Investigation of the haemolytic effects of Ancylostoma ceylanicum: observations on infected dogs in vivo and human and dog blood in vitro.

Investigations into the probable role of haemolysins in the causation of hookworm anaemia have been undertaken in living infected dogs. Secondly, the effects of living hookworms and various worm products on erythrocytes in vitro have been assessed. In dogs infected with varying numbers of A. ceylanicum, severe microcytic anaemia developed in the most heavily infected animals six weeks after infection. Erythrocytes from the latter animals showed significantly greater autohaemolysis in the presence of added glucose. When serum bilirubin and methaemalbumin, plasma haemoglobin, urinary urobilinogin and osmotic fragility of their red cells were measured, however, no evidence of haemolysis was detected. Erythrocytes from these animals appeared normal under scanning electron microscopy. In in vitro studies varying concentrations of adult worm extract had no effect on the haemolysis of either dog or human erythrocytes in the presence or absence of glucose nor on their mechanical fragility. There was no increase in 51Cr release from dog or human labelled red cells when incubated with either adult worm extract or excretory/secretory products of worms. Living adult worms caused an increase in 51Cr release from human but not dog labelled erythrocytes. Thus, the role of haemolysins in the genesis of hookworm anaemia is minimal.