Cheyletiella (Mange) in Cats

© Chailleux, N & Paradis, M http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=339606

Cheyletiellosis is a very contagious dermatosis caused by relatively large (500 μm × 350 μm) mites living on the skin surface. Cheyletiella mites are obligate parasites and have a life cycle of approximately 3 to 4 wk in total. They are not host specific and may transfer readily between dogs, cats, and rabbits. In addition to direct transmission, infestation may occur indirectly via fomites such as leashes, grooming tools, or even other, larger arthropods, such as fleas, lice, and flies ( 1). Eggs are bound to hair shafts, which, when shed, can also act as an environmental reservoir of infection ( 1, 2, 3). Given this lack of host specificity and the fact that the mites are capable of surviving away from the host for at least 10 d in suitable environmental conditions, it is imperative that all in-contact pet mammals, their paraphernalia, and their environment be included in the treatment program. However, environmental treatment is not always performed nowadays, as long as treatment duration is adequate. Indeed, treatment duration, which should cover a minimum period of 6 to 8 wk, is directly influenced by the severity of the infestation, the number of animals involved, the acaricidal product chosen, and whether or not there is concomitant topical or environment decontamination, or both.

Scaling and pruritus are the main signs of the disease in animals ( 1, 2, 3). The intensity of the pruritus is usually mild to moderate, but sometimes appears disproportionate to the apparent low numbers of mites. This might be due to a hypersensitivity reaction to the mite ( 19). An asymptomatic carrier state also exists and this should be borne in mind when tackling problem cases in which repeated reinfestation and zoonotic transmission is occurring. Humans in contact with pets carrying Cheyletiella spp. are at risk of becoming transiently infested themselves, producing an uncomfortable, pruritic dermatosis, characterized by papular lesions that, typically, appear on the arms, legs, trunk, and buttocks ( 1, 2, 3). However, as Cheyletiella spp. are not capable of reproducing on humans, appropriate treatment of the pet host should prevent further infestation, making human acaricidal therapy unnecessary.

The ease of finding the mite or its eggs is variable. It can be especially difficult in cats because of their natural grooming habits. Diagnosis is made by direct viewing of the mite, microscopic examination of the products of superficial skin scrapings, acetate tape preparations or flea combing (with or without dissolution of hair and debris with KOH), or faecal flotations ( 1, 4, 5, 6). The “KOH and flotation technique” has been reported to be one of the most reliable methods. However, this test was negative in 58% of clinically infested cats in 1 study ( 4). In the present study, positive results were obtained in only 4/15 (26.6%) cats with this technique, as compared with 5/15 (33.3%) with fecal flotation. Although not performed very frequently, faecal flotation may indeed be particularly useful for the detection of ingested mites and ova in cats, due to their grooming habits. In spite of the fact that a minimum of 3 diagnostic procedures were used simultaneously in each cat, a positive result was obtained in only 8/15 (53.3%). Therefore, in many cases, the diagnosis can be confirmed only by the response to treatment with an acaricidal trial. Moreover, an appropriate acaricidal trial is always required in order to rule out cheyletiellosis.

There are currently no licensed veterinary products specifically indicated for the treatment of cheyletiellosis. The mites are susceptible to several of the insecticidal and acaricidal formulations that are available, however, weekly applications of lime sulphur dips, pyrethrin sprays or shampoos, in conjunction with regular treatment of the environment, are also effective ( 1). Alternative topical treatment options are applications of a 0.25% fipronil spray (not available in Canada) ( 20). Animals that resent or do not tolerate topical therapy can be treated systemically with ivermectin. It is practical, economical, and very effective when administered at a dose of 200 to 400 μg/kg BW, PO, q7d or SC and pour-on, q14d to cover a minimum period of 6 to 8 wk ( 1, 4, 5, 6, 8). However, it is an off-label use in cats and dogs, and idiosyncratic reactions in collies and other herding breeds, as well as neurological signs in cats, particularly kittens, have been reported ( 9, 10, 11). In dogs, milbemycin oxime, another macrocyclic lactone, has been shown to be effective in the control of cheyletiellosis, but its use has not been reported in cases of feline cheyletiellosis ( 19).