Lymphatic filariasis caused by Brugia malayi in an endemic area of Narathiwat Province, southern of Thailand.

Lymphatic filariasis caused by Brugia malayi is highly prevalent in Narathiwat province of Thailand. The World Health Organization has aimed to eliminate the disease globally by the year 2020. To achieve the goal, assessment of the real disease situation should be integrated as part of the control program. The preliminary data for long-term study of the disease situation in this endemic area is necessary for the elimination program of lymphatic filariasis. By using the conventional microscopic method, the microfilarial rate of B. malayi in an endemic area of Narathiwat province was 1.38 per cent. The microfilarial densities ranged from 17 microfilariae/ml to 1,250 microfilariae/ml median = 50. The highest prevalence was found in the age group > 45-60 (4.69%). The lowest microfilarial rate was in the age group < or = 15 (0.37%). The infection in males was about three fold the number in females. A PCR-based method was employed to detect a B. malayi-specific Hha I repetitive DNA sequence with high specificity and sensitivity. The PCR assay will be useful in assisting the elimination program of lymphatic filariasis in control and monitoring the disease in Thailand.

Field trial of the ICT filariasis for diagnosis of Wuchereria bancrofti infections in an endemic population of Thailand.

The ICT Filariasis, a rapid card test format, which is based on qualitative detection by monoclonal antibody of the circulating antigen of Wuchereria bancrofti adult worm, is a new diagnostic test of choice for determining the infections under field conditions. By using clinical and recall techniques and microscopy (thick smear and capillary tube technique) as reference, we assessed the efficiency of the ICT card test in sera from 225 subjects living in W. bancrofti-endemic villages of Tak Province, Thailand, who were recruited during a cross-sectional community survey. The ICT card test gave a 20% antigen positive rate, while other tests gave lower positive rates of the same 5.8% by clinical and recall techniques and thick smear, and 5.3% by capillary tube technique, respectively. The ICT card test had a specificity of 100% when sera from microfilaremic subjects were positive, as when sera from W. bancrofti non-endemic subjects either with Brugia malayi microfilaremia or with other parasites, and those from normal controls were all negative by the test. When done in W. bancrofti microfilaremia sera, the ICT card test had a sensitivity of 100% using a microscopy as reference, and 84.6% when using clinical and recall techniques. However, the ICT card test was more sensitive than the others when done in endemic normal sera (14% positive). Such findings compared well with findings in endemic area of South America, suggested its usefulness to detect W. bancrofti infections in endemic area, especially on the Thai-Myanmar border.