Regular Articles / Articles RéguliersRibeiroia ondatrae (Trematoda: Digenea) infection induces severe limb malformations in western toads (Bufo boreas)

Abstract

Widespread reports of malformed amphibians in North America have prompted investigations into the cause(s) and implications of the phenomenon. Recently, a trematode parasite (Ribeiroia ondatrae) was identified as the probable cause o

Prevalence of Skeletal and Eye Malformations in Frogs From North-Central United States: Estimations Based on Collections From Randomly Selected Sites

“…Many of the current reports fall within the acute category. However, in contrast to historical reports, the current observations are characterized by malformed animals among multiple species at a single site, multiple sites with high malformation prevalence spread over wide areas, and recurrence of malformed animals in the same site in successive years (Ouellet et al, 1997;Gardiner and Hoppe, 1999;Johnson et al, 1999;Converse et al, 2000;Helgen et al, 2000;Hoppe, 2000). Malformation rates at some sites can be very high.…”

“…In addition, these infections caused the bony triangle formation in hindlimbs that has been noted as a retinoid effect (Gardiner and Hoppe, 1999) suggesting that the parasites may produce retinoids or stimulate retinoid-regulated pathways. Malformation induction was dependent on the parasite species because infection with Alaria mustelae cercariae did not result in abnormal limb development (Johnson et al, 1999). These experimental infections produced only hindlimb and forelimb malformations and not the other forms that have been consistently found in wild populations.…”

“…Experimental infections of Hyla regilla (Johnson et al, 1999) and Bufo boreas (Johnson et al, 2001) with cercariae from the trematode parasite Ribeiroia sp. produced multiple types of hindlimb malformations, including missing or shortened limbs as well as multiple digits and limbs.…”

“…Malformation rates at some sites can be very high. Johnson et al (1999) reported an average of 12.3% malformed Hyla regilla from 13 sites and Helgen et al (2000) sampled several sites that yielded 40-65% malformed Rana pipiens, while matching reference sites yielded no greater than 1% malformed specimens. Ouellet et al (1997) matched 14 agricultural sites, in which an average of 12% of the frogs had malformations, with 12 non-agricultural sites, in which they found only 0.7% malformed specimens.…”

Parasites of the American White Pelican

“…The example involving harm to amphibians concerns the cathamaesiid digenean Ribeiroia ondatrae. The metacercaria of this species produced limb malformations in a wide range of amphibians (frogs, toads, newts, and salamander) in wild and experimental hosts (Johnson et al 2002), with survivorship declining significantly with increasing cercarial exposure (Johnson et al 2001). Unlike the examples of diplostomids where the pelicans and catfish are the only known hosts, R. ondatrae infects a few different vertebrate definitive hosts in addition to pelicans as well as numerous amphibian second intermediate hosts and several snail species of the planorbid genus Planorbella as first intermediate hosts.…”