Anaemia in Schistosomiasis with Particular Reference to Its Causation

The clinical picture of schistosomiasis and its symptomatology of anaemia represent an important health problem in parts of the tropics. The multiple factors responsible for production of anaemia are reviewed. In this work an attempt was made to answer the questions raised by these earlier investigations. Particular attention was given to the question whether haemolysis involved in pathogensis of anaemia is due to an immunological process. Haematological changes were studied in mice infected with S. nansoni. It was found that, animals infected with light doses of cercariae developed progressive anaemia, reticulocytosis and enlarged spleen. Radioactive studies showed considerable shortening of the erythrocyte life span, associated with destruction of these cells in the spleen. These findings confirmed that the anaemia was of a haemolytic nature. The main mechanism responsible for the severe haemolysis during the subacute and chronic stages of infection (22 - 80 weeks) was found to be immunological. Evidence for this included the serological abnormalities, i.e. positive direct agglutination test, slight elevation of serum gamma globulins, and the presence of similar globulins in eluates from pooled red cells of infected mice, thus indicating that the red cell membrane was coated with immune complexes. In addition "holes" on the surface of the erythrocytes taken from a number of infected mice were also seen ultra- structurally. This finding suggests that complement fixation was involved in the immunological process. The other possible mechanism for haemolysis, was that worm/egg toxins either lyse red cells directly or through the damaged tissues. It was postulated that this factor might play a role before the immune process took place. Evidence was obtained that the following were contributory factors aggravating the anaemia, a)Non-continuous blood loss in animals heavily infected, b)Phagocytosis of damaged red cells inside the enlarged spleen. In the present study it was also shown that at later stages of infection along with severe anaemia, progressive glomerulonephritis was produced in mice infected with light doses of cercariae. An immunological mechanism for induction of the renal damage is postulated.