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.

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.

Prevalence of parasitic infections among Thai patients at the King Chulalongkorn Memorial Hospital, Bangkok, Thailand.

Parasitic diseases are still considered to be a major public health problem. Most patients with parasitic infections are asymptomatic and therefore remain undetected. Asymptomatic parasitic infections are usually discovered by routine parasite examination. To determine the result of parasite examination at the Parasitology Unit, Out Patient Department, King Chulalongkorn Memorial Hospital, Bangkok, Thailand, the authors collected the data of individuals examined for parasite infections from June to December 1997. A total of 6,231 Thais provided the data for analysis. Evidence of parasitic infections was found in 557 (8.94%) cases. The disease was most prevalent in males (57.3%), and in the age group >15-30 years old (11.13%). The population from the Northeast of Thailand was found to harbor parasites with the highest prevalence rate (17.03%), while it was 11.90 per cent in the northern group. The parasitic prevalence rates in the West, East, South and Central regions were 10.60 per cent, 8.90 per cent, 7.74 per cent, and 4.92 per cent, respectively. The parasite most commonly identified was Strongyloides stercoralis (33.39%), while giardiasis was the most common protozoan infection (14.36%). The highest infection rates of S. stercoralis, hookworms, Opisthorchis viverrini, and Gnathostoma spinigerum were found in northeasterners. People from the North of Thailand were infected mostly with G. lamblia. People of working-age from northeastern as well as northern regions harbored pathogenic parasites with high prevalence rates. To prevent parasitic infections, health education for these high risk groups should be provided.