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A Practical Guide to Feline Dermatology

Cheyletiellosis

Aetiopathogenesis

Cheyletiellosis is an underdiagnosed mite infestation which causes real problems in some catteries. It is caused by Cheyletielła blakei, a mite specific to the cat, from the family Cheyletidae (Table 3 :1) ^3,1°. However, Cheyletielła yasguri and Cheyletielła parasitivorax are sometimes found in the cat^u0. Cheyletiellid mites live at the skin surface, feeding on cutaneous debris³¹⁰. Extemal surroundings seem to play an important part in transmission as the parasites appear to be able to survive off the host for at ieast a month ^l0. Cheyletiellosis is seen mainly in young cats (less than 1 year old) but adults can be asymptomatic carriers^l0. In catteries (especially involving Persians), it can be endemic with a high morbidity ^3,l°. Its incidence may be similar to that of dermatophytosis in some colonies. Humans may be affected (pruritic rash on the arms and trunk) in 20-30% of cases ^2,1°.

Clinical features

Cheyletiellosis affects principally the head and trunk and is characterised by pruritus, sometimes marked, erythema, papules, localised or diffuse hair loss, scaling and crusting (Figs 3 : 9,10). In the adult cat, cheyletiellosis can present as miliary dermatitis¹³’¹⁰.

Diagnosis

Tape strips (scotch test) do not always demonstrate adult cheyletiellids (Table 3:1) (Fig. 3 : e) but eggs are readily found attached to hairs ^u. Better success can be achieved if this procedurę is combined with coat brushings.

Coat brushings enable the collection of scalę, skin debris and parasites onto a piece of paper. The materiał is then examined microscopically.

Treatment

hermectin * (200-400 pg/kg), given once or twice (4 weeks apart), by subcutaneous injection, gives excellent results ^uo. It should not be given to cats less than 4 months old.

Fipronil ** in spot-on or spray formulation is also effective when given twice, 3 weeks apart.

Other topical acaricides (e.g. amitraz) may also be used according to standard protocols'.

When groups of cats are affected, ivermectin is the best treatment. Control of cheyletiellosis must include treatment of all in-contact animals, whether or not they are affected, and thorough cleaning of the environment'.

Trombiculiasis

Aetiopathogenesis

Trombiculiasis is a seasonal (summer and autumn) mite infestation caused by the 6-legged Trombicula autumnalis larva (Table 3 : 1), a mite from the family Trombiculidae, which lives in rotting organie materiał ^M. Its life cycle lasts about 50-70 days ³. Only the larvae are parasitic, affecting most animal species (e.g. dog, cat, man and poultry). In people, they cause very pruritic papular lesions on the limbs and trunk²³.

Trombicula autumnalis larvae cause disease through the proteolytic, irritant, and probably allergic effects of products in their saliva.

Clinical features

Trombiculiasis occurs mainly on the head (base of the pinnae, Henry’s pocket, neck) and feet (around the digits) and is characterised by erythema, excoriations, hair loss, erosions and crusts^1,3A8 (Figs 3 : 11-16). Pruritus is very severe and persists long after the larvae have gone '. Systemie signs (e.g. fever) are sometimes seen '.

* This product is not licensed for use in the cat and responsibility for its use falls on the prescribing veterinary surgeon.

** This product is not licensed for this indication in the cat and responsibility for its use falls on the prescribing veterinary surgeon.

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