IgM rheumatoid factor in cattle immunized against babesiosis.

Polyclonal bovine IgM-rheumatoid factors (IgM-RFs) were examined in sera of cattle immunized against babesiosis. An enzyme-linked immunosorbent assay (ELISA) was used enabling rapid screening of serum samples. Results obtained indicate a rise of serum IgM-RF levels with age in healthy bovines. However when animals of similar age and pertaining to the same herd were examined, levels of serum IgM-RF exhibited a wide distribution range. Mean values in 60 sera of 2 yrs old clinically healthy heifers originating from a single herd were of 452.60 +/- 201.26 e.u. at 1 in 1,000 serum dilution and of 202.37 +/- 137.86 e.u. at 1 in 4,000 serum dilution. In a herd where repeated vaccination of dams against babesiosis was carried out 3 to 6 weeks before delivery either with live Babesia bovis parasites or soluble antigens of in vitro grown organisms, no significant differences in mean IgM-RF values were found between revaccinated animals and a control group. Nor did the mean values of serum IgM-RF of calves born to the respective groups of dams exhibit significant differences. It thus appears that immunization of healthy cattle against this parasite does not affect mean serum IgM-RF levels.