathologic changes, such as marked hyperplasia and stenosis of the canal. Oral anti-inflammatory dosages of prednisone or prednisolone (0.5 to 1 mg/kg q24h) can be used initially and then tapered to the minimum alternate-day dosage that controls the clinical signs. I typically recommend oral glucocorticoids for cases of Pseudomonas otitis and for dogs that have undergone deep ear flushing. Oral glucocorticoids can also be helpful to reduce pain and discomfort, particularly a few days before the owners clean and medicate the ears. I often combine opioids, such as oral tramadol at 2 to 4 mg/kg q84 to q12h, with oral glucocorticoids in severely painful cases. When longer-term treatment is expected, alternate-day glucocorticoid therapy may be indicated, with careful monitoring for adverse effects.

Cyclosporine

Oral cyclosporine (Atopica, us.atopica.com) may be considered a medical option for dogs with severe proliferative otitis externa when surgery is not an option. In a pilot study,16 5 client-owned dogs were treated with cyclosporine at 5 mg/kg q12h for a minimum of 12 weeks. All dogs were evaluated clinically every 4 weeks to monitor progress; they all showed significant clinical improvement based on owner and clinical assessments. Individual owners also commented on improved disposition, hearing, and quality of life. I have seen limited benefits with oral cyclosporine in end-stage disease (Figure 8), but the drug may be considered in cases when surgery cannot be performed.

Figure 8. End-stage otitis.

CLIENT EDUCATION AND FOLLOW-UP VISITS

It is very important to talk to clients about the lengthy process of managing otitis, including the need for proper home therapy and frequent follow-up visits, pain management, quality of life, long-term prognosis, and medical costs. Clients must also be taught how to clean the ears and place ear medications. Dogs with otitis should be reevaluated with otic examination and cytology every 2 to 4 weeks, depending on severity, to assess response to therapy. It is important to treat ear infections until 1 week past clinical improvement and negative ear cytologic results for most bacterial and yeast infections. For multidrug-resistant and Pseudomonas ear infections, I usually recommend treatment until 1 week past negative cytologic and culture results.

MAINTENANCE/PREVENTIVE EAR CARE AT HOME

Some type of maintenance otic therapy is usually required, such as a cleaning and drying agent (to keep the ear canal free of wax buildup), antimicrobial ear cleaners (eg, for recurrent ear infections), and sometimes topical glucocorticoids (for severe hyperplasia or stenosis, when surgery is not an option).

SURGICAL MANAGEMENT

Surgical management may be recommended (Table 3), particularly in cases of otic tumors and chronic end-stage otitis, when all medical therapeutic attempts are made, after detailed discussion of potential benefits, risks, and postsurgery complications. Histopathology and bacterial culture of removed tissue or masses should always be performed. Advanced imaging before surgery is ideal.

References

  1. Harvey RG, Patterson S. Otitis Externa: An Essential Guide to Diagnosis and Treatment. Boca Raton, FL: CRC Press; 2014.
  2. Gotthelf LN. Small Animal Ear Diseases: An Illustrated Guide. 2nd ed. Philadelphia, PA: Elsevier Saunders; 2004.
  3. Saridomichelakis MN, Farmaki R, Leontides LS, et al. Aetiology of canine otitis externa: a retrospective study of 100 cases. Vet Dermatol 2007;18(5):341-347.
  4. Griffin CE. Otitis externa and media. In: Griffin CE, Kwochka KW, MacDonald JM, eds. Current Veterinary Dermatology, The Science and Art of Therapeutics. St Louis, MO: Mosby–Year Book; 1993:245-262.
  5. Ginel P, Lucena R, Rodriguez JC, Ortega J. A semiquantitative cytological evaluation of normal and pathological samples from the external ear canals of dogs and cats. Vet Dermatol 2002;13(3):151-156.
  6. Defalque V, Rosser EJ Jr, Peterson AD. Aerobic and anaerobic bacterial microflora of the middle ear cavity in normal dogs. 20th Proc North Am Vet Dermatol Forum 2005:159.
  7. Graham-Mize CA, Rosser EJ. Comparison of microbial isolates and susceptibility patterns from the external ear canal of dogs with otitis externa. JAAHA 2004;40(2):102-108.
  8. Cole L, Kwochka KW, Kowalski JJ, Hillier A. Microbial flora and antimicrobial susceptibility patterns of isolated pathogens from the horizontal ear canal and middle ear in dogs with otitis media. JAVMA 1998;212(4):534-538.
  9. Patterson S, Tobias KM. Atlas of Ear Diseases of the Dog and Cat. Ames, IA: Wiley-Blackwell; 2012.
  10. Rosychuk RAW. Management of otitis externa. Vet Clin North Am Small Anim Pract 1994;24(5):921-952.
  11. White PD. Medical management of chronic otitis in dogs. Compend Contin Educ Pract Vet 1999;21:716-722.
  12. Paterson S. Topical ear treatment—options, indications and limitations of current therapy. J Small Anim Pract 2016;57(12):1-11.
  13. Koch SN, Torres MF, Plumb DC. Canine and Feline Dermatology Drug Handbook. Ames, IA: Wiley-Blackwell; 2012.
  14. Patterson S. Ototoxicity. Proc WCVD 6 2008:227-230.
  15. Papich MG. Ciprofloxacin pharmacokinetics and oral absorption of generic ciprofloxacin tablets in dogs. Am J Vet Res 2012;73(7):1085-1091.
  16. Hall J. Oral cyclosporine in the treatment of end state ear disease: a pilot study. Proc 18th Annu Meeting Am Acad Vet Dermatol Am Coll Vet Dermatol 2003:217.

Sandra Koch is an associate professor of veterinary dermatology at the College of Veterinary Medicine, University of Minnesota. She is primarily involved with clinical service and teaching. Dr. Koch’s special interests include allergic and infectious skin diseases, particularly multidrug- and methicillin-resistant Staphylococcus skin and ear infections and dermatologic therapies. She is the primary author of a therapeutic drug book, Canine and Feline Dermatology Drug Handbook.

 

The post Dermatology DetailsThe Challenge of Chronic Otitis in Dogs From Diagnosis to Treatment appeared first on Today's Veterinary Practice.


Chris Reeder, DVM, DACVD
BluePearl Veterinary Partners, Franklin, Tennessee

Cytology is one of the most important yet commonly underused tools in veterinary medicine. It is a quick, easy, and inexpensive means of gathering a tremendous amount of diagnostic information, much the same as running fecal floats, blood smears, and serum chemistries/complete blood counts. According to Christopher et al in the Journal of the American Veterinary Medical Association, “Cutaneous/subcutaneous cytology are most accurate for diagnosis of lesions, whereas liver cytology is least accurate.”1 Moreover, Ruocco et al report that “Exfoliative cytology for diagnostic purposes is rarely used in dermatology despite the rapid and reliable results which this procedure can offer in many clinical conditions.”2 Knowing how to take cytologic samples and how to interpret those samples can be critical to an animal’s health, disease management, and overall wellbeing.

OBTAINING SAMPLES

Ear Canal

The best method for obtaining material from the ear is with a cotton-tipped applicator; however, the health of the ear may limit access to sampling sites. For example, if a dog has end-stage proliferative ear disease, the degree of stenosis may make insertion of the applicator into the ear canal impossible. A 5-French red rubber catheter may be used to obtain samples from more stenotic ear canals. If a dog has a patent ear canal with a ruptured or absent tympanic membrane, sampling of the middle ear may be possible. In these cases, a red rubber or tomcat catheter can be used to obtain the sample while the patient is under general anesthesia. If the tympanic membrane is intact, a myringotomy using a spinal needle will be required. Specific techniques on myringotomy may be found in Mueller and Kirk’s Small Animal Dermatology, 7th edition.

  • Try to obtain a sample at the junction of the vertical and horizontal canals. This is approximately the farthest it is possible to see into the ear without an otoscope.
  • Roll this material onto a glass slide. I like to write “R” for right and “L” for left on the slide to identify the side from which each sample was obtained (Figure 1).

FIGURE 1. Ear cytology: Right and left markers.

Griffin et al found that heat fixing versus not heat fixing otic exudate on glass slides before staining did not increase or decrease the number of Malassezia yeast organisms found on cytologic evaluation.3 I prefer the slide to be heat fixed, then stained with a quick stain (eg, DiffQuik).

Claw Skin Folds

Two methods exist for taking samples from claw folds (cuticle areas):

  • Using the edge of a glass slide to obtain the debris (usually a waxy substance) by scraping from distal to proximal in a scooping motion at a 30° to 45° angle.
  • Using a cotton-tipped applicator broken in half. The stick portion should have a beveled edge. Use the beveled edge to gently scrape or extract material from around the proximal claw/claw skin folds and rub it onto a glass slide (Figure 2). This method may be preferable to using a glass slide directly in these areas, which can be challenging and could result in the slide breaking. The amount of material/debris will be very small.

FIGURE 2. Sampling claw folds.

The slide should be heat fixed and a quick stain used for preparation.

Skin Surface

In my experience, skin cytology is the diagnostic test most commonly missed in everyday referral cases. I find direct impression smears to be most rewarding.

  • Obtain a sample by scraping the skin with the edge of a glass slide at a 30° to 45° angle (Figure 3). This technique is useful for the paws, ventrum, pustules, papules, facial folds, and other areas.

FIGURE 3. Skin scraping

  • Consider tape preps, which tend to be more useful in areas that are very dry or difficult to access with a slide, such as interdigital spaces, facial or tail folds, and periocular areas.
  1. Using a clear, cellophane-type tape, press the sticky portion directly onto the area of interest.
  2. Stain the sample only by using the stain and counterstain (red and purple), then affix the tape directly to a glass slide for evaluation.
  3. Note that fixative will remove the sticky portion along with the sample.

INTERPRETING CYTOLOGIC RESULTS

Basic Microscopy

Always start at low power! The most common mistake made in viewing cytologic preparations is going directly to 100× magnification. Starting at 4× allows identification of specific areas of the slide for examination at higher powers. It also enables observation of findings that might be missed at 100×, such as acantholytic cells and Demodex mites (Figures 4 and 5).

As the magnification increases, so should the light intensity. When looking for Demodex mites or fungal spores, lower the condenser so that the light intensity does not “burn” through these organisms.

FIGURE 4. Acantholytic cells.

FIGURE 5. Demodex mite.

Inflammatory Cells

Inflammatory cells are seen in almost all skin cytologic examinations and occasionally on ear canal and claw fold cytology. The presence of different inflammatory cells may be a guide to suspect certain diseases, such as pemphigus complex, cutaneous lupus, mucocutaneous pyoderma, or even allergies.

Neutrophils

Neutrophils are acute inflammatory cells that destroy infectious organisms and are the main component of pus. Intracellular bacteria should be scanned for because the presence of these bacteria is the true definition of skin infection. The presence of numerous bacteria with no intracellular bacteria may be the result of immunosuppression (eg, Cushing’s disease, hypothyroidism, neoplasia) or bacterial overgrowth. In light of current concerns about resistance to antimicrobial drugs, I recommend treating these cases topically with an antimicrobial product (eg, chlorhexidine, micronized silver, Triz EDTA) as the first step. Neutrophils release many proteolytic enzymes responsible for inflammation and tissue damage (Figure 6).

FIGURE 6. Neutrophils.

Eosinophils

Eosinophils are filled with red (eosinophilic) granules (Figure 7). Eosinophils produce numerous cytokines and mediators to kill microorganisms and attract other cells, such as mast cells. These cells are also phagocytic and are capable of ingesting bacteria and fungi. Finding eosinophils on skin cytology suggests the presence of parasites, fungi, or food allergies. Eosinophils are rarely found in dogs with atopic dermatitis, although they are common in cats.

FIGURE 7. Eosinophils.

Lymphocytes

Lymphocytes are usually seen later in the course of skin disease and are not usually found in large numbers. Small, medium, and large lymphocytes may be seen. These cells direct activities of other cells (eg, neutrophils, eosinophils, keratinocytes) through the release of various messaging molecules, or cytokines. Large lymphocytes are sometimes seen in dogs with cutaneous lymphoma (Figure 8).

FIGURE 8. Atypical lymphocytes (consistent with cutaneous lymphoma).

Mast Cells

Mast cells are also found later in a disease process (Figure 9). They are the major producer of histamine and are involved to a large extent in allergic skin disease. Usually they are seen only in ulcerated areas of dermal mast cell tumors.

FIGURE 9. Mast cell (center).

Nuclear Streaming

When cells rupture during sampling, nuclear content (DNA) is often seen on cytology. Nuclear streaming looks like fine threads of eosinophilic material (Figure 10). It does not indicate anything other than the rupturing of cells during sample collection. It can help to outline fungal spores, bacteria, and yeast, so look for these organisms in areas with larger amounts of nuclear streaming.

FIGURE 10. Nuclear streaming.

Parasites

Demodex, Otodectes, scabies, or other mites may be visible on cytologic preparations if the infection is severe enough. These are large organisms and are best evaluated with 4× to 10× magnification. They are not common but are of diagnostic value if seen.

Fungi

Fungal spores from dermatophytes (ringworm) can be seen within neutrophils, can be free, or can be present within nuclear streaming. These very small, round organisms have a clear halo and basophilic center (Figure 11). They are about half the size of an average red blood cell.

Insert T1703C10Fig11.jpg

Yeast

Two genera of yeast are seen: Malassezia species are more common in the United States than Candida species, which tend to be more common in Europe. Malassezia species have been described as peanut-, snowman-, footprint-, or bowling pin–shaped basophilic organisms. These organisms are defined as a broad-based budding yeast.

FIGURE 11. Fungal spores

Bacteria

Bacteria are the most common infectious organisms I find on cytologic examination. Two distinct shapes are most common: cocci and rods. Cocci are round, basophilic bacteria found individually, in clusters, or in large groups (Figure 10). If intracellular cocci are found, a true infection is present. Rods are often found individually or in sets of 2 placed end to end, called diploid rods (Figure 12). Cocci are most often Staphylococcus or Streptococcus species. Rods are often Escherichia coli, Pseudomonas species, or Klebsiella species. Remember, quick stains stain all bacteria purple; they do not distinguish gram-positive from gram-negative bacteria. Bacterial cultures should be performed any time rods are seen on cytology. Bacteria always go in and out of focus when the fine focus on the microscope is used, whereas melanin granules have a refractory/reflective quality.

FIGURE 12. Rods with inflammatory cells.

Melanin Granules

Melanin granules are commonly mistaken for bacteria and are normally seen on pigmented areas of the skin. They are golden to brown in color and mostly rod-shaped; they have a refractive/reflective quality when going in and out of fine focus (Figure 13). Melanin granules are usually seen attached to keratinocytes, but they can be seen free on the slide.

FIGURE 13. Melanin granules.

Keratinocytes

Most keratinocytes are octagonal to square and squamous in composition. Keratinocytes may display some interesting features that may be normal or abnormal, such as inclusion of keratohyaline granules or rounded acantholytic cells.

Keratohyaline Granules

These granules are present in immature skin cells in the granular layer and are involved in “cementing” the cells together when fully mature. All species have these granules, which may be seen in keratinocytes that are chronically irritated (eg, in allergic dogs/cats). Keratohyaline granules are large eosinophilic granules. Dogs have round granules and cats have rod-shaped granules (similar to eosinophils; Figure 14).

Acantholytic Cells

These keratinocytes have lost their intercellular connections deeper in the epidermis and are usually found in animals with immune-mediated disease, such as pemphigus. Occasionally, severe bacterial infections and dermatophytosis can cause these cells to develop. Acantholytic cells are “fried egg”–shaped, with a deeply basophilic, centrally located nucleus (Figure 4). These are very important to recognize and are considered abnormal in any animal.

FIGURE 14. Keratohyaline granules.

 References

  1. Christopher MM, Hotz CS, Shelly SM, Pion PD. Use of cytology as a diagnostic method in veterinary practice and assessment of communication between veterinary practitioners and veterinary clinical pathologists. JAVMA 2008; 232(5):747-754.
  2. Ruocco E, Brunetti G, Vecchio M Del, Ruocco V. The practical use of cytology for diagnosis in dermatology. J Eur Acad Dermatol Venereol 2011; 25(2):125-129.
  3. Griffin JS, Scott DW, Erb HN. Malassezia otitis externa in the dog: the effect of heat-fixing otic exudate for cytological analysis. J Vet Med 2007; 54(8):393-448.

Chris Reeder, DVM, DACVD, is a graduate of Auburn University’s College of Veterinary Medicine and board-certified in veterinary dermatology. Dr. Reeder has published several articles both nationally and internationally and enjoys lecturing to local and national audiences on dermatology. He has served on several committees for the American College of Veterinary Dermatology, including the credentials committee and ad hoc exam committee. Dr. Reeder’s special interests include otitis externa, dermatopathology, and immune-mediated skin disease.

The post Dermatology DetailsDermatology Diagnostics: Cutaneous Cytology appeared first on Today's Veterinary Practice.


Lori Thompson, DVM, DACVD
Animal Allergy and Dermatology Center of Indiana
Indianapolis, Indiana

Today’s Veterinary Practice introduces our new column, How I Treat. This column is based on the popular How I Treat sessions presented at the annual NAVC Conference in Orlando, Florida (navc.com/conference). This column features interviews with leading veterinary specialists on pertinent clinical topics, with the goal of bringing practitioners essential information on therapeutic approaches.

In this How I Treat interview, Lori Thompson, DVM, DACVD, answers our questions about key treatment protocols for otitis media/interna. Otitis media—inflammation of the middle ear structures, occurs in dogs and cats of all ages and presents unilaterally or bilaterally.1 Untreated otitis media can lead to otitis interna—inflammation of the inner ear structures—or to rupture of an intact tympanic membrane with subsequent otorrhea or otitis externa.1

Q. If a culture is not available to provide guidance on antimicrobial therapy, what is the best antibiotic approach to ensure successful treatment?

A. If a culture of the middle ear is not available or feasible, the antibiotic choice is best based on cytologic findings. If cocci are the predominant bacteria present, Staphylococcus is most likely. Whereas, chains of cocci often represent Streptococcus and rod-shaped bacteria are likely Pseudomonas.

When choosing an antibiotic to treat otitis media, select one that is known to penetrate bone; then dose at the higher end of the dosing range (Table 1). Because higher doses of antibiotics are needed, marbofloxacin remains the best fluoroquinolone choice in cats due to the reported risk of retinal damage when enrofloxacin is used at doses higher than 5 mg/kg Q 24 H.

Remember that cytology and culture samples from the horizontal ear canal and from the middle ear may vary significantly in the same patient. For this reason, if a culture from the middle ear is not available to provide guidance with regard to antibiotic selection, cytologic evidence demonstrating the type of infection present in the middle ear (cocci only versus mixed infection) is very important to help guide treatment recommendations.

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Q. How long should antibiotic therapy be continued?

A. Antibiotic therapy should be continued for 7 to 10 days past clinical resolution. In patients with otitis media/interna, it is not uncommon to sustain uninterrupted antibiotic therapy for 6 to 12 weeks. Because it is difficult for antibiotics to reach target organisms within the middle ear, use doses at the higher end of the reference range.

Given the frequency of mixed infections and the presence of organisms with unpredictable susceptibility patterns, antibiotic selection should be based, whenever possible, on culture and sensitivity results obtained from the middle ear. This is especially important given the longer course of treatment often required, similar to a patient with osteomyelitis.

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Perforated eardrum in 10-year-old West Highland white terrier with a history of chronic otitis externa secondary to atopy.

Q. Are anti-inflammatories and/or analgesics part of your therapeutic strategy?

A. Absolutely! The role of pain management in the treatment of otitis externa/media/interna is extremely undervalued and underutilized. Otitis media/interna, just like cases of osteomyelitis, can be extremely painful. Since our patients are typically stoic, their levels of pain can easily be underestimated.

There are several good choices available to clinicians for pain management; effective choices for the management of otitis media/externa are listed in Table 2. Advise owners to monitor for less obvious indicators of pain, such as decreased interaction, anorexia, and lethargy, in combination with more obvious signs, such as vocalization, shying away, and avoidance.

Anti-inflammatories, such as systemic corticosteroids or nonsteroidal anti-inflammatory drugs (NSAIDs), are almost always indicated as well. However, NSAIDs must not be used in combination with systemic corticosteroids due to the potential for side effects.

Whenever possible, I favor the use of systemic corticosteroids over NSAIDs in patients with otitis media/interna. Corticosteroids not only decrease the intense inflammation found in middle ear disease, but also have been found to decrease the amount and viscosity of the exudate and mucus produced within the bulla. By decreasing the inflammation present, the amount of free space within the bulla and horizontal ear canals increases, allowing better access for medication and improved epithelial migration.

The 2 most commonly used corticosteroids in the treatment of otitis media/interna are listed in Table 2. In my experience, triamcinolone appears to be more effective in decreasing the proliferative changes associated with chronic otitis and has fewer adverse side effects (eg, excessive drinking, urination).

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Q. Is there a role for topical therapy in treatment of otitis media/interna?

A. There is indeed a role for topical therapy. Usually, the clinician’s best chance for resolution is to create a treatment plan that utilizes a multimodal approach that combines topical therapy and systemic therapy with pain management.

It is important to remember that both topical and systemic medications carry the risk of ototoxicity —drug- or chemical-related damage to the inner ear that may affect hearing and balance. Therefore, it may be best to use products that can be infused into the tympanic bulla with minimal to no risk of ototoxicity; these include:

  • Antibiotics: Enrofloxacin, ticarcillin, and ceftazidime
  • Antifungals: Clotrimazole, miconazole, and nystatin
  • Aqueous forms of anti-inflammatories: Dexamethasone and fluocinolone
  • Ceruminolytics: Cerumene (a squalene) and Tris-EDTA flush.
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Acute otitis media in a 2-year-old standard poodle (post myringotomy).

Ruptured tympanum in a cocker spaniel with a history of chronic otitis externa.

Ruptured tympanum in a cocker spaniel with a history of chronic otitis externa.

 

References

  1. Kahn CM (ed). Otitis media and interna. The Merck Veterinary Manual, 10 ed. Whitehouse Station, NJ: Merck & Co, 2010, pp 486 antimicrobial susceptibility of Pseudomonas aeruginosa in biofilm in vitro. Vet Dermatol 2014; 25(2):120-123.
  2. Robson DG, Burton G, Bassett R. Correlation between topical antibiotic selection, in vitro bacterial antibiotic sensitivity and clinical response in 16 cases of canine otitis externa complicated by P aeruginosa. Proc North Am Vet Derm Forum, 2010.

author_l-thompsonLori Thompson, DVM, DACVD, owns Animal Allergy and Dermatology Center of Indiana in Indianapolis. Dr. Thompson is also an active member of the American College of Veterinary Dermatology and American Academy of Veterinary Dermatology, a consultant for VIN, and serves as the chairperson for the AVMA task force on veterinary compounding legislation. After receiving her DVM from Purdue University, Dr. Thompson practiced small animal medicine before completing a 3-year residency in veterinary dermatology.

 

The post How I Treat…Otitis Media/InternaAn Interview with Dr. Lori Thompson appeared first on Today's Veterinary Practice.

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Sandra N. Koch, DVM, MS, DACVD, University of Minnesota

Canine demodicosis is a common inflammatory parasitic skin disease believed to be associated with a genetic or immunologic disorder. This disease allows mites from the normal cutaneous biota to proliferate in the hair follicles and sebaceous glands, leading to alopecia, erythema, scaling, hair casting, pustules, furunculosis, and secondary infections.1-3 The face and forelegs to the entire body surface of the dog may be affected.1-3

Three morphologically different types of Demodex mites exist in dogs:

  1. Demodex canis: The most common form of Demodex (Figure 1)
  2. D cornei: A short-body form, likely a morphological variant of D canis4 (Figure 2)
  3. D injai: A long-body form1-3 (Figure 3)

Published studies indicate similar efficacy of treatment regardless of the type of mite.1,2

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Figure 1. Demodex canis identified on skin scrapings

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Figure 2. Short-bodied form: Demodex cornei.

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Figure 3. Long-bodied form: Demodex injai.

THERAPEUTIC APPROACH

Effective treatment of generalized demodicosis requires a multimodal approach.1,2 In order to establish prognosis and provide a successful treatment, it is very important to evaluate the:

  • Age of onset
  • Extent and location of skin lesions
  • Presence of secondary infections
  • General health of the dog.1,3,5

Independent of age, it is important to identify and treat any predisposing or contributing factors in order to achieve a successful outcome.1-3

AGE OF ONSET

Juvenile-Onset

Demodicosis may occur in dogs 18 months of age or younger as a result of an immunocompromised state associated with endoparasitism, malnutrition, or health debilitation. Puppies may also develop demodicosis due to an immature immune system or mite-specific immunoincompetency.1,3 The increased prevalence in certain breeds indicates a hereditary basis for juvenile-onset demodicosis, particularly for the generalized form.3

Adult-Onset

In dogs older than 18 months of age, demodicosis may occur as a result of immunosuppression due to drugs (eg, glucocorticoids, ciclosporin, oclacitinib maleate, chemotherapy) or systemic disease (eg, hyperadrenocorticism, hypothyroidism, neoplasia, malnutrition, parasitism).1,3 Therefore, dogs with adult-onset demodicosis should have a detailed physical examination and full diagnostic workup (Table 1) performed to identify underlying diseases.

Evidence has indicated that successful treatment of an underlying disease may contribute to remission of demodicosis.1,3 However, up to 56% of dogs with adult-onset canine demodicosis have been reported to have no detectable underlying disease.2

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EXTENT & LOCATION OF LESIONS

Localized Form1

  • Four skin lesions or fewer
  • Lesion diameter ≤ 2.5 cm

Prognosis for localized demodicosis is good, as most lesions resolve spontaneously within 6 to 8 weeks.1,3 Topical therapy with benzoyl peroxide shampoo or gel may be recommended.1,3

Generalized Form1

  • More than 4 skin lesions
  • Lesion diameter > 2.5 cm (Figures 4 and 5)
  • And/or feet are affected
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Figure 4. Generalized demodicosis.

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Figure 5. Generalized demodicosis.

Overall prognosis for resolution of skin lesions is good (Figure 6), but prognosis depends on the patient’s health status and underlying conditions or presence of immunosuppression.1,3

Spontaneous remission in a subset of young dogs has been reported to be 30% to 50%3; however, the true incidence of spontaneous resolution of generalized demodicosis is unknown.

Relapses of generalized demodicosis are not uncommon.1 Dogs may be euthanized as owners may be unable to afford cost of therapy or commit to the necessary intense management.1-3 In some patients with refractory or noncurable demodicosis, treatment may be lifelong.1,2

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Figure 6. Patient from Figures 4 and 5 after treatment for demodicosis.

PRESENCE OF SECONDARY INFECTIONS

Secondary bacterial and yeast skin and ear infections are common problems associated with canine demodicosis, which aggravate the skin disease and cause or contribute to pruritus.1,3 Identifying and treating these secondary infections is very important to the successful treatment of demodicosis.1,3

Topical and/or oral antibiotics may be prescribed according to clinical signs and cytology. Bacterial culture and susceptibility testing should be performed in patients that do not respond to antibiotic therapy or have a history of multiple antibiotic courses, in an attempt to identify and treat resistant bacteria.

Most dogs benefit from weekly antimicrobial baths with benzoyl peroxide or chlorhexidine shampoos.1,3

MITICIDAL THERAPIES

Multiple conventional and newer therapeutic options currently exist for generalized demodicosis (Table 2);1-3,6 however, most of these therapies are extralabel, can be difficult to administer, and may lead to adverse effects. Miticidal therapy may need to be adjusted according to the dog’s response and tolerance.

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Amitraz Therapy

Amitraz (Mitaban, zoetisus.com) is a monoamine oxidase inhibitor approved by the FDA for treatment of generalized demodicosis in dogs older than 4 months of age.5

There is good evidence to recommend weekly amitraz rinses for the treatment of canine demodicosis.1,5 However, based on published reports, amitraz seems to be less efficacious in adult-onset demodicosis.1

Recommended concentrations range from 0.025% to 0.06% once weekly to every other week,1,3,5,6 but other protocols have been reported (Table 3). Clinical efficacy increases with increased concentration and shorter treatment intervals.1 Dogs should be treated in well-ventilated areas. For heavily infested dogs, or dogs with medium or long coats, clipping the hair coat is advisable.1,3

Transitory sedation and depression, pruritus, lethargy, hyperglycemia, bradycardia, polydipsia, polyuria, vomiting, and diarrhea may occur.3,6 Marked ataxia and lethargy are rare.3 Amitraz use should be avoided in Chihuahuas and toy breeds as they are reportedly sensitive to amitraz.2

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Macrocyclic Lactone Therapy

While macrocyclic lactones are not licensed in the United States for treatment of canine demodicosis, they are widely used by veterinarians due to their known efficacy.

Certain precautions should be taken when using macrocyclic lactones:

  • Macrocyclic lactones should not be administered to herding breeds and their crosses, including collies, Shetland sheepdogs, Old English sheepdogs, border collies, bearded collies, and Australian shepherds.
  • These dogs have a higher risk of depression, ataxia, coma, and death due to their predisposition to the ABCB1-1Δ (MDR-1) gene mutation.3,6
  • Prior to prescribing macrocyclic lactones in these breeds, it is recommended that evaluation for the ABCB1-1Δ genotype be performed or alternative treatment pursued.
  • A polymerase chain reaction test is available from Washington State University (vetmed.wsu.edu).
  • In dogs without the ABCB1-1Δ mutation, including puppies, use of lower doses or gradual dose increase of macrocyclic lactones—on a daily or weekly basis—is usually recommended due to possible drug neurotoxicity.1,3,7
  • Do not implement macrocyclic lactone therapy in patients without up-to-date negative heartworm tests or in those with heartworm disease.6 Other heartworm preventives should be discontinued during treatment.6

Milbemycin oxime (Interceptor, elanco.us) is licensed in the U.S. as a heartworm and intestinal parasite preventive in dogs older than 4 weeks of age. There is good evidence to recommend milbemycin (1–2 mg/kg PO Q 24 H) for treatment of canine demodicosis.1,5 Milbemycin is better tolerated by dogs compared with other macrocyclic lactones, and may have a higher margin of safety. However, it should be used carefully in dogs with the ABCB1-1Δ gene mutation due to reports of neurologic side effects in these dogs.1

Ivermectin use (0.3–0.6 mg/kg PO Q 24 H) for treatment of canine demodicosis is supported by good evidence.1,3,6 To mask its bitter taste, ivermectin may be mixed with fruit sauce or ice cream. Do not use concurrently with spinosad (ie, Comfortis and Trifexis [elanco.us]) due to a drug interaction, which results in severe neurologic adverse effects.8

Doramectin use (0.6 mg/kg PO or SC weekly or twice weekly) for treatment of canine generalized demodicosis is supported by some evidence.1,3,5-7 A recent retrospective study, which included 232 dogs, demonstrated that weekly SC injections of doramectin was a useful and well tolerated treatment for canine generalized demodicosis; remission was reported in 94.8% of the dogs.9

Moxidectin use (0.2–0.5 mg/kg PO Q 24 H) for treatment of canine demodicosis is supported by good evidence.1,3,5,6

Moxidectin 2.5% + imidacloprid 10% (Advantage Multi, bayerdvm.com) is a spot-on medication approved for prevention of fleas, heartworm, and intestinal parasites in dogs of at least 7 weeks of age. This product:

  • Has good evidence supporting its use as a weekly treatment for dogs with juvenile-onset demodicosis or mild forms of the disease, or those that cannot receive or tolerate amitraz or macrocyclic lactones1,3,5,10,11
  • Seems to be well tolerated without the potential toxicity associated with other avermectin products, and is safe for dogs with the ABCB1-1Δ mutation1,10,11
  • Was shown to have a much higher success rate when administered weekly or every 2 weeks versus monthly in mildly affected, juvenile-onset patients compared with moderately or severely affected dogs.1,10,11

In dogs prone to recurrent demodicosis, I recommend use of Advantage Multi Q 4 weeks to help prevent relapses.

Isoxazoline Therapy

The following isoxazolines are flavored, chewable tablets newly available as veterinary prescriptions and labeled for the prevention and treatment of flea and tick infestations in dogs:

  • Fluralaner (Bravecto, merck.com)
  • Afoxolaner (Nexgard, merial.us)
  • Sarolaner (Simparica, zoetisus.com).

These medications can be used in young dogs of at least 6 months (fluralaner and sarolaner) and 8 weeks (afoxolaner) of age.

Mechanism of Action. Fluralaner, afoxolaner, and sarolaner have similar mechanisms of action, antagonistically binding primarily to the arthropod gamma-aminobutyric acid and glutamate receptor regulated chloride channel and inhibiting the arthropod nervous system, causing paralysis and death. They possess potent, fast, and long-lasting insecticide and acaricide effects, offering 4 (afoxolaner and sarolaner) and 12 (fluralaner) weeks of protection.

Adverse Effects. These products are generally quite safe. The most frequently reported adverse effects include vomiting, diarrhea, anorexia, lethargy, and flatulence. Specific considerations include:

  • Afoxolaner should be used with caution in dogs that have a history of seizures.
  • Sarolaner may cause neurologic signs, including tremors, ataxia, and seizures.
  • Fluralaner is labeled as safe for use in breeding, pregnant, and lactating dogs, as well as in dogs with the ABCB1-1Δ gene mutation.

Use in Demodicosis. Recently, these medications have been anecdotally suggested as an alternative efficacious treatment for canine demodicosis. To date, 3 studies investigating the use of this new class of parasiticide for the treatment of canine demodicosis have been published.12-14 Note, in the following studies, that Advocate is the European version of Advantage Multi.

One open study12 compared the effect of Bravecto (fluralaner; single dose) with Advocate (moxidectin + imidacloprid; applied Q 28 days) in 16 dogs with generalized demodicosis. Dogs treated with fluralaner had lower mean mite counts after treatment (99.8% on day 28, and 100% on days 56 and 84) compared to those treated with moxidectin/imidacloprid (98% on day 28, 96.5% on day 56, and 94.7% on day 84). Statistically, on days 56 and 84, significantly fewer mites were found on dogs treated with fluralaner compared with those treated with moxidectin/imidacloprid. Reduction of mite counts was consistent with reduction in clinical signs in both groups.

A similar study13 compared the efficacy of Nexgard (afoxolaner) with Advocate (moxidectin + imidacloprid), both administered biweekly on days 0, 14, 28, and 56, in 8 dogs with generalized demodicosis. Dogs treated with afoxolaner had lower mite counts after treatment (99.2%, 99.9%, and 100% on days 28, 56, and 84, respectively) compared with those treated with moxidectin/imidacloprid (89.8%, 85.2%, and 86.6% on days 28, , and 84 respectively). On days 28, 56, and 84, mite reductions were significantly higher in dogs treated with afoxolaner; skin condition in these dogs also improved significantly from day 28 to day 84.

Another recent study14 investigated the efficacy of Simparica (sarolaner; doses on days 0, 30, and 60) compared with Advocate (moxidectin + imidacloprid; weekly applications from days 0 to 81) for the treatment of 16 dogs with generalized demodicosis for 91 days. The study demonstrated that dogs treated with sarolaner had significant mite count reduction after the first dose (97.1% and 99.8% at days 14 and 29, respectively), with no live mites detected at 44 days and thereafter. Dogs treated with moxidectin/imidacloprid experience mite count reduction of 84.4% and 95.6% at days 14 and 29, respectively, with no mites detected at 74 days and thereafter. All dogs in both groups showed marked improvement in clinical signs.

The results of these studies are encouraging because this new treatment modality offers the potential to provide effective and safe control of canine demodicosis, with low administration frequency, while helping prevent and control fleas and ticks.

Therapies Lacking Evidence of Efficacy

According to evidence-based studies, there is currently insufficient evidence to recommend treatment of canine demodicosis with amitraz collars, closantel, deltamethrin, vitamin E, muramyl dipeptide, phoxime, and herbal and homeopathic products.1 There is current evidence against use of weekly pour-on or injectable ivermectin, lufenuron, ronnel, oral selamectin, and levamisole.1

SUPPORTIVE THERAPY

It is extremely important to improve nutrition by feeding a balanced, age-appropriate diet and treating intestinal parasites or other stress factors, particularly in puppies, stray or rescued, and sick dogs.1-3

Most dogs with demodicosis are treated on an outpatient basis; however, dogs with severe generalized demodicosis, pododermatitis, deep pyoderma, sepsis, pain, fever, dehydration, and complications from underlying diseases may require hospitalization for supportive care. Fluids, systemic antibiotics, and pain medications may be required.

Dogs Affected by Demodicosis: Therapeutic Precautions

Avoid glucocorticoids, progestogens, ciclosporin (Atopica, novartis.com), and oclacitinib maleate (Apoquel, zoetisus.com) due to their immunosuppressive effects.1,3 These agents may inhibit the host immune response, preventing resolution of Demodex infection or inducing relapses. Apoquel is contraindicated in patients with demodicosis or a history of demodicosis.

Avoid use of other P-glycoprotein inhibitors when administering avermectins, such as azole antifungals and ciclosporin, due to potential synergistic toxicosis.1,3

Do not administer macrocyclic lactone medications to herding breeds and their crosses, including collies, Shetland sheepdogs, Old English sheepdogs, border collies, bearded collies, and Australian shepherds, as there is a higher risk of depression, ataxia, coma, and death due to their predisposition to the ABCB1-1Delta gene mutation.3,5

Relapses may occur at times of stress, such as estrus, pregnancy, lactation, and systemic diseases.1,3

MONITORING & DURATION OF TREATMENT

One of the most common reasons for treatment failure is ending therapy too soon.1 Clinical resolution usually occurs 0.5 to 6 months sooner than parasitologic cure.3 Therefore, it is important to rely on length of therapy, rather than clinical appearance, to finalize treatment since clinically improved dogs may still harbor mites.

  1. Perform recheck visits and skin scrapings every 4 weeks to monitor response.
  2. Continue treatment until 2 consecutive negative skin scrapings are obtained.1,3 A minimum of 4 to 6 skin scraping sites should be negative.3 Usually, at least 3 to 4 months of treatment are needed.
  3. If there is no reduction in mite numbers after several skin scrapings, especially if active mite reproduction is seen (eggs, larvae, and nymphs), reinvestigate for the presence of underlying causes or consider an alternative treatment.1,3
  4. Monitor patients for 12 months after treatment is discontinued, with rechecks and skin scrapings performed every 3 to 4 months to monitor for relapses.1,3 Relapses were reported in 10% to 45% of patients.3 One study demonstrated that the largest percentage of recurrence of disease occurred within the first few months after treatment discontinuation.4 Interestingly, the same study also demonstrated that older dogs were more sensitive to side effects of therapy but were generally clear of mites more quickly than younger dogs.4
  5. Consider life-long therapy in dogs that respond to therapy clinically but do not have negative skin scrapings and in those with frequent relapses despite proper treatment duration.1,3 Based on recently published guidelines for the treatment of demodicosis, Demodex resistance to acaricidal therapy has not been reported.1

Remember, during monitoring, the presence of any live, dead, and/or fragments of Demodex mites on skin scrapings should be considered positive, indicating the need for continued treatment.1,3

CLIENT EDUCATION

Client education is extremely important.1,3 Clients should know and understand the following:

  • Dogs with adult-onset demodicosis need a complete workup for possible underlying conditions.
  • About 10% of dogs with localized demodicosis may progress to generalized form.
  • Treatment of generalized demodicosis may be lengthy and costly.
  • Clinical signs often improve before parasitologic cure; therefore, frequent rechecks and skin scrapings are important to achieve treatment success.
  • There is a possibility of recurrence after treatment discontinuation, especially if therapy is ended prematurely, leading to disease relapse.
  • Some dogs can be controlled but not cured, particularly those treated with immunosuppressive drugs that cannot be discontinued or with unidentified, uncontrolled, or noncurable underlying conditions.
  • According to current evidence-based guidelines, dogs with demodicosis requiring parasiticidal therapy should not be bred due to potential heredity.1

In addition, the pros, cons, and contraindications of various treatment options should be explained to clients.

IN SUMMARY

In most dogs, demodicosis has a good prognosis for cure as long as underlying diseases are identified and treated properly. Treatment should be monitored monthly with multiple skin scrapings and extended beyond clinical and microscopic cure to minimize recurrences. Canine demodicosis can be a challenge to treat; however, the future is brighter with multiple therapeutic options available and the advancement of new, potentially safer, efficacious, and easier-to-administer therapies, such as the isoxazolines.

References

  1. Mueller RS, Bensignor E, Ferrer L, et al. Treatment of demodicosis in dogs: 2011 clinical practice guidelines. Vet Dermatol 2012; 23(2):86-96, e20-1.
  2. Singh SK, Kumar M, Jadhav RK, Saxena SK. An update on therapeutic management of canine demodicosis. Vet World 2011; 4(1):41-44.
  3. Miller WH, Griffin CE, Campbell KL. Parasitic skin diseases. Muller & Kirk’s Small Animal Dermatology, 7th ed. St. Louis: Saunders, 2013, pp 310-313.
  4. Sastra N, Ravera I, Villanueva S, et al. Phylogenetic relationships in three species of canine Demodex mite based on partial sequences of mitochondrial 16S rDNA. Vet Dermatol 2012; 23(6):509-e101.
  5. Arsenovic M, Pezo L, Vasic N, et al. The main factors influencing canine demodicosis treatment outcome and determination of optimal therapy. Parasitol Res 2015; 114(7):2415-2426.
  6. Koch SN, Torres SMF, Plumb DC. Canine and Feline Dermatology Drug Handbook. Oxford: Wiley-Blackwell, 2012, pp 73-338.
  7. Bissonnette S, Paradis M, Danealu I, et al. The ABCB1-1D mutation is not responsible for subchronic neurotoxicity seen in dogs of non-collie breeds following macrocyclic lactones treatment for generalized demodicosis. Vet Dermatol 2009; 20:60-66.
  8. Hutt JH, Prior IC, Shipstone MA. Treatment of canine generalized demodicosis using weekly injections of doramectin: 232 cases in the USA (2002-2012). Vet Dermatol 2015; 26(5):345-349.
  9. Dunn ST, Hedges L, Sampson KE, et al. Pharmacokinetic interaction of the antiparasitic agents ivermectin and spinosad in dogs. Drug Metab Dispos 2011; 39(5):789-795.
  10. Paterson TE, Halliwell RE, Fields PJ, et al. Canine generalized demodicosis treated with varying doses of a 2.5% moxidectin + 10% imidacloprid spot-on and oral ivermectin: Parasiticidal effects and long-term treatment outcomes. Vet Parasitol 2014; 205(3-4):687-696.
  11. Mueller RS, Meyer D, Bensignor E, et al. Treatment of canine generalized demodicosis with a spot-on formulation containing 10% imidacloprid and 2.5% moxidectin (Advocate, Bayer Healthcare). Vet Dermatol 2009; 20(5-6):441-446.
  12. Fourie JJ, Liebenberg JE, Horak IG, et al. Efficacy of orally administered fluralaner (Bravecto) or topically applied imidacloprid/moxidectin (Advocate) against generalized demodicosis in dogs. Parasit Vectors 2015; 8:187-193.
  13. Beugnet F, Halos L, Larsen D, de Vos. Efficacy of oral afoxolaner for the treatment of canine generalised demodicosis. Parasite 2016; 23:14 Published. Parasite 2016; 23(14): 1-8.
  14. Six RH, Becskei C, Mazaleski MM, et al. Efficacy of sarolaner, a novel oral isoxazoline, against two common mite infestations in dogs: Demodex spp and Otodectes spp. Vet Parasitol 2016 (in press). doi.org/10.1016/j.vetpar.2016.02.027, published. Vet Parasitol 2016; 222: 62-22.

 

author_s-koch

Sandra Koch, DVM, MS, DACVD, is an associate professor of veterinary dermatology at University of Minnesota College of Veterinary Medicine. She is primarily involved with clinical service and teaching, and her special interests include allergic and infectious skin diseases, particularly multidrug- and methicillin-resistant Staphylococcus skin and ear infections and dermatologic therapies. She is the primary author of Canine and Feline Dermatology Drug Handbook.

 

The post Dermatology DetailsUpdates on the Management of Canine Demodicosis appeared first on Today's Veterinary Practice.

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