Picture this: microscopic tenants residing on your cat's skin, typically minding their own business. These tiny lodgers are Demodex mites, and they are usually harmless inhabitants of the skin of most mammal species, including cats. However, when a cat's immune system falters, these otherwise peaceful mites can proliferate unchecked, leading to a condition known as demodicosis.
Understanding Demodicosis in Cats
Demodex mites are part of the natural skin fauna in cats and do not typically cause any issues. There are three main species of Demodex mites in cats, but only two are problematic. Demodex cati and Demodex gatoi can trigger skin diseases in cats, with symptoms ranging from excessive grooming (also called fur mowing) to raw, weepy eosinophilic granuloma complex lesions or the appearance of dry, seed-like scabs, often referred to as miliary dermatitis. Cats with demodicosis usually experience itching.
While demodectic mange is relatively common in dogs, it is a much rarer occurrence in cats.
Two Types of Mites, Three Types of Trouble
Demodex cati and Demodex gatoi are the primary Demodex mites affecting cats, with a third species recently identified but yet unnamed. Demodex cati is long and slender, resembling a short-nosed alligator, while Demodex gatoi is shorter, stubbier, and almost tailless. The unnamed mite is slightly larger than Demodex gatoi but shares a similar short-tailed appearance.
Demodex cati resides deep within hair follicles, making it more susceptible to treatment, unlike Demodex gatoi, which dwells closer to the skin's surface and can be more elusive.
Diagnosis and Differentiation
Diagnosing demodicosis often involves skin scrapings or similar sampling techniques. In some cases, mites may be found in fecal samples, especially when cats groom and ingest their skin mites, as seen with Demodex gatoi infection. If skin scrapes come back negative for an itchy cat, examining a fecal sample can be a complementary approach to rule out mite involvement. Identifying the specific mite species is crucial as it determines treatment and prognosis.
Demodex cati infections are relatively straightforward to diagnose due to the mites' higher numbers. In contrast, Demodex gatoi can trigger significant inflammation with only a small mite population, making them more challenging to detect. Diagnosis may rely on the response to treatment.
Treatment for Demodex Cati
Demodex cati, residing deeper within hair follicles, responds well to treatment. Effective options include topical fluralaner (Bravecto®), oral ivermectin or milbemycin, and moxidectin topical products like Advantage Multi® used off-label every two weeks. Lime sulfur dips, historically used, have been largely replaced by more user-friendly topical products. However, a Demodex cati infection may indicate an underlying issue with the cat's immune system, necessitating further testing.
Treatment for Demodex Gatoi: A Family Affair
Demodex gatoi is highly contagious among cats, and if one cat is confirmed or strongly suspected to have it, all cats in the household must be treated. The primary treatment involves six weekly dips in a two-percent lime sulfur solution, which, unfortunately, has an unpleasant odor and can stain fabric, jewelry, and fur. These dips should be performed even on asymptomatic cats as carriers can infect others. If no improvement is observed after three weekly dips, an alternative diagnosis should be considered.
Treatment for Cats Testing Negative for Mites
Detecting Demodex cati is relatively straightforward, and a negative skin scrape is generally reliable. If there's uncertainty, one of the topical treatment plans can address any undetected mites. However, Demodex gatoi is trickier to find, and systemic treatments may not reliably target it. In such cases, a trial of lime sulfur dips may be initiated. If cats respond positively, three more weekly dips should follow. All household cats should undergo the same treatment regimen. Keep in mind that a positive response to lime sulfur dip does not confirm demodicosis, but it does indicate that further investigation and treatment may be warranted, especially if other cats are showing symptoms.
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