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- Author or Editor: Craig A. Thompson x
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Abstract
In collaboration with the American College of Veterinary Pathologists
Abstract
ObjectiveβTo determine the seroprevalence for Neospora caninum in a population of beef calves in a feedlot and the association of serologic status with postweaning weight gain and carcass measurements.
DesignβLongitudinal observational study.
Animalsβ1,009 weaned beef steers from 92 herds.
ProcedureβSamples were obtained from all steers at time of arrival at a feedlot. Serologic status for Neospora spp was determined, using an agglutination test. Results of serologic testing were compared with calf growth and carcass data, using multivariate regression with generalized estimating equations.
ResultsβOf 1,009 calves, 131 (12.98%) were seropositive, and 54 of 92 (58.7%) consignments had β₯ 1 seropositive calf. Median within-consignment prevalence for consignments in which there was β₯ 1 seropositive calf was 20%. Seropositive status was associated with significant reductions in average daily gain, live body weight at slaughter, and hot carcass weight and an increase in ribeye area-to-hot carcass weight ratio. Seropositive status also was associated with significant increases in cost of treatment and significant reductions in income. Sick seropositive calves had the highest cost of treatment. An economic loss of $15.62/calf was projected for seropositive calves.
Conclusions and Clinical RelevanceβSignificant reductions in postweaning weight gain, carcass weight, and economic return were associated with detection of antibodies to N caninum in beef calves in a feedlot. (J Am Vet Med Assoc 2000;217: 1356β1360)
Abstract
ObjectiveβTo determine the epidemiologic plausibility of a sylvatic transmission cycle for Neospora caninum between wild canids and beef cattle.
DesignβSpatial analysis study.
Animalsβ1,009 weaned beef steers from 94 beef herds in Texas.
ProcedureβCalves were grouped on the basis of seroprevalence for N caninum and ecologic region in Texas. The Morans I test was used to evaluate spatial interdependence for adjusted seroprevalence by ecologic region. Cattle density (Number of cattle/259 km2 [Number of cattle/100 mile2] of each ecologic region) and abundance indices for gray foxes and coyotes (Number of animals/161 spotlight-transect [census] km [Number of animals/100 census miles] of each ecologic region) were used as covariates in spatial regression models, with adjusted seroprevalence as the outcome variable. A geographic information system (GIS) that used similar covariate information for each county was used to validate spatial regression models.
ResultsβSpatial interdependence was not detected for ecologic regions. Three spatial regression models were tested. Each model contained a variable for cattle density for the ecologic regions. Results for the 3 models revealed that seroprevalence was associated with cattle density and abundances of gray foxes, coyotes, or both. Abundances of gray foxes and coyotes were collinear. Results of a GIS-generated model validated these spatial models.
Conclusions and Clinical RelevanceβIn Texas, beef cattle are at increased risk of exposure to N caninum as a result of the abundance of wild canids and the density of beef cattle. It is plausible that a sylvatic transmission cycle for neosporosis exists. (J Am Vet Med Assoc 2000;217:1361β1365)
