Dengue outbreak in an Indo-Myanmar boarder area: epidemiological aspects and risk factors.

During October 2007, a large outbreak of suspected dengue fever (DF) was reported in Moreh township, Manipur: the first widespread outbreak in Northeast India. A cross sectional study was carried out in Moreh. The information on outbreak was collected and then described in time, place and person characteristics to arrive at aetiological hypotheses. Two hundred and eighty two serum samples were collected. Ninety one samples were reported positive for acute infection with dengue virus. Co-circulation of all the four dengue virus serotypes (1-4) and concurrent infection of 2 & 3, 1 & 3, and 1 & 4 serotypes was found. Predominant clinical features of the patients were fever (100%), headache (39%), vomiting (9.8%) and joint pain (4.16%). Haemorrhagic manifestation was recorded in one patient who subsequently died. Entomological surveys revealed profuse breeding of Aedes mosquitoes in all the affected municipal wards with high HI (37.5-71.43%), CI (53.84-86.95%) and BI (80-208.33%). Presence of IgM antibody, co-circulation of all the serotypes and concurrent infection with more than one serotype in the same individual confirmed the outbreak due to dengue virus infection. Preventive and control measures undertaken following the epidemiological investigation helped in controlling the outbreak.

Distribution of potential dengue vectors in major townships along the national highways and trunk roads of northeast India.

Surveys were conducted in some townships along the national highways and trunk roads of northeast India to detect breeding of Aedes mosquitos in used/waste tire dumps piled outdoors by the tire repairing shops during summer season of 1996-1997. The breeding of both the potential vectors of dengue, viz. Aedes aegypti and Ae. albopictus were detected, prevalence rate being in the range of 30.0-88.0 (CI = container index value). The preponderance of Ae. aegypti was considerably much higher than that of Ae. albopictus and all the urban and semiurban areas coming up along the side of the roads were observed to be infested with Ae. aegypti. With respect to transmission of dengue, this study clearly indicates that waste tire dumps in every urban agglomeration should receive primary attention in view of their relative contribution to the abundance and dispersal of these vector mosquitos.

Biting cycles of some potential vector mosquitos of Japanese encephalitis of Assam, India.

Biting activities of five potential vector species of Japanese encephalitis (JE) were observed in a JE affected district of Assam, India. Most of the species exhibited two peak periods of biting activity, one in early hours and other around midnight. However, in case of Culex fuscocephala several peaks were observed throughout the night.

Host feeding patterns of Culex vishnui sub group of mosquitoes in Dibrugarh district of Assam.

The host feeding patterns of three species of mosquitoes belonging to vishnui sub group, Culex tritaeniorhynchus, Culex vishnui and Culex pseudovishnui, the most prevalent species in Dibrugarh district were determined by analysing their blood meals. All 3 species were found be essentially zoophilic. High percentage of pig feeding was observed in Culex tritaeniorhynchus (40 per cent) and Culex vishnui (35.3 per cent) in comparison to other prevalent species in this area. In contrast Culex pseudovishnui another member of this group was not attracted to pigs (0.4 per cent). Few human feeds were recorded for Culex tritaeniorhynchus (0.4 per cent), Culex vishnui (0.4 per cent) and Culex pseudovishnui (0.8 per cent), indicating their occasional contact with human hosts. Considering the importance of this group as proven vectors of Japanese encephalitis the relevance of these results to JE transmission in this area are discussed.