Correlation of population indices of female Culex tritaeniorhynchus with Japanese encephalitis viral activity in Kapuk, Indonesia.

Nineteen consecutive monthly light trap collections of mosquitoes were made between October 1978 and April 1980 in Kapuk, Indonesia. Kapuk is a small suburb of Jakarta where pigs are raised in close proximity to rice paddies which are breeding sites for Culex tritaeniorhynchus. Japanese encephalitis (JE) virus is believed to be endemic and has been recovered from mosquitoes and pigs in the area on several occasions. A total of 18,435 female Cx. tritaeniorhynchus were allocated to 359 pools of approximately 50 per pool. Virus isolations were attempted in both Vero and BHK-21 cells and agents producing cytopathic effect were identified in a micro-neutralization test. Nineteen strains of JE were recovered from the 359 pools of Cx. tritaeniorhynchus tested. The light trap index of female Cx. tritaeniorhynchus (X) and the relative frequency of pools positive for JE (Y) for each month of the study were plotted and correlation coefficients (r) calculated after transforming the mosquito population data logarithmically and the relative frequencies of isolation by arcsine square root. The close fit of the data (p less than 0.001) to an inverse linear model (1/y = a + b log10X) suggests a close dependence of JE viral activity on the population dynamics of Cx. tritaeniorhynchus. Three additional strains of JE were recovered from other Culex spp. at the same study site. One strain each was isolated from individual pools of Cx. gelidus, Cx. vishnui and Cx. fuscocephala. Cx. tritaeniorhynchus was more frequently infected with JE than the other species tested.

Comparative sensitivity of mosquito inoculation and mammalian cell culture for isolation of some arboviruses in Indonesia.

The sensitivity of parenteral inoculation of colony reared male Aedes aegypti and mammalian cell cultures for isolation of Japanese encephalitis virus and dengue virus were compared. The mosquito inoculation technique proved to be more sensitive for the isolation of dengue virus from the sera of febrile patients than did the mammalian cell cultures (Vero and BHK21) employed in these studies. Mosquito inoculation proved to be no more sensitive that the mammalian system for the isolation of Japanese encephalitis virus from field caught female mosquitoes.

Epidemic appearance of a new influenza strain in Asia.

An outbreak of influenza associated with increased absenteeism among school-age children occurred during May and June 1975 in Tapei, Taiwan. The virus strain has recently been shown to be antigenically similar to A/Victoria/3/75 which is now active in other areas of the Pacific.