Dermatitis associated with microfilariae (Filarioidea) in 10 dogs

Area of Science:

• Veterinary Dermatology
• Parasitology
• Canine Pathology

Background:

• Filarial nematodes can cause various dermatological conditions in animals.
• Dermatitis in dogs can have multiple etiologies, including parasitic infections.
• Accurate identification of causative agents is crucial for effective treatment.

Purpose of the Study:

• To diagnose and characterize dermatitis associated with microfilariae in dogs.
• To identify the specific nematode species responsible for the observed dermatitis.
• To differentiate the condition from infections by other filarial parasites like Dirofilaria immitis.

Main Methods:

• Clinical examination of affected dogs.
• Dermatohistopathology including microscopic evaluation of skin biopsy samples.
• Identification of nematode morphology and species.
• Diagnostic tests for Dirofilaria immitis (antigen and antibody tests, Knott/filter tests).

Main Results:

• Ten dogs in the western US presented with single or multiple skin lesions (papules, plaques) with alopecia, scarring, erythema, ulceration, or crusting.
• Pruritus was a common clinical sign.
• Microscopic findings included perivascular, periglandular, and interstitial inflammation with eosinophils and plasma cells, and dermal/subdermal scarring.
• Microgranulomas containing microfilariae were observed in six dogs; microfilariae were found free in the dermis/subcutis, not within vessels.
• The causative nematode was identified as Acanthocheilonema sp. (syn: Dipetalonema).
• Diagnostic tests for Dirofilaria immitis were negative in all tested dogs.

Conclusions:

• Acanthocheilonema sp. microfilariae can cause dermatitis in dogs.
• The clinical and histopathological findings are distinct from typical Dirofilaria immitis infections.
• Accurate identification of Acanthocheilonema sp. is important for differentiating this cause of canine dermatitis.