Treating Common Skin Conditions of Dogs and Cats in Community Medicine Practice

Treatment of skin disease in veterinary medicine must take into account evidence-based treatments, ability of clients to administer prescribed treatments, individual patients’ tolerance and responses, and responsible antimicrobial stewardship. Establishing treatment plans based on these principles can be especially challenging in community medicine practice, in which treatment frequently needs to be based on presumptive diagnosis and barriers to care. In these circumstances, it is important to consider broadly efficacious and cost-effective treatments while promoting good antimicrobial stewardship. This article briefly outlines treatment recommendations for ectoparasitic infestations, bacterial and Malassezia skin infections, dermatophytoses, and allergies in cats and dogs, with specific emphasis on community veterinary medicine.

Ectoparasites

Ectoparasite treatments vary in spectrum and efficacy, making it difficult for veterinarians to select the best one for each patient. Common classes of ectoparasite treatments are summarized in TABLE 1. When deciding which formulation to use in community medicine practice, considerations must include cost, ease of administration, duration, and effectiveness. Isoxazoline-based products cover a broad range of safety and effectiveness, enabling their use as a treatment trial for many ectoparasitic infections, including demodicosis and sarcoptic mange. When only fleas are suspected, options include less expensive medications with a more limited spectrum. At times, combination products with heartworm and intestinal parasite coverage can be considered. Although more expensive per dose, long-acting medications alleviate the need for clients to administer doses at home, which can increase compliance and decrease overall costs, including time at the veterinary clinic and flares resulting from inadequate follow-up. These benefits should be weighed against the initial cost.

Topical therapies and environmental treatment may also be needed. Washable fabrics should be washed at temperatures of at least 55 °C (131 °F) and then sprayed (along with the rest of the environment) with a pyrethroid-containing product to help kill fleas, lice, and Cheyletiella.⁹ Animals, particularly cats, should be evacuated when these products are used due to potential pyrethroid toxicity. Weekly to daily vacuuming of floors is also recommended.

If clinical signs of unconfirmed ectoparasitic infections fail to improve with treatment within 3 to 4 weeks, the patient should be reassessed and the diagnoses re-evaluated.⁹ Infection with fleas and other ectoparasites frequently require treatment for several months. For patients with demodicosis, 2 negative skin scrapings at 1-month intervals are recommended.¹⁰

Bacterial and Malassezia Skin Infections

Topical Therapy

Topical products typically contain ingredients effective against bacterial and yeast (Malassezia) infections or overgrowth, which may be clinically difficult to differentiate from one another without a microscope and the ability to perform cytology. Topical therapy alone is recommended for localized lesions, mild generalized superficial infections, and maintenance to prevent recurrence as both conditions are typically secondary to underlying disease.¹¹ Topicals are also recommended for synergistic effect whenever systemic medication is prescribed.¹² Topical treatments are frequently less expensive than systemic therapy, and evidence of success with less risk for toxicity has been reported.¹² In addition, many of these products are available over the counter, empowering clients to obtain them if they face barriers to returning to the clinic.

Bacterial and yeast skin infections can be treated with topical medications containing 3% to 4% chlorhexidine or 2% chlorhexidine and 2% miconazole or other topical azoles.^13-16 These products are available as shampoos, lotions, mousses, sprays, and wipes. Shampoos are useful for penetrating the canine hair coat and reaching the skin,¹⁷ as well as for mechanical removal of crusts, scale, and debris and disruption of biofilms.¹² However, frequent baths may be challenging due to time constraints, patient temperament, and the need to access bathing facilities. When bathing is not possible, mousses and sprays can be used in combination with shampoos or as alternatives for topical treatment. Carefully clipping the hair short on affected areas can facilitate better contact with the skin and help prevent product build-up.

For clients who may not be able to afford or access commercially available products, dilute vinegar and bleach solutions (TABLE 2) are inexpensive antimicrobial therapy options. However, if too concentrated, these solutions can lead to skin irritation and thus must be made correctly. Dilute vinegar is made by mixing equal parts white vinegar and water, applying it to the skin, and allowing it to air dry.¹⁸ These solutions are applied to the skin for 10 minutes before being rinsed off or allowed to air dry and can also provide anti-inflammatory properties.¹⁹

Antibiotics and antifungals are also available in topical formulations, including creams and ointments. Creams offer deeper penetration into the skin; ointments can serve to create a soothing, protective, occlusive barrier. Many veterinary products labeled for the treatment of otitis externa contain antibiotics and antifungals and can be used off-label on skin. Many of these products also contain a steroid to decrease inflammation; however, topical steroids should be used cautiously and for short durations to avoid side effects. Sprays can also be used to cover larger areas.

Systemic Therapy

Bacterial Infections

For patients with severe superficial or deep pyoderma, or when topical therapy alone is not effective, systemic antibiotic therapy is warranted. When prescribing antibiotics empirically, use first-tier antibiotics, such as cephalexin (TABLE 3).²⁰

Second-tier antibiotics, such as fluoroquinolones, should only be used in the face of a culture indicating no susceptibility to first-tier antibiotics.²⁰ They should not be recommended based only on the failure of a first-tier antibiotic as resistance patterns can be unpredictable. Although less expensive, ciprofloxacin should not be used in veterinary medicine because its bioavailability and probability of effectiveness are variable and low and the likelihood of bacterial resistance is increased.²⁴

Use of third-tier antibiotics such as linezolid and vancomycin is discouraged for skin infections in animals.²⁰

Traditional anecdotal recommendations for treatment duration is to continue superficial pyoderma treatment for 1 week beyond clinical resolution and deep pyoderma treatment for 2 weeks beyond clinical resolution. Generally, most cases of superficial pyoderma are resolved after 3 weeks of treatment, although rapid improvement is seen in the first 1 to 2 weeks.²⁰ Deep pyodermas usually resolve after 4 to 8 weeks of treatment.²⁵ If the infection does not improve after 2 weeks of empiric antibiotic therapy or if new lesions appear while the patient is receiving antibiotics, resistance should be suspected and bacterial culture and susceptibility should be performed.²⁰

Recheck examinations are valuable for guiding the duration of antibiotic therapy. Rechecks can help reduce the overall cost of treatment and risk for rapid recurrence. Patients should be re-examined 2 to 4 weeks after starting a systemic antibiotic and while the antibiotic therapy is still ongoing. In-person rechecks with the use of cytology are ideal, but when not possible, telemedicine can be considered. If the client is not able to bring the patient back for a recheck, consider aggressive topical therapy alone. Ideally, when dispensing systemic antibiotics, emphasize the critical importance of the patient’s return.²⁰

Malassezia Infections

If Malassezia dermatitis is severe or if topical therapy alone fails to resolve it, systemic medication may be necessary. Ketoconazole, itraconazole, and fluconazole at dosages of 5 to 10 mg/kg PO q24h have evidence for efficacy in dogs.¹² Ketoconazole is typically the least expensive and may be the best option for community medicine practice. However, although possible with any azole antifungal, liver toxicity is more likely with ketoconazole. For cats, itraconazole should be the first choice.¹² Resolution of Malassezia dermatitis is typically seen within 3 to 4 weeks of treatment.¹² For patients undergoing long-term therapy with these medications, baseline and liver enzyme monitoring should be recommended.

Dermatophytoses

Itraconazole and terbinafine are recommended for the treatment of dermatophytosis in cats and dogs.²⁶ Itraconazole is typically used at 5 mg/kg PO q24h. Because itraconazole concentrates in the skin and hair, alternate-week treatment (1 week on, 1 week off) has been used successfully in cats.²⁷ This protocol reduces the cost and stress associated with medications. Compounded itraconazole should not be used in either species. Terbinafine is used at 20 to 40 mg/kg and is more efficacious at higher doses.²⁶ Terbinafine concentrates in feline hair; however, pulse-therapy protocols in animals are not well researched.²⁶ Ketoconazole can also be used in dogs at a dose of 5 to 10 mg/kg PO q24h but may be less effective than itraconazole or terbinafine.²⁶ Medication should be continued until 2 cultures spaced 2 weeks apart are negative.²⁶ For patients receiving long-term therapy, baseline and liver enzyme monitoring should be recommended.

For cats and dogs, topical treatment and environmental decontamination are also recommended to prevent fomite contamination. Shampoos containing 2% chlorhexidine and 2% miconazole or lime sulfur dips (although not currently available as veterinary formulations) can be used twice weekly.²⁶ Dilute household bleach (1:100) or accelerated hydrogen peroxide effectively cleans nonporous surfaces.²⁸ Laundry can be cleaned with 2 washing cycles on the longest setting at any temperature.²⁶

Allergies

Treating allergies in cats and dogs can be time-consuming, complicated, and frustrating for clients and clinicians due to the variable clinical signs, chronicity, and potential comorbidities. Treatment can be divided into short-term treatments aimed at controlling acute flares and long-term treatments aimed at preventing flares or prolonging the time between flares. However, allergies cannot be cured, and lifelong treatment is necessary.

Short-Term Treatment

The 3 most important goals of short-term treatment are to treat any ongoing infection (as described above), relieve itching, and control inflammation. The medications most commonly used to provide rapid relief of pruritus are oclacitinib (Apoquel) and lokivetmab (Cytopoint), both manufactured by Zoetis (zoetisus.com), as well as glucocorticoids (TABLE 4). Of these, glucocorticoids are the most cost-effective, providing more benefit than oclacitinib and lokivetmab for inflamed skin and can be used when no contraindications exist. For patients with localized signs, topical glucocorticoids can be used to provide rapid relief.³¹ Not all patients tolerate or respond the same to these medications; therefore, switching to another if significant reduction in pruritus is not seen or the patient develops an intolerance may be necessary. However, if the pruritus does not respond to glucocorticoids, the diagnosis should be re-evaluated.³¹

Long-Term Treatment

Proactive management of allergies can not only improve the patient’s quality of life but can decrease the client’s lifelong costs of managing flares and the risk for antibiotic resistance associated with frequent secondary infections. Common long-term treatment for allergies in dogs can include oclacitinib, lokivetmab, low-dose glucocorticoids, cyclosporine, and antihistamines; topical steroids, topical colloidal oatmeal or ceramides; essential fatty acids; hydrolyzed or novel protein diets (for food allergies); and allergen-specific immunotherapy (for atopic dermatitis). In challenging cases, a combination of therapies may be needed.

Although elimination diet trials and allergen-specific immunotherapy are ideal for long-term management of allergies, they may not be possible for clients who face barriers to care, including financial barriers. For those patients, long-term medical management should be used. Many options are available; however, glucocorticoids are inexpensive and, if the only effective and affordable treatment, can be used long term at the lowest dose and frequency needed to control clinical signs. Antihistamines and essential fatty acids can be used as steroid-sparing agents but are seldom sufficient as sole therapy. Although they add to the overall cost of treatment, blood work and urinalysis should be recommended every 6 months to 1 year when using medications for symptomatic treatment.

Conclusions

Cost-effective treatments with high margins of safety and broad effectiveness are especially useful in community medicine. Whenever possible, topical treatments should be used to increase the range of effectiveness, decrease risk for side effects, and promote good antimicrobial stewardship. Simple yet effective plans should be considered to decrease caretaker burden.³² When implementing treatment, nonjudgmentally discuss the feasibility of recommendations with clients. Sending clients home with written information and instructions helps alleviate misunderstanding or inaccurate memory of instructions. Recheck examinations are also valuable for assessing adequate response to recommended therapy. When legal and applicable, telemedicine may be an option. If the patient does not respond as expected to treatment, the diagnosis should be re-evaluated.

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