Impacts of bullfrog production on dispersion and acquired tolerance to chytrid fungus

Abstract

Global biodiversity has been suffering a worrying reduction at all levels, and measures and actions aimed at species conservation have become essential. Currently, amphibians represent the most endangered vertebrate group, with one of the main threats being chytridiomycosis, an emerging infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd), which is a flagellated pathogen that is efficient in its transmission, either by water or contact between individuals. The development of the disease compromises osmoregulatory, electrolytic, and cardiac functions, which can lead to death. The fungus may also produce toxins that interfere with the immune responses of the host, although the physiological effects are still poorly studied. The bullfrog is a species that has been identified as tolerant to chytridiomycosis and is marketed worldwide for human consumption. Currently it has become invasive in many countries adversely affecting native anurofauna. Because farmed bullfrogs present high fungal prevalence and trade is global, this species has also become an international vector of the pathogen. In addition, it is possible that the mass production of this species increases its tolerance to the infection, as bullfrogs act as a Bd supershedder in natural environments. The lack of biosafety protocols in the infrastructure of farms and commercialization of bullfrogs have raised concern about the possible negative impacts on native species. Thus, it is necessary to understand the role of this species and its mass production in the dissemination of Bd. Therefore, we aim at testing if farmed bullfrogs suffer artificial pressure that resulted in a higher tolerance when compared to native populations, and the possible function of the bullfrog farms as Bd supershedder.