The pathology of E. ovis

Abstract

Extract

Sir, — In your September issue, Sutton (3) suggests that the anaemia of E. ovis infection is due to intravascular haemolysis. The pathology he describes is almost identical to that described by Dacie(l) in autoimmune haemolytic anaemia in man; sheep recently exposed to active E. ovis infection are usually positive to the Coombs test(2) and show spherocytosis; in my experience, haemoglobinuria is rarely, if ever, seen in E. ovis infection but is common in intravascular haemolytic conditions in sheep; and, finally, what appears to be haemoglobinaemia in sheep infected with E. ovis may be due to the rupture of abnormally fragile red cells during, or after, collection of the blood. On this evidence, it seems likely that incomplete antibodies are involved in the red cell destruction that characterises E. ovis infection, and that the process takes place extravascularly, by phagocytosis.