Genetic differences among Haplorchis taichui populations in Indochina revealed by mitochondrial COX1 sequences.

Haplorchis taichui is an intestinal heterophyid fluke that is pathogenic to humans. It is widely distributed in Asia, with a particularly high prevalence in Indochina. Previous work revealed that the lack of gene flow between three distinct populations of Vietnamese H. taichui can be attributed to their geographic isolation with no interconnected river basins. To test the hypothesis that interconnected river basins allow gene flow between otherwise isolated populations of H. taichui, as previously demonstrated for another trematode, Opisthorchis viverrini, we compared the genetic structures of seven populations of H. taichui from various localities in the lower Mekong Basin, in Thailand and Laos, with those in Vietnam, using the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene. To determine the gene flow between these H. taichui populations, we calculated their phylogenetic relationships, genetic distances and haplotype diversity. Each population showed very low nucleotide diversity at this locus. However, high levels of genetic differentiation between the populations indicated very little gene flow. A phylogenetic analysis divided the populations into four clusters that correlated with the country of origin. The negligible gene flow between the Thai and Laos populations, despite sharing the Mekong Basin, caused us to reject our hypothesis. Our data suggest that the distribution of H. taichui populations was incidentally associated with national borders.

Effect of albendazole and mebendazole on soil-transmitted helminth eggs.

Primary school children from Nakhon Si Thammarat Province, Thailand, on endemic area of soil-transmitted helminths, were selected for study. The infected children were divided into two groups and pair-matched according to intensity of infections: group I were given albendazole (400mg) single dose and group II were given mebendazole (100mg) twice daily for 3 days. On the day following treatment, the number of Trichuris eggs in the stool markedly increased and the egg shape was also altered. These phenomena did not occur in Ascaris infections since 100% cure rate were obtained using both drugs. Incomplete ovicidal effect of the drugs to Trichuris and Ascaris eggs were demonstrated, embryos were observed to develop within the treated eggs and they hatched after feeding them to experimental animals. In hookworm infection, albendazole stimulated the females to release more eggs after medication, but both drugs showed complete ovicidal effect upon examining the eggs from the second bowel movement.

Use of delipidized antigens of Taenia solium metacestodes in IgG-ELISA for detection of neurocysticercosis.

The development of IgG-ELISA for detecting neurocysticercosis is aimed at the routine laboratory, and requires a particular antigen preparation, an acceptable number of serum samples to be tested (both homologous and heterologous) and patients with a diversity of helminthic infections to rule out cross-reactions. This study characterizes IgG-antibodies from cases of neurocysticercosis by assaying the sera against ether-delipidized antigens (5 microg/ml) prepared from metacestodes of Taenia solium. The test had a sensitivity of 90% and a specificity of 83%. IgG-antibodies from heterologous serum samples elicited a number of false positives (25/147) from six different helminthic infections, ie paragonimiasis, echinococcosis, opisthorchiasis, ascariasis, taeniasis and fascioliasis. In additional tests to detect antibody levels to these stage-related antigens, one of three serum samples from T. solium-infected cases gave negative at OD value of 0.187 while the others yielded 0.472 and 0.576. Conversely, assays of all serum samples from neurocysticercosis cases reacted against antigens from Echinococcus granulosus cystic fluid, Paragonimus heterotremus and Opisthorchis viverrini adult worms. In comparison, the antigens from these three species yielded higher mean OD values when assayed against the corresponding infected serum samples. Furthermore, neurocysticercosis cases yielded OD values that are separate and distinct from those of paragonimiasis cases.

Repeated doses of albendazole against strongyloidiasis in Thai children.

Fifty children aged 5 to 12 years whose fecal examination confirmed of strongyloidiasis were divided into 2 groups. One group (Group I) of 26 received 400 mg albendazole once a day for 3 consecutive days. The other group (Group II) of 24 received the same dosage but repeated a week later. Simple smear fecal examination was performed for 3 consecutive days before treatment, and stool cultures were performed on Days 13, 14, 15 21, 22 and 23 after treatment. Evaluation of successful treatment or cure was based on the absence of larvae in 6 culture specimens. The cure rates were 80.8% in Group I and 91.7% in Group II (p = 0.18). Side effect consisted of mild and transient vomiting in one patient in each group. Although the difference in cure rates between the two drug regimens was not statistically different, two courses of treatment (Group II) resulted in a higher cure rate.

The impact of primary health care intervention on reinfection of soil-transmitted helminths in the community.

A study to evaluate the impact of primary healthy (PCH)care practices on the prevention of reinfection of soil-transmitted helminths (STH) was carried out in Nakhon Si Thammarat Province, southern Thailand. Fecal samples from the inhabitants of Ban Paruhas, the implementing village, and Ban Pungsing, the control village, were examined following mass treatment with a three-day regimen of albendazole (400 mg). Training of health volunteers, implementation of a health education program through village broadcasting system and improvements in sanitation including increasing the number of latrines were carried out at Ban Paruhas village. After one year of implementation, prevalence and intensity of STH in both villages were determined using Kato-Katz's method. Pre- and post intervention stool examination results were compared. The overall prevalence of STH at post-intervention decreased significantly in both villages, with a greater degree of reduction appearing in ascariosis and hookworm infections in the village where PHC was implemented.