Limb deformities as an emerging parasitic disease in amphibians: evidence from museum specimens and resurvey data

Publication Type:

Journal Article

Authors:

Johnson, Pieter T. J.; Lunde, Kevin B.; Derek A. Zelmer; Werner, J. Kirwin

Source:

Conservation Biology, Society for Conservation Biology, Volume 17, Issue 6, p.1724-1737 (2003)

Call Number:

A03JOH01IDUS

URL:

http://www.colorado.edu/eeb/facultysites/pieter/documents/Johnson%20et%20al%202003.pdf, http://onlinelibrary.wiley.com/doi/10.1111/j.1523-1739.2003.00217.x/abstract

Keywords:

amphibian decline, amphibian deformities, emerging disease, Glypthelmins, Hyla regilla, malformations, Megalodiscus, Megalodiscus sp, Pacific treefrog, parasites, Pseudacris regilla, Ribeirioia, trematode

Abstract:

Widespread reports of malformed amphibians are of growing conservation concern. Although accounts of mass malformations (>5%) in North American amphibian populations date back to the 1940s, they are often poorly documented and are rarely explained. The authors reviewed available information for nine historical accounts from California, Colorado, Idaho, Mississippi, Montana, Ohio, and Texas reported between 1946 and 1988. They then asked the following questions: 1) Which of these cases were associated with Ribeiroia (Trematoda: Digenea) infection? 2) Are malformations still occurring at these sites? And 3) if so, have the frequency or types of abnormalities changed? Each site was resurveyed between 1999 and 2002, and original voucher specimens were redescribed and examined for trematode infection. Direct identification and classification by discriminant function analysis indicated that historical malformations at six of eight sites were associated with infection by Ribeiroia, dating back as far as 1946. Malformations recorded historically at these sites were consistent with the documented effects of Ribeiroia infection, including extra limbs, cutaneous fusion, and bony triangles. Of the six sites that still supported amphibians upon resurvey, three continued to support severe limb malformations at frequencies of 7–50% in one or more species. Although no pesticides were detected, amphibians from each of these sites were infected with Ribeiroia metacercariae. Taken together, these results suggest that Ribeiroia infection has historically been an important cause of mass malformations in amphibians. The authors conclude that although parasite-induced malformations are not a new phenomenon, there is qualitative evidence suggesting that their prevalence has increased recently, and the authors highlight the need for long-term research to evaluate the impacts of malformations on amphibian population viability.