Co-infection with systemic candidiasis and diphtheritic aspergillosis in a Buffalo calf

Mycotic infections in neonatal calves are often undiagnosed but pose significant risks, especially in immunocompromised neonates. In this study, we report a rare case of co-infection with systemic candidiasis and diphtheritic aspergillosis in a 13-day-old female Murrah buffalo calf presented for necropsy at ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly. Gross examination revealed pneumonic changes with a well-demarcated nodule in the right caudal pulmonary lobe. Adherent mycotic pseudo membranes over the tracheal mucosa, and type I b haemorrhagic ulcers in the abomasum were also detected. Histopathological examination revealed fungal pseudo-hyphae, budding yeasts within pulmonary microabscesses, bronchiolar epithelium, and vessels, along with angioinvasion. The abomasum exhibited transmural necrotizing mycotic abomasitis with fungal hyphae invading submucosal vessels. Aseptically collected heart blood and lung tissue samples cultured on Sabouraud Dextrose Agar (SDA) yielded C. tropicalis. Tracheal swabs inoculated on SDA revealed growth of Aspergillus fumigatus and Aspergillus flavus. This study highlights that in calves with immature immune systems, opportunistic fungal infections are more likely, and the risk is further heightened by injudicious alteration of antibiotic regimens and corticosteroid therapy; such practices should be avoided to prevent mixed infections.