ABORTION AND NEONATAL MORTALITY DUE TO TOXOPLASMA GONDII IN BIGHORN SHEEP (OVIS CANADENSIS)

Elis A Fisk; E Frances Cassirer; Katey S Huggler; Allan P Pessier; Laura A White; Joshua D Ramsay; Elizabeth W Goldsmith; Holly R Drankhan; Rebecca M Wolking; Kezia R Manlove; Todd Nordeen; John T Hogg; Kyle R Taylor

doi:10.7589/JWD-D-22-00057

ABORTION AND NEONATAL MORTALITY DUE TO TOXOPLASMA GONDII IN BIGHORN SHEEP (OVIS CANADENSIS)

J Wildl Dis. 2023 Jan 1;59(1):37-48. doi: 10.7589/JWD-D-22-00057.

Authors

Elis A Fisk^{1

2}, E Frances Cassirer³, Katey S Huggler⁴, Allan P Pessier^{1

2}, Laura A White^{1

2}, Joshua D Ramsay^{1

2}, Elizabeth W Goldsmith^{1

2}, Holly R Drankhan^{1

2}, Rebecca M Wolking^{1

2}, Kezia R Manlove⁵, Todd Nordeen⁶, John T Hogg⁷, Kyle R Taylor^{1

2}

Affiliations

¹ Washington Animal Disease Diagnostic Laboratory, 1940 SE Olympia Ave., Pullman, Washington 99164-7034, USA.
² Department of Veterinary Microbiology and Pathology, Washington State University College of Veterinary Medicine, PO Box 647040, Pullman, Washington 99164-7040, USA.
³ Idaho Department of Fish and Game, 3316 16th St., Lewiston, Idaho 83501, USA.
⁴ Department of Fish and Wildlife Sciences, University of Idaho, 875 Perimeter Dr., Moscow, Idaho 83844, USA.
⁵ Department of Wildland Resources and Ecology Center, Utah State University, 5230 Old Main Hill, NR 206, Logan, Utah 84322, USA.
⁶ Nebraska Game and Parks Commission, 2200 N 33rd St., PO Box 30370, Lincoln, Nebraska 68503, USA.
⁷ Montana Conservation Science Institute Ltd., 5200 Miller Creek Rd., Missoula, Montana 59803, USA.

PMID: 36648765
DOI: 10.7589/JWD-D-22-00057

Abstract

Low lamb recruitment can be an obstacle to bighorn sheep (Ovis canadensis) conservation and restoration. Causes of abortion and neonate loss in bighorn sheep, which may affect recruitment, are poorly understood. Toxoplasma gondii is a major cause of abortion and stillbirth in domestic small ruminants worldwide, but no reports exist documenting abortion or neonatal death in bighorn sheep attributable to toxoplasmosis. Between March 2019 and May 2021, eight fetal and neonatal bighorn lamb cadavers from four western US states (Idaho, Montana, Nebraska, and Washington) were submitted to the Washington Animal Disease Diagnostic Laboratory for postmortem examination, histologic examination, and ancillary testing to determine the cause of abortion or neonatal death. Necrotizing encephalitis characteristic of toxoplasmosis was identified histologically in six of eight cases, and T. gondii infection was confirmed by PCR in five cases with characteristic lesions. Other lesions attributable to toxoplasmosis were pneumonia (3/5 cases) and myocarditis (2/5 cases). Protozoal cysts were identified histologically within brain, lung, heart, skeletal muscle, adipose tissue, or a combination of samples in all five sheep with PCR-confirmed T. gondii infections. Seroprevalence of T. gondii ranged from 40-81% of adult females sampled in the Washington population in October and November 2018-2021, confirming high rates of exposure before detection of Toxoplasma abortions in this study. Of 1,149 bighorn sheep postmortem samples submitted to Washington Animal Disease Diagnostic Laboratory between January 2000 and May 2021, 21 of which were from fetuses or neonates, a single case of chronic toxoplasmosis was diagnosed in one adult ewe. Recent identification of Toxoplasma abortions in bighorn sheep suggests that toxoplasmosis is an underappreciated cause of reproductive loss. Abortions and neonatal mortalities should be investigated through postmortem and histologic examination, particularly in herds that are chronically small, demographically stagnant, or exhibit reproductive rates lower than expected.

Keywords: Ovis canadensis; Toxoplasma gondii; Abortion; bighorn sheep; toxoplasmosis.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Abortion, Veterinary / epidemiology
Abortion, Veterinary / microbiology
Animals
Animals, Newborn / parasitology
Conservation of Natural Resources
Female
Pregnancy
Seroepidemiologic Studies
Sheep
Sheep Diseases* / diagnosis
Sheep Diseases* / mortality
Sheep Diseases* / parasitology
Sheep, Bighorn*
Toxoplasma* / isolation & purification
Toxoplasmosis, Animal* / diagnosis
Toxoplasmosis, Animal* / epidemiology