Parasitological monitoring of helminth control program in Northern Thailand.

Nan Province, located in northern Thailand, is hyperendemic for parasite infections; the helminthic infection rate in 1,010 schoolchildren was 60.0% in 2001. Mass anthelmintic chemotherapy has been conducted with schoolchildren, and selective treatment has been given to people in the community, from 2002. The modified cellophane thick smear method was used to examine the prevalence and intensity of helminth infections in schoolchildren and community people once a year during the period 2002-2004. The prevalence of helminth infections decreased slowly from 60.0 to 40.3% in schoolchildren and from 70.8 to 60.0% in the older age population. Three parasite species were common: hookworm, Ascaris and Haplorchis, an intestinal trematode. Hookworm presented throughout the whole district. Ascaris infection occurred at high rates in some villages, while in some villages none was found. The villages where Ascaris infection was nil had high rates of Haplorchis infection, and vice versa. Most hookworm and Trichuris infections were of light intensity. Heavy intensity infection was found in 12.8-18.1% of Ascaris cases examined. Parasite infection rates in Chaloem Phra Kiat District can be classified as low prevalence.

Paragonimiasis prevalences in Saraburi Province, Thailand, measured 20 years apart.

Saraburi Province, Central Thailand has been a paragonimiasis-endemic area since 1956. This study compared the prevalences of human paragonimiasis in two villages near Chet Khot Waterfall, Kaeng Khoi District, investigated in 1984-1985 and 2005. The results from the 1980s showed 6.3% and 1% of villagers were positive for Paragonimus eggs in sputum and stool, respectively. In 2005, Paragonimus eggs were not found in feces or sputum. An IgG-ELISA for paragonimiasis was conducted on 33 serum samples collected in the 1980s, 23 collected in 2005 and 25 diagnosed with other parasitic infections. Ninety percent of the samples from the eighties were positive for paragoimiasis, and 43% from 2005 were positive, equivalent to 10.9% and 4.9% of the total population examined in the 1980s and 2005, respectively. Serodiagnosis is currently the best method for detecting paragonimiasis. The positive cases in the 1980s were age 10-60 years and in 2005 were age 34- 67-years-old. The prevalence and intensity of Paragonimus metacercariae in fresh Waterfall crabs collected from Chet Khot Waterfall were significantly lower in the 1980s than in 2005. The prevalence of paragonimiasis in this endemic area has decreased to the level that no egg-producing cases were detected. No infections were found in villagers age < 30 years, despite the high density of metacercariae in the crabs, indicating a change in the habit of eating raw food among the younger people.

In vitro susceptibility and genetic variations for chloroquine and mefloquine in Plasmodium falciparum isolates from Thai-Myanmar border.

In vitro drug susceptibility to chloroquine (CQ) and mefloquine (MF) were assessed in 39 P. falciparum isolates from the Thai-Myanmar border area. To further characterize CQ- and MF-resistance profiles in this area, we also analyzed pfcrt K76T mutation that is critical for CQ resistance, and pfmdr1 polymorphism that has an association with MF resistance. Eighteen isolates were successfully examined by in vitro tests for CQ, and 17 of them had resistance to the drug. Geometric mean concentration of CQ that inhibited the growth of parasites at 50% (IC50) was 371 +/- 227 nM (105-971 nM). Sixteen isolates were successfully examined by in vitro tests for MF, and 8 of them were resistant to the drug. Geometric mean of IC50 for MF was 41 +/- 31 nM (4-125 nM). Genotypes of drug resistance, such as pfcrt and pfmdr1 mutations, were also analyzed. All the 39 isolates had the same haplotype (CVIET) for PfCRT at its 72-76th amino acids. A pfmdr1 Y86 mutation was found in 95% of isolates. A pfmdr1 D1042 mutation was also present in 7 isolates, while no pfmdr1 Y1246 mutation was observed. These results indicated a correlation between CQ resistance and the pfcrt T76 and pfmdr1 Y86 mutations.

The current situation regarding the establishment of national ethical guidelines for biomedical research in Thailand and its neighboring countries.

This study discusses the establishment of ethical guidelines for ethical review for biomedical research performed in Thailand, and to some extent, in neighboring countries. There are differences, from country to country, at national and institutional levels regarding guidelines for ethical review committees. Only a handbook issued by Mahidol University describes guidelines for human genetic research and on research dealing with reproductive technology. Both these areas require special consideration to avoid violating human dignity, rights, and confidentiality. This indicates that further efforts should be made to establish research guidelines and/or principles dealing with the human genome.

The Asian center of international parasite control (ACIPAC): five years of achievement. I. Introduction.

ACIPAC has made an effort to promote the concept of the school-based approach to malaria and STH control, mainly through human resource development, which could be eventually extended to any other health promotion program. Implementation of SSPP resulted in the establishment of national policies on parasite control and/or school health in some partner countries. It also provides a good opportunity for the formulation of partnerships among health and education sectors and international partners, although it did cause some problems concerning the enrollment of persons of authority from partner countries, and the staff of JICA resident offices as well. As described in the Joint Evaluation Report, ACIPAC is expected to further contribute to human resource development and to strengthening human resource and information networking at regional and global levels.

The use of flow cytometry as a diagnostic test for malaria parasites.

A total of 453 clinical blood samples were determined for malaria parasites by flow cytometric assay (FCM) and reagents from Sysmex Corporation, Japan. In this study, the FCM greatly simplified and accelerated parasite detection, with sensitivity of 91.26%, specificity 86.28% and accuracy 87.42%. Overall, the parasite counts by flow cytometric measurement correlated well with the parasitemia measured by microscopic assay (regression coefficient = 0.9409). The detection limit was 0.05-0.1% parasitemia. No evidence of malaria parasites in either blood donor volunteers or other disease patients groups was determined by FCM. However, 48 samples who had been treated with antimalarial drugs and whose parasite microscopic counts were negative, showed false-positive results. When the data of these 48 samples were analyzed, they were found to have high levels of reticulocytes, ranging from 2.0-18.9%. This finding suggested that a high reticulocyte concentration in the blood may interfere with the performance of the FCM. Further improvement, by eliminating this interference, will make the FCM one of the most promising tests for malaria diagnosis.

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.

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.

Role of a mouse monoclonal IgE antibody in passive transfer of immunity to Schistosoma japonicum infection

We have been able to produce a mouse monoclonal IgE antibody specific to an adult worm antigen extracted from Schistosoma japonicum (Sj). The antibody was able to elicit passive cutaneous anaphylaxis in the rat skin against Sj with the highest titer of 1:256,000 but did not cross-react with S. mansoni antigen. The antibody recognized a 97-kDa molecule expressed on the surface of mechanically transformed schistosoma of S. japonicum. Passive transfer of the antibody into mice in the early stage of challenge infection resulted in a partial but significant reduction of recovery of adult worms. Induction of eosinophilia by an oral administration of embryonated eggs of Toxocara canis prior to challenge infection enhanced the reduction.