Malaria parasites adjust sex ratio to help disease spread

29 May 2008

Malaria parasites ensure the successful spread of the disease by being able to produce more sons than daughters when conditions are difficult, according to research published today in the journal Nature.

The research, led by Dr Sarah Reece, a Wellcome Trust Research Career Development Fellow at the University of Edinburgh, could provide vital clues in the fight to stop the disease spreading. Determining when the parasites are likely to favour producing one sex over the other could assist the development of anti-malarial drugs and vaccines.

The discovery shows that malaria parasites are much more sophisticated than previously thought. They can respond to changes in their social situation and environment, something that is traditionally associated with more complex animals such as insects, birds and mammals.

Usually, malaria parasites will tend to produce more daughters than sons, because all of the females are expected to find a mate. However, in harsher conditions, for example when under attack from a person's immune system, or when competition to breed is high among the parasites, it is beneficial to have more sons, to increase the overall chance of their genes being passed on.

"We have long suspected that malaria parasites adjust their production of males and females to ensure their spread, and we have now shown that this is the case," said Dr Reece. "We hope that by understanding the family planning strategy of these parasites, ways can be found to stop the spread of malaria."

The research was funded by the Wellcome Trust, the Natural Environment Research Council and the Biotechnology and Biological Sciences Research Council.

Image: Exflagellating male gametocyte; Wellcome Images

Reference

Reece, S et al. Sex ratio adjustment and kin discrimination in malaria parasites. Nature, published 29 May 2008.