Prevalence of Helminthic Infections among Inhabitants of Lao PDR

The prevalence of helminthic infections was surveyed on a total of 6,178 residents (males 2,549 and females 3,629) in 102 villages of 9 provinces in Lao PDR between 2007 and 2011 under the project of Korea-Laos Collaborative Project for Control of Foodborne Trematode Infections in Lao PDR. Fecal specimens were collected and examined by the Kato-Katz thick smear and Stoll's egg counting techniques. The overall liver/intestinal helminth egg positive rate was 71.9% with a single or mixed infections with Opisthorchis viverrini and minute intestinal flukes (Ov/MIF), Ascaris lumbricoides, hookworms, Trichuris trichiura, Trichostrongylus sp., echinostomes, Taenia spp., and others. Ov/MIF revealed the highest prevalence (55.6%) followed by hookworms (27.8%) and T. trichiura (6.5%). The endemic regions with the highest prevalence of Ov/MIF were Savannakhet, Khammouane, Vientiane (Nam Ngum), Champasak (Khong Island), and Saravane Province. High prevalences of A. lumbricoides (33.8%), hookworms (47.8%), and T. trichiura (32.6%) were observed in Phongsaly, Luang Prabang, and Vientiane (Nam Ngum) areas, respectively. The results of this study highlight helminth parasites of current public health significance in different areas of Lao PDR.

Current Status of Human Taeniasis in Lao People's Democratic Republic

Human taeniasis was investigated in Lao People's Democratic Republic (Lao PDR) between 2000 and 2011 as part of the nation's helminthiasis survey. A total of 55,038 inhabitants, including 29,846 school children, were examined using the Kato-Katz and scotch-tape anal swab method, and morphological observation of adult worms. Molecular identification of Taenia tapeworms was performed by multiplex PCR or DNA sequence analysis of the mitochondrial cox1 gene. Taenia eggs were present at a rate of 1.5% (845/55,038) in the subject population. Adult tapeworms were identified as T. solium or T. saginata by analyzing the collectable stool specimens (n=126). Three specimens identified as T. solium were found in Luang Prabang, while the remaining 123 specimens, which were T. saginata, were found in Bokeo, Bolikhamxay, Champasak, Houaphan, Khammouane, Luang Namta, Luang Prabang, Oudomxay, Phongsaly, Saysomboune, Saravane, Savannakhet, Xayaboury, Xekong, Xieng Khouang Province, and Vientiane Municipality.

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.

Indochinamon ou (Crustacea: Potamidae) as a New Second Intermediate Host for Paragonimus harinasutai in Luang Prabang Province, Lao PDR

Paragonimus harinasutai metacercariae were found in a species of freshwater crab, Indochinamon ou, collected in a small stream of Namback District, Luang Prabang Province, Lao PDR. Adult flukes were recovered after experimental infection of the metacercariae to dogs. Metacercariae were round or slightly elliptical, 0.666 x 0.626 mm in average size, and had a thin cyst wall of about 20 microm in thickness, a black excretory bladder, convoluted ceca, and some pinkish materials in the body. Adults were somewhat elongated, 95.2 x 36.5 mm in average size, covered with single-tipped tegumental spines, had a smaller oral sucker than the ventral sucker, a moderately branched ovary, and 5-6 lobulated testes. Eggs were ovoid and bilaterally symmetrical in shape, 79 x 45 microm in average size, and had a uniformly thickened shell. By the present study, it has been confirmed that I. ou is a new second intermediate host for P. harinasutai.

Skin test for paragonimiasis among schoolchildren and villagers in Namback District, Luangprabang Province, Lao PDR.

As a part of a broader effort to determine the status of Paragonimus species infection in Lao PDR, an epidemiological survey was conducted on villagers and schoolchildren in Namback District between 2003 and 2005. Among 308 villagers and 633 primary and secondary schoolchildren, 156 villagers and 92 children evidenced a positive reaction on a Paragonimus skin test. Only 4 schoolchildren out of 128 skin test-positive cases had Paragonimus sp. eggs in their sputum, all of which was collected on 1 day. Several types of crabs, which were identified as the second intermediate host of the Paragonimus species, were collected from markets and streams in a paragonimiasis endemic area for the inspection of metacercariae. Among the examined crabs, only "rock crabs" (Indochinamon ou) harbored Paragonimus sp. metacercariae, and it is speculated that the life cycle of Paragonimus sp. was maintained via rock crabs in Namback District, Lao PDR.