two genetic disorders, the sickle cell (deformed red blood cell) trait and alpha thalassemia (a type of anaemia), are known to provide a natural defence against malaria. This prompted scientists to think their occurrence together would be even more potent. However, a recent study among 2,000 Kenyan children by scientists at the Kenyan Medical Research Institute reveals the combination, in fact, cancels each other out, leaving the individuals susceptible to the malarial parasite (Nature Genetics, Vol 37, No 11, November, 2005).
Individuals with sickle cell trait were found to have a 90 per cent less chance of being hospitalised due to malaria. Similarly, children with alpha thalassemia, common in Africa, were found less likely to die of malaria.
But when present together, their protective effect becomes less, depending on the sub-type of thalassemia gene involved. The research group, led by Thomas Williams, said the finding is valuable to researchers as a stark example of the genetic interactions that can occur in malaria and their effects.