First Report of Anopheles annularis s.l., An. maculatus s.s., and An. culicifacies s.l. as Malaria Vectors and a New Occurrence Record for An. pseudowillmori and An. sawadwongporni in Alipurduar District Villages, West Bengal, India.

A comprehensive entomological survey was undertaken in Alipurduar District, West Bengal, from 2018 to 2020 and in 2022. This study was prompted by reported malaria cases and conducted across nine villages, seven Sub-Centres, and three Primary Health Centres (PHCs). Mosquitoes were hand-collected with aspirators and flashlights from human dwellings and cattle sheds during the daytime. Both morphological and molecular techniques were used for species identification. Additionally, mosquitoes were tested for Plasmodium parasites and human blood presence. Mosquito species such as An. barbirostris s.l., An. hyrcanus s.l., An. splendidus, and An. vagus were morphologically identified. For species like An. annularis s.l., An. minimus s.s., An. culicifacies s.l., and An. maculatus s.s., a combination of morphological and molecular techniques was essential. The mitochondrial cytochrome c oxidase gene subunit 1 (CO1) was sequenced for An. annularis s.l., An. maculatus s.s., An. culicifacies s.l., An. vagus, and some damaged samples, revealing the presence of An. pseudowillmori and An. fluviatilis. The major Anopheles species were An. annularis s.l., An. culicifacies s.l., and An. maculatus s.s., especially in Kumargram and Turturi PHCs. Plasmodium positivity was notably high in An. annularis s.l. and An. maculatus s.s. with significant human blood meal positivity across most species. Morphological, molecular, and phylogenetic analyses are crucial, especially for archived samples, to accurately identify the mosquito fauna of a region. Notably, this study confirms the first occurrence of An. pseudowillmori and An. sawadwongporni in West Bengal and implicates An. maculatus s.s., An. culicifacies s.l., and An. annularis s.l. as significant vectors in the Alipurduar region.

Risk factors for typhoid in Darjeeling, West Bengal, India: evidence for practical action.

OBJECTIVE: To identify risk factors for typhoid and propose prevention measures. METHODS: Case-control study; we compared hospital-based typhoid cases defined as fever>38 degrees C for >or=3 days with four-fold rise in 'O' antibodies on paired sera (Widal) with community, age and neighbourhood matched controls. We obtained information on drinking water, fruits, vegetables, milk products and sanitation; and calculated matched odds ratios (MOR) and attributable fractions in the population (AFP) for the risk factors or failure to use prevention measures. RESULTS: The 123 typhoid cases (median age: 25 years, 47% female) and 123 controls did not differ with respect to baseline characteristics. Cases were less likely to store drinking water in narrow-mouthed containers (MOR: 0.4, 95% CI: 0.2-0.7, AFP 29%), tip containers to draw water (MOR: 0.4, 95% CI: 0.2-0.7, AFP 33%) and have home latrines (MOR: 0.5, 95% CI: 0.3-0.8, AFP 23%). Cases were more likely to consume butter (OR: 2.3, 95% CI: 1.3-4.1, AFP 28%), yoghurt (OR: 2.3, 95% CI: 1.4-3.7, AFP 34%) and raw fruits and vegetables, including onions (MOR: 2.1, 95% CI: 1.2-3.9, AFP 34%), cabbages (OR: 2.8, 95% CI: 1.7-4.8, AFP 44%) and unwashed guavas (OR: 1.9, 95% CI: 1.2-3, AFP 25%). CONCLUSION: Typhoid was associated with unsafe water and sanitation practices as well as with consumption of milk products, fruits and vegetables. We propose to chlorinate drinking water at the point of use, wash/cook raw fruits and vegetables and ensure safer preparation/storage of local milk products.

A malaria outbreak in Naxalbari, Darjeeling district, West Bengal, India, 2005: weaknesses in disease control, important risk factors.

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.

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.

The shift from public to private health care providers and malaria deaths in Jalpaiguri district, West Bengal, India, 2006.

We investigated an increase in malaria deaths in order to formulate control measures. A search of records in health care facilities for cases of death following fever, with a blood smear or rapid antigen test positive for Plasmodium falciparum, identified 77 fatalities. Of these, 72 (93%) occurred in hospitals (78% of which in the 24 hours following admission). Of 60 family members of the patients who died interviewed, 70% reported that the patient had received care from unqualified rural private practitioners available round the clock. Among 100 of these rural practitioners assessed, 21% knew anti-malarial dosage and 7% knew malaria severity criteria. There were 65% and 42% vacancies among 240 community health worker and 12 microscopist positions, respectively, in the public sector in the area. As a result, the mean interval between active case search rounds in the community was 35 days (standard: 14) and the median time between blood slide collection and radical treatment was 12 days (standard < 2 days). Deficiencies in the public health system may have led to a shift towards rural practitioners. Poor management of malaria may have contributed to deaths. We posted microscopists and community health workers in the area to restore appropriate malaria management in the public sector.

Scrub typhus in Darjeeling, India: opportunities for simple, practical prevention measures.

To identify risk factors for scrub typhus in Darjeeling, India, we compared 62 scrub typhus cases (acute fever with eschar and specific IgM) with 62 neighbourhood controls. Cases were more likely to live close to bushes [matched odds ratio (MOR) 10; 95% CI 2.3-63] and wood piles (MOR 3.5; 95% CI 1.5-9.5), to work on farms (MOR 10; 95% CI 2.7-63), to observe rodents at home (MOR 3.6; 95% CI 1.4-11) and at work (MOR 9; 95% CI 2.4-57), and to rear domestic animals (MOR 2.4; 95% CI 1.1-5.7). Cases were less likely to wash after work (MOR 0.4; 95% CI 0.1-0.9) and change clothes to sleep (MOR 0.2; 95% CI 0.1-0.5). A cleaner, rodent-controlled environment may prevent exposure to scrub typhus. Personal protection measures and better hygiene could further reduce individual risk.