Research: Hidden parasites

6 December 2005

Measuring levels of a secreted parasite protein (PfHRP2) may provide a way to estimate total malaria parasite loads.

The numbers of malaria parasites circulating in the bloodstream can be calculated using blood films. But this does not reveal how many parasites are sequestered in narrow blood vessels – and these are responsible for the worst symptoms of malaria.

Arjen Dondorp et al. at the Wellcome Trust's South-east Asia Major Overseas Programme have looked for a better way to assess total parasite load. They measured bloodstream levels of a protein secreted by the parasite – histidine-rich protein-2 (PfHRP2) – in people with malaria of varying severity and in parasites cultured in vitro. Severity of disease correlated with increasing concentrations of PfHRP2, while the in vitro studies allowed the group to link PfHRP2 concentrations to parasite numbers.

The group suggests that measuring PfHRP2 levels would allow the total parasite load to be calculated, revealing the likely size of the sequestered parasite population.

External links

• Dondorp AM et al. Estimation of the total parasite biomass in acute falciparum malaria from plasma PfHRP2. PLoS Med 2005;2(8):e204.