Experimentally induced anaplasmosis in neonatal isohemolytic anemia-recovered calves.

Anaplasma marginale infections were induced in 3 calves previously affected with neonatal immunohemolytic anemia (NIA). Similar infections were induced in 6 splenectomized and 7 intact calves. The response to infection by 3 calves (NIA recovered) closely resembled infections seen in splenectomized calves, being markedly more severe than similar infections in intact calves. Spleens from 3 (NIA recovered) calves after splenectomy were about one-tenth normal size. Marked recrudescing anaplasmal infections were not detected after splenectomy of the calves (NIA recovered), whereas marked recrudescing infections were observed after splenectomy of 2 intact calves having recovered from the primary infections.