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. I. Virological and epidemiological studies.

Virological studies were carried out during an epidemic of dengue hemorrhagic fever in Central Java, Indonesia in 1976. Dengue virus was isolated from the acute sera of 45 of 69 patients (65%). The isolation rate was higher in primary than secondary cases. Dengue 3 was the predominant serotype being transmitted (27 isolates), but both dengue 1 (8 isolates) and dengue 4 (10 isolates) were also being transmitted. A composite picture of magnitude and duration of viremia showed that many patients were circulating over 10(8) MID50 per milliliter dengue 3 virus for the first 3 days of illness and that viremia persisted for 5-6 days in some persons. If all shock cases were considered, there was no relationship between dengue serotype and severity of disease. All three confirmed fatal cases, however, were associated with dengue type 3 infections.

Epidemic dengue hemorrhagic fever in rural Indonesia. II. Clinical studies.

Clinical observations were made on 95 serologically or virologically confirmed dengue fever cases during an epidemic in a rural area of Indonesia in December 1976. The age distribution was similar to that observed in patients with dengue hemorrhagic fever in Jakarta, a highly endemic urban area. The observed disease ranged in severity from undifferentiated fever to shock and death. The majority of patients had acute onset of fever with nausea, vomiting, headache, and abdominal pain. Hepatomegaly was observed in only 19% of the patients. A positive tourniquet test was the most frequently observed hemorrhagic manifestation, but epistaxis was observed in 20% and hematemesis in 6% of the patients. Dengue shock syndrome was observed in 37% of the patients. There were four deaths, three of which were confirmed as due to dengue infection by virus isolation. The data suggest that one, and possibly two, of the fatal cases with virus isolation were primary infections, based on the results of hemagglutination-inhibition test using all four dengue antigens.

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.

Virological surveillance for dengue haemorrhagic fever in Indonesia using the mosquito inoculation technique.

A dengue haemorrhagic fever surveillance system in Indonesia, based on virological and clinical observations, is described. The system uses the mosquito inoculation technique for virus isolation and is simple, economical, and well suited for endemic areas where support and facilities are limited. The data suggest that with good cooperation between the hospital and the virology laboratory, new serotypes and possibly even new strains of virus can be identified before the onset of epidemic activity. This type of virological surveillance may make it possible to prevent major epidemics in the future.

Serological study of amoebiasis and toxoplasmosis in the Malili area, South Sulawesi, Indonesia.

Results of a serology survey in September 1972 for Entamoeba histolytica and Toxoplasma gondii antibodies among 915 volunteers from the Malili area of South Sulawesi (Celebes), Indonesia are presented. Indirect hemagglutination antibody titers for amoebiasis were found in 22.7% of the sampled population while 9.5% demonstrated antibody titers greater than or equal to 1:128. The frequency distribution of antibody titers were similar by sex and age. There was no significant correlation between stool positivity and seropositivity. Indirect hemagglutination antibody titers for T. gondii were detected in 62% of the population sampled, and titers greater than or equal to 1:32 were demonstrated in 29% of the samples tested. The distribution of antibody titers was similar in males and females. In both sexes the prevalence of IHA antibody titer against T. gondii increased with age. There was no consistent association between altitude and prevalence of seropositive samples.

Dengue with haemorrhage and shock in Jakarta, Indonesia.

Pediatric patients with fever and haemorrhage were studied in Jakarta, Indonesia between May 1973 and January 1974. Eighty-one of 104 demonstrated unequivocable evidence of dengue with clinical findings similar to those reported associated with dengue haemorrhagic fever in Thailand. The majority of patients had extremely high antibody titers against dengue measured by both hemagglutination-inhibition and by plaque reduction neutralization tests and all four types of dengue virus were isolated. Eight of the patients died.