Comparative Study of DNA Extraction Methods for the PCR Detection of Intestinal Parasites in Human Stool Samples.

Stool samples typically contain PCR inhibitors; however, helminths are difficult to lyse and can cause false-negative PCR results. We assessed the effective methods for extracting DNA from different kinds of intestinal parasites. We compared the most common DNA extraction methods from stool samples, including the phenol-chloroform technique with or without a bead-beating step (P and PB), a QIAamp Fast DNA Stool Mini Kit (Q), and a QIAamp PowerFecal Pro DNA Kit (QB). Genomic DNA was extracted from 85 stool samples collected from patients infected with Blastocystis sp., Ascaris lumbricoides, Trichuris trichiura, hookworm, and Strongyloides stercoralis. DNA quantity and DNA quality were evaluated via spectrophotometry, and DNA integrity was assessed by PCR. We found that P and PB provided higher DNA yields (~4 times) than when using Q and QB. However, P showed the lowest detection rate of PCR (8.2%), wherein only S. stercoralis (7 out of 20 samples) was detected. QB showed the highest detection rate of PCR (61.2%). After plasmid spikes, only 5 samples by QB were negative while 60 samples by P were still negative. Remarkably, QB could extract DNA from all the groups of parasites that we tested. These results indicate that QB is the most effective DNA extraction method for the diagnosis and monitoring of intestinal parasites via PCR.

Bacillus thuringiensis Cry5B is Active against Strongyloides stercoralis in vitro.

Strongyloidiasis, caused by Strongyloides stercoralis infection, is an important neglected tropical disease that causes significant public health problems in the tropics and subtropics. The disease can persist in hosts for decades and may be life-threatening because of hyperinfection and dissemination. Ivermectin (mostly) and albendazole are the most common anthelmintics used for treatment. Albendazole is suboptimal for this parasite, and although ivermectin is quite effective in immunocompromised patients, a multiple-course regimen is required. Furthermore, reliance on a single drug class for treating intestinal nematodes is a recipe for future failure. Therefore, it is important to discover new anthelmintics to treat or prevent human strongyloidiasis. One promising candidate is the Bacillus thuringiensis crystal protein Cry5B. Cry5B is highly potent against parasitic nematodes, for example, hookworms and Ascaris suum. Here, we investigated the potential of Cry5B against S. stercoralis. Multiple stages of S. stercoralis, including the first larval stage (L1s), infective stage (iL3s), free-living adult stage, and parasitic female stage, were all susceptible to Cry5B as indicated by impairment of motility and decreased viability in vitro. In summary, Cry5B demonstrated strong potential as an effective anthelmintic for treatment and transmission control of human strongyloidiasis, justifying further experiments to investigate in vivo therapeutic efficacy.

Development of Conventional Multiplex PCR: A Rapid Technique for Simultaneous Detection of Soil-Transmitted Helminths.

Soil-transmitted helminths (STHs) are the most common intestinal parasites infecting humans worldwide. STH infections are a major cause of morbidity and disability. Accurate diagnostic tools are pivotal for assessing the exact prevalence of parasitic infections. Microscopic examination and culture techniques have been used to observe the presence of eggs or larvae of parasites in stool samples, but they are time-consuming and have low sensitivity. Therefore, accurate, simple, and inexpensive diagnostic techniques are still required for simultaneous detection of STH infections. Although molecular-based techniques, such as real-time PCR and multiplex real-time PCR, have been developed, they are not suitable for routine diagnosis due to the requirement for expensive reagents and instruments. In this study, we established a conventional multiplex PCR for simultaneous rapid detection of Ascaris lumbricoides, Necator americanus, and Strongyloides stercoralis in stool samples. Our results show that the multiplex PCR could detect the DNA of STHs at a very low target gene concentrations (lower than 1 pg) with no cross-amplification. Multiplex PCR had five times higher sensitivity than the formalin-ethyl acetate concentration technique (FECT) in the detection of multiple infections, and two times higher for detection of S. stercoralis. However, multiplex PCR was comparable to FECT in the detection of A. lumbricoides and N. americanus. In conclusion, this method could be used as an alternative method for the detection of STHs, especially for S. stercoralis.

The Genetic Polymorphisms of 24 Base Pair Duplication and Point G102S of Human Chitotriosidase to Bancroftian Filariasis at the Thai⁻Myanmar Border.

Lymphatic filariasis, caused by lymphatic filarial parasites, Wuchereria bancrofti, and Brugia malayi, causes significant morbidity and disability to 120 million people in the tropics and subtropics. Chitin has an important role for embryogenesis in adult worms and is a component of microfilaria sheath. Human chitotriosidase (CHIT1) is a chitin-degrading enzyme which provides a protective role against chitin-containing pathogens. Here, we determined the association of CHIT1 polymorphisms with susceptibility to bancroftian filariasis (BF) in 88 individuals at the Thai⁻Myanmar border. Two common polymorphisms of CHIT1, contributing inactive CHIT protein, including 24 base pair (24 bp) duplication in exon 10, and p. G102S in exon 4 were genotyped by allele-specific Polymerase Chain Reaction (PCR) and PCR sequencing, respectively. Unexpectedly, genotype frequencies of 24 bp duplication insertion homozygous (INS/INS) were significantly higher in endemic normal (EN) (40.0%) than BF patients (31.4%). In contrast, genotype frequencies of p. G102S homozygous (A/A) in BF patients (21.6%) was higher than in EN (19.0%) without statistical difference. Mutant allele frequencies of 24 bp duplication were 0.6125 (98/160) and p. G102S were 0.392 (69/176). Genotype and allele frequencies of CHIT1, 24 bp duplication, and p. G102S, showed no association with BF patients.

A Simple Genotyping Method for Rapid Differentiation of Blastocystis Subtypes and Subtype Distribution of Blastocystis spp. in Thailand.

Blastocystis spp. is one of the most common protozoa of humans and animals worldwide. The genetic diversity of Blastocystis spp. might be associated with a wide range of symptoms. However, the prevalence of each subtype is different in each country. Until now, there is no standard method for subtyping of Blastocystis spp. We developed a sequential restriction fragment length polymorphism (RFLP) analysis for the rapid differentiation of human Blastocystis subtypes. A large-scale study was also conducted to determine the subtype distribution of Blastocystis spp. in Thailand. Stool samples were collected from 1025 school-age students in four regions of Thailand. Blastocystis infections were identified by direct smear, formalin ethyl-acetate concentration technique (FECT), Boeck and Drbohlav's Locke-Egg-Serum (LES) medium culture, and polymerase chain reaction (PCR) of small-subunit ribosomal DNA (SSU rDNA). Subtypes of Blastocystis spp. were determined by RFLP. Phylogenetic tree of partial SSU rDNA sequences of Blastocystis spp. was constructed using the Maximum Likelihood (ML) method. Out of 1025 students, 416 (40.6%) were positive for Blastocystis spp. Using two steps of RFLP reactions, we could determine subtype one⁻three among these students. Subtype 3 was the most common subtype (58.72%) in Thai students, followed by subtype 1 (31.2%), and subtype 2 (10.1%). Blastocystis subtype 3 was the most prevalent in all regions of Thailand. The subtype distribution of Blastocystis spp. in Thailand was different from other countries.

The Experimental Infections of the Human Isolate of Strongyloides Stercoralis in a Rodent Model (The Mongolian Gerbil, Meriones Unguiculatus).

Strongyloidiasis is life-threatening disease which is mainly caused by Strongyloides stercoralis infection. Autoinfection of the parasite results in long-lasting infection and fatal conditions, hyperinfection and dissemination (primarily in immunosuppressed hosts). However, mechanisms of autoinfection and biology remain largely unknown. Rodent models including mice and rats are not susceptible to the human isolate of S. stercoralis. Variations in susceptibility of the human isolate of S. stercoralis are found in dogs. S. ratti and S. venezuelensis infections in rats are an alternative model without the ability to cause autoinfection. The absence of appropriate model for the human isolate of strongyloidiasis hampers a better understanding of human strongyloidiasis. We demonstrated the maintenance of the human isolate of the S. stercoralis life cycle in the Mongolian gerbil (Meriones unguiculatus). The human isolate of S. stercoralis caused a patent infection in immunosuppressed gerbils, more than 18 months. The mean number of recovery adult parasitic worms were 120 ± 23 (1.2% of the initial dose) and L1s were 12,500 ± 7,500 after day 28 post-inoculation (p.i.). The prepatent period was 9⁻14 days. Mild diarrhoea was found in gerbils carrying a high number of adult parasitic worms. Our findings provided a promising model for studying biology and searching new alternative drugs against the parasites. Further studies about the hyperinfection and dissemination would be performed.

A Cross-Sectional Study on Intestinal Parasitic Infections in Children in Suburban Public Primary Schools, Saraburi, the Central Region of Thailand.

Intestinal parasitic infection rate among school-aged children in Thailand has been decreasing. However, certain intestinal parasites remain problematic in some regions. This cross-sectional study was conducted between February and September 2016 in three suburban government primary schools (KK, BR, and HK), Saraburi, Thailand. Stool was collected from 263 asymptomatic subjects (4-15 years old), using simple direct smear, formalin-ether concentration, Boeck and Drbohlav's Locke-Egg-Serum (LES) medium culture, and agar plate culture. A self-administered questionnaire was used to collect data about lifestyle and socioeconomic status. The overall rate of intestinal parasites was 22.1% (15.6% single infection and 6.5% multiple infections). The helminths involving the digestive system found were Strongyloides stercoralis (1.5%) and Opisthorchis viverrini (0.4%). For protozoan infection, the major cause was Blastocystis hominis (17.5%). The other protozoa included Endolimax nana (4.6%), Entamoeba coli (3.4%), Entamoeba histolytica/Entamoeba dispar (1.1%), and Giardia intestinalis (0.8%). The sensitivity for the detection of B. hominis increased with the LES culture technique. The infection rate of each organism was not significantly different among the three schools except for B. hominis which showed the highest prevalence in the HK school (P = 0.001). This was correlated with the questionnaire results in which the HK school showed the highest risk of drinking contaminated water (P = 0.004). The present study emphasized the persistent problems of protozoan infections among suburban school-aged children. Lifestyle was still an important factor for intestinal parasitic infections among suburban school-aged Thai children in this study. Health education as well as routine surveillance was necessary to control the infections.

PREVALENCE OF INTESTINAL PROTOZOAN INFECTIONS AMONG CHILDREN IN THAILAND: A LARGE-SCALE SCREENING AND COMPARATIVE STUDY OF THREE STANDARD DETECTION METHODS.

A significant impact of intestinal parasitic infections on public health has mostly been neglected. Parasitic infections are one of risk factors for malnutrition in children. In this study, a large-scale screening of intestinal parasitic infections among children in 16 schools in 6 regions of Thailand was performed. In addition, we compared sensitivity of methods currently employed for detection of intestinal parasitic infection. Fecal samples collected from 1,909 students were examined for intestinal parasites by simple smear, formalin-ethyl acetate concentration (FECT), and Locke-egg-serum (LES) medium culture methods. Seven hundred and thirteen samples were infected with at least one intestinal parasite. The highest prevalence (82.8%) was found in Kanchanaburi Province, western Thailand. Blastocystis spp was the most common (32.8%) parasite, followed by Giardia duodenalis (4.2%), Ascaris lumbricoides (3.6%), hookworms (1.6%), Entamoeba histolytica (0.7%), Trichuris trichiura (0.5%), Enterobius vermicularis (0.5%), Strongyloides stercoralis (0.4%), minute intestinal flukes (0.2%), and Taenia spp (0.1%). Mixed parasitic infections were found in 121 students. In a comparative study, we found that FECT was more sensitive (74.0%) than simple smear (55.0%) method for detecting helminths. However, sensitivity of these two methods is not significantly different for protozoan detection (31.2% by simple smear and 33.5% by FECT). LES culture technique was the most sensitive method (77.5%) for detecting Blastocystis spp. Our results indicate a high prevalence of intestinal parasite infection among Thai students. More sensitive methods should be developed for a large-scale screening of intestinal protozoan infection.

Molecular survey of the head louse Pediculus humanus capitis in Thailand and its potential role for transmitting Acinetobacter spp.

BACKGROUND: Head louse infestation, which is caused by Pediculus humanus capitis, occurs throughout the world. With the advent of molecular techniques, head lice have been classified into three clades. Recent reports have demonstrated that pathogenic organisms could be found in head lice. Head lice and their pathogenic bacteria in Thailand have never been investigated. In this study, we determined the genetic diversity of head lice collected from various areas of Thailand and demonstrated the presence of Acinetobacter spp. in head lice. METHODS: Total DNA was extracted from 275 head louse samples that were collected from several geographic regions of Thailand. PCR was used to amplify the head louse COI gene and for detection of Bartonella spp. and Acinetobacter spp. The amplified PCR amplicons were cloned and sequenced. The DNA sequences were analyzed via the neighbor-joining method using Kimura's 2-parameter model. RESULTS: The phylogenetic tree based on the COI gene revealed that head lice in Thailand are clearly classified into two clades (A and C). Bartonella spp. was not detected in all the samples, whereas Acinetobacter spp. was detected in 10 samples (3.62%), which consisted of A. baumannii (1.45%), A. radioresistens (1.45%), and A. schindleri (0.72%). The relationship of Acinetobacter spp. and the head lice clades showed that Acinetobacter spp. was found in clade A and C. CONCLUSIONS: Head lice in Thailand are classified into clade A and B based on the COI gene sequences. Pathogenic Acinetobacter spp. was detected in both clades. The data obtained from the study might assist in the development of effective strategies for head lice control in the future. Detection of pathogenic bacteria in head lice could raise awareness of head lice as a source of nosocomial bacterial infections.

Detection of Leishmania siamensis DNA in saliva by polymerase chain reaction.

Polymerase chain reaction was used to detect Leishmania siamensis DNA from clinical samples collected from six leishmaniasis patients during 2011-2012. The samples used in this study came from bone marrow, blood, buffy coat, saliva, urine, and tissue biopsy specimens. Saliva was a good source for L. siamensis DNA by polymerase chain reaction. L. siamensis DNA was also found in saliva of an asymptomatic case-patient. Levels of L. siamensis DNA in saliva decreased until being undetectable after treatment. These levels could be used as a marker to evaluate efficacy of the treatment. A larger study is needed to evaluate this method as a screening and survey tool to study the silent background of Leishmania infection among the at-risk population.

Quiescent innate response to infective filariae by human Langerhans cells suggests a strategy of immune evasion.

Filarial infection is initiated by mosquito-derived third-stage larvae (L3) deposited on the skin that transit through the epidermis, which contains Langerhans cells (LC) and keratinocytes (KC), among other cells. This earliest interaction between L3 and the LC likely conditions the priming of the immune system to the parasite. To determine the nature of this interaction, human LC (langerin(+) E-cadherin(+) CD1a(+)) were generated in vitro and exposed to live L3. LC exposed to live L3 for 48 h showed no alterations in the cell surface markers CD14, CD86, CD83, CD207, E-cadherin, CD80, CD40, and HLA-DR or in mRNA expression of inflammation-associated genes, such as those for interleukin 18 (IL-18), IL-18BP, and caspase 1. In contrast to L3, live tachyzoites of Toxoplasma gondii, an intracellular parasite, induced production of CXCL9, IP-10, and IL-6 in LC. Furthermore, preexposure of LC to L3 did not alter Toll-like receptor 3 (TLR3)- or TLR4-mediated expression of the proinflammatory cytokines IL-1ß, gamma interferon (IFN-γ), IL-6, or IL-10. Interestingly, cocultures of KC and LC produced significantly more IL-18, IL-1α, and IL-8 than did cultures of LC alone, although exposure of the cocultures to live L3 did not result in altered cytokine production. Microarray examination of ex vivo LC from skin blisters that were exposed to live L3 also showed few significant changes in gene expression compared with unexposed blisters, further underscoring the relatively muted response of LC to L3. Our data suggest that failure by LC to initiate an inflammatory response to the invasive stage of filarial parasites may be a strategy for immune evasion by the filarial parasite.

Functional and phenotypic characteristics of alternative activation induced in human monocytes by interleukin-4 or the parasitic nematode Brugia malayi.

Human monocytes from patients with patent filarial infections are studded with filarial antigen and express markers associated with alternative activation of macrophages (MΦ). To explore the role of filaria-derived parasite antigen in differentiation of human monocytes, cells were exposed to microfilariae (mf) of Brugia malayi, and their phenotypic and functional characteristics were compared with those of monocytes exposed to factors known to generate either alternatively (interleukin-4 [IL-4]) or classically (macrophage colony-stimulating factor [MCSF]) activated MΦ. IL-4 upregulated mRNA expression of CCL13, CCL15, CCL17, CCL18, CCL22, CLEC10A, MRC1, CADH1, CD274, and CD273 associated with alternative activation of MΦ but not arginase 1. IL-4-cultured monocytes had a diminished ability to promote proliferation of both CD4(+) and CD8(+) T cells compared to that of unexposed monocytes. Similar to results with IL-4, exposure of monocytes to live mf induced upregulation of CCL15, CCL17, CCL18, CCL22, CD274, and CD273 and downregulation of Toll-like receptor 3 (TLR3), TLR5, and TLR7. In contrast to results with MCSF-cultured monocytes, exposure of monocytes to mf resulted in significant inhibition of the phagocytic ability of these cells to the same degree as that seen with IL-4. Our data suggest that short exposure of human monocytes to IL-4 induces a phenotypic characteristic of alternative activation and that secreted filarial products skew monocytes similarly.

A single dose of doxycycline in combination with diethylcarbamazine for treatment of bancroftian filariasis.

Standard treatment of lymphatic filariasis with diethylcarbamazine (DEC) is associated with systemic adverse reactions, thought to be due to the release of microfilariae material and Wolbachia endosymbiotic bacteria into the blood. Combination treatments with doxycycline for 3-8 weeks are more effective than standard treatment. However, long-term use of antibiotics may contribute to drug resistance and are not practical for use in remote areas. We assessed whether a single dose of doxycycline combined with the standard DEC regimen would reduce the incidence and severity of adverse reactions and increase the efficacy of standard treatment. Forty-four subjects from Tak Province were recruited into the randomized double-blind clinical trial study: 25 received DEC (300 mg) combined with a placebo, and 19 received DEC (300 mg) combined with doxycycline (200 mg). The incidences of adverse reactions to standard treatment were lower in the doxycycline group (45.5%) than in the placebo group (58.8%). Severe reactions occurred only in the placebo group (3 of 25 subjects). The severity of adverse reactions was significantly lower in the doxycycline group (mean score 0.45) than in the placebo group (mean score 1.17). The levels of IL-6 and Wolbachia DNA in the plasma were significantly lower in the doxycycline group. The filarial antigen levels were significantly lower in the doxycycline group at months 6 after treatment.

Association between Toll-like receptor 2 (TLR2) polymorphisms and asymptomatic bancroftian filariasis.

Lymphatic filariasis is mainly caused by the filarial nematodes Wuchereria bancrofti and Brugia malayi. Wolbachia, intracellular symbiotic bacteria in filarial parasite, is known to induce immune response predominantly through Toll-like receptor 2 (TLR2). This study was performed to investigate the association between polymorphisms of the TLR2 gene and susceptibility to asymptomatic bancroftian filariasis. A total of 142 unrelated asymptomatic bancroftian filariasis patients and 151 endemic normal controls in Tak province, Thailand were recruited into this study. The -196 to -173 deletion (del) polymorphism in the 5' untranslated region was investigated by allele-specific polymerase chain reaction. Two single nucleotide polymorphisms, +597 T>C and +1350 T>C, in exon 3 were identified by polymerase chain reaction-restriction fragment length polymorphism analysis. Furthermore, we analyzed the functional difference between the TLR2 -196 to -173 del and wild-type (wt) alleles using the luciferase reporter assay. All three polymorphisms were associated with a higher risk of asymptomatic bancroftian filariasis and were in strong linkage disequilibrium with each other. The TLR2 haplotype -196 to -173del/+597C/+1350C was strongly associated with an increased risk of asymptomatic bancroftian filariasis. The TLR2 -196 to -173 del allele had a significantly lower transcriptional activity than wt allele. The results of our study indicate that TLR2 -196 to -173 del, +597 T>C and +1350 T>C polymorphisms are associated with asymptomatic bancroftian filariasis in Thailand. Our functional study also supports this finding with respect to differential TLR2 gene expression by -196 to -173 del polymorphism.

Screening for intestinal parasitic infections among Myanmar migrant workers in Thai food industry: a high-risk transmission.

The impact of intestinal parasitic infections on public health has been neglected. Millions of Myanmar natives have migrated to work in Thailand. We performed a study of intestinal parasitic infections in Myanmar-migrants working in the Thai food industry. A total of 338 Myanmar migrant workers in a food plant at Samut Sakhon Province, Thailand, were recruited for this study. 284 (84%) returned requested stool samples. Samples were examined for intestinal parasites by means of simple smear, formalin-ether concentration, Locke-Egg-Serum medium, and Harada-Mori culture methods. We found parasites in 177 (62.3%) migrants (29 of 46 males; 148 of 238 females). The majority (89.3%) were infected with parasites transmitted by fecal-oral route, including Blastocystis hominis (41.5%), Trichuris trichiura (22.2%), Giardia lamblia (14.1%), and Ascaris lumbricoides (1.8%). Mixed infections were common (40.7%). The highest prevalence (73.3%) was found among migrants from Kohsong city, Myanmar. This high parasite infection rate in Myanmar migrant workers is an obvious public health hazard.

Computer-assisted instruction in parasitology: a cross-over design.

We report here the results of the study using CAI compared to the hard copy for study of lessons in parasitology. We evaluated the CAI compared to hard copy lessons in 60 students, attending the third-year parasitology course at Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. The students were randomly divided into two groups (30 each). The lessons tested were Ascaris lumbricoides and Enterobius vermicularis, which were prepared as CAI and hard copy form. Using a cross-over design, the first group was provided CAI form on the topic of A. lumbricoides, then switched to hard copy form on the topic of E. vermicularis. The second group was provided hard copy form on the topic of A. lumbricoides, then switched to CAI form on the topic of E. vermicularis. After 30 minute reading, the 10-multiple choice question test was provided for each topic. There was no significant difference of the scores between 2 groups. The most students (91.67%) had more satisfaction when using CAI compared to hard copy in terms of easy to use, convenient to use, less time consuming, more understandable, more attractive to read, and less stress for study. There were 32.8% students complaining that reading hard copy was boring. Other comments were stress when reading (2%), more difficult (17.2%) and more time needed to search specific information (17.2%), and wasting papers (17.2%). However 58.6% still complained problems when using CAL. About 25% had physical discomfort (e.g. Headache, eye pain), and 25% had difficulty to access to use CAI (e.g. no computers available, problems with computer or network error). We suggested that instructors should create and improve CAI lessons in biomedical sciences both in quantity and quality (e.g. content with details, pictures, narrations).

Study of specific IgG subclass antibodies for diagnosis of Gnathostoma spinigerum.

Gnathostoma spinigerum infection is endemic in Thailand and many Asian countries. Current diagnosis is the skin test and enzyme-linked immunosorbent assay (ELISA) for IgG antibody against the G. spinigerum third-stage larvae (L3), but cross-reactivity is common. We evaluated the sensitivity and specificity of anti-G. spinigerum L3 IgG subclass antibodies for diagnosis of 43 patients with gnathostomiasis. The majority of patients with gnathostomiasis (91%) had eosinophilia. While the anti-G. spinigerum L3 IgG1 antibody provided the highest sensitivity (98%), the anti-G. spinigerum L3 IgG2 antibody had the highest specificity (88%). The ELISA that detected anti-G. spinigerum L3 IgG1 antibody could be a reliable laboratory screening test, while anti-G. spinigerum L3 IgG2 antibody could be used to confirm the diagnosis.

Prevalence of bancroftian filariasis on the Thai-Myanmar border.

To achieve the goal of eliminating lymphatic filariasis by the year 2020, close monitoring systems and effective control strategies need to be implemented and the real disease burden needs to be assessed. Bancroftian filariasis is endemic at the Thai-Myanmar border. However, there are only limited data on the prevalence of this disease in Thailand available. We employed microscopic examination, together with ELISA kits to detect W. bancrofti-specific Og4C3 circulating antigen and specific anti-filarial IgG4 antibodies to determine the burden of bancroftian filariasis in an endemic area at the Thai-Myanmar border in Umphang District, Tak province, Thailand. A total of 433 Thai-Karen blood samples were analyzed. The microfilarial rate determined by microscope was 6% and the W. bancrofti-specific Og4C3 antigenemia rate was 22%, while the specific anti-filarial IgG4 antibody rate was 54%. There were statistically significant higher levels of W. bancrofti-specific Og4C3 antigen in the microfilaremic-antigenemic group than in the amicrofilaremic-antigenemic group (unpaired Student's t-test; p < 0.001), similar to the specific anti-filarial IgG4 antibody results (unpaired Student's t-test; p < 0.001). A statistically significant correlation of moderate degree between the presence of W. bancrofti-specific Og4C3 antigen and of specific anti-filarial IgG4 antibody was found in the amicrofilaremic group (r = 0.474, p < 0.001), but not in the microfilaremic group (r = 0.291, p > 0.05). Our study revealed a very high prevalence of bancroftian filariasis in this endemic area and thus emphasized the importance of using highly sensitive and specific diagnostic tools to evaluate the true prevalence of the disease.

Comparative assessment of an Og4C3 ELISA and an ICT filariasis test: a study of Myanmar migrants in Thailand.

Detection of circulating filarial antigen has now emerged as an alternative method for the diagnosis of bancroftian filariasis. We compared two antigen detection assays, an Og4C3 ELISA and an ICT (immunochromatography) Filariasis test, for the diagnosis of Wuchereria bancrofti infections in migrant Myanmar workers in Tak province, Western Thailand. A total of 337 Myanmars participated in this study. The microfilarial rate was 3.3%. The Og4C3 ELISA could detect 19.1% of bancroftian filariasis while the ICT test detected 12.7%. Both antigen assays could detect all microfilaremics. The Og4C3 ELISA detected 14.8% of amicrofilaremics while the ICT test identified 8.1%. Those who were positive for the ICT test were also positive by the Og4C3 ELISA. Those Og4C3 positive cases, that were ICT negative (ICT-ve/Og4C3+ve) had statistically significant (p < 0.05, unpaired t-test) lower Og4C3 antigen levels (409.5 units, range 117-2,389) than those that were ICT positive (ICT+ve/Og4C3+ve) (5,252.0 units, range 130-28,062). Our results emphasize the problem of bancroftian filariasis in Myanmar migrants working in Thailand. Close monitoring and control of this disease in Myanmar migrants are of public health importance. Antigen detection systems are promising tools for the surveillance of bancroftian filariasis.