Prevalences of human herpesvirus 6 and human herpesvirus 7 in normal Thai population.

Prevalences of human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7) DNA were investigated in normal Thai population. Peripheral blood mononuclear cells (PBMC) and saliva were collected from 238 healthy adults in five provinces which might be a representative of each part of the country, and 120 normal children in one province. Prevalences of HHV-6 DNA PBMC were 45.5-74.3% in adults and 78.3% in children, and in saliva, very low prevalences were detected; 5.7-8.6% in adults and 15.0% in children, respectively. Additionally, all HHV-6 DNA detected in this study were variant B. Comparingly to those of HHV-7 DNA, the prevalences were significantly higher than those of HHV-6, ie, 82.9-91.4% in PBMC of adults, 85% in PBMC of children, 84.8-89.0% in saliva of adults and 92.5% in saliva of children. HHV-6 and HHV-7 isolation from saliva specimens were also performed. No HHV-6 could be isolated from any samples, whereas, in the present study, HHV-7 could be isolated as 90.0% from children and as 20.0-54.5% from adults.

Long residual activity of Bacillus sphaericus 1593 against Culex quinquefasciatus larvae in artificial pools.

The microbial larvicide, Bacillus sphaericus 1593, was evaluated against Culex quinquefasciatus larvae in artificial pools at Huay Kwang area in Bangkok between March and October 1985. This study was aimed at determining the residual activity of B. sphaericus 1593 in waste water under field conditions. The larvicidal activity of B. sphaericus 1593 was found to persist for at least 5 months in artificial pools containing waste water. The populations of B. sphaericus 1593 in the test water fluctuated, decreasing by approximately 4.25 and 3.47 log10 colony forming unit (cfu)/ml from the original concentrations in 60 and 80 days after application and then increasing approximately 2.92 and 2.77 log10 cfu/ml in 92 and 72 days for pools No. 1 and No. 2, respectively. This evidence indicates that B. sphaericus 1593 can recycle in such conditions.

Bionomics of Anopheles maculatus complex and their role in malaria transmission in Thailand.

The bionomics of Anopheles maculatus complex and its role in malaria transmission were conducted in Pakchong and Sadao districts, Nakhon Ratchasima and Songkhla provinces, respectively, from January 1984 to July 1985. In Pakchong, An. maculatus species A was the most dominant species, followed by species B form F and species C which was rare. The densities of species A and species B form F were high between July and November, with their peaks in October. Biting activities of both species occurred through out the night, with a major peak during the first quarter of the night on all seasons. In Sadao, only An. maculatus species B form E was detected with peak densities between February and June. Biting activities of this species varied according to seasons. The prevalence of mosquitoes was influenced by monthly rainfall, relative humidity and air-temperature. All species of female An. maculatus complex studied prefered to feed on animal rather than on human, and tended to bit human more outdoors than indoors, and thus exhibiting a zoophilic and exophagic behaviour. Life expectancies of An. maculatus species A ranged from 1.6 to 6.6 days, species B form F from 1.1 to 8.1 days, and species B form E from 0.7 to 21.2 days. The natural malaria infection rate was very low. Out of 4,430 guts dissected, only 0.23% were found infected with oocysts. There were no sporozoites detected in the 4,472 dissected salivary glands.