Impact of weather variables on mosquitoes infected with Japanese encephalitis virus in Kurnool district, Andhra Pradesh.

OBJECTIVE: To assess the virus infection in mosquitoes during different seasons and correlated with various climatic factors. METHODS: The field collected vectors were screened for Japanese encephalitis (JE) virus after dessication using ELISA method. Most of the positive pools were recorded from Culex tritaeniorhynchus (Cx. tritaeniorhynchus) and Culex. gelidus (Cx. gelidus) during JE transmission season (winter) and some positive pools were also reported during non JE transmission periods (i.e. summer and rainy seasons). RESULTS: The minimum infection rates (MIR) of 1.75 from Cx. tritaeniorhynchus and 0.17 from Cx. gelidus has been reported in the year 2002 at the beginning of the study and the values were found nil at the end of the study (2006) from the study areas of Kurnool district. CONCLUSIONS: From this study it is noted that MIR of Cx. gelidus and Cx. tritaeniorhynchus were modulated by various meteorological parameters. The mosquito vector abundance increases after the monsoon period (winter) and lowest in dry season (summer). Similarly, MIR fluctuated between seasons with higher MIR recorded after monsoon period and lower in the rest of season. Impact of these metrological parameters in JE virus infected mosquitoes is discussed in this paper.

Glass Capping of Bacterial Culture Flasks

The use of cotton plug as closure of a bacterial culture flask had been reported to have many disadvantages such as inhibitory nature of cotton to certain microbes, chances of contamination during handling and accumulation of used cotton as biological waste. To overcome the disadvantages of cotton plugs, we have developed a new method of capping bacterial culture flasks. In the present study, three sets of experiments were conducted, one was to find out the efficiency of bacterial growth in culture flasks closed by either glass caps or cotton plugs and the second set was to find out the chances of getting contamination of sterile broth closed by either glass caps or cotton plugs and the third set was to find out the evaporation of water in conical flasks closed by glass caps or cotton plug. The results showed that the bacterial cultures closed by glass caps showed better growth with less chance of contamination and evaporation of the culture media. By this method, the bacterial culture work is made very simpler than using cotton plug.

Field- and laboratory-based active dengue surveillance in Chennai, Tamil Nadu, India: observations before and during the 2001 dengue epidemic.

BACKGROUND: Dengue cases are reported every year in the city of Chennai, Tamil Nadu, India. Since April 2001, longitudinal field- and laboratory-based active dengue surveillance has been carried out in Chennai to study dengue trends. METHOD: A serologic survey of people in Chennai using the hemagglutination inhibition test (HIT) was performed to determine evidence of prior exposure to dengue virus infections. Dengue virus infections and their serotypes were demonstrated in vectors. The serum samples from clinical dengue patients were analyzed for dengue virus-specific immunoglobulins M (IgM) and G (IgG) antibodies by 2 commercial ELISA kits. RESULTS: There was an increase in the percentage of children with monotypic antibody responses to dengue in the later survey (April 2.2%, September 9.93%). DEN-3 serotype infections were demonstrated in male Aedes aegypti mosquitoes collected in September 2001. Dengue virus infection was diagnosed in 74.5% (143/192) of cases. While dengue-specific IgM responses were predominant among infants with dengue fever, IgG and mixed responses (M + G) were seen in 85% of the children with severe forms of dengue. CONCLUSION: The findings from these investigations suggest that antibody surveys in children and virus detection in vectors may be included as early warning system parameters in laboratory-based proactive dengue surveillance.