The incidence of Coxiella burnetii antibodies in cattle in the Transvaal.

With the use of the complement fixation test, 8,900 cattle were tested for antibodies to Coxiella burnetii. These were randomly selected from 178 different farms in 37 districts in the Transvaal. The percentage of cattle in the sample with positive antibody titres was equal to 7.78%, with a standard error of 0.28%. Because of the large size of the sample, asymptotic normality can be relied upon and the population confidence interval calculated. This was found to be greater than or = 0.07 and less than or = 0.085 at a 99% confidence level. Hence we are 99% confident that between 7% and 8.5% of the cattle in the Transvaal had antibodies to Coxiella burnetii during the period March 1985 to July 1986. The proportion of cattle with C. burnetii antibodies was also estimated for each of the 37 districts tested. Every district tested had some evidence of C. burnetii. The percentage of positive titres ranged from less than 1%-30% per district. This suggests that C. burnetii is probably an endemic disease of the cattle population of the Transvaal. A higher proportion of cattle had antibody titres in the central and south-eastern parts of the Transvaal. This distribution may be linked to the distribution of Boophilus species ticks which occur in the same areas of the Transvaal.