Sensitivity and specificity of microscopic and molecular techniques for the diagnosis of taeniasis.

BACKGROUND AND OBJECTIVES: The diagnostic challenges associated with T. solium continue to hamper control efforts of the world's most significant foodborne parasite and leading cause of epilepsy in low and middle-income countries. This study aimed to validate two conventional PCRs for taeniasis and estimate the diagnostic performance of microscopic and molecular tools. METHODS: Formalin and ethanol-fixed samples were tested by formalin-ethyl acetate concentration technique (FECT), Malachite smear, McMaster2 method, rrnS PCR and cox1 PCR. Initial validation of PCR methods was completed on 45 microscopy positive individuals. After validation, the performance of microscopic methods and the rrnS were estimated using samples from 1,156 individuals in Laos. Bayesian latent class models (BLCMs) and a composite reference standard were used to estimate diagnostic sensitivity and specificity. RESULTS: On preliminary validation the rrnS was able to detect 27/45 (60.00 %) infections whereas the cox1 detected 21/45 (46.67 %). As a result, the cox1 was excluded from further performance analysis. Microscopy methods and the rrnS were highly specific with estimates above 99.02 % regardless of analytical method. The rrnS was the most sensitive test by informed BCLM (91.45 %, CrI: 73.41-99.52 %) followed by the FECT (71.20 %, CrI: 50.53-85.48 %), McMaster2 (51.31 %, CrI: 32.00-71.29 %) and Malachite smear (32.23 %, CrI: 15.40-54.47 %). DISCUSSION: The inability to validate the cox1 PCR suggests that it may not be suitable in its current form for routine characterisation of Taenia spp. detected by microscopy. The rrnS presents a suitable alternative to the cox1, however, requires its products to be sequenced. Given the low prevalence of taeniasis in most populations, this should be a feasible approach that may be able to be integrated with existing soil-transmitted helminth surveys that often use FECT for microscopic diagnosis.

The challenges of detecting Taenia solium and neurocysticercosis in low and middle-income countries: A scoping review of Lao People's Democratic Republic.

OBJECTIVE: Taenia solium is a tapeworm of global importance due to the burden of disease associated with human epilepsy caused by neurocysticercosis. Unfortunately, diagnostic challenges impede control efforts in many low and middle-income countries. This review examines publications concerning Taenia species in the Lao PDR with a focus on T. solium to inform future research and control programmes. METHODS: PubMed and Scopus databases were primary sources of evidence. Publications must have reported taeniasis or T. solium results from Lao PDR. Publications repeating results or samples were combined into unique projects. RESULTS: A total of 64 publications were included and summarised into 46 projects. The majority of projects applied faecal microscopy as their only diagnostic technique. As a result, the specific species of Taenia was often not determined. Only five projects used molecular techniques to identify the species observed. Only case report of neurocysticercosis has been published. The northern region was included in half the number of projects compared to the south, despite being a high-risk area T. solium. CONCLUSIONS: The diagnostic challenge of determining the species of Taenia present in a faecal sample presents a significant limitation to the control of T. solium in Lao PDR and is an experience that is relevant to many other low and middle-income countries. There must be an improved understanding of the distribution and frequency of T. solium if disease control efforts are to be intensified to reduce the burden of neurocysticercosis, as encouraged by WHO and others. It is hoped that this can be achieved through non-biological risk mapping tools and the more frequent application of molecular tools to routine sample collection. Diagnostic tools that are applicable to low resource settings should be a priority area of research for T. solium.

Echinostoma aegyptica (Trematoda: Echinostomatidae) Infection in Five Riparian People in Savannakhet Province, Lao PDR.

Human infection with Echinostoma aegyptica Khalil and Abaza, 1924 (Trematoda: Echinostomatidae) is extremely rare. In this study, we confirmed E. aegyptica infection in 5 riparian residents living along the Mekong River in Savannakhet Province, Lao PDR. The patients revealed eggs of Opisthorchis viverrini/minute intestinal flukes, echinostomes, and other parasites in fecal examinations using the Kato-Katz technique. Following treatment with praziquantel 30-40 mg/kg and pyrantel pamoate 10-15 mg/kg in a single dose and purging with magnesium salts, adult specimens of various helminth species were collected. Among the trematodes, echinostome flukes of 4.5-7.6 mm in length (n = 134; av. 22.3 specimens per case) were of taxonomic interest and subjected in this study. The flukes were morphologically characterized by having total 43-45 collar spines arranged in 2 alternating rows (corner spines usually 5 on each side) and compatible with previous descriptions of E. aegyptica. The patients were mixed-infected with other helminths, so specific clinical manifestations due to this echinostome fluke were difficult to determine. The present paper describes for the first time human E. aegyptica infections in Lao PDR. This is the second report of human infection (2nd-6th cases) with E. aegyptica in the world following the first one from China.

Echinochasmus caninus n. comb. (Trematoda: Echinostomatidae) Infection in Eleven Riparian People in Khammouane Province, Lao PDR.

Adult specimens of Echinochasmus caninus n. comb. (Verma, 1935) (Trematoda: Echinostomatidae) (syn. Episthmium caninum Yamaguti, 1958) were recovered from 11 riparian people who resided along the Mekong River in Khammouane Province, Lao PDR. In fecal examinations done by the Kato-Katz technique, the cases revealed eggs of Opisthorchis viverrini/minute intestinal flukes, hookworms, and in 2 cases echinostome eggs. To recover the adult helminths, praziquantel 30-40 mg/kg and pyrantel pamoate 10-15 mg/kg in a single dose were given and purged with magnesium salts. Various species of trematodes (including O. viverrini and Haplorchis spp.), cestodes, and nematodes were recovered from their diarrheic stools. Among the trematodes, small echinostome flukes (n=42; av. 3.8 specimens per case) of 0.7-1.2 mm in length are subjected in this study. They are morphologically characterized by having 24 collar spines interrupted dorsally and anterior extension of vitellaria from the cirrus sac or genital pore level to the posterior end of the body. Particularly based on this extensive distribution of vitellaria, the specific diagnosis was made as Echinochasmus caninus. The cases were co-infected with various other helminth parasites; thus, clinical manifestations specific for this echinostome infection were difficult to determine. The present paper describes for the first time human E. caninus infections in Lao PDR. Our cases marked the 4-14th human infections with this echinostome around the world following the 3 previous cases reported from Thailand.

Echinostoma ilocanum Infection in Two Residents of Savannakhet Province, Lao PDR.

Adult specimens of Echinostoma ilocanum (Garrison, 1908) Odhner, 1911 (Trematoda: Echinostomatidae) were recovered from 2 riparian people who resided along the Mekong River in Savannakhet Province, Lao PDR. In fecal examinations done by the Kato-Katz technique, they revealed echinostome eggs together with eggs of Opisthorchis viverrini (and minute intestinal fluke eggs) and hookworms. To recover the adult flukes, they were treated with praziquantel 30-40 mg/kg in a single dose and purged with magnesium salts. A total of 658 adult fluke specimens were recovered from the 2 people; 456 from case 1 and 202 from case 2. Specimens from case 1 consisted of 335 echinostomes (301 E. ilocanum and 34 species undetermined), 120 O. viverrini, and 1 Haplorchis taichui, and those from case 2 consisted of 36 E. ilocanum, 134 O. viverrini, and 32 H. taichui. Thus, the number of E. ilocanum specimens was 337 in total (average per person, 168.5). From this study, it is suggested that foodborne intestinal flukes and liver flukes are highly prevalent along the Mekong River in Savannakhet Province. The present report describes for the first time human infections with E. ilocanum in Lao PDR.

Ultrasonographic investigation of cholangiocarcinoma in Lao PDR.

Opisthorchis viverrini is a group 1 carcinogen that causes cholangiocarcinoma (CCA). Although opisthorchiasis is known to be severely endemic to several areas along the Mekong River in Lao PDR, the CCA status of residents of this region is still under investigation. In this study, we analyzed the results of abdominal ultrasonography (US) performed on 6113 residents in 9 provinces (Vientiane Municipality, Savannakhet, Phongsaly, Khammouane, Saravane, Champasak, Vientiane, Xieng Khuouang, and Luang Prabang provinces) of Lao PDR from 2007 to 2011. Overall, 51 cases (0.83%) were detected with suspected CCA. The CCA rates in Vientiane Municipality and in Savannakhet and Khammouane provinces were 1.45%, 1.58%, and 1.09%, respectively. However, in the other 6 provinces, the rate of CCA averaged only 0.26%. In the 3 provinces with higher rates of CCA, bile duct dilatation (grade ≥ 2) was also significantly more prevalent (P < 0.0001). These results are concordant with previous reports showing a higher endemicity of opisthorchiasis in Vientiane Municipality and in Savannakhet and Khammouane provinces.

First molecular identification and report of genetic diversity of Strongyloides stercoralis, a current major soil-transmitted helminth in humans from Lao People's Democratic Republic.

Strongyloidiasis is a major soil-transmitted helminth (STH) disease that affects people worldwide. We present updated data on prevalence in the Lao People's Democratic Republic (Lao PDR) in 2015, arising from a community cross-sectional helminthiasis survey. Fecal samples were collected from 327 individuals across three provinces in Lao PDR (Luang Prabang in the north, Khammouane in the center, and Champasack in the south). Agar plate culture and Kato-Katz methods were used to examine duplicate stool samples from each participant to detect Strongyloides stercoralis and co-infecting helminths. Overall prevalences of S. strercoralis human hookworm, Taenia spp., Trichuris trichiura, Ascaris lumbricoides, and Enterobius vermicularis were 41.0, 28.1, 4.9, 4.0, 1.5, and 0.9 %, respectively. The prevalence of miscellaneous trematodiases (including opisthorchiasis) was 37.9 % and of Schistosoma mekongi infection was 0.3 %. Strongyloidiasis is a current major STH disease in Lao PDR. We also report the molecular-phylogenetic identification of S. stercoralis adult males collected from 40 representative human strongyliodiasis fecal samples. DNA was extracted, amplified, and sequenced from a portion of the mitochondrial cox1 gene and the nuclear 18S ribosomal DNA. Phylogenetic analyses indicated that all specimens sequenced belonged to S. stercoralis (Bavay, 1876) Stiles and Hassall, 1902. The cox1 sequences exhibited great diversity (24 haplotypes) in Lao PDR. This is the first molecular identification and report of genetic diversity of S. stercoralis in humans from Lao PDR. An effective parasite control program is needed to reduce the serious health impacts.

Intestinal Helminths Recovered from Humans in Xieng Khouang Province, Lao PDR with a Particular Note on Haplorchis pumilio Infection.

A survey of intestinal helminths was undertaken in riparian people in Xieng Khouang Province, Lao PDR. Fecal specimens were collected from 643 people (289 males and 354 females) residing in 4 districts (Nonghet, Kham, Phoukout, and Pek) and were examined by the Kato-Katz technique. The overall helminth egg positive rate was 41.2%, and hookworms revealed the highest prevalence (32.7%) followed by Trichuris trichiura (7.3%) and Ascaris lumbricoides (5.6%). The positive rate for small trematode eggs (STE), which may include Opisthorchis viverrini, heterophyids, and lecithodendriids, was 4.4%. For recovery of adult helminths, 12 STE or nematode/cestode egg-positive people were treated with 40 mg/kg praziquantel and 15 mg/kg pyrantel pamoate, and then purged. Mixed infections with 2 Haplorchis species (H. pumilio and H. taichui), Centrocestus formosanus, Opisthorchis viverrini, a species of cestode (Taenia saginata), and several species of nematodes including hookworms and Enterobius vermicularis were detected. The worm load for trematodes was the highest for H. pumilio with an average of 283.5 specimens per infected person followed by C. formosanus, H. taichui, and O. viverrini. The worm load for nematodes was the highest for hookworms (21.5/infected case) followed by E. vermicularis (3.2/infected case). The results revealed that the surveyed areas of Xieng Khouang Province, Lao PDR are endemic areas of various species of intestinal helminths. The STE found in the surveyed population were verified to be those of heterophyids, particularly H. pumilio.

Infection Status of Zoonotic Trematode Metacercariae in Fishes from Vientiane Municipality and Champasak Province in Lao PDR.

The infection status of fishborne zoonotic trematode (FZT) metacercariae was investigated in fishes from 2 localities of Lao PDR. Total 157 freshwater fishes (17 species) were collected in local markets of Vientiane Municipality and Champasak Province in December 2010 and July 2011, and each fish was examined by the artificial digestion method. Total 6 species of FZT metacercariae, i.e., Opisthorchis viverrini, Haplorchis taichui, Haplorchis yokogawai, Haplorchis pumilio, Centrocestus formosanus, and Procerovum varium, were detected in fishes from Vientiane Municipality. The metacercariae of O. viverrini were detected in 50 (49.5%) out of 101 fishes (6 species), and their average number was 154 per fish infected. The remaining 5 species of heterophyid metacercariae were detected in 36.8%, 65.8%, 9.4%, 23.9%, and 5.1% fishes examined, and their average densities were 12, 1,038, 4, 15, and 13 per infected fish, respectively. In fishes from Champasak Province, 3 species of FZT metacercariae, i.e., O. viverrini, H. taichui, and H. yokogawai, were detected. Only 2 O. viverrini metacercariae were found in only 1 Barbonymus schwanefeldi. The metacercariae of H. taichui and H. yokogawai were detected in 60.0% and 50.0% of fishes examined, and their average densities were 47 and 28 per fish infected. By the present study, it has been confirmed that several species of FZT metacercariae are prevalent in fishes from Vientiane Municipality, with P. varium being a new member of FZT in Lao PDR. In comparison, FZT metacercariae are less prevalent in fishes from Champasak Province.

Risk factors for Opisthorchis viverrini and minute intestinal fluke infections in Lao PDR, 2009-2011.

The purpose of this report is to compare the prevalence of Opisthorchis viverrini/minute intestinal fluke (Ov/MIF) in Lao People's Democratic Republic according to different regions and evaluate the effect of ingestion of raw freshwater fish on the infection. Demographic data, behavioral data, and symptoms were obtained, and the Kato-Katz method was used for the diagnosis of Ov/MIF. In total, 3,046 individuals were enrolled. The risk factors associated with acquisition of Ov/MIF were raw fish consumption and province. Khong Island showed the highest prevalence (odds ratio = 80.1, 95% confidence interval = 47.9-133.9, P < 0.001) compared with other districts, and raw fish consumption was related to Ov/MIF infection. Administration of praziquantel to entire populations, education (avoiding consumption of raw food dishes and improved hygiene), and access to clean water and sanitation should be considered.

Prevalence of Haplorchis taichui among humans and fish in Luang Prabang Province, Lao PDR.

This study confirmed the prevalence of the intestinal fluke Haplorchis taichui (Trematoda: Heterophyidae) among people and fish in Luang Prabang Province, Lao PDR. Fecal specimens were collected from 559 riparian people (229 males and 330 females), residing in 4 Districts (Luang Prabang, Xieng Ngeun, Pak Ou, and Nam Bak) and were examined by the Kato-Katz fecal smear technique. The overall helminth egg positive rate was 64.9%. The positive rate for small trematode eggs (STE), which may include H. taichui and other heterophyids, Opisthorchis viverrini, and lecithodendriids, was 15.2%. For recovery of adult helminths, 10 STE-positive people were treated with 40mg/kg praziquantel and 15mg/kg pyrantel pamoate, and then purged. Mixed infections with 3 Haplorchis species (H. taichui, H. pumilio, and H. yokogawai), a species of cestode (Taenia saginata), and several species of nematodes including Enterobius vermicularis and hookworms were found. The worm load for trematodes was exclusively high for H. taichui with an average of 7691 specimens per infected person, followed by H. yokogawai (8.3 specimens) and H. pumilio (4.1 specimens). Out of 207 freshwater fish (17 species) purchased in a market in Luang Prabang District, 138 (67%) harboured H. taichui metacercariae (metacercarial burden per fish; 520). Lower prevalence of fish and lower metacercarial density were observed for H. yokogawai (52% and 50 per fish, respectively) and H. pumilio (18% and 3 per fish, respectively). STE found in the surveyed population of Luang Prabang Province were verified to be those of intestinal fukes, particularly H. taichui.

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.

Human neurocysticercosis case and an endemic focus of Taenia solium in Lao PDR.

A male patient with neurocysticercosis was identified in Montai Village, Xay District, Oudomxay Province, Lao PDR in February 2004. He had a history of diagnosis for neurocysticercosis by a CT scan in Thailand after an onset of epileptic seizure in 1993. A pig in the same district was found to contain Taenia solium metacestodes (=cysticerci); the slaughtered pig body contained more than 2,000 cysticerci. In addition to morphological identification, molecular identification was also performed on the cysticerci by DNA sequencing analysis of the mitochondrial cox1 gene; they were confirmed as T. solium metacestodes. The patient is regarded as an indigenous case of neurocysticercosis infected in an endemic focus of T. solium taeniasis/cysticercosis in Oudomxay Province, Lao PDR.

Hyperendemicity of Haplorchis taichui infection among riparian people in Saravane and Champasak province, Lao PDR.

In this study, we found that Haplorchis taichui, a heterophyid intestinal fluke, is highly prevalent, with heavy worm loads, among riparian people in Saravane and Champasak province, Lao PDR. Fecal specimens were collected from 1,460 people (717 men and 743 women) in 12 riparian (Mekong river) districts and were examined by the Kato-Katz fecal smear technique. The overall helminth egg positive rate was 78.8% and 66.4% in Saravane and Champasak province, respectively. The positive rate for small trematode eggs (STE), which included H. taichui and other heterophyids, Opisthorchis viverrini, and lecithodendriids, was 69.9% and 46.3% in Saravane and Champasak province, respectively. To obtain adult flukes, 30 STE-positive people were treated with 40 mg/kg praziquantel and then purged. Whole diarrheic stools were collected 4-5 times for each person and searched for fluke specimens using a stereomicroscope. Mixed infections with various species of trematodes (H. taichui, Haplorchis pumilio, O. viverrini, Prosthodendrium molenkampi, Centrocestus formosanus, and Echinochasmus japonicus) and a species of cestode (Taenia saginata) were found. However, the worm load was exceptionally high for H. taichui compared with other trematode species, with an average of 21,565 and 12,079 specimens per infected person in Saravane and Champasak province, respectively, followed by H. pumilio (41.9 and 22.5, respectively) and O. viverrini (9.4 and 1.5, respectively). These results show that diverse species of intestinal and liver flukes are prevalent among riparian people in Saravane and Champasak province, Lao PDR, with H. taichui being the exceptionally dominant species.

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.

Centrocestus formosanus (Heterophyidae): human infections and the infection source in Lao PDR.

In Lao People's Democratic Republic (PDR), we detected 7 patients infected with Centrocestus formosanus (1-122 adult specimens) after praziquantel treatment and purgation, together with several other trematode species including Opisthorchis viverrini and Haplorchis taichui. The patients were all men, 23-42 yr-of-age. Three subjects were from Vientiane Municipality and 1 each were from Khammouane, Saravane, Champassak, and Xiengkhouang Province. The patients had frequently eaten raw freshwater fish and were experiencing variable degrees of epigastric pain and indigestion accompanied by occasional diarrhea, although the relationship of these symptoms with C. formosanus infection was unclear. Centrocestus formosanus specimens were ovoid, 0.46 mm (0.41-0.52 mm) long, and 0.18 mm (0.16-0.20 mm) wide (n = 10) and were equipped with 32 circumoral spines on the oral sucker. The uterine eggs were 33.2 µm long (31.8-34.9 µm) and 18.5 µm wide (17.4-19.8 µm) (n = 20). Analysis of the nucleotide sequence of the 18S ribosomal RNA gene of our specimens (Laotian isolate) revealed 100% homology with that of an isolate from the United States reported in GenBank. Several species of freshwater fish collected from Xiengkhouang Province revealed a 17.0% prevalence (9 of 53 fish examined) for C. formosanus metacercariae. The results suggest that human C. formosanus infections have been masked by other trematode infections.

Echinostome flukes receovered from humans in Khammouane Province, Lao PDR.

Echinostome eggs were detected in 22 (1.1%) of 2,074 people residing in riparian villages along the Mekong River in Khammouane Province, Lao PDR. In order to recover the adult flukes, 9 persons were treated with praziquantel and purged with magnesium salts. A total of 55 echinostome specimens (4 species) were recovered from the 9 persons. Echinostoma revolutum (8 specimens) was recovered from 3 persons, Artyfechinostomum malayanum (8 specimens) was from 2 persons, Echinochasmus japonicus (33 specimens) was from 7 persons, and Euparyphium sp. (6 specimens) was from 1 person. In Lao PDR, only human infections with E. japonicus were previously known. Therefore, the present study describes human infections with E. revolutum, A. malayanum, and Euparyphium sp. for the first time in Lao PDR. These results indicate that the surveyed villages of Khammouane Province, Lao PDR are low-grade endemic foci of echinostomiasis.

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.

High prevalence of Haplorchis taichui, Phaneropsolus molenkampi, and other helminth infections among people in Khammouane province, Lao PDR.

The prevalence of liver and intestinal helminth infections, including Opisthorchis, Haplorchis, Phaneropsolus, hookworms, Enterobius, and Taenia, was surveyed in Khammouane province, Lao PDR. Fecal specimens were collected from 1,242 people (590 men and 652 women) in 3 Mekong riverside villages and were examined by the Kato-Katz thick smear technique. The overall helminth egg positive rate was 81.1%. The positive rate for small trematode eggs, including Opisthorchis viverrini, heterophyids, and lecithodendriids, was 81.1% and the positive rate for hookworms was 6.7%. To obtain adult worms, 35 people who were positive for small trematode eggs were treated with 20-30 mg/kg praziquantel and 10-15 mg/kg pyrantel pamoate, and then purged. Diarrheic stools were collected from 33 of these people and searched for helminth parasites using a stereomicroscope. Mixed infections with various helminths (Haplorchis taichui, Haplorchis yokogawai, Prosthodendrium molenkampi, Phaneropsolus bonnei, echinostomes, hookworms, Trichostrongylus spp., Trichuris trichiura, Enterobius vermicularis, and/or Taenia saginata) were found. The total number of helminth specimens collected was 20,907 (approximately 634 per person). The most common species was H. taichui, followed by P. molenkampi, O. viverrini, P. bonnei, E. vermicularis, hookworms, and Trichostrongylus spp. These results show that diverse species of intestinal nematodes, trematodes, and cestodes are infecting humans in Khammouane province, Lao PDR.

Differential diagnosis of Taenia asiatica using multiplex PCR.

Taenia asiatica and T. saginata are frequently confused tapeworms due to their morphological similarities and sympatric distribution in Asian regions. To resolve this problem, a high-resolution multiplex PCR assay was developed to distinguish T. asiatica infections from infection with other human Taenia tapeworms. For molecular characterization, the species specificity of all materials used was confirmed by sequencing of the cox1 gene. Fifty-two samples were analyzed in this study, comprising 20 samples of T. asiatica genomic DNA from China, Korea, and the Philippines; 24 samples of T. saginata from Belgium, Chile, China, Ethiopia, France, Indonesia, Korea, Laos, the Philippines, Poland, Taiwan, Thailand, and Switzerland; and 10 samples of T. solium from Cape Verde, China, Honduras, and Korea. The diagnostic quality of the results obtained using PCR and species-specific primers designed from valine tRNA and NADH genes was equal to that based on the nucleotide sequencing of the cox1 gene. Using oligonucleotide primers Ta4978F, Ts5058F, Tso7421F, and Rev7915, the multiplex PCR assay was useful for the differentially diagnosing T. asiatica, T. saginata, and T. solium based on 706-, 629-, and 474-bp bands.