Prevalence of the Intestinal Flukes Haplorchis taichui and H. yokogawai in a Mountainous Area of Phongsaly Province, Lao PDR

Phongsaly Province, located in the northernmost area of Lao PDR, was previously suggested to be endemic for the liver fluke Opisthorchis viverrini infection. To confirm, or rule out, this suggestion, the Phonxay village in the Khoua District, Phongsaly Province, was selected for a survey. Ten volunteers (8 men and 2 women aged 31-57 years) who consumed raw freshwater fish and had gastrointestinal troubles were treated with a single dose of praziquantel (40 mg/kg) and pyrantel pamoate (10 mg/kg) and purged with magnesium sulfate to recover any worm parasites. Eight of the 10 volunteers expelled 1 or more species of trematodes, nematodes, or cestodes (worm positive rate; 80%). The worms were morphologically identified as H. taichui (861 worms from 8 people), H. yokogawai (59 from 6 people), Phaneropsolus bonnei (1 from 1 person), Trichostrongylus sp. (2 from 2 people), Ascaris lumbricoides (2 from 1 person), Enterobius vermicularis (11 from 3 people), and Taenia saginata (1 strobila with scolex from 1 person). The results indicate that the mountainous area of Phongsaly Province, Lao PDR, is not endemic for the liver fluke but endemic for intestinal flukes, in particular, Haplorchis taichui and H. yokogawai

Arbovirus Infections in Pilot Areas in Laos

Since 1993, virological and seroepidemiological survey of arbovirus infections was conducted in pilot areas in Laos under the World Health Organization-Japan International Cooperation Agency-Laos trilateral Primary Health Care Project. Human sera were obtained at the laboratory in Khammouane Provincial Hospital, and at Sok Yai village in Vientiane Municipality, and antibodies to Japanese encephalitis (JE), dengue (DEN) and chikungunya (CHIK) viruses were assayed by neutralization test. The sera were classified according to the age groups. In Khammouane area, antibody-positive rates to DEN-1, 2, and 3 reached high (over 90%) by 11-15 years old and kept high thereafter. Antibody-positive rates to DEN-4 and JE increased with age and reached over 50% by 21-30 and 31-40 years old, respectively. In Sok Yai area, antibody-positive rates to DEN-2 and 3 were over 50% in all age groups. The positive rate of DEN-1 antibody reached 50% by 11-15 years old and increased with age. Although DEN-4 and JE antibody-positive rates fluctuated among age groups, they tended to increase with age. JE antibody survey in swine sera indicated that the JE virus was active during the rainy season. Positive rate of CHIK antibody tended to increase with age and reached over 50% in older age groups. These results indicate that DEN-1, 2, and 3 viruses are circulating more frequently in these areas. DEN-4, JE and CHIK viruses also exist with less activity. In terms of the primary health care for the prevention and control of arbovirus infections, the project team conducted health education and environmental sanitation in Sok Yai village. They also organized several training courses on the diagnosis and treatment of JE and DEN for junior doctors, health workers, and laboratory technicians

Epidemiological Situation of Dengue Infection in Lao P. D. R.

In 1979, 37 cases of dengue hemorrhagic fever (DHF) were reported to the Ministry of Health for the first time in Laos. In 1985, a total of 1,759 cases of DHF was reported as the first epidemic. In 1987, larger epidemics of DHF occurred with a total of 6,567 cases in the Vientiane Municipality and a total of 3,098 cases in four provinces. The morbidity rate of the outbreak in Vientiane was as high as 1,530/100,000. In the end of 1988, an Aedes Control Unit (ACU) was set up in the Vientiane Municipality to reduce the Aedes larva density and strengthen health education to the residents. Since 1989, DHF epidemic such as seen in 1985 or 1987 has not occurred in Vientiane so far. Activities of the ACU seem to be efficacious in reducing the larva density, judged by the Breteau and House indices obtained. However, another approach to show the reduction of dengue virus transmission has not been tried yet. In 1990, a seroepidemiological study on inhabitants in the Vientiane Municipality was performed. The results indicated followings: (1) The percentage prevalences of neutralizing (N) antibodies to dengue (DEN) 1-4 viruses increased with age, but the prevalences of N antibodies to DEN 3 and DEN 4 were lower than those to DEN 1 and DEN 2 viruses. (2) The geometric mean titer of N antibody to DEN 2 was highest among 4 serotypes in every age group. (3) By the age of 15 years, the majority (90%) of the inhabitants were infected with two or more serotypes of DEN virus

Analysis of the effectiveness of control measures against Schistosoma mekongi using an intra- and inter-village model in Champasak Province, Lao PDR

Schistosomiasis mekongi is prevalent in the Khong district of Lao PDR, made up of one big island. Khong, and numerous small islands in the Mekong River. Schistosoma mekongi is spread by Neotricula aperta as the intermediate host along the Mekong River. Therefore, even if an epidemic of S. mekongi were stamped out in a certain village, infection may recur if the source of infection is a village located in the upper reaches of the Mekong River. The purpose of this study was to construct a mathematical model for the transmission of S. mekongi among villages from the upper to lower Mekong River to estimate the effect of control measures against it. The chief characteristic of the present model is competence in dealing with the spread of infection among villages through the Mekong River in consideration of the reduction in longevity of cercariae and miracidia and their diffusion in the river. The model also takes into account seasonal fluctuation in the water level of the Mekong River, which affects human behavior in terms of water contact. The results of simulations indicated that the prevalence of schistosomiasis mekongi would be suppressed to a low level for a long time in a village further downstream when universal mass treatment is performed in villages further upstream simultaneously