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.

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.

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.

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 liver and intestinal fluke infections among residents of Savannakhet Province in Laos.

The prevalence of liver and intestinal fluke infections was surveyed on residents of Savannakhet Province, Laos. Fecal specimens were collected from a total of 981 residents in 4 Mekong riverside villages and examined by the Kato-Katz thick smear technique. The results revealed that the overall helminth egg positive rate was 84.2%, and the positive rate for small trematode eggs, including Opisthorchis viverrini, heterophyids, or lecithodendriids, was 67.1%. To obtain adult flukes, 38 small trematode egg positive cases were treated with a 20-30 mg/kg single dose of praziquantel and purged. Diarrheic stools were then collected from 29 people and searched for helminth parasites using stereomicroscopes. Mixed infections with O. viverrini and 6 kinds of intestinal flukes were found, namely, Haplorchis taichui, Haplorchis pumilio, Haplorchis yokogawai, Prosthodendrium molenkampi, Phaneropsolus bonnei, and echinostomes. The total number of flukes collected was 7,693 specimens (av. no. per treated person; 265.3). The most common species was O. viverrini, followed by H. taichui, P. molenkampi, echinostomes, H. pumilio, P. bonnei, and H. yokogawai. The results indicate that foodborne liver and intestinal fluke infections are prevalent among residents of Savannakhet Province, Laos.