The use of the enzyme-linked immunosorbent assay (ELISA) in serological diagnosis of Mycoplasma bovis in dairy cattle.

Between December 1985 and March 1987 an enzyme-linked immunosorbent assay (ELISA) was used with 3774 sera to estimate the prevalence of antibodies to Mycoplasma bovis in sera from three age groups of cattle in four dairies in California and to test for possible associations between the presence of M. bovis antibodies and the age or breed of the cattle and the farm. Unadjusted and adjusted associations were evaluated using the chi-square test for associations and multiple logistic regression analysis, respectively. There was a tendency for the proportion of cattle seropositive for M. bovis to increase steadily and approximately linearly with age (p less than 0.05). There was also a statistically significant relationship between a M. bovis seropositive test and being from Farm IV (p less than 0.05). Farm IV was the largest of the four dairies and this association may be due to the effect of herd size. These findings confirm the ubiquitous distribution of antibodies to M. bovis in dairy cattle in California and also support previous reports of herd size as an important factor in mycoplasmal mastitis.