Rapid Identification of Paragonimiasis Foci by Lay Informants in Lao People's Democratic Republic

Paragonimiasis is a neglected pulmonary disease provoked by a food-borne trematode parasite. The infection may develop into severe pulmonary disease, often diagnosed with delay and confused with tuberculosis. Globally an estimated 21 millions people are infected. Human infection is acquired through consumption of raw crab, crayfish or wild boar. Typically infections occur clustered in foci of few to several villages where nutritional habits allow transmission. A major challenge for control is to identify the transmission foci. We evaluated a questionnaire approach using lay-informants at the village level to identify paragonimiasis foci and suspected cases. We sent a 4-item questionnaire to 49 village-leaders of a district in rural Lao PDR asking them to report patients with key symptoms of paragonimiasis, i.e. “chronic cough” and “blood in sputum”. The evaluation showed that lay-informants' report had a high sensitivity to identify suspected cases of paragonimiasis using “blood in sputum” as indicator. The approach allowed identifying 3 new, previously unknown foci of transmission in the district. We conclude that lay-informant questionnaires using easily identifiable key symptoms are simple to carry out and are promising low-cost tools for paragonimiasis control

Cercarial Density in the River of an Endemic Area of Schistosomiasis Haematobia in Kenya

The cercarial density in natural water and number of infected Bulinus globosus were monitored over a one-year period to identify the transmission foci in an endemic area of schistosomiasis haematobia in Kenya. Overall prevalence and intensity of infection of the study community were 59.2% and 10.9 eggs/10 ml of urine. Cercariometry was carried out on 456 occasions at 20 study sites while snail sampling was done on 465 occasions at the same sites over a one-year period. Cercariometry was exclusively done at flowing water habitats. The results showed the focality and seasonality of transmission. Cercariae were detected on 44 occasions at 11 sites. The detections were made on seven occasions at two study sites, six occasions at one site, four occasions at four sites, three occasions at one site, two occasions at two sites, and one occasion at one site. Densities of 1?4 cercariae/100 liters of water were found on 31 occasions. Five to nine cercariae/100 liters of water were found on seven occasions, 10?19 cercariae/100 liters of water were found on two occasions, and high cercarial densities greater than 20 cercariae/100 liters of water were found on four occasions. The highest count was 52 cercariae/100 liters of water. The presence of cercariae in natural water was shown to depend on the water temperature, but the intensity and duration of sunlight did not affect the presence of cercariae in water. The monthly variability of cercarial density was proportional to the number of infected snails. Cercarial density was highest in March and April, in the middle of the rainy season, whereas no cercariae were detected in cool dry season. The snail population peaked late in March, the beginning of the long rainy season, remained high for two months, and decreased rapidly late in May when heavy rain occurred. The overall infection rate of snails was 7.3% and the majority of infected snails were collected from March to May. There was no definite correlation between the presence or absence of cercariae and infected snails. Cercariae were frequently found where infected snails were absent and cercariae were sometimes absent where infected snails were present. Cercariometry and snail sampling remain quite complementary in identifying the transmission foci of schistosomiasis

ケニア国クワレ地区のビルハルツ住血吸虫症の流行地におけるBulinus globosusとCleopatra ferrugineaの相互作用

Snail survey data collected in a small village in Kenya from April 1984 to March 1991 were used to analyze the interaction between Bulipuus globosus (intermediate host of Schistosoma haematobium) and Cleopatra ferruginea (unsusceptible snail). An inverse correlation was observed between the two snail populations. This finding leads to the suggestion that C. ferruginea has limiting effects on B. globosus population. The relative penetrative activity of S. haematobium miracidia into the two snail species was also examined. Miracidia penetrated C. ferruginea as well as B. globosus. Although selective mass-chemotherapy has been repeated every 2 years in our study area, the low infection rates in B. globosus were recorded in the year when large numbers of C. ferruginea and small numbers of B. globosus were collected. Therefore, C. ferruginea seems to diminish the transmission of S. haematobium; C. ferruginea reduce the number of S. haematobium miracidia which reach to B. globosus

Water, Livelihood and Health in Attapeu Province in Lao PDR

This paper presents the results of an investigation on water-borne infectious diseaseconducted among the people of Attapeu province from 2003 to 2008. Regardless of the lastcholera epidemic in Attapeu province, Lao PDR in the year 1999, the local peoples'awareness of cholera was remarkably low, as demonstrated by the knowledge survey ondiarrheal diseases performed in the province in 2006. In the case study material, derivedfrom continuous field observations on malaria among permanent residents in relocatedvillages in Sanxay district from 2004 to 2008, the infection rate among febrile cases was ashigh as 45% in the early resettlement period, while it was proved that the rate fell later to1.9-14%. Judging from the environmental condition of this settlement area, this papermakes clear the persistent threat of malaria. Furthermore, among the villagers, hookworminfection was highly prevalent. However, liver fluke infections were scarce and noascariasis was found from parasitic stool examination in 2007. Water quality analysis ofthe water sources resulted in remarkably safe water from tube wells from 2003 to 2008

Relationships between Schistosoma malayensis and other Asian schistosomes deduced from DNA sequences

At least three Schistosoma species can infect humans in South-East Asia. The most widespread of these is S. japonicum Katsurada, 1904 which may represent a species complex and occurs in many countries including China, Japan and the Philippines. The second species is S. mekongi Voge, Bruckner and Bruce, 1978 which is endemic to a small area near the junction of Laos, Cambodia and Thailand. Most recently described is S. malayensis Greer, Ow-Yang and Yong, 1988 from a restricted area of peninsular Malaysia. This is primarily a parasite of rats but has also been found in people Davis, on the basis of snail intermediate host phylogeny and biogeography, proposed that S. malayensis and S. mekongi are sister taxa relative to S. japonicum. The three studies on allozymes among these taxa also support this hypothesis

Paragonimus paishuihoensis metacercariae in freshwater crabs, Potamon lipkei, in Vientiane Province, Lao PDR

Among Paragonimus species, P. paishuihoensis is one of the most mysterious and poorly understood species. Metacercariae are characterized by having a unique dendritically branched excretory bladder. However, the morphology of the adult worm remains unknown. To date, metacercariae of this species have been reported only in China and Thailand. In this study, we first found P. paishuihoensis metacercariae in freshwater crabs, Potamon lipkei, in Hinheub District, Vientiane, Lao PDR, with a prevalence of 77.7% and the average intensity of 10.3 (range 1-28) metacercariae per crab. The molecular data based on ITS2 and CO1 markers indicated that P. paishuihoensis from Laos and Thailand were almost completely identical and were close to members of the Paragonimus bangkokensis/Paragonimus harinasutai complex. Attempts to infect experimental animals (cats, dogs, and rats) with P. paishuihoensis were unsuccessful, suggesting that these animals might be unsuitable definitive hosts for the species. Further studies are necessary to elucidate the taxonomic status and life cycle of P. paishuihoensis