Bovine fetal anoxia observed in pregnant beef heifers experimentally inoculated with Anaplasma marginale

Six heifers in the third trimester of gestation were inoculated with Anaplasma marginale carrier blood. Laparohysterotomies were performed under local anesthesia at varying stages of anemia induced by anaplasmosis and the placental blood gas exchange was examined. Laparohysterotomies were similarly performed on three uninoculated control heifers and the placental blood gas exchange compared to the fetuses recovered from anemic (inoculated) heifers. Blood samples from the dam and fetus were recovered at the time of surgery and arterial blood gases and pH determined. A decline in fetal oxygen tension accompanied the maternal anemia. The evidence suggests that third trimester fetal death in heifers experimentally inoculated with Anaplasma marginale is due to fetal anoxia.