An epidemiological study on Opisthorchis viverrini infection in Lao villages.

The prevalence of liver fluke, Opisthorchis viverrini, infection in rural and urban communities was studied in Khammouane Province in Lao PDR. The infection was the commonest among the villagers examined, showing the positive rates of 52.9% and 55.0% in two rural communities and 60.7% in an urban community, respectively. The infection rate reached up to 20% or more within 4 years after birth and increased with age to a plateau in the age group over 20 years. The highest prevalence rate was over 80% in the age group of 35-54 years. The age-related patterns of infection in males and females were almost the same, although there were some sex-related differences by village and by age group. Infection with Opisthorchis viverrini appears to be a serious public health problem strongly associated with the frequent eating habit of raw fish in low land Laos.

Plasmodium ovale infections detected by PCR assay in Lao PDR.

Plasmodium ovate infection was demonstrated in 5 out of 143 inhabitants in a village in Lao PDR by blood microscopy and PCR assay. Although the specimen confirmed to be positive for P. ovale by microscopical examination was only one, the target sequences in the 18S rRNA genes of malaria parasite detected in all of the five cases were consisted with those of P. ovale by the PCR assay. This is the first report concerning the presence of so many cases with P. ovale infection in Lao PDR.

An epidemiological survey on intestinal parasite infection in Khammouane Province, Lao PDR, with special reference to Strongyloides infection.

To estimate the current prevalence of intestinal helminth infection in Lao PDR, a parasitological survey was conducted in three villages in Khammouane Province in December 1996, with special reference to Strongyloides infection. A total of 669 fecal samples were collected in the villages and examined by agar-plate culture method and Kato-Katz thick smear method. Intestinal helminths were demonstrated in 82% of the samples as follows: Ascaris lumbricoides (30.5%), Trichuris trichiura (23.7%), hookworm (28.8%), Strongyloides stercoralis (19.0%), Enterobius vermicuralis (3.4%), Opisthorchis viverrini (56.7%) and Taenia sp (3.0%). The infection rates of S. stercoralis were 27.5% and 18.4% in two rural villages, but only 9.4% in an urban village. The highest prevalence rate of Strongyloides infection was obtained in the age group from 20 to 29 years old, although the infection rate already reached 10% in the age group under 10 years old. The prevalence was consistently higher in male subject than females in almost all age groups.

Current status of malaria infection in a southeastern province of Lao PDR.

In Khammouane, a southeastern province in Lao PDR, active case detection (ACD) surveys for malaria infection on the villagers in three villages were conducted four times from December, 1995 to August, 1996. The malaria infection was demonstrated in 5.3-10.5% of the villagers throughout the year in 2 villages located in mountainous forest, but the infection was rarely observed in the other village located in the plain along the Mekong River, in which only 4 malaria cases were detected in August, 1996. Although the positive rate of malaria parasites among the villagers was not so significantly different in the rainy season compared with the dry season, the intensity of infections (ie parasitemia) was significantly higher in the rainy season. More than 90% of the positive villagers were children under 15 years old. Most infections were due to Plasmodium falciparum.

Prevalence of intestinal parasitic infection among children in two villages in Lao PDR.

The prevalence of intestinal parasitic infection among 128 children under 15 years old in two villages in Khammouane Province, southeastern Lao PDR, was investigated. Overall prevalence of helminth infection was 77.3%; the prevalence was 64.8% in children under 6 years, 88.5% in those aged 6-10 years and 81.8% in the age group above 11 years. The prevalent helminths found in the subjects were Ascaris lumbricoides (48.4%), Trichuris trichiura (43.8%), hookworm (37.5%) and Opisthorchis viverrini (37.5%). Intestinal protozoan infection was demonstrated in 14.1%; Giardia lamblia was the most prevalent (8.6%) protozoan species.