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The burrowing mites, Sarcoptes and Notoedres, belong to the family Sarcoptidae which can cause scabies, a pruritic, contagious skin disease in animals and humans. Notoedres cati is the burrowing mite typically associated with feline scabies (Foley 1991) while Sarcoptes is associated with sarcoptic mange in dogs and humans. Notoedres mites are smaller than Sarcoptes, have ‘thumb print’-like dorsal striations, shorter limb stalks and a dorsal anus compared with the terminal anus, dorsal pegs and spines seen on Sarcoptes species (Scott and others 2001).
While information on canine sarcoptic mange is available, little is known about feline scabies. To the authors' knowledge, no cases of feline notoedric mange have been reported in the UK since the 1960s (Joyce 2010), with only sporadic reports from other parts of the world where it is considered epizootic (Delucchi and Castro 2000, Itoh and others 2004). Similarly, sarcoptic mange due to Sarcoptes scabiei in cats has only been reported infrequently worldwide. Three cases of pruritic skin disease associated with S scabiei in cats have been reported in continental Europe and North America (Bussieras 1984, Hawkins and others 1987, Kontos and others 1998), while a single case without pruritus was described in Taiwan (Huang and others 1998). Furthermore, feline scabies may also be associated with systemic disease or concurrent skin disease (Huang and others 1998, Malik and others 2006). In the UK, only two cases of mange in cats due to S scabiei have been described, both were non-pruritic upon presentation, and while one was systemically healthy (Kershaw 1989), the other was feline immunodeficiency virus (FIV) positive (Malik and others 2006). Although information on zoonotic transmission in some case reports is limited, pruritic papules on the forearms of in-contact humans were reported in these two UK cases. This short report describes a third UK case of sarcoptic mange in a pruritic cat, accompanied by suspected transmission to its owner. This case highlights the importance of considering an uncommon ectoparasitic infestation in the differential diagnoses of pruritus in cats.
The patient was a 19-year-old male neutered domestic shorthaired cat of 4.35 kg bodyweight, from the southeast of England, that presented with acute onset generalised pruritus with areas of hair loss, scaling and crusting, and multiple erythematous papules on the flanks and lateral thorax (Fig 1). Physical examination revealed a palpably enlarged thyroid gland and moderate amounts of dental calculus. The cat had been diagnosed with hyperthyroidism and hypertension in 2009 which had since been well controlled with thiamazole (Felimazole; Dechra Veterinary Products Limited) and amlodipine (Istin; Pfizer Ltd). There were no other skin lesions and no prior history of skin disease. The owner had, however, reported development of a pruritic, non-papular, erythematous skin rash on the forearms and abdomen concurrently with the cat's skin disease. The cat was FIV/ feline leukaemia virus (FeLV) negative, had been routinely dewormed and vaccinated until a few years prior to presentation, but ectoparasite prophylaxis had not been used. There were no other animals in the house, the patient had free outdoor access, and foxes were frequent visitors to the garden. Imidocloprid (Advantage; Bayer) had been applied once at the onset of clinical signs, two weeks before presentation, without any obvious improvement. Skin scrapes from the affected skin demonstrated abundant round-bodied, short-legged burrowing mites, which were identified as S scabiei by the presence of a terminal anus and dorsal spines and pegs (Fig 2). Following the diagnosis of sarcoptic mange, selamectin (Stronghold; Pfizer Ltd) was applied (14 days after imidocloprid) on two subsequent occasions four weeks apart. The lesions and pruritus started to improve one week after the first treatment with selamectin, and the crusting had resolved completely by the second application. The owner's pruritic rash resolved without treatment two to four weeks after the first selamectin application to the cat.
Pruritus and scaling were the main presenting clinical signs of scabies in this cat, and the infestation was associated with a pruritic rash in the owner. Although few cases of feline scabies have been described, pruritus and crusting appear to be variable in cats, and zoonotic transmission has not been reported consistently. This is in contrast with dogs where the main clinical signs are erythema, papules and crusts with intense pruritus, irrespective of the dog's health status. While several of the feline scabies cases had been systemically ill, concurrent disease or immunodeficiency in dogs (and in humans) seems to be associated with an uncommon distinct clinical entity of scabies (‘Norwegian scabies’) (Jackson 1995, Paterson and others 1995). This form is characterised by large numbers of mites found on skin scrapes, which is in contrast with the typically few mites associated with canine disease indicating that host immunity plays an important role in the development of disease. In the present case, mite numbers were numerous and it is possible that the underlying hyperthyroidism and hypertension contributed to development of the disease. However, these conditions are not directly linked to immunosuppression, and both were well controlled medically at the time of presentation. Epidemiologically, transmission from fox to cat to human was suspected based on the cat's observed sleeping behaviour both in a presumed fox den during the day and on the owner's lap in the evening. Although there is evidence in the UK for Sarcoptes infestation in foxes (Bates 2003), the epidemiology and routes of transmission are still unproven. It is possible that the recent increases in the urban fox population, and closer habitation with humans, could expose a greater number of cats and dogs to the risks of infestation.
While sarcoptic mange is a rare condition in domestic cats in the UK, this case highlights that it should be considered as a differential diagnosis for feline pruritus, particularly in animals where zoonotic transmission is suspected. The prolonged residual activity of some topical insecticide treatments commonly used in cats will help to prevent disease, but skin scrapings should be performed where such indications are not included, or when zoonotic spread may have occurred. In view of the lifelong implications of allergic skin disease, it is important to rule out ectoparasitic infestations, such as scabies, in every case, as the prognosis for cure of sarcoptic mange in the cat is excellent.
The authors would like to thank David May, Clare Treacher, RVN and Professor Ken Smith for their technical assistance.
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