Hookworms in the aetiology of tropical iron deficiency anaemia: Radio-isotope studies

Abstract

1. 1) The relation between hookworm infestation and anaemia was investigated before and after multiple vermifuges by estimating intestinal blood and iron loss with 51Cr. and 59Fe. 2. 2) Maximum blood loss was 180 ml. and iron 33 mg. daily for a worm load of 834 A. duodenale and 249 N. americanus. A loss of 30 ml. daily for a load of only 166 worms was encountered. Augmentation of dietary iron absorption that is associated with increased marrow activity and depleted iron stores, is incapable of meeting these excessive losses. Such losses deplete the iron stores and lead to anaemia. There were great variations in the blood losses in different patients, and in the same patient on different days. 3. 3) The amount of iron lost depended on the haemoglobin level of the patient at the time the loss occurred. 4. 4) The blood loss was correlated with worm loads and species and was greater for A. duodenale. Both A. duodenale and N. americanus are found in Kenya, most patients having both. Loads up to 850 adult A. duodenale and 2,400 N. americanus were recorded by counting adult worms after multiple vermifuges. 5. 5) Removal of worms reduced the blood loss to nil, but did not improve the haemoglobin level unless iron therapy was also given. Iron therapy without removal of worms cured the anaemia, but the haemoglobin fell again once iron therapy was stopped, unless the worms were removed. 6. 6) Patients previously infected with hookworms and who had taken vermifuges, but no iron, presented with gross anaemia but no worms; others taking iron, but no vermifuge, had heavy worm loads but no anaemia. Other factors obscuring the relation between hookworms and anaemia are the migratory habits of the worms leaving few or many bleeding points, the situation of the worms whether over a large or small blood vessel, the rapidity with which bleeding points are sealed, etc. When these factors as well as worm loads and species are taken into consideration, there is always a close correlation between hookworms and anaemia. Failure to make allowances for them has led to the mistaken view that hookworms and anaemia are not related. 7. 7) Even multiple vermifuges will not produce egg-negative stools, but by reducing worm loads will cut blood loss to insignificant amounts. 8. 8) N. americanus was shown to be more resistant to all vermifuges than A. duodenale perhaps because of its small size and its location in the intestinal villi where vermifuges may not easily penetrate. 9. 9) There was little evidence that diet was associated directly with hookworm anaemia; an adequate diet will not diminish the chances of infection or reduce blood loss. Low economic status was, however, closely linked with insanitary habits and the less frequent use of footwear, both paramount factors affecting the risks of infection. 10. 10) The specific deficiency in hookworm anaemia is iron, and it will respond to oral iron provided this is given in sufficient amounts to raise the haemoglobin level to normal and replace the depleted iron stores. Inadequate iron therapy is the commonest cause of failure to respond, but untreated intercurrent infections will also prevent a full remission of the anaemia. Parenteral iron has no advantage over oral iron provided the latter is taken. 11. 11) Other sources of iron loss that may aggravate the iron deficiency anaemia are discussed. 12. 12) Vermifuge campaigns, fortification of diet with iron, the use of footwear and improvement in sanitation, are measures that should be adopted to reduce worm loads and the associated anaemia.