Ks. Barling et al., Spatial associations among density of cattle, abundance of wild canids, and seroprevalence to Neospora caninum in a population of beef calves, J AM VET ME, 217(9), 2000, pp. 1361-1365
Veterinary Medicine/Animal Health
JOURNAL OF THE AMERICAN VETERINARY MEDICAL ASSOCIATION
Objective-To determine the epidemiologic plausibility of a sylvatic transmi
ssion cycle for Neospora caninum between wild canids and beef cattle.
Design-Spatial analysis study.
Animals-1,009 weaned beef steers from 94 beef herds in Texas.
Procedure-Calves were grouped on the basis of seroprevalence for N caninum
and ecologic region in Texas. The Morans I test was used to evaluate spatia
l interdependence for adjusted seroprevalence by ecologic region. Cattle de
nsity (Number of cattle/259 km(2) [Number of cattle/100 mile(2)] of each ec
ologic region) and abundance indices for gray foxes and coyotes (Number of
animals/161 spotlight-transect [census] km [Number of animals/100 census mi
les] 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.
Results-Spatial interdependence was not detected for ecologic regions. Thre
e spatial regression models were tested. Each model contained a variable fo
r cattle density for the ecologic regions. Results for the 3 models reveale
d that seroprevalence was associated with cattle density and abundances of
gray foxes, coyotes, or both. Abundances of gray foxes and coyotes were col
linear. Results of a GIS-generated model validated these spatial models.
Conclusions and Clinical Relevance-In Texas, beef cattle are at increased r
isk of exposure to N caninum as a result of the abundance of wild canids an
d the density of beef cattle. It is plausible that a sylvatic transmission
cycle for neosporosis exists.