Infestation with the sarcoptic mites Sarcoptes scabiei and Notoedres cati is common in pigs, dogs, and cats throughout the world (Also see Mange). In the USA, sarcoptic mange is rare in horses, cattle, and sheep and is considered a reportable disease. Papular eruptions progress to scaling, crusting, and excoriations of the ear margins and other parts of the body. Pruritus is severe. Transmission is by direct contact with infected animals or contaminated fomites. Diagnosis is based on clinical signs, history of exposure, and discovery of mites on multiple skin scrapings. Negative scrapings do not rule out the diagnosis, however, because the mite is often difficult to find. If the diagnosis is suspected, treatment should be instituted. Mites are much easier to find on skin scrapings of cats with notoedric acariasis. Treatment options include lime sulfur dips (safe in all species) every 5 days for 3–5 treatments, insecticidal dips such as amitraz (in dogs only) 2–3 treatments 2 wk apart, and ivermectin at 200–300 mg/kg, PO or SC, every 1–2 wk for 2–4 treatments. Treatment response is not consistent when using lime sulfur dips or amitraz in small animals; therefore, these topicals are not good options for a treatment trial (ie, mites are not found on skin scrapings).
Ivermectin is widely used to treat sarcoptic mange in dogs, and has been used to treat notoedric mange in cats, but is not approved by the FDA for these indications. Therefore, every caution should be taken and clients specifically informed of inherent risks with this drug. Dog breeds susceptible to ivermectin toxicity include Collies, Shetland Sheepdogs, Australian Shepherds, English Shepherds, Longhaired Whippets, McNabs, Silken Windhounds, and Old English Sheepdogs. Before using ivermectin in any of these breeds, a genetic test for the mutation of the MDR1 gene, which encodes for the multidrug transporter P-glycoprotein, should be performed. (This test is currently available at the University of Washington.) Oral milbemycin oxime has been reported to be safe and effective in the treatment of canine sarcoptic mange but is not FDA approved for this purpose. The recommended treatment protocol is 2 mg/kg once weekly for 4 treatments. Selamectin has also shown efficacy in the treatment of canine sarcoptic mange. The recommended protocol is 4 applications at 2-wk intervals. Because mites can survive off the host for a variable amount of time, all bedding, brushes, tack, and fomites should be treated as well. It is recommended that all in-contact animals also be treated because of the contagious nature of these acarioses.
Nonburrowing psoroptic mites cause a pruritic otitis externa in horses. Horses may present with head shaking and a drooping ear. Diagnosis is confirmed by finding the mites on skin scraping or in otic exudate, but mites may be difficult to find in the ear canal. Psoroptic mange is a reportable disease in some regions. Ivermectin at 200 mg/kg, PO, every 2 wk for 2 treatments has been shown to be effective.
Last full review/revision July 2011 by Sheila Torres, DVM, PhD, DACVD; Scott A. Dee, DVM, MS, PhD, DACVM