Increasing incidence of malaria in Kurseong, Darjeeling District, West Bengal, India, 2000-2004

In Kurseong, Darjeeling District, India, malaria caused concern but insufficient information was available. We analysed surveillance data to estimate the burden of malaria and to examine trends. Confirmed malaria reports were reviewed and climatic records were collected. The annual parasite incidence (API; number of cases/population) and the annual blood examination rate (ABER; number of slides examined/population) were calculated to assess case detection activities, and the slide positivity rate (SPR; number of slides positive/total number examined) was calculated to assess transmission trends. The API increased from 2 to 7.8 per 1000 population between 2000 and 2004 (no deaths), with a high incidence among all age groups. Two foothill areas with forests and slow-moving streams accounted for 88% of the 697 cases in 2004. The average 2000-2004 ABER was 4.8%, below the 10% examination target of the National Anti-Malaria Programme. The proportion of Plasmodium falciparum increased from 62% in 2000 to 77% in 2004. More than 50% of P. falciparum in the area were chloroquine resistant. The SPR increased from 8.1% in 2000 to 11.9% in 2004 and peaked during monsoons. Annual rainfall increased from 2000 to 2003. Malaria transmission increased, with an increasing proportion of P. falciparum in a context of resistance to chloroquine. We recommend increasing case detection and using artemisinin-based combination therapy to treat P. falciparum malaria.