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.

Mosquitoes of Bali Island, Indonesia: common species in the village environment.

Routine sampling of mosquito populations in rural villages was carried out during 13 months at 4 locations in southern Bali Island, Indonesia. Sampling was by light trapping and early night resting collections around animal stables. Specimens collected were preserved for assay of arthropod-borne viruses; 104,608 specimens representing 20 species were prepared in 2681 pools for viral assay. Anopheles barbirostris and An. subpictus have been shown to be important vectors of Brugia malayi and B. timori and of malaria and Wuchereria bancrofti in other parts of Indonesia but have not been incriminated in transmission of disease agents in Bali. Anopheles vagus may be involved in filarial transmission in other regions but is not regarded as important in Bali. Culex fuscocephala, Cx. gelidus and Cx. tritaeniorhynchus have been incriminated in the transmission of Japanese encephalitis virus in Indonesia and Cx. vishnui has been similarly implicated in other countries. The populations of these mosquitoes are compared and plotted against rainfall. The potential of the more common species as vector of some human pathogens is discussed.

Vector studies and epidemiology of malaria in Irian Jaya, Indonesia.

Human populations in the low-land littoal of southwestern Irian Jaya are exposed to holoendemic malaria, principally caused by P. falciparum. The spleen rate in children of ages 2-9 years, in 4 villages ranged from 78% to 97%, and parasite prevalences were from 21% to 52%. Three known vectors of malaria, An. farauti, An. koliensis and An. punctulatus, were present, the latter two being most abundant. One specimen of each of the latter two species, upon dissection, was found carrying sporozoites in thoracic tissue. Larval habitats were numerous in peridomestic sites, including drainage ditches, natural ground pools and plots of Ipomea reptans; thus the vector populations were always in close contact with the human populations.