Asymptomatic Blastocystis-infected Persons as Potential Carriers of Disease in Thailand.

Aim: Blastocystis spp. is currently classified as a gastrointestinal protozoan parasite and has become quite a controversial organism. This study was aimed to obtain information about the prevalence of Blastocystis infection among an otherwise healthy, asymptomatic Thai population. Study Design: Retrospective study. Place and Duration of Study: The study areas were the Border Patrol-police station (Subdivision 12), Sa Kaeo Province; the Home for Mentally Handicapped Childcare, Ban Rajawadee, in Nonthaburi Province; Silpakorn University, Nakhon Pathom Province and the Intercity Motorway Division, Department of Highways, Bangkok. The study was carried during 2010-2013. Methodology: Fecal examination was performed by direct simple smear test on 3,940 out of 6,537 Thais of different genders, ages, occupations, and residential locations who joined the annual health check-up program serviced by the Faculty of Tropical Medicine, Mahidol University. Results: It was found that 1.0% (40/3,940) presented with Blastocystis infection was asymptomatic of clinical symptoms at a male to female ratio of 2.3:1.0. Blastocystis infection was predominantly found in the age group 41-50 years (47.5%, 19/40). Border Patrol-policemen (Subdivision 12), who resided and worked in rural areas of Sa Kaeo Province near the border between Thailand and Cambodia had significantly higher prevalence of Blastocystis infection (2.8%) than the staff of the Intercity Motorway Division, Department of Highways, in urban Bangkok (0.1%). Other occupations located in suburban areas, such as workers at the Home for Mentally Handicapped Childcare, Ban Rajawadee, in Nonthaburi Province, who worked closely with mentally handicapped children, and officials and lecturers at Silpakorn University, Nakhon Pathom Province, also had significantly higher prevalence rates than Intercity Motorway Division staff in urban Bangkok, with prevalence rates of 4.20% and 2.55%, respectively. Food handlers and cooks who prepared and sold food in Silpakorn University had similar prevalence rates of Blastocystis infection as Intercity Motorway Division staff. Conclusion: This study revealed that Blastocystis infected patients probably did not show obviously clinical symptoms in asymptomatic carriers, who can spread infections to others and environments.

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.

Paragonimiasis in Nan Province, northern Thailand.

Two cases of paragonimiasis were identified within the hill-tribe population living on the Thai-Laotian border of Nan Province, northern Thailand, where information on Paragonimus was then still limited. The patients were in the habit of eating improperly cooked crabs and freshwater prawns. A survey for natural intermediate hosts to complete the life cycle was in progress at that time, and the detection of paragonimiasis cases indicated that there was persistence of paragonimiasis in the endemic area of Nan Province.

Efficacy of benzimidazole carbamate on an intestinal fluke co-infected with nematodes.

The efficacy of a single dose of benzimidazole, drugs commonly used for the treatment of Ascaris and hookworm, was evaluated against one of the tiny-sized intestinal flukes, Haplorchis sp in the endemic area where mixed infections of roundworms and flatworms existed. At day 7 after treatment, albendazole (400 mg) induced 42.5% cure rate, mebendazole (500 mg) a cure rate of 32.4%, on the other hand, praziquantel (40 mg/kg) gave 94.6% cure rate and the placebo at 15.9%. At the single dose, benzimidazole could not completely expelled the haplorchid; but could reduce one third to two fifth of the infection, similar to the drugs efficacy against Trichuris infection.

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.