Amphibian chytrid fungus and ranaviruses in the Northwest Territories, Canada.
Pathogens can cause serious declines in host species, and knowing where pathogens associated with host declines occur facilitates understanding host-pathogen ecology. Suspected drivers of global amphibian declines include infectious diseases, with 2 pathogens in particular, Batrachochytrium dendrobatidis (Bd) and ranaviruses, causing concern. We explored the host range and geographic distribution of Bd and ranaviruses in the Taiga Plains ecoregion of the Northwest Territories, Canada, in 2007 and 2008. Both pathogens were detected, greatly extending their known geographic distributions. Ranaviruses were widespread geographically, but found only in wood frogs. In contrast, Bd was found at a single site, but was detected in all 3 species of amphibians in the survey area (wood frogs, boreal chorus frogs, western toads). The presence of Bd in the Northwest Territories is not congruent with predicted distributions based on niche models, even though findings from other studies at northern latitudes are consistent with those same models. Unexpectedly, we also found evidence that swabs routinely used to collect samples for Bd screening detected fewer infections than toe clips. Our use and handling of the swabs was consistent with other studies, and the cause of the apparent lack of integrity of swabs is unknown. The ranaviruses detected in our study were confirmed to be Frog Virus 3 by sequence analysis of a diagnostic 500 bp region of the major capsid protein gene. It is unknown whether Bd or ranaviruses are recent arrivals to the Canadian north. However, the genetic analyses required to answer that question can inform larger debates about the origin of Bd in North America as well as the potential effects of climate change and industrial development on the distributions of these important amphibian pathogens.
Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada. dschock@ucalgary.ca
Danna M
DM
Schock
Gregory R
GR
Ruthig
James P
JP
Collins
Susan J
SJ
Kutz
Suzanne
S
Carrière
Robert J
RJ
Gau
Alasdair M
AM
Veitch
Nicholas C
NC
Larter
Douglas P
DP
Tate
Glen
G
Guthrie
Daniel G
DG
Allaire
Richard A
RA
Popko
D000818:Animals; D001001:Anura; D008411:Chytridiomycota; D004266:DNA Virus Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D009181:Mycoses / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D015873:Northwest Territories / Q000453:epidemiology; D017995:Ranavirus