Dengue vector mosquitos at a tourist attraction, Ko Samui, in 1995.

On Ko Samui, Thailand there were two epidemics of dengue hemorrhagic fever (DHF) in 1966 and 1967, followed by endemics up to 1994. Aedes aegypti and Aedes albopictus were the vectors. From January to July 1995, 51 cases of DHF were reported, out of these were many foreigners who still suffer from dengue fever and return home with negative impression. We carried out an entomological survey around the island and collected the mosquitos to detect dengue virus by digoxigenin-cDNA probe. The data revealed that Aedes aegypti and Aedes albopictus still were abundant and some were infected with dengue virus. Visual larval survey indices (HI, CI and BI) were 90.4, 61.3 and 301.3 respectively. Biting rate (BR) of Aedes mosquitos was high, the average indoor and outdoor BR were 9.7 and 100.8 mosquitos/man-hour. From 13 pools of mosquitos, 8 strains of dengue virus were detected (61.5%). The results may encourage the local authorities to improve vector surveillance and control before the famous island becomes an unpleasant island.

Humoral immune responses in hamsters infected with Opisthorchis viverrini.

The kinetics and nature of humoral immune responses to somatic and excretory-secretory (ES) antigens were investigated in hamsters experimentally infected with different numbers of Opisthorchis viverrini. ES antigens were obtained from the in vitro culture of adult flukes and somatic antigens were aqueous extracts of adult flukes. Antibodies in the serum and bile of infected animals were determined by the microhaemagglutination technique, using glutaraldehyde fixed sheep red blood cells sensitized with these parasite antigens. Antibody responses to both somatic and ES antigens were detected in the serum from the second week of infection onward. The peak response was noted at the end of the second month and declined slowly thereafter. Antibody levels in animals with heavy infections (100 metacercariae) appeared earlier but declined more rapidly than in animals with light infections (25 metacercariae). The serum antibodies were highly sensitive to mercaptoethanol throughout the course of infection (23 weeks). Antibodies also appeared in the bile obtained at the time of sacrifice but their titres were rather low compared with those in the serum. Like serum antibodies, biliary antibodies were reactive with both somatic and ES antigens. Biliary antibodies were of the secondary IgA type. These findings are discussed in relation to pathogenesis of the disease process and to the possible usefulness in immunodiagnosis.