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Interviews and physical examinations for filarial disease were conducted in Howrah near Calcutta, West Bengal, India, in a study area where long term quantitative entomological studies have disclosed high intensity, year round exposure to Wuchereria bancrofti. Little elephantiasis or other serious filariasis-related disease was noted, but half the males over 20 years of age had genital lesions of various types. Ninety-two percent of households had at least one resident with microfilaremia or presumptive clinical evidence of filarial disease.

Thirty-four strains of Asian and Pacific mosquitoes belonging to 22 species of 7 genera were compared for oral and/or parenteral susceptibility to infection with 1 or more strains of each of the 4 dengue serotypes. Surprisingly, several species of common man-biting Aedes were much more susceptible to oral infection with each of the 4 dengue serotypes than was Aedes aegypti. These species included Aedes albopictus and members of the scutellaris group of the subgenus Stegomyia found on South Pacific islands. Mosquito strains and species relatively susceptible to 1 dengue serotype usually were relatively susceptible to the others also. Almost all species of Aedes tested were uniformly susceptible to parenteral infection with the dengue viruses but, with the exception of a species of Tripteroides, species of all other genera were comparatively resistant to that mode of infection. Dengue viruses usually replicated to about the same extent in orally-infected mosquitoes as they did in parenterally-infected specimens of the same species. Seventeen species of mosquitoes of 7 genera also were tested for parenteral susceptibility to infection with Japanese encephalitis virus. With the possible exception of 2 species of Anopheles, the virus replicated to about the same degree in all species tested and achieved levels considerably higher than did any of the dengue viruses in the same mosquito strain and species held under the same conditions.

During the fall of 1981, a new method for the routine isolation and identification of dengue viruses in Puerto Rico was implemented utilizing C6/36 cell cultures and serotype specific antidengue monoclonal antibodies. A blind comparison of the monoclonal antibody indirect fluorescent antibody test (IFAT) and the complement fixation (CF) test for identification of 89 newly isolated dengue viruses of all four serotypes from the Caribbean, Asia and Africa showed 100% agreement. Although virus isolation rates were slightly lower than with the mosquito inoculation technique, use of the C6/36 cell culture system was much less time-consuming and allowed the processing of larger numbers of sera. Beginning in November 1981, a new virologic surveillance system was begun in Puerto Rico. Acute sera from persons with suspected dengue were selected for virus isolation attempts on the basis of geographic area of residence on the island, day after onset the blood was taken and clinical signs and symptoms. These sera were processed for virus isolation in C6/36 cell cultures, and virus isolates were identified by the IFAT using the monoclonal antibodies. Using this system, 2,702 sera were tested from November 1981 through August 1982. Dengue virus was isolated from 518, for an isolation rate of 19.2%. Dengue 1 was the predominant virus until December 1981, when dengue 4 became dominant. The changing patterns of dengue 1 and 4 distribution by time and geographic location on Puerto Rico were followed. This system allows the dengue viruses being transmitted in an area to be monitored with a minimal amount of effort and provides the early warning capability necessary to predict epidemic dengue.

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.

Prior laboratory studies and field observations suggested that it might be possible to reduce the size of the population of, or eliminate, Aedes polynesiensis by the introduction of Aedes albopictus. The former mosquito is the principal vector of nonperiodic filariasis caused by Wuchereria bancrofti and the latter is a closely related species refractory to the development of human filariae. The practicability of such competitive displacement was studied by a field trial on a remote coral atoll where there was an established population of A. polynesiensis. Three strains of Al albopictus were liberated at separate localities on the atoll and their fate was followed for 4 years. One strain disappeared within 12 months after release and the other two disappeared within 48 months. It was not clear whether A. albopicuts failed to become established because the strains were unsuitable, the general environment was inappropriate, or A. polynesiensis was present in such numbers that A. albopictus rarely succeded in mating with its own species.

Formulations of temephos (Abate) and Bacillus thuringiensis var. israelensis (B.t.i.) on corncob and dried coconut husk carriers were tested for slow-release insecticide properties against Aedes aegypti larvae in Puerto Rico. Granular formulations of 5% and 10% temephos gave continuous larval control in used automobile tires for 27 to 124 days and 34 to 162 days, respectively. Temephos on radial sections of corncob and coconut husk chips gave good larval control in tires for 27 to 63 and 61 to 134 days, respectively, depending on the size of the carrier. Small (2-3 g) and large (3-5 g) coconut husk chips tested in 167 liter drums provided continuous control for 55 to 105 days, respectively. Granular formulations of B.t.i. controlled Ae. aegypti in tires for 19 to 33 days, and B.t.i. briquets exhibited larvicidal activity in large containers for 26 to 78 days.