Ministry of Environment
Emerging infectious diseases are recognized as one of the leading causes of amphibian declines worldwide. A number of amphibian diseases are of concern in BC, including chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) and the more recently discovered Batrachochytrium salamandrivorans (Bsal). Emerging infectious diseases are defined as those that are recently recognized, new in a population, or rapidly increasing in incidence, virulence or geographical range. Although ranaviruses are associated with many individual amphibian mass mortality events, direct evidence of disease-induced amphibian declines is stronger for chytridiomycosis.
Amphibians also suffer from a variety of other diseases including a suite of illnesses caused by ranaviruses in the family Iridoviridae; red-leg syndrome from Aeromonas sp.; chlamydophilosis, and mycobacteriosis caused by a variety of bacteria; saprolegniasis caused by oomycete water molds; choromomycosis and basidiobolomycosis caused by a diversity of fungal pathogens; and a variety of parasitic skin diseases caused by protozoan and invertebrate parasites. Many of these diseases are secondary infections that animals contract due to poor health, unfavourable environmental conditions or poor husbandry practises. These diseases are not thought to be responsible for declines in wild amphibian populations.
Another emerging amphibian conservation issue is the high levels of deformities, especially limb deformities that have been observed in metamorphosing and adult amphibians in North America. Current evidence indicates that infestation by a digenetic trematode, Ribeiroia ondatrae, is the primary cause of such deformities. Ribeiroia spp. have a complex life cycle involving planorbid snails, amphibians and water birds. The outbreak of deformities in the past decade may be caused by Ribeiroia parasitism interacting with other environmental factors such as pesticide pollution, nutrient run-off, and increased predation pressure.
The baseline prevalence of amphibian malformations and the occurrence of emerging parasite outbreaks remain to be systematically surveyed in British Columbia. In collaboration with the Wildlife Health Program, we have designed a hygiene protocol to prevent the spread of amphibian diseases.
We also have two baseline surveillance programs to better understand the presence and distribution of amphibian diseases and mortalities in B.C.
» Surveillance for Amphibian Mass Mortalities in British Columbia (SAMM B.C.) [PDF 251KB]
» Sampling Protocol for Assessing Prevalence of Batrachochytrium dendrobatidis [PDF 375KB]
The report ‘The Emerging Infectious Diseases in BC Amphibians’ provides more information and you can also contact the B.C. Frogwatch coordinator if you need further information.