Introduction.

This study was conducted to estimate the seroprevalence and culture prevalence of paratuberculosis in purebred beef cattle in Texas and to estimate risks of ranch management practices associated with paratuberculosis.

Methods.

Approximately 7000 letters of invitation were mailed to beef cattle producers in Texas. Of 648 respondents, 115 were selected and completed the study. All cattle over 2 years old in a herd, up to 50 cattle, were sampled cattle. The IDEXX ELISA was used on serum, and cattle with SP values >0.25 were cultured for fecal MAP using a centrifugation technique and Herold s Egg Yolk media twice at 2 laboratories. Analyses of survey data included univariate analysis of management factors, backward stepwise regression analysis and Bayesian mapping of spatial risk.

Results.

For the ELISA test, 36/4609=2.95% of cattle and 50/115=43.5% of herds were positive. For culture 9/136=6.6% of samples or 9/4609=0.2% of cattle, and 9/50=18% of seropositve herds or 9/115=7.8% of total herds were positive. Breed was classified as: Brahman, Brahman-influence (Beefmaster, Brangus, Santa Gertrudis, Braford, Simbrah) and non-Brahman. The risk factors identified (P < 0.05) for seropositive herds were having: 1) Brahman, relative risk(RR)=16.0, or Brahman-influence, (RR)=4.0 vs. non-Brahman cattle, 2) a dairy-breed nurse cow for calves to suckle, RR=2.0, 3) the presence of running water sources, RR=0.47, 4) observed signs of Johne's Disease on the ranch, RR=2.68. The spatial analysis identified the region of greatest risk for seropositive herds as the central and southern parts of eastern Texas.

Discussion.

The increased likelihood for Brahman and Brahman-influence cattle to be seropositive may be due to increased susceptibility to infection or a difference in immune response to exposure. The difference in likelihood for seropositive herds by region may be due to an increased prevalence of infection or an increased prevalence of microorganisms which cross-react with the ELISA test.