A field trial with etofenprox (OMS 3002) as a residual insecticide against malaria vectors, in Tanjung Bunga district, east Flores, Indonesia.

An operational trial of Vectron (Etofenprox, OMS 3002) was conducted in East Flores Regency, Nusa Tenggara Timur Province. The compound (Etofenprox 10EW) was applied as indoor residual spray and as an impregnation treatment for bednets in two separate areas. Dosage in both cases was 0.2 g/m2. A third area, designated as control, was untreated. In bioassay tests, bamboo surfaces gave 100% mortality for 150-160 days post spray, while wooden surfaces and treated bednets both gave complete mortality for at least 120 days. Malaria cases monitored by successive malariometric surveys showed steady declines in positivity rates, particularly in children.

Colonization of Anopheles barbirostris from Central Java, Indonesia.

The colonization of Anopheles barbirostris from Central Java is described. Locally acquired materials and ambient laboratory temperature, humidity, and daylight proved acceptable for continuous rearing. A simple, inexpensive larval diet based on a 10:4 powdered mixture of beef and rice hulls proved advantageous.

Toxorhynchites amboinensis larvae released in domestic containers fail to control dengue vectors in a rural village in central Java.

The efficacy of Toxorhynchites amboinensis larvae for control of dengue vectors in household water storage containers was tested in a rural village in Central Java, Indonesia. Concrete cisterns and clay jars were the most common types of containers used for long-term water storage, although smaller numbers of metal drums were also used. All containers in use in the village received 5-10 second- or third-instar Tx. amboinensis larvae biweekly for 7 months. Vector surveillance (adult and larval) was conducted biweekly between treatments. No differences in man-biting rates or larval population indices were noted between the treatment and control areas. It is hypothesized that the multiplicity of larval habitats in this rural area accounted for the lack of impact of predator releases, which were directed solely toward artificial containers.

A survey for arboviral antibodies in sera of humans and animals in Lombok, Republic of Indonesia.

Sera were collected from humans, cattle, horses, goats, ducks, chickens, wild birds, bats and rats in Lombok, Indonesia, and were tested by haemagglutination inhibition (HI) for antibodies to JE, ZIKA, CHIK and RR. Selected sera were tested by microneutralization tests for antibodies to the following viruses: JE, ZIKA, MVE, TMU, LGT, KUN, SEP, DEN-2, CHIK, RR, GET, SIN, BUN, BAT and BAK. Human sera had JE HI antibody in 135 (30%) of 446 tested. Neutralization tests indicated that DEN-2, ZIKA, TMU, KUN and SEP may have caused flavivirus infections. Antibodies to other arboviruses tested for were not found. HI and neutralization tests on animal sera indicated possible flavivirus infections with JE, MVE, KUN and SEP, and also that infections with BAT and BUN had occurred among domestic animals. No neutralizing antibodies were found for alphaviruses or other viruses used in the tests.

Scrub typhus survey of Biak and Owi islands: ectoparasites of small mammals and rickettsial isolations.

A survey of smnall mammals and their ectoparasites was conducted on the islands of Biak and Owi, Indonesia, in August 1976. Two species of chiggers known to serve as vectors of scrub typhus were found: Leptotrombidium (Leptotrombidium) deliense from Rattus exulans, R. ruber, and R. r. septicus; L. (L.) flectcheri from R. exulans, R. leucopus and R. r. septicus. Rickettsia tsutsugamushi was isolated from the spleens of R. exulans and R. r. septicus. The favored ecotype of the chigger and rat hosts of R. tsutsugamushi appeared to be coarse, low-lying native vegetation on a porous coralline soil. These and similar nearby coral islands should be considered high risk areas for scrub typhus.

Variation in susceptibility to oral infection with dengue viruses among geographic strains of Aedes aegypti.

The comparative susceptibility of 13 geographic strains of Aedes aegypti to oral infection with dengue viruses was studied by feeding the mosquitoes on a virus-erythrocyte-sugar suspension. Significant variation in susceptibility to four dengue serotypes was observed among the geographic strains tested. Mosquito strains which were more susceptible to one serotype were also more susceptible to the other serotypes, suggesting that the factors controlling susceptibility were the same for all types. The amount of virus required to infect mosquitoes orally varied inversely with the susceptibility of the geographic strain. Thresholds of infection were not the same for dengue types 1, 2, 3 and 4. There was no apparent difference in infectivity between prototype and recently isolated strains of dengue types 1 and 3. Crossing experimentibility as the resistant parent. No difference was observed between resistant and susceptible mosquito strains in the rate or the amount of viral replication after infection by the parenteral route, or in their ability to transmit dengue 2 virus after infection by the oral route.

Epidemic dengue hemorrhagic fever in rural Indonesia. III. Entomological studies.

Entomological studies were carried out during a dengue hemorrhagic fever epidemic in Central Java in December 1976. Both Aedes aegypti and Aedes albopictus were widely distributed in Bantul, but the latter species was more abundant. Comparative studies on the vector competence of the two species showed that Ae. albopictus had a higher susceptibility than Ae. aegypti to oral infection with all four dengue serotypes. The two species were equally compentent in transmitting the Bantul strain of dengue 3 virus after parenteral infection. The data suggest that Ae. albopictus could have been an important vector in this epidemic, but no direct observations were obtained to define the respective contribution of either Ae. albopictus or Ae. aegypti.

Studies on the susceptibility of a large urban population of Aedes aegypti to infection with dengue viruses.

A large urban population of Aedes aegypti in Jakarta, Indonesia was studied for one year to determine whether it was homogeneous in terms of susceptibility to dengue viruses and whether seasonal changes in susceptibility to dengue viruses occurred. Mosquitoes from several districts in Jakarta showed a low but homogeneous susceptibility to dengue 2 virus from November 1975 to April 1976. In June 1976, increased susceptibility to dengue 2 virus was observed among some of the subpopulations of Ae. aegypti, and higher infection rates and increased variation were observed among these mosquitoes during the rest of the study period. Correlation with confirmed DHF cases in Jakarta was discussed.

New hosts of Breinlia booliati with observations on its distribution in Southeast Asia.

Breinlia booliati Singh & Ho, 1973 first described from Peninsular Malaysia has been shown to infect a large range of murids ranging in distribution from southern Thailand, Peninsular Malaysia, Sarawak to Ciloto, Indonesia. Probably further work will reveal a greater host range as well as its geographical distribution. The vectors involved in its transmission need to be elucidated.