Abstract
An outbreak of malaria in Naxalbari, West Bengal, India, in 2005 was investigated to understand determinants and propose control measures. Malaria cases were slide-confirmed. Methods included calculation of annual blood examination rates (ABER, number of slides examined/population), collection of water specimens from potential vector-breeding sites, sorting of villages in categories depending on the number of abandoned wells within two kilometers radius and review of the DDT spray coverage. Cases were compared with matched neighbourhood controls in terms of personal protection using matched odds ratios (MOR). 7,303 cases and 17 deaths were reported between April 2005 and March 2006 with a peak during October rains (Attack rate: 50 per 1,000, case fatality: 0.2%). The attack rate increased according to the number of abandoned wells within 2 kilometres radius (P < 0.0001, Chi-square for trend). Abandoned wells were Anopheles breeding sites. Compared with controls, cases were more likely to sleep outdoors (MOR: 3.8) and less likely to use of mosquito nets and repellents (MOR: 0.3 and 0.1, respectively). DDT spray coverage and ABER were 39% and 3.5%, below the recommended 85% and 10%, respectively. Overall, this outbreak resulted from weaknesses in malaria control measures and a combination of factors, including vector breeding, low implementation of personal protection and weak case detection.
Highlights
While malaria is mostly an endemic disease, it may occur as outbreaks, for example in areas with low seasonal transmission [1]
Neighbours with no fever for the last three months were selected as healthy controls and matched for age and sex to malaria casepatients identified by active case detection in September 2005
Of the 7,303 blood smears testing positive for malaria, 4,779 (65%) had P. vivax, 1,517 (21%) had P. falciparum and 1,007 (14%) had P. falciparum and P. vivax. 3,679 (50%) cases were detected by active detection
Summary
While malaria is mostly an endemic disease, it may occur as outbreaks, for example in areas with low seasonal transmission [1]. In India, the national malaria control programme is based upon (1) indoor residual spraying with DDT and other insecticides, (2) insecticide-treated nets, (3) larval control (page number not for citation purposes). Standard national programme procedures, case detection is both active and passive. Community health workers search for cases of fever in homes every two weeks to collect blood smears. Health care workers in health care facilities collect blood smears among patients presenting with fever. While the national programme struggles to control malaria in India, outbreaks remain common in various areas, including Northeastern states [4,5], Uttar Pradesh [6], and Gujarat [7]
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