Action: Add salt to ponds to reduce chytridiomycosis
- One study in Australia found that following addition of salt to a pond containing the chytrid fungus, a population of green and golden bell frogs remained free of chytridiomycosis for at least six months.
The chytrid fungus Batrachochytrium dendrobatidis has been found to survive in lake water for seven weeks after introduction (Johnson & Speare 2003). Treating the aquatic environment may help to reduce the effect of the disease on amphibians. Salt is often used for fungal diseases in aquaculture and for veterinary treatments of fish and amphibians (Wright & Whitaker 2001; Mifsud & Rowland 2008) and has been found to kill the chytrid fungus (Johnson et al. 2003).
Johnson M.L., Berger L., Philips L. & Speare R. (2003) Fungicidal effects of chemical disinfectants, UV light, desiccation and heat on the amphibian chytrid Batrachochytrium dendrobatidis. Diseases of Aquatic Organisms, 57, 255–260.
Johnson M. & Speare R. (2003) Survival of Batrachochytrium dendrobatidis in water: quarantine and disease control implications. Emerging Infectious Diseases, 9, 922–925.
Mifsud C. & Rowland S.J. (2008) Use of salt to control ichthyophthiriosis and prevent saprolegniosis in silver perch, Bidyanus bidyanus. Aquaculture Research, 39, 1175–1180.
Wright K.M. & Whitaker B.R. (2001) Pharmacotherapeutics. Pages 309–330 in: K. M. Wright, B. R. Whitaker & F. L. Malabar (eds) Amphibian Medicine and Captive Husbandry, Krieger Publishing Company.
Supporting evidence from individual studies
A study in 2000–2001 of captive green and golden bell frogs Litoria aurea in Sydney, Australia (White 2006) found that following addition of salt to a constructed pond the population remained free of chytridiomycosis for at least six months. Thirty-three of 40 green and golden bell frog tadpoles released survived to juvenile frogs in the salted pond. However, growth appeared slower in salt water than fresh water (first metamorph: 49 vs 43 days; last metamorph: 123 vs 76–80 days). Following addition of salt, the two striped marsh frogs Limnodynastes peroni tested were negative for chytridiomycosis. Striped marsh frogs had introduced chytridiomycosis to the pond and it had killed all but one of the previous green and golden bell frog population. Following the initial outbreak of chytridiomycosis, uniodized table salt was added to the pond to achieve 1 parts per trillion (ppt) sodium chloride (3% sea water) in December 2000. Forty tadpoles were then released into the pond and were monitored weekly.