Acute mortality in California salamander (Ambystoma californiense) and Santa Cruz long-toed salamander (Ambystoma macrodactylum croceum) caused by Ribeiroia ondatrae (Class: Trematoda)

Abstract/Summary

In early September 2019, a morbidity and mortality event affecting California tiger salamanders (Ambystoma californiense) and Santa-Cruz long-toed salamanders (Ambystoma macrodactylum croceum) in late stages of metamorphosis was reported in a National Wildlife Refuge in Santa Cruz County, California, US. During the postmortem disease investigation, severe integumentary metacercarial (Class: Trematoda) infection, associated with widespread skin lesions, was observed. Planorbid snails collected from the ponds of the refuge within seven days of the mortality event were infected with Ribeiroia ondatrae, a digenetic trematode that can cause malformation and death in some amphibians. We suggest that sustained seasonal high water levels due to active habitat management along with several years of increased rainfall led to increased bird visitation, increased over-wintering of snails, and prolonged salamander metamorphosis, resulting in a confluence of conditions to create a hyper-parasitized state. This case is most likely the result of a suspected change in the environment with cascading change in parasite-host dynamics giving rise to more intense disease presentations of a well-known and -studied parasite.

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