Ichthyophonus-like infection in wild amphibians from Québec, Canada

Abstract

ABSTRACT. Myositis associated with infection by Ichthyophonus-like organisms was diagnosed in 35 of 260 (13%) wild amphibians collected in Quebec, Canada, from 1959 to 1964 , and 1992 to 1999 (n = 230). Infection was diagnosed in 17 green frogs Rana clamitans, 9 wood frogs R, sylvatica, 4 red-spotted newts hrotophthalmus viridescens, 3 bullfrogs R. catesbeiana, 1 spring peeper Pseudacris crucifer, and 1 pickerel frog R. palustris. The spring peeper and one of the bullfrogs were collected in 1964 from the Mont Saint-Hilaire Biosphere Reserve, indicating long-term presence of the organism. Spores of the organisms invaded striated muscle fibers and were associated with variable degrees of granulomatous and eosinophilic inflammation. Infection was considered fatal in 2 green frogs, 1 wood frog, and 1 red-spotted newt. It was considered potentially significant in 3 additional green frogs in which up to 100% of the fibers of some muscles were replaced by spores associated with a severe granulomatous reaction. Ultrastructural features of Ichthyophonus-like spores included a thick trilaminated wall, a paramural cytoplasm, multiple nuclei, oval rnitochondria with short tubulo-vesicular cristae and numerous ribosomes. This report represents 4 new host records and shows that ichthyophonosis is enzootic in amphibians from Quebec.

Thermal biology of newts (Notophthalmus viridescens) chronically infected with a naturally occurring pathogen

“…The lesions were consistent with those described elsewhere for Ichthyophonus in amphibians (Herman, 1984;Mikaelian et al, 2000) and ranged from small, typically longitudinally arrayed discrete nodules to larger swellings that involved more than 50% of the length of the animal (see below). Herman (1984) reported that newts in apparently advanced stages of Ichthyophonus infection exhibited ulcerated lesions that had been secondarily invaded by bacteria.…”

“…The cause of the lesions was identified by the National Wildlife Health Center in Madison, Wisconsin, as an Icthyophonus-like fungus. My own observations and those of others (Herman, 1984;Mikaelian et al, 2000;Green et al, 2002) suggest that the Ichthyophonus-like organism may have been an endemic pathogen in newts for some time, only now becoming more prevalent.…”

“…Reports suggest that some of the pathogens may have only recently moved into new areas and species while others may have been present in the environment and only just increased in incidence or pathogenicity (Daszak et al, 2001;Green et al, 2002;Rachowicz et al, 2005). While morbidity and mortality associated with Ichthyophonus in amphibians have been reported (Mikaelian et al, 2000;Green et al, 2002), the physiological consequences of these infections remain largely unexplored and deserve attention (Wikelski and Cooke, 2006). Moreover, newts are keystone predators in certain ecosystems (Smith, 2006) and their physiological responses to infection may have significant consequences for the composition of those ecosystems.…”

“…However, Woodhams et al (2003) reported that frogs infected with the chytrid pathogen, Batrachochytrium dendrobatidis, were cured when incubated at elevated temperatures. Little is known about the transmission and course of Ichthyophonus-like infections in newts (Mikaelian et al, 2000). Fish must ingest Ichthyophonus-infected prey in order to acquire the organism (Mikaelian et al, 2000).…”

Infection of Spotted Salamanders (Ambystoma maculatum) with Ichthyophonus-like Organisms in Virginia

“…Furthermore, Ichthyophonosis appears to be enzootic in Quebec, Canada, where a variety of frogs and one redspotted newt displayed infection with this organism (Mikaelian et al, 2000). To our knowledge, this is the first report of the infection of adult Ambystoma maculata by Ichthyophonus-like organisms in Virginia.…”