Dermatitis associated with microfilariae (Filarioidea) in 10 dogs

Dermatitis associated with microfilariae of a nematode of the superfamily F ilarioidea was diagnosed in 10 dogs from the western United States. Clinica lly, lesions were single or multiple papules and plaques with alopecia, sca rring, erythema, ulceration, or crusting. Eight dogs had lesional pruritus. Microscopically, there was perivascular, periglandular, to interstitial in flammation, with many eosinophils and/or plasma cells, and scarring affecti ng the dermis and subcutis. Microgranulomas containing microfilaria were se en in six dogs. Microfilariae were noted in microgranulomas or free in the dermis or subcutis, but not in vessels. In one case, an adult female nemato de emerged from a biopsy sample that was placed in physiologic saline. Stud y of this nematode revealed that it was a filarioid of the family Onchocerc idae; it was identified as Acanthacheilonema sp. (syn: Dipetalonema). Antig en tests of five dogs were negative for Dirofilaria immitis. The Knott test s and/or filter tests of nine dogs were negative for microfilariae. An indi rect fluorescence antibody test of one dog was also negative for D. immitis . One dog was not evaluated for microfilariae.