92 (104)

9

A Practical

In massm infestations involving contamination of the emironment with immature stages, cat own-ers may be bitten by young adult fleas emerging from their cocoons in search of a host^l4. Papular lesions are seen, particularly on the limbs, ankles, trunk, waist and even the arms¹³ (Figs 9 : 11-13).

Pruritus can vary significantly from one place to another depending on the population density of fleas present in the environment.

Corticosteroid responsiveness is a feature of all inflammatory dermatoses. FAD is initially respon-sive to corticosteroids although this becomes less marked with time.

Response to insecticidal treatment must be noted precisely. A definite response is an important part of the history. If response is partial or non-existent, the possible reasons for treatment failure must be investigated: underdosing, lack of treatment of the environment or in-contact animals^l5.

Clinical examination

FAD should be considered before any other pruritic dermatosis when a cat is presented with miliary dermatitis, self-induced alopecia or certain types of eosinophilic granuloma complex (principally eosinophilic plaąues). A fuli allergy differential diagnosis, must of course be constructed.

Demonstration of fleas

Demonstration of fleas or their faeces is difficult, sometimes impossible. Cats with flea bite allergy nibble and lick themselves morę than other cats, effectively removing fleas from their bodies. The search for adult fleas is usually carried out in the perineal and inguinal regions and under the chin¹⁶. Even thorough inspection is often unrewarding but using a flea comb can help considerably. Combing for a few minutes after applying an insecticidal spray is probably the best way of demonstrating adult fleas.

If neither adult fleas nor eggs can be found, it may be possible to demonstrate flea faeces. These smali pieces of debris are reddish brown and shaped like commas or fragments of plates (Fig. 9 : 14). After careful combing, the collected faecal droppings are placed on a damp piece of blotting paper. The droppings are madę up of haemoglobin crystals which readily dissolve to form reddish brown stains. Flea faeces can be examined under the microscope to reveal their characteristic shape and colour (Fig. 9 : 15). This can convince the owners that their pet really does have fleas and also that flea droppings are nice to look at! This search only proves worthwhile in relatively massive infestations or in a cat which grooms inadeąuately (e.g. when animal is tired, depressed, obese...).

The most obvious sign of a heavy environmental burden of young adult fleas is human infestation with “carpet fleas” i.e. young adult fleas, recently emerged from their cocoons. Eventually, eggs and larvae can also be seen on the animals’ bedding.

Segments of Dipylidium caninum around the anus or even in the environment, are a sign of infestation by Ctenocephalides felis felis ^{l l7}.

Differential diagnosis

The differential diagnosis of FAD includes all pruritic dermatoses: allergic skin disorders (food intoler-ance, atopic dermatitis), infestation with Otodectes cynotis, Cheyletiella blakei or lice, Felicola subros-tratus and Linognathus setosus, and also pruritus associated with behavioural disorders. Sometimes, diagnosis is madę difficult by the possible association of FAD with one of these other dermatoses ‘•²’⁵'⁶. Histopathological examination of skin biopsies is of no major benefit, revealing only an inflammatory dermatosis with variable eosinophilia. Blood eosinophilia and anaemia are sometimes reported.

Allergy testing

Diagnosis of FAD by intradermal testing has been at the heart of the veterinary fascination with allergy and dermatology and yet paradoxically, the poor reliability of this procedurę, especially in the cat, has actually discouraged many practitioners.

Allergenic extracts of Ctenocephalides felis felis

Whole body extracts of Ctenocephalides felis felis, obtained by grinding up fleas and extracting the protein, are used in both diagnosis and immunotherapy. They contain a mixture of proteins of various molecular weights. Studies looking at whole body extracts and salivary gland extracts separated into fractions onto polyacrylamide gel have revealed about 15 fractions of 14-150 kD ¹⁸‘²². The composi-tion of whole body extracts, and therefore antigenicity, is variable which poses problems of repro-

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