Sarcoptes and Cheyletiella (Proceedings)


Sarcoptes and Cheyletiella (Proceedings)

Aug 01, 2009

Any time you are faced with an atopic patient who has sudden intensification of pruritus, these mites should be an important part of your diagnosis. Similarly, these mites should be part of your differential diagnosis in any older animal with a sudden onset of pruritus. Most importantly, any time you are faced with a pruritic cat or dog, these mites should be an important part of your differential diagnosis.

Sarcoptic mange is a very contagious disease caused by Sarcoptes scabiei var. canis in dogs. This usually presents as an incredibly pruritic process. Papules, scales and heavy serous crusting are commonly detectable at the elbows, hocks, face and pinnae and ventral trunk. Sarcoptic mange can also present as "Scabies incognito", manifested by severe pruritus without lesions. Any age, breed or sex is susceptible.

Cheyletiellosis is also very contagious and can be caused by C. blakei (primarily cats), C. yasguri (primarily dogs) and C. parasitovorax (primarily rabbits). Host specificity is somewhat controversial. The clinical signs may consist of mild to severe scaling over the dorsal trunk with no to mild pruritus to multifocal papules and severe pruritus. Cheyletiellosis varies in frequency in different areas of the country and the world.

Diagnosis of sarcoptic mange is made via superficial skin scrapings. The mites may be difficult to find. So the diagnosis is often made via trial therapy for mites. Cheyletiellosis is diagnosed via tape impression, superficial scraping or fecal flotations. This mite is also difficult to find on routine diagnostics so diagnosis is often made via trial therapy for mites.

Selamectin is licensed as a topical spot-on formulation for the control and treatment of canine scabies. This solution is labeled for usage once monthly. However, most dermatologists currently use the Revolution on an extralabel protocol every other week for 3 applications. Although this is not licensed for usage in cheyletiellosis, it seems to be effective at the every other week for 3 application protocol.

Ivermectin can be given by subcutaneous injection, orally or topically. Most often this is dosed at either 200-400 mcg/kg weekly (orally) to every other week (subcutaneously) for 4-6 weeks. This is also an off label usage. When considering this medication, you should be cognizant of the potential issues in certain highly susceptible breeds or dogs carrying the MDR1 gene mutation as the potential side effects may range from ataxia, tremors, blindness, coma to death. We usually slowly increase the dosage from 50 mcg/kg/day to 100mcg/kg/day to 150 mcg/kg/day to 300 mcg/kg/day monitoring carefully for side effects.

Milbemycin oxime has been used at a dosage of 2 mg/kg weekly PO for 3-5 weeks and is quite effective for canine scabies. At these dosages, it is a safe alternative therapy to ivermectin in high risk breeds. This same protocol has been used for cheyletiellosis, but relapses seem to be more frequent with this mite.

A 2.5% moxidectin spot-on formuation has been used for the treatment and control of canine sarcoptic mange, but is not label approved for this usage in the US. This has been used every other week for 3 treatments.

Other topical rinses that can be used are lime sulfur rinses and amitraz rinses. Lime sulfur rinses for both mites are generally used at 2% weekly for 4-6 weeks. Side effects are the odor, potential staining and tarnishing of jewelry. When using on cats, it is best to apply an E-collar to keep them from licking. Otherwise, they may develop vomiting or diarrhea. Amitraz rinses at 250 ppm every other week for 2-3 rinses can be used for sarcoptic mange. Amitraz rinses are not approved for this usage.

Since both these mites are highly contagious, all in contact animals should be treated. Additionally, it is very good to remind people that both these mites are also potentially zoonotic. Nobody likes surprises! If lesions are present on the humans, they may persist for 7-14 days, but typically new lesions do not develop. However, I always recommend consulting their physicians if lesions are present or if they have specific questions regarding themselves.