BRUCELLOSIS IN ADULT BEEF-CATTLE OF MEXICAN ORIGIN SHIPPED DIRECT-TO-SLAUGHTER INTO TEXAS

Objective-To compare prevalence estimates of brucellosis (BR) in adult beef cattle that originated from different slates and regions of Mexi co and that were shipped direct-to-slaughter into Texas during 1995. D esign-Epidemiologic survey. Animals-About 65,000 adult beef cattle. Pr ocedure-Blood samples were collected during postmortem examinations an d were tested for serum antibodies to Brucella abortus, using the part icle concentration fluorescence immunoassay and automated complement-f ixation test. Prevalence estimates and 95% confidence intervals of BR were calculated by state of origin in Mexico. The difference among pre valence estimates of BR in cattle from different states and regions wa s tested for significance (P<0.05), using the proportion test. Results -On the basis of serologic test results, the overall prevalence estima te of BR was 0.32%. The prevalence estimate of BR in cattle from the s tate of Chihuahua (0.10%) was significantly different than that in cat tle from the states of Nuevo Leon (0.23%), Zacatecas (0.34%), Durango (0.47%), Chiapas Tamaulipas (2.71%), Aguascalientes (7.89%), and Campe che (12.24%). In addition, prevalence estimates of BR in cattle were s ignificantly different among the northern (0.22%), south-central (3.18 %), and south coastal (9.42%) regions of Mexico. Clinical Implications -Results of this study indicate that the number of cattle exposed to B abortus may be significantly different among states and regions of Me xico. Current import sanitary requirements should continue to mitigate potential risk of transmission of BR from sexually intact cattle of M exican origin to Texas cattle.