Canine and feline demodicosis - Veterinary Medicine
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Canine and feline demodicosis
You know demodectic mange frequently occurs in dogs. Now it appears to be more common in cats than previously thought, and new species have been discovered. Find out the latest on diagnosing and treating this frustrating skin disease.


VETERINARY MEDICINE


Diagnosis

Multiple deep skin scrapings are recommended to detect the hair-follicle-dwelling D. cati mites. The skin scraping technique is similar to that for D. canis. Superficial skin scrapings can be used to detect the superficial mite D. gatoi. Scrapings obtained with broad strokes enable the evaluation of the largest surface area for D. gatoi. Demodex gatoi mites may be easier to find in samples from the lateral forelimbs and the intrascapular region, possibly because these areas are less susceptible to self-grooming and, thus, mite removal. Acetate tape preparations can also be used to detect D. gatoi. Regardless of the type of mite, always sample multiple sites.

Because of the grooming behavior of cats, Demodex species mites may also be found on fecal examination. Especially in cases in which D. gatoi is suspected, it may be helpful to perform skin scrapings on other cats in the household since asymptomatic cats may be less likely to remove this potentially contagious mite from the skin as a result of overgrooming. ?

Negative cytologic examination results from skin scrapings do not definitively rule out D. gatoi infection. Empirical therapy for D. gatoi infection is sometimes administered to pruritic cats to rule out demodicosis before pursuing additional testing for pruritic diseases or diagnosing psychogenic alopecia.

TREATING FELINE DEMODICOSIS

Feline demodicosis is less prevalent than canine demodicosis. Hence, less information is available regarding treatment. Treatment includes correcting any underlying disease as well as miticidal therapy.

Lime sulfur dips are the safest option and have been used at 1.6% to 2% every five to seven days for four to six or more weeks in cats infested with D. gatoi and D. cati.10 Lime sulfur dips can also be used on pruritic cats suspected to have D. gatoi infection. The higher concentration is more effective in eliminating these mites. Patient tolerance is enhanced by using a pump-up garden sprayer for application. Use lime sulfur on all in-contact cats when faced with D. gatoi infection, as this mite is potentially contagious to other felids.12,37 Using an Elizabethan collar is recommended until the product dries to prevent oral ingestion.

Although 0.0125% to 0.025% amitraz applied twice weekly to every other week is effective in treating infections with both species of feline demodectic mites,39 we do not recommend its routine use given other alternatives and the risk of toxicosis.

Topical organophosphates were reported to be effective in treating infections with both mites,40 but these chemicals are not recommended since safer alternatives are available.

No side effects were seen when three cats with D. cati infection were treated with doramectin (600 g/kg subcutaneously weekly) for no more than three injections.31 This treatment resolved the demodicosis.

Anecdotally, ivermectin given orally at 300 to 600 g/kg daily to every other day has been used to treat feline demodicosis. Ivermectin formulations containing the least amount of propylene glycol are recommended for cats. Because of the risk of neurotoxicosis41 and no perceived improved efficacy when compared with lime sulfur, ivermectin use is discouraged.

Weekly application of selamectin for six weeks did not eliminate D. cati or D. gatoi infections.42 We have not found the topical application of fipronil to be effective in controlling infestation with either mite.

Demodectic otitis can be treated topically with a 0.01% solution of ivermectin (Acarexx—Idexx) or a 0.1% solution of milbemycin oxime (MilbeMite Otic Solution), but they are not labeled for this use.

CONCLUSION

Canine and feline demodicosis are dermatologic conditions that you can diagnose by recognizing the clinical signs and using proper sampling techniques. Treatment failure is rarely due to resistant mites. More frequent causes of treatment failure include poor pyoderma control, premature discontinuation of therapy, unsuccessful control of underlying conditions, and the use of immunosuppressants such as glucocorticoids. Amitraz, ivermectin, and milbemycin oxime are recommended for treating canine demodicosis. Lime sulfur, especially, and ivermectin are recommended to treat feline demodicosis.

Download a client handout on demodicosis at http://veterinarymedicine.dvm360.com/Demodicosis.

Download a consent form for extralabel ivermectin usage at http://veterinarymedicine.dvm360.com/Consent.


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Source: VETERINARY MEDICINE,
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