Oral mycoses in avian scavengers exposed to antibiotics from livestock farming

Abstract

The exposure to antimicrobial pharmaceuticals as environmental contaminants can exert direct and indirect detrimental effects on health of wildlife. Fungal infections pose a major threat to domestic, captive-housed wild and free-ranging wild animals worldwide. However, little is known about their role in disease in birds in the wild. Here, we evaluated the incidence of thrush-like lesions in the oral cavity of wild nestling cinereous vultures (Aegypius monachus), griffon vultures (Gyps fulvus), Egyptian vultures (Neophron percnopterus) and golden eagles (Aquila chrysaetos) exposed to veterinary antibiotics via the consumption of medicated livestock carcasses. Lesions, which varied in number, size and location, were more frequent in the cinereous (77.8%, n=9) and griffon vultures (66.7%, n=48) than in the Egyptian vultures (28.6%, n=21) and golden eagles (28.6%, n=7). In all individuals (100%, n=24) of a subsample of the affected nestlings, yeast species were isolated from thrush-like oral lesions and identified using a well-established system based on their carbohydrate assimilation profiles and other complementary tests. Fourteen yeast species from seven genera (Candida, Meyerozyma, Pichia, Yarrowia, Cryptococcus, Rhodotorula and Trichosporon) were isolated from the lesions of the four host species. We found differential infections and effects depending on host age-related exposure or susceptibility to different yeast species across the development of nestling griffon vultures. This unprecedented outbreak of oral mycoses is alarming because of the delicate conservation status of several of the affected species. The role of livestock antibiotics in the transition of yeast species from commensal to opportunistic pathogens should be evaluated in an attempt to avoid the detrimental effects of contamination and disease on host health, as well as on the transmission of fungal emerging pathogens among wildlife populations and species, and their dissemination across livestock and human populations.

Keywords: Antimicrobials; Candidiasis; Livestock; Scavengers; Yeast species.