High levels of aflatoxin (AFB1) in feed predisposed breeding bulls to unusual mortality due to Pasteurella infection despite vaccination

Ingestion of high level of aflatoxin predisposed the breeding bulls to succumb to pasteurella infection. Out of 35 (7 buffalo and 28 cattle) breeding bulls of different breeds, 15(43%) cattle bull died in a short span of 3 weeks. Animals exhibited staggering gait, anorexia, depression and raised body temperature. No mortality occurred in buffalo bulls despite severe nervous symptoms like frothing, teeth grinding, convulsions, muscular twitching, posterior paresis, fetlock knuckling and frequent fall. Gross lesions included subcutaneous oedema, muscular haemorrhages and excessive straw colored fluid in abdominal and thoracic cavities. Congestion and hemorrhages of varying degree were observed in the abomasum, intestinal mucosa, lungs, spleen, kidneys, heart and lymph nodes. Liver was friable and yellowish in color. Microscopic lesions corroborated with the gross lesions. Wheat bhoosa and feed concentrate were found to contain 1.75 ppm and 1.50 ppm aflatoxin Bl, respectively. Blood smears and tissue impressions were found positive for pasteurella organisms in untreated animals.