Human sparganosis in Thailand: an overview.

Human sparganosis is caused by cestode larvae (spargana) of the genus Spirometra, which exploit copepods as the first intermediate host. A wide range of amphibians, reptiles, birds, and mammals serve as second intermediate/paratenic hosts. Human infections occur mainly by ingesting raw intermediate/paratenic hosts. Cases are found mainly in China, Japan and Korea, and sporadically also in Thailand and other Asian countries. In the period 1943-2010, there were 52 reported cases of sparganosis in Thailand. The average patient age was 32 years (range 11-82 years). From the available patient information, the prevalence of sparganosis infection was higher among females than males, at a ratio of F:M=2:1 (27:15). Patients have mainly been found in the northeast, north, and central regions of Thailand, with only a few in the south. Although a single subcutaneous nodular lesion was the most common feature, about one third of patients had ocular lesions. In particular, patients having ocular lesions were about half of total cases reported pre-1990, with several confirmed cases' applying fresh frog muscle as a poultice to relieve sore eyes, according to traditional medicine. In Thailand, sparganosis is not merely a food-borne disease but is also caused by the traditional belief of applying frog muscles (contaminated with sparganum) to sore eyes.

Comparison of three antigen preparations to detect Trichinellosis in live swine using IgG-ELISA.

A swine infected with Trichinella spiralis is a source of transmission to human through consumption of raw or improperly cooked pork. Detection of larvae is suitable for carcasses, so that pigs in households or farms can be examined serologically for trichinellosis. This study compared antigens, crude (CAg), excretory-secretory (ESAg) and surface (SAg), for their potential use in IgG-ELISA. Serum samples were collected from 5 experimentally infected swine with T. spiralis (pTs), 147 positive cases of 9 other parasitic infections, 12 mixed infections of other parasites, and 35 normal controls. At the same 100% sensitivity, specificity of tests was in a range of 98-77%. ESAg was the best source of antigen with specificity of 98.3% at cut-off value of 0.439. False positives included coccidiasis (1/86) and mixed infections (2/39). For CAg, trichuriasis (2/11), coccidiasis (5/86), and mixed infections (8/39) gave cross-reactions and some of these samples had OD values far above cut-off value of 0.332. Cross-reactions of SAg were Oesophagostomum spp-like GI-nematode infection (1/1), unidentified GI-nematode infections (2/3), trichuriasis (5/11), coccidiasis (29/86) and mixed infections (4/39). Thus, ESAg has the highest potential in serodiagnosis, with antibody to T. spiralis in pigs being detected at the earliest 16 day post-infection. However, crude antigen demonstrated a good specificity at 91.8%, and this antigen has a potential to be used as a detection of choice for swine trichinellosis, but the antigen preparation must be improved for higher specificity.

Molecular and serological survey on taeniasis and cysticercosis in Kanchanaburi Province, Thailand.

A community-based field survey on taeniasis and cysticercosis was performed in two villages in Thong Pha Phum District, Kanchanaburi Province, central Thailand, where 3 Taenia species, T. solium, T. saginata and T. asiatica, are sympatrically occurring. Four (0.6%) out of 667 stool samples were egg-positive for Taenia sp. by Kato-Katz technique. Three out of those four persons and other three persons who were Taenia egg-negative but having a recent (<1 year) history of discharging worms in stool were treated with niclosamide. One Taenia egg-positive woman was not treated because of severe ascites. After treatment, three persons expelled long strobilae with scolices and two persons expelled strobilae without scolex. One Taenia egg-positive person did not expel any worms post-treatment. Among 5 persons, four expelled a single worm, whereas one expelled multiple worms, may be 6 worms but not confirmed by detection of scolices. One scolex was armed with hooklets, whereas 2 others did not. Multiplex PCR of 10 expelled proglottids (including 6 estimated worms from one patient) revealed that one sample was T. solium, one T. saginata, and 8 T. asiatica. A total of 159 residents agreed to receive a serological test for cysticercosis. By ELISA using partially purified glycoprotein antigen, 9 cases, 5 and 4 from villages A and B respectively, were found to be sero-positive. The five and an additional sample on the border line from village A were evaluated using confirmative immunoblot using recombinant chimeric antigen. Among the six samples, four including the border line sample were confirmed to be cysticercosis by immunoblotting. One of the 4 persons had neurological symptoms with nodular lesions in the brain by computed tomography. These 4 confirmed or suspected cysticercosis cases were free of T. solium worms, but two of them including confirmed NCC case had a past (>1 year) history of expelling proglottids in the stool.

Evidence of hybridization between Taenia saginata and Taenia asiatica.

There has long been a debate as to the specific status of the cestode Taenia asiatica, with some people regarding it as a distinct species and some preferring to recognize it as a strain of Taenia saginata. The balance of current opinion seems to be that T. asiatica is a distinct species. In this study we performed an allelic analysis to explore the possibility of gene exchange between these closely related taxa. In total, 38 taeniid tapeworms were collected from humans living in many localities including Kanchanaburi Province, Thailand where the two species are sympatric. A mitochondrial DNA (mtDNA)-based multiplex PCR tentatively identified those parasites as T. asiatica (n=20) and T. saginata (n=18). Phylogenetic analyses of a mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and two nuclear loci, for elongation factor-1 alpha (ef1) and ezrin-radixin-moesin (ERM)-like protein (elp), assigned all except two individual parasites to the species indicated by multiplex PCR. The two exceptional individuals, from Kanchanaburi Province, showed a discrepancy between the mtDNA and nuclear DNA phylogenies. In spite of their possession of sequences typical of the T. saginata cox1 gene, both were homozygous at the elp locus for one of the alleles found in T. asiatica. At the ef1 locus, one individual was homozygous for the allele found at high frequency in T. asiatica while the other was homozygous for the major allele in T. saginata. These findings are evidence of occasional hybridization between the two species, although the possibility of retention of ancestral polymorphism cannot be excluded.

Sympatric occurrence of Taenia solium, T. saginata, and T. asiatica, Thailand.

We confirmed sympatric occurrence of Taenia solium, T. saginata, and T. asiatica in western Thailand. DNA analysis of morphologically identified T. saginata, in a dual infection with T. solium, indicated it was T. asiatica. To our knowledge, this report is the first of T. asiatica and a dual Taenia infection from Thailand.

Taeniasis, cysticercosis and echinococcosis in Thailand.

Taeniasis is one of the major food-borne parasitic zoonoses in Thailand. During the years 1957-1997, the prevalence was low in most parts of the country. Recent (2000-2005) country prevalence was lower than 1%. A high prevalence (5.9%) was found among 1450 villagers from 30 villages in the North, and among 1233 stool samples from 19 provinces in the Northeast (2.8%). Taenia saginata was the dominant species. Cysticercosis in Thailand is somewhat under-reported/recorded. During the period 1965-2005, diagnosis was based on techniques other than serodiagnosis, giving a total of cysticercosis cases of less than 500. However, an immunoblot technique using delipidized cyst antigen showed 314 positive cases out of 754 samples tested in 2000-2005. Reports of neurocysticercosis appeared more often than cutaneous cysticercosis. A total of 24 cases of echinococcosis, mostly hydatid cysts (only 2 cases of alveolar cysts), were recorded during 1936-2005. These records included 3 cases of foreigners seeking surgery in hospitals in Bangkok. Most Thai patients were migrant workers from the Middle East, and only a few cases were indigenous. The prevalence of cysticercosis and echinococcosis is increasing resulting from sensitive modern diagnostic tests. Taeniasis will persist in Thailand as the consumption of raw/half-cooked meat dishes is still a normal practice for Thai people.

Diagnostic values of IgG4 in human gnathostomiasis.

The diagnostic values of immunoglobulin G subclass antibodies from patients with gnathostomiasis were assessed by immunoblot technique. Antigen was prepared from crude extracts of Gnathostoma spinigerum advanced third-stage larvae obtained from naturally infected eels. The sera were obtained from 14 parasite-confirmed gnathostomiasis cases, 63 patients with other helminthic infections and 13 healthy controls. Nine prominent IgG4 reactive bands appeared with molecular weights of 94, 51, 47, 43, 38, 24, 21, 20 and 15 kDa. The diagnostic sensitivity of each of the nine reactive bands ranged from 100% to 64.3% in 14 parasite-confirmed gnathostomiasis cases. All (100%) confirmed cases recognized the 21 kDa antigenic band, but not other helminthic infections or parasite-free control. Recognition of 21 kDa antigen in G. spinigerum advanced third-stage larvae crude extracts is the most specific diagnostic marker for human gnathostomiasis, with 100% sensitivity and specificity. The 20 and 24 kDa protein bands were additional diagnostic bands for confirming diagnosis of infection where the 21 kDa band was faint. No specific binding of IgG1, IgG2, or IgG3 antibodies was observed in any sera from confirmed gnathostomiasis cases.

Diploscapter coronata infection in Thailand: report of the first case.

A 73-year-old Thai woman living in Mueang District, Saraburi Province, central Thailand presented with numerous hookworm-like nematodes, finally revealed as Diploscapter coronata, by fecal culture. The patient exhibited no significant clinical signs of the gastrointestinal or genitourinary systems, and was generally not ill as a result of this unusual infection. Less commonly, patients have presented with symptoms and signs of Diploscapter coronata infection. However, potentially serious consequences can occur where people have exposure to an environment that has been contaminated with infected feces, or more specifically, infective eggs; such conditions could lead to human infection with Diploscapter coronata worms. This was the first reported occurrence of human Diploscapter coronata infection in Thailand.

Waterborne zoonotic helminthiases.

This review deals with waterborne zoonotic helminths, many of which are opportunistic parasites spreading directly from animals to man or man to animals through water that is either ingested or that contains forms capable of skin penetration. Disease severity ranges from being rapidly fatal to low-grade chronic infections that may be asymptomatic for many years. The most significant zoonotic waterborne helminthic diseases are either snail-mediated, copepod-mediated or transmitted by faecal-contaminated water. Snail-mediated helminthiases described here are caused by digenetic trematodes that undergo complex life cycles involving various species of aquatic snails. These diseases include schistosomiasis, cercarial dermatitis, fascioliasis and fasciolopsiasis. The primary copepod-mediated helminthiases are sparganosis, gnathostomiasis and dracunculiasis, and the major faecal-contaminated water helminthiases are cysticercosis, hydatid disease and larva migrans. Generally, only parasites whose infective stages can be transmitted directly by water are discussed in this article. Although many do not require a water environment in which to complete their life cycle, their infective stages can certainly be distributed and acquired directly through water. Transmission via the external environment is necessary for many helminth parasites, with water and faecal contamination being important considerations. Human behaviour, particularly poor hygiene, is a major factor in the re-emergence, and spread of parasitic infections. Also important in assessing the risk of infection by water transmission are human habits and population density, the prevalence of infection in them and in alternate animal hosts, methods of treating sewage and drinking water, and climate. Disease prevention methods, including disease surveillance, education and improved drinking water treatment are described.

Soil-transmitted helminthiases and health behaviors among schoolchildren and community members in a west-central border area of Thailand.

The prevalence of soil-transmitted helminthic infections and health behaviors related to infections in schoolchildren and villagers of a community (4 hamlets) was studied in Hauy Kayeng subdistrict, Thong Pha Phum district, in the north of Kanchanaburi Province. The intestinal helminth infection rate of the schoolchildren was 15.6%. Hookworm infection was the most prominent (9.8%), followed by Trichuris trichiura (6.2%), and Ascaris lumbricoides (2.2%). The community showed higher prevalence rates and was infected with more types of intestinal helminths than the schoolchildren. Thirty-five point two percent (35.2%) of the residents were infected with soil-transmitted helminths, 30.5% with hookworm, 3.4% with A. lumbricoides and 2.2% with T. trichiura. Almost all hookworm cases (94.3%) were light intensity infections, while only 1.3% were heavy infections. Moreover, the hookworm infection rate in the community was found to be much higher when a stool culture method was used (39.1%). With this technique, 2.3% Strongyloides stercoralis infections were detected in the community population. Examination of the health behavior of the study samples showed that approximately 75% always defecated in a toilet. Schoolchildren who always wore shoes comprised 67%, which was lower than the community, at 85%.

Intestinal helminthic infections in schoolchildren in Cambodia.

During the period January to December 1998, the National Malaria Center (CNM) carried out a parasitological survey of schoolchildren in rural and semi-urban areas, to assess intestinal helminthic infections in schoolchildren in the central parts of Cambodia. In the rural areas, there were four schools in Stung Treng Province (all situated along the Mekong River), five schools in Kratie Province (around rubber plantations), six schools in Kampong Chhnang Province (along Tonle Sap Lake); and in the semi-urban areas, three schools in Beng Tumpon Commune and five schools in Chbar Ampeou Commune (Mean Chey District) were selected for study. By Kato-Katz technique, the prevalence of soil-transmitted helminthic infections in schoolchildren in both the rural and urban areas was high. The infection rate was between 10-40% for Ascaris, 2-17% for Trichuris and 5-65% for hookworm. Schistosomiasis and opisthorchiasis were found in the schoolchildren living along the Mekong River (Stung Treng Province); the infection rate of S. mekongi ranged from 12 to 43%. These infections in children were with hepatomegalies. An intervention in an urban area (Chraing Chamres) showed that after repeated treatment with mebendazole 500 mg single dose every 6 months, the prevalence of all parasites had dropped to about one third of the initial level.

Risk factors of helminthiases among schoolchildren in southern Thailand.

School-age children are particularly at risk of soil-transmitted helminthiasis (STH), which affects their growth and development. Hence, school-based helminthiasis control has been discussed and conducted as one of cost-effective ways in developing countries. A parasite control program is to be planned and conducted in an evidence based way as one of practical medical fields. However, a prevalence is likely to be influenced by various factors such as local environment and residents' behavior and so on. As few reports mentioning the relation of the prevalence and children's behavior and practice have been published, we conducted a survey to investigate such relation by asking children directly. Two hundred and eighty pupils in grade 3 to grade 5 were enrolled, who were in the two schools in Nakhon Si Thammarat Province, southern Thailand. A cross-sectional study was conducted in February and in November 2001, on the relationship between helminthiasis and children's knowledge and practice by using Kato-Katz method and a questionnaire, respectively. Hookworm (Hw) was the most predominant helminth followed by Trichuris. Boys had more intensive Hw infection than girls (p = 0.022), and wore shoes less frequently than girls (p < 0.001). The pupils who nearly acquired Hw infection after the first stool examination had lower levels of the knowledge of STH comparing to those who did not (p = 0.011). This study suggests that a prior survey can identify unique local factors as a part of diagnostic process, the results of which are useful for teachers to understand some points of health education at schools and can be applied as indicators for monitoring and evaluation.

Studies on concomitant antigens of Bithynia funiculata for detection of antibody to Opisthorchis viverrini: effect of different centrifugal speeds on antigen preparation.

Antigens derived from somatic extracts of Bithynia funiculata, an intermediate snail host of O. viverrini, have been demonstrated to be highly heterogeneous in molecular weight (MW). These antigens have been suggested to be of potential use for serodiagnosis. In this study, B. funiculata somatic antigens were extracted using five different centrifugal speeds, namely 10,000 (C1); 20,000 (C2); 30,000 (C3); 40,000 (C4) and 50,000 (C5) rpm, with the aim of removing some non-specific antigens and determining the optimal centrifugal speed to obtain the highest efficiency of the test for which they will be used. The enzyme-linked immunosorbent assay technique was used to compare the reactivity of the five different centrifugal speed-prepared antigens. The sensitivity and specificity of all five antigens were compared by testing against sera from 81 opisthorchiasis patients, 30 parasite-free healthy individuals and 50 individuals infected with other helminthic infections, using mean + 4SD of all healthy individuals as the cut-off value. The sensitivity of these antigens was 69.1, 84.0, 80.2, 84.0 and 70.4, respectively; while the specificity was 66.2, 76.2, 82.5, 86.2 and 71.2, respectively. Immunoreactive components of each antigen were analyzed by SDS-PAGE and Western blot technique. The assay showed that three pairs of antigens with MW of 29 and 30, 47 and 50, and 86 and 90 kDa of all five antigens, which have previously been shown to be highly immunogenic, still reacted with a pooled serum from patients with opisthorchiasis. However, the C4 antigens gave more distinct components. Our results showed that 40,000 rpm is the optimal speed for antigen preparation for use in the serological diagnosis of opisthorchiasis, as demonstrated by the most satisfactory results of both sensitivity and specificity in the indirect ELISA and Western blot technique.

Hookworm infections of schoolchildren in southern Thailand.

A study of hookworm infections of schoolchildren was conducted in Nakhon Si Thammarat Province, southern Thailand. Of the 2,940 hookworms that were recovered from the children, almost all (99.9%), were Necator americanus, only three (0.1%) were identified as Ancylostoma duodenale, and all were female worms. An estimation of the worm burden of and the worm expulsion from the schoolchildren indicated there were 17 cases of light intensity hookworm infection. Fifteen cases (88.2%) expelled worms in numbers that corresponded with the worm burden that was estimated from the number of eggs per gram of feces. Two cases (11.8%) expelled more worms than predicted. In 16 moderate intensity cases, five (31.3%) expelled worms in a quantity that corresponding with the estimated worm burden. Eleven cases (68.7%) expelled fewer worms than predicted. All cases of heavy intensity infection expelled fewer worms than predicted.

School-based helminthiases control: I. A baseline study of soil-transmitted helminthiases in Nakhon Si Thammarat Province, Thailand.

A baseline study of soil-transmitted helminthiases was carried out in Nakhon Si Thammarat Province, southern Thailand. The study sites were Wat Krou Chou Primary School and nearby villages in Sichon district, and Wat Thang Phoon Primary School and nearby villages in Chalerm Phrakiat District. Surveys of the schoolchildren's stools were conducted by the Kato-Katz technique. The results showed that 23.7% of schoolchildren in Wat Krou Chou and 24.7% of those in Wat Thang Phoon were infected with soil-transmitted helminths, with a 24.1% overall infection rate. The major infection was hookworm (22.2% and 19.6%) and the minor one was trichuriasis, (2.9% and 8.7% respectively). The intensity of infection was similar in both schools, 85.7% and 90.2% respectively for light intensity hookworm. Schoolchildren with hookworm infection were not anemic. The hemoglobin value of children with hookworm infection was not significantly different from that of uninfected children. Data regarding the health behavior of children's parents in both schools were reported.