Current and Emerging Amphibian & Reptile Diseases

Current and Emerging
Amphibian & Reptile Diseases

Over the past few decades, emerging infectious diseases have caused population declines and extinctions of amphibian and reptile species worldwide. Pathogens that pose a potential threat to Canadian amphibian and reptile populations include:

Chytrid Disease

Caused by the fungus Batrachochytrium dendrobatidis (Bd), this disease has driven the decline or complete extinction of over 200 species, mainly frogs, worldwide. The fungus has been detected throughout much of Canada, although disease outbreaks are not known to be common. Bd has aquatic zoospores that infect the skin layer of an animal and can lead to anorexia, lethargy, and excessive skin shedding or thickening, which may prevent breathing, thermoregulation, and nutrient/water intake. American Bullfrogs, which are invasive around the world, appear immune and may be carriers of the fungus. On Vancouver Island, Bd has been detected on about 50% of individual invasive Bullfrogs.

Additional Resources

CWHC Chytridiomycosis Fact Sheet

Salamander Chytrid Disease

Caused by the fungus Batrachochytrium salamandrivorans (Bsal), this disease recently spread from Asia to Europe where it caused over 96% mortality in wild populations of Fire Salamanders. Bsal has not yet been reported in North America, but the potential for introduction through global pet trade poses a significant risk to our native species of salamanders and newts. Bsal has aquatic zoospores that infect the skin layers of an animal and can lead to skin lesions, anorexia, lethargy, ataxia, and death. If accidentally introduced to North America, experts warn that Bsal could trigger a salamander mass-extinction. Release of infected salamanders imported for the pet trade, or the improper disposal of terrarium/aquarium water in which they were kept, is the most likely route of introduction. Any water released from aquariums or ponds should be done on land and away from household drains, sewers, or other bodies of water.

Additional Resources

Ranaviruses

Ranaviruses are DNA (as opposed to RNA) viruses of the family Iridoviridae that have caused severe infections in a number of ectothermic taxa, including amphibians, reptiles, and fish worldwide. They cause a sudden onset of severe illness with gruesome symptoms (e.g. massive hemorrhaging, fluid accumulation under the skin, and bloating), followed by death within hours or days. Ranavirus infections can cause 90-100% mortality in populations and can affect multiple species at the same time. Ranaviruses have been responsible for disease outbreaks in many areas across Canada. They are transmitted through ingestion of infected organic material, water, and substrates, as well as skin injuries and by blood-feeding parasites like mosquitoes. 

Additional Resources

CWHC Ranavirus Fact Sheet

Snake Fungal Disease (SFD)

Caused by the fungus Ophidiomyces ophiodiicola, this emerging disease can lead to severe illness and death in snakes. It has been detected in wild snakes throughout northeastern North America, including several locations in southern Ontario. Reported population level effects have been highly variable, but SFD has resulted in up to 100% mortality in small, isolated populations. Signs of snake fungal infection include opaque infected eyes and roughened crusty scales. A proactive approach to preventing the spread of SFD and managing outbreaks is necessary to combat this new threat.