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CROSS-SPECIES TRANSMISSION OF GIARDIA: INOCULATION OF BEAVERS AND MUSKRATS WITH CYSTS OF HUMAN, BEAVER, MOUSE, AND MUSKRAT ORIGIN
Citation:
Erlandsen, S., L. Sherlock, M. Januschka, D. Schupp, F. III, W. Jakubowski, AND W. Bemrick. CROSS-SPECIES TRANSMISSION OF GIARDIA: INOCULATION OF BEAVERS AND MUSKRATS WITH CYSTS OF HUMAN, BEAVER, MOUSE, AND MUSKRAT ORIGIN. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-88/509.
Description:
Giardia cysts isolated from humans, beavers, mice and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. iardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers ormuskrats, were whown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infection in the Mongolian gerbil model. noculation of beavers with 5 x 10-5 Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. he mean prepatent period was 13.1 days. n infective dose experiment, using 5 x 10-1 to 5 x 10-5 viable G. lamblia cysts collected by fluorescence- activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. canning electron microscopy of beaver small intestine revealed that attachment of G. lambia trophozoites produced lesions in themicrovillous border. noculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10-5. he inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats or Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. ur results clearly demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts. uskrats could be infected with Giardia cysts derived from beavers, but the latter cannot be infected with the binary cysts characteristic of G. ondatrae. ecause of their association with waterborne outbreaks of giardiasis, the beaver and muskrat must be considered as possible intermediate reservoirs for Giardia spp. capable of infecting humans. owever, because of the evidence for their harboring different Giardia species than has been desbribed for humans, plus the potential contributions from other unevaluated sources, such as birds and even humans, it is not possible at this time to assign a major role in waterborne transmission to these animals.