Objective: To implement a disease monitoring system in federal, municipal, and private abattoirs in Baja California, Mexico and to estimate annual prevalence of tuberculosis (TB) in beef and dairy cattle slaughtered and inspected in 1995 and 1996.
Design: Epidemiologic survey.
Animals: About 200,000 cattle (95% beef, 5% dairy).
Procedures: Lymph node and tissue specimens with lesions suggestive of TB were fixed in neutral-buffered 10% formalin and embedded in paraffin. Sections were stained with H&E and Ziehl-Neelsen and examined for typical tuberculous lesions and acid-fast bacilli. Annual prevalence and 95% confidence intervals were estimated.
Results: Prevalence of TB in all slaughtered cattle was 0.12 and 0.46% in 1995 and 1996, respectively (beef cattle, 0.02 and 0.05%, respectively; dairy cattle, 2.0 and 8.3%, respectively). Tuberculosis cases/1,000 slaughtered cattle were linearly associated with monthly volumes of tissue submissions.
Clinical implications: It is critical to quantify the monitoring activity at abattoirs to better estimate the prevalence of TB in slaughtered cattle. Annual prevalence of TB was significantly greater in dairy cattle than in beef cattle. Veterinarians and cattle producers in this region are encouraged to develop and work on herd plans aimed at controlling and eradicating TB.