High prevalence of Wuchereria bancrofti infection among Myanmar migrants in Thailand

This study aimed to obtain a more accurate idea of the prevalence of Wuchereria bancrofti infection in the Myanmar migrant population. It compared estimates produced using three methods: 1) microscopical examination for microfilaria (mff) in thick smears of night-blood; 2) detection of the circulating parasite antigen Og4C3 using a commercial enzyme-linked immunosorbent assay (ELISA); and 3) ELISA-based assessment of serum levels of specific anti-filarial immunoglobulin (Ig) G4. The randomly selected subjects include 371 Myanmar migrants aged 2-56 years. All of the mff observed were identified as W. bancrofti. Mff had a prevalence estimate of 8% which is slightly higher to earlier estimates based on the examination of smears. However 38 (10%) of the subjects were seropositive for the Og4C3 antigen and 11 (3%) of the 342 subjects considered amicrofilaremic were antigen- positive. The estimate of prevalence based on the demonstration of anti-filarial IgG4 in the serum was a remarkable 42%. Overall 44% of the subjects had at least one marker of infection: microfilaremia; seropositivity for Og4C3; and/or seropositivity for anti-filarial IgG4. Based on the results it is suggested that there is a need to re-evaluate the national programs for the control and surveillance of lymphatic filariasis in Thailand. Further studies on the cost-effectiveness of each of the available diagnostic tests would provide essential data for those making the decisions about national health-care policies.