Determination of the prevalence of lymphatic filariasis among migrant workers in Kuwait by detecting circulating filarial antigen

The main objective of this study was to determine the prevalence of filarial infection among migrant workers in Kuwait. The study was conducted from April 2000 to November 2003. A total of 1050 migrant workers (> 90 % from the Indian subcontinent) from filarial endemic countries and 260 individuals residing in Kuwait as controls (50 healthy Kuwaiti blood donors, 50 microfilaria-negative individuals from endemic areas and 160 patients with other parasitic infections) were screened for filarial infection. All specimens were tested for microfilaraemia by microscopy of nucleopore-filtered blood (NFB) and detection of circulating filarial antigen (CFA) by an immunochromatographic test (ICT) and the TropBio assay. The overall prevalence of filarial antigenaemia was 18.3% (1192 individuals) using the ICT and 20.3% (213 individuals) using the TropBio assay. Thirty-two cases (3 %) of Wuchereria bancrofti were detected by microscopy and the mean microfilaria count in these cases was 816 microfilariae ml(-1). CFA was detected only in two of the 260 control subjects. Statistical analysis to calculate the sensitivity, specificity and prevalence of infection was carried out using maximum-likelihood statistical methods. The overall sensitivity and specificity of the ICT and TropBio assay to detect CFA were comparable. Compared with NFB microscopy, the sensitivity of the ICT was 93.8% and specificity ranged from 84 to 100%. The sensitivity and specificity of the TropBio assay were 90.1 and 100%, respectively. However, the ICT failed to detect CFA in two cases with a microfilarial load of < 20 microfilariae ml(-1). In conclusion, the prevalence of filarial infection among the migrant workers in Kuwait was 18.3% as determined by the ICT.