Field investigation of Bithynia funiculata, intermediate host of Opisthorchis viverrini in northern Thailand.

A survey of freshwater snail, Bithynia funiculata, was conducted in four locations, Doi Saket, Mueang, Saraphi and Mae Rim Districts of Chiang Mai Province, northern Thailand, between June and October, during the rainy season of 2004. A total of 2,240 snails was collected and classified into 7 families and 15 genera; of which 352 B. funiculata were obtained. B. funiculata was found most abundant in July and September. The infection rate of trematode cercariae in B. funiculata was 9.6% (19/352), while that of pleurolophocercous was 0.3% (1/352). Virgulate cercaria was the most common type, followed by lophocercous, monostome and pleurolophocercous. B. funiculata prefers habitats with clear water, which was less than 30 cm depth, temperatures between 24.48 and 31.78 degrees C, dissolved oxygen 2.03-7.66 mg/l, saturated dissolved oxygen 26.70-95.00%, conductivity 0.000-0.2642 mS/cm, turbidity 16.00-288.00 NTU and pH 6.58-7.56. Geographic Information System (GIS) analysis using loose soil mixed with clay revealed that the breeding grounds of this snail species was in the paddy fields and village environs of the Ping, Kuang and Fang river basins.

Effect of microwave irradiation on the blow fly Chrysomya megacephala (F.) (Diptera: Calliphoridae).

Chrysomya megacephala (F) is a blow fly species of medical importance, being pestiferous and a mechanical carrier of various microorganisms to human food. Various strategies to reduce the fly population in endemic areas are needed. We investigated the effects of microwaves at 2,450 MHz, with third-instar exposure times of 7, 10, 15, 30 and 60 seconds on the larvae. Survival of the larvae was monitored by their emergence. About 60% of the larvae lived after 7 seconds of exposure, most died by 15 seconds, and all were dead at 30 and 60 seconds. The number of survivals decreased with increasing exposure times. This indicates the effect of microwave irradiation on fly larval survival.