Hematology of experimental acute Sarcocystis bovicanis infection in calves. I. Cellular and serologic changes

Of four Holstein-Friesian calves infected with 200,000 sporocysts of Sarcocystis bovicanis, three became ill and died on days 35, 55, and 59 of a 63-day experiment. No control calves became ill or died. Three of the four infected calves developed normocytic normochromic anemia with about a 50% decrease in hemoglobin concentration on days 25 through 35, and had hyperbilirubinemia from day 25 or 26 to death (day 35); this disappeared when the anemia stabilized in surviving calves. Packed cell volume increased slowly after day 35 in the surviving anemic calves. Indirect and direct Coombs' tests were negative throughout the experiment in the control and infected calves. A reduction in numbers of neutrophils and lymphocytes paralleled the crisis of anemia in the infected calves. Serum antibody titers to S. bovicanis antigen were increased substantially in all infected calves 35 days or more after inoculation.