AARC Blog #1 - Chytrid
Dr. Teresa Bousquet
Exotic Animal Veterinarian and AARC Board Member
Many herp-savy people are aware that there has been a catastrophic decline in amphibian populations world-wide over the last few decades. There are a number of factors that are causing this decline, including habitat loss, global warming, and pollution. One factor that is poorly understood, but that you may have heard of, is the emergence of Batrachochytrium dendrobatidis (Bd). Bd is a highly infectious fungal disease, and many scientists believe that it has resulted in the extinction of some amphibian species, and that more may be heading in that direction. No one is completely sure where this pathogen came from, but international trade of African Clawed frogs (Xenopus laevis) and/or American bullfrogs (Lithobates catesbeiana) is thought to play a significant role in its spread around the world.
Bd has been shown to be able to infect all major classes of amphibians, though some species and populations are more susceptible than others. Bd is found on all continents where amphibians live, both in captive and wild populations. In adult animals, it attacks the skin, where it interferes with electrolyte balance, causing a spike in blood potassium levels, acidification of the blood, slowing of the heart, and ultimately cardiac arrest. Symptoms in adults vary from sudden death with no apparent signs, to abnormal posture and behavior, lethargy, loss of reflexes, roughening, sloughing, and reddening of the skin, and increased time soaking in water. In the tadpoles, the fungus causes damage to the mouthparts, leading to decreased food intake, slowed metamorphosis, failure to thrive, and death. Symptoms are difficult to detect, given the size of the patients, but they may have abnormal swimming, and discoloration of the mouthparts.
Chytrid can be spread by direct contact between an infected individual with a non-infected individual, but also indirectly through fomites (any object or substance capable of carrying infectious organisms), such as contaminated soil, contaminated water, boots, equipment, etc.
For keepers of captive amphibians, we always recommend quarantining new animals for 30-60 days prior to introducing them into an established population. There are some tests available through your herp-savy veterinarian to check new animals for Bd, which ideally should be completed during this quarantine period. Hard surfaces and cages should be cleaned with quaternary ammonium, didecyl dimethy ammonium chloride, sodium hypochlorite, ethanol and Virkon. All of these must be rinsed extremely thoroughly before returning amphibians to the enclosures. If you ever have suspicions that you might have infected individuals in your collection, please contact a herp-savy veterinarian immediately for advise on testing and preventing further spread.
To reduce the risk of spreading Chytrid from captive populations to wild populations, captive individuals must never be released into the wild. Some species can carry Bd without showing clinical symptoms, but can still transmit it to susceptible animals. Water from captive tanks should never be poured into storm drains, which are not treated before flowing into lakes and rivers.
To avoid accidentally spreading Chytrid between wild populations, boots, clothing and equipment must be thoroughly cleaned and disinfected between herping trips. Do not relocate amphibians between bodies of water. If you ever find evidence of a mass mortality event, please report it to your local Fish and Wildlife office, and the Alberta Volunteer Amphibian Monitoring Program.
For more information, please see the following websites: