Asymptomatic malaria in West Bengal

Print edition : March 22, 2013

SCIENTISTS of the Calcutta School of Tropical Medicine, in association with the Department of Health and Family Welfare of the Government of West Bengal, have found high prevalence of asymptomatic malaria in a tribal population of 1,040 individuals in Purulia district. The findings of the study, which was carried out in June 2012, have been published in Journal of Clinical Microbiology.

A significant proportion (8.4 per cent) of the population was infected with Plasmodium falciparum without any clinical manifestations. They “do not seek treatment, thus acting as reservoir of the parasite and maintaining the natural cycle”, said the paper. Thus, asymptomatic infection poses an important obstacle to eliminating malaria, and the Malaria Control Programme should address this hidden parasite burden properly, the researchers have pointed out.

India is one of the 11 countries in the south-eastern WHO region with nearly 980 million people at risk of malaria. According to the WHO’s estimated cases, India contributes the largest number of cases outside Africa. India’s official statistics suggest that P. falciparum accounts for half of the clinical cases in India. Jalpaiguri and Purulia are the two districts in West Bengal that have recorded the largest number of P. falciparum cases in the last few years.

The Purulia study is the first systematic attempt to identify such asymptomatic cases in West Bengal. Of the 8.4 per cent prevalence, 6.8 per cent of the cases were parasitologically confirmed true carriers and 1.6 per cent were suspected carriers.

The parasite strains of the study were found to be resistant to chloroquin. However, these strains were sensitive to artemisinin-based combination therapy (artesunate + sulphadoxine-pyrimethamine), recommended by the national malaria control programme.