Equine Piroplasmosis Fetal Infection
Equine piroplasmosis results from infection with either Theileria equi or Babesia caballi. There have been very rare instances of Babesia bovis infection documented in horses. Infection has been reported in horses, mules, donkeys and zebra with zebras acting as an important reservoir of infection in Africa. This is a tick transmitted disease with over 14 species of ticks in the genera Rhipicephalus, Hyalomma and Dermacentor acting as vectors.
Infection of pregnant mares with Theileria equi at any stage in pregnancy is quite common. The consequence of infection depends on the stage of infection but includes reproduction failure (involved in up to 11% of all failures in South Africa), abortion, neonatal piroplasmosis and birth of asymptomatic carriers. Infection with Theileria equi can be persistent with development of carrier mares which can produce further infected fetuses, randomly in subsequent pregnancies. Aborted fetuses usually demonstrate anaemia, moderate to marked icterus, petechiae on visceral and serosal surfaces, hydrothorax, splenomegaly and hepatomegaly. (Image top right) Kidney reveals moderate nephrosis with icteric change. (bottom right) Parasitaemia is usually high.