Progressive serum protein changes in experimental infections of calves with Trypanosoma vivax

Abstract

Thirteen calves were each infected with one of 3 strains of Trypanosoma vivax by syringe passage of blood or by cyclical transmission with Glossina morsitans. The concentrations of IgM, IgG and a 7Sγ 1 serum protein were measured before and at short intervals after infection. Infection was characterized by a marked rise in IgM concentration commencing about 10 days and a rise in IgG concentration commencing about 65 days after infection. IgM levels usually remained high in untreated infections, but occasionally fell to normal indicating that raised IgM was not completely reliable as a diagnostic method. Successful treatment resulted in a fall in IgM concentration to normal in about 4 weeks and IgG concentration did not rise. There was no indication of low molecular weight IgM in one calf whose IgM concentration was very high. There was a striking fall in the concentration of the 7Sγ 1 protein which then fluctuated, perhaps related to parasitaemia, and was very low in calves which died. Natural agglutinins to foreign red cells, especially chicken cells, rose in infection.