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1 Department of Biology, University of Nebraska at Omaha, Omaha, Nebraska, 68182, USA
2 Utah Division of Wildlife Resources, 515 E 5300 S, Ogden, Utah 84405, USA
6 Corresponding author (email: suef{at}iastate.edu)
ABSTRACT:
Isolated, nonmigratory populations of bighorn sheep (Ovis canadensis) may experience high exposure to lungworms (Protostrongylus spp.) through a build-up of fecal material. However, semiarid climates may hinder lungworm transmission by limiting terrestrial gastropods, the intermediate hosts. We assessed potential for lungworm transmission, documented occurrence of transmission, and identified habitat types where transmission was likely to occur on ranges of two recently introduced populations of bighorn sheep in northern Utah. Gastropods were collected weekly on Antelope Island and the Newfoundland Mountains, May–August 2001–02, from each of the four major habitat types (riparian, rock, desert shrub, and grass). Distribution of 113 bighorn sheep groups was observed, and 421 fecal pellet groups were collected to estimate lungworm levels. A total of 1,595 gastropods representing five genera were collected from both ranges. Vallonia made up 85% of all gastropods collected. Of 980 gastropods collected on Antelope Island in 2002, only Vallonia were found infected with protostrongylid-type larvae (10 of 980=1%). Lungworm prevalence in bighorn fecal samples was 97% on Antelope Island and 90% on the Newfoundland Mountains. Lungworm prevalence in lambs indicated lungworm transmission was occurring on Antelope Island. Lungworm transmission was likely occurring in riparian habitat due to abundant gastropods, presence of infected gastropods, and reliance by bighorn sheep on few water sources. Differences in spatial distribution between ram and nursery groups may partly explain higher fecal larvae counts in nursery than in ram groups. We suggest lungworm levels in bighorn sheep on semiarid ranges may increase in dry years as bighorn sheep concentrate use on fewer perennial water sources.
Key words: Antelope Island, bighorn sheep, gastropod, intermediate host, lungworm, Newfoundland Mountains, Ovis canadensis, Protostrongylus spp.
3 Current address: Wyoming Game and Fish Department, 117 S. Sublette Ave., Pinedale, Wyoming 82941, USA
4 Current address: Department of Natural Resource Ecology and Management, Iowa State University, Ames, Iowa 50011, USA
5 Current address: Minnesota Department of Natural Resources, 500 W. Lafayette Blvd., St. Paul, Minnesota 55155, USA
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