Chytridiomycosis (Batrachochytrium dendrobatidis): outbreak in a captive frog population

Abstract

Objective: The objective of this study was to perform a retrospective data analysis of frog mortalities in an off-exhibit frog room at an aquarium, in relation to a Batrachochytrium dendrobatidis (Bd) outbreak. It was hypothesized that the majority of the deaths occurring from 10/1/10 to 2/28/11 could be attributed to Bd infection. Furthermore, it was also predicted that infected individuals would be located in close proximity. Methods: Utilizing the aquarium’s electronic record database, information was gathered on the frogs in the off-exhibit frog room. Information available included: medical history, necropsy report, PCR results (if available), and frog location. Based on these data frogs were categorized as Bd positive, Bd suspect, Bd negative, and unknown. Results: The total mortality rate in the room was 26% (49/192). The majority of dead frogs, 61% (30/49), were shown to be either chytrid positive or suspect chytrid. It was also found that 38% of enclosures with any mortality had multiple (greater or equal to 2) deaths per enclosure. The chytrid-positive individuals were located within the same 1/3 of the room. The medical records of Bd positive and suspect Bd frogs were examined and their clinical signs before death were evaluated. The most common clinical signs included poor body condition (41%) and skin sloughing (24%). Conclusions & Clinical Relevance: The results support the virulent nature of Bd and its ability to cause high mortality in captive frogs. This study emphasizes the importance of maintaining both biosecurity and a high index of suspicion for Bd in captive frog populations.