Cutaneous and Systemic Pyogranulomatous Reaction following Administration of a Spot-on Formulation of an Insecticide - a Case Report

An eight year old female spayed 5 kg mix breed dog was presented with a 3 month history of a skin ulcer that first occurred 5 days after administration of an imidacloprid spot-on formulation. the dog also had erosive and crusted lesions on the dorsum and head, a firm nodule on the tongue and an ocular infection. the rest of the physical examination was un-remarkable. Blood work showed a neutrophilia, hypoalbuminemia, hypercholesterolemia and an elevated alkaline phosphatase activity. Serum cortisol levels were 4.74 μg/dl before and 20.6 μg/dl after ACtH administration. Cytology of the skin lesions showed neutrophils, macrophages and cocci. Biopsy showed a pyogranulomatous dermatitis and panniculitis. The dog’s general condition deteriorated and it died. Necropsy revealed pus in the subcutaneous adipose tissue and the mesentery, and a pyogranulomatous reaction in the lungs, liver and heart. No organisms were detected with special stains. to the best of the author’s knowledge this is the first reported observation of a possible association between imidacloprid application and a pyogranulomatous reaction.