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

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.

Blood arsenic concentrations in felids.

The presence of measurable quantities of arsenic in the blood of most terrestrial species signifies an exposure that often warrants further investigation regarding source and potential veterinary intervention and treatment. However, some species, such as felids, have a genetic predisposition to retain arsenic in their blood; circulating concentrations of the heavy metal, albeit abnormal for most species, may actually present as a normal or expected finding. To make sense of this disparity, the authors queried a veterinary diagnostic laboratory database over a time period of 10 years (2008-2018) to discern the range of arsenic concentrations observed in various felids. All felid whole blood samples tested for heavy metals contained measurable concentrations of arsenic; this contrasts with other companion animals such as dogs which generally had arsenic concentrations below detectability. From these data, the authors present a working reference interval for whole blood arsenic in both domestic and captive-raised big cats. Veterinary diagnostic reference intervals are important parameters for the clinical management of animal health. Reference intervals for enzymes, hormones, minerals, vitamins and therapeutic drugs specific to organ function and health are becoming increasingly well defined for most companion and production animal species, and often dictate the clinician's decisions regarding therapeutic approaches. A conundrum arises, however, when the presence or detection of a heavy metal that is otherwise deemed potentially 'toxic' to most species is an 'expected', or 'normal', finding in another. Such is the case with whole blood heavy metal screens for the feline patient. The presence of blood arsenic is a common finding in both domestic and big cats raised in captivity. If not placed into the context of a range of known results, the finding may be erroneously interpreted as evidence for acute heavy metal intoxication. The current study reviews feline whole blood heavy metal submissions for arsenic concentrations to the Michigan State University Veterinary Diagnostic Laboratory between 2008 and 2018.