Natural infection of trematodes in Lymnaea (Radix) auricularia rubiginosa in water reservoirs in Amphoe Muang, Khon Kaen Province.

Lymnaea (Radix) auricularia rubiginosa (Michelin, 1831) was surveyed in 54 reservoirs of 18 districts in Amphoe Muang, Khon Kaen Province during February to May 1994. Lymnaeid snails were found in the water of 20 reservoirs, of which 16 reservoirs contained clear water and 4 turbid water. Two of the four turbid water reservoirs received drainage water from Khon Kaen Town. Two thousand four hundred and eight L. auricularia rubiginosa were collected and examined by shedding and crushing. Trematode infection occurred in 163 (6.77%) of 2,408 L. auricularia rubiginosa and some snails were infected with more than one cercarial species. Ninety-nine snails (4.11%) were infected with echinostomes, while mixed infection of echinostomes with Fasciola gigantica and with schistosomes was found in 5 snails (0.21%) and 2 snails (0.08%), respectively. Only 1 snail (0.04%), 19 snails (0.79%) and 37 snails (1.54%) were infected with F. gigantica, schistosomes and unidentified species, respectively. The mean size of infected snails was 6.89 +/- 2.02 mm (6.20-22.36) while the mean of sampled snails was 13.46 +/- 3.64 mm (4.00-26.55). The water plants which were found in reservoirs and presented with snails, were creeping water primose (Jusstaea repens), water lily (Nymphaea sp), water hyacinths (Eichornia crassipes) and grass.

Problem of fascioliasis in animal husbandry in Thailand.

One of the most important parasitic diseases in adult cattle and buffalo in Thailand is fascioliasis, caused mainly by Fasciola gigantica. The economic loss from fascioliasis in cattle and buffalo throughout Thailand has been assessed at not less than 100 million Baht. Recent investigations have been shown that the average prevalence of F. gigantica in cattle and buffalo in Thailand was 11.8%. However, the prevalence varies considerably between villages, ranging from 0 to 85%. The prevalence is high in areas surrounding dams or large ponds in which Lymnaea auricularia rubiginosa, the intermediate host of F. gigantica is found. An epidemiological study revealed that the disease has a seasonal pattern from which the following conclusion for control of the disease can be drawn. Strategic liver fluke treatment of all cattle and buffalo which are older than 8 months should be carried out once a year in September. In addition, animals in poor condition should be treated in April to prevent severe losses, especially in high prevalence areas or where strategic treatment was missed. Problems of liver fluke control include the lack of knowledge about the parasite on the part of the farmers and the lack of availability of drug supplies at the village level, both of which are important to allow strategic treatment of animals. To approach these problems, the government had developed "Farmer Self-Help Worm Control Program" in seven provinces in Northeast Thailand which is operated by village farmers trained as program "keymen". This program is very effective and will be extended throughout Thailand in the next Seventh Social and Economic Development Plan.