Common throughout Europe. More dog related, the predominant species in some countries e.g. Ireland, France and Greece. Vector for a number of parasites including the small intestine tapeworm Dipylidium caninum as well as Bartonella spp..
Infestation is highly variable depending on the frequency of exposure, duration of infestation, presence of secondary infections and the degree of hypersensitivity. Non–allergic animals may have few clinical signs and allergic animals can show pruritus, alopecia, broken hairs, papules and erythematous macules with crusts. Moist dermatitis is typically seen in the dorsal lumbar and tail region. Lesions can extend to thighs and abdomen. Secondary pyotraumatic dermatitis, pyoderma and seborrhoea are commonly seen. In chronic cases the skin shows thickening of the dermis with acanthosis, hyperkeratosis and lichenification. Additionally, in young, old or debilitated animals, heavy infestations will cause anaemia.
Low numbers of fleas may remain undetected. Combing the coat facilitates the collection of flea faeces and collected material can be combed onto damp white tissue where black spots of faeces can be detected surrounded by a red ring of undigested blood. A combination of the presence of fleas or flea faeces can confirm the diagnosis of flea allergy dermatitis (FAD). There are a number of allergy tests, with no single test being the gold standard, which may assist. Diagnosis can be further complicated as FAD–affected dogs are more likely than non-FAD dogs to be atopic or have other allergies (e.g. food allergy).