Border and imported bancroftian filariases: Baseline seroprevalence in sentinel populations exposed to infections with Wuchereria bancrofti and concomitant HIV at the start of diethylcarbamazine mass treatment in Thailand

Abstract

Border bancroftian filariasis caused by Wuchereria bancrofti nocturnally subperiodic mainly exists in Karens residing alongside the Thailand-Myanmar border. Imported bancroftian filariasis caused by W. bancrofti nocturnally periodic mainly exists in cross-border Myanmar migrants. We analyzed seroprevalence data based on W. bancrofti adult worm antigen (Ag) loads and human immunodeficiency virus (HIV) immunoglobulins in the sentinel population samples which were studied prior to the start of the diethylcarbamazine (DEC) mass treatment phase in the PELF during fiscal years 2002-2006. In the Karens, the cumulative infection prevalence (36.8% serological antigen positivity or SAP) was specific for age (p<0.001) but universal for gender (p=0.77). The infection intensity (median Ag load=60,827 antigen units or AU/ml) was specific for age (p=0.031) and for males (p=0.016). In the Myanmars, infection prevalence (24.0% SAP) was universal for age (p=0.961) and for gender (p=0.676). The infection intensity (median Ag load=19,068 AU/ml) was universal for age (p=0.433) but specific for females (p=0.027). Overall, the Ag loads between the groups were significantly different (p=0.014). In analysis of concomitant HIV and W. bancrofti infections, 7 (3.2%) Myanmars infected with HIV 1 and 3 (5.7%) with concomitant infections, subjected to biannual DEC treatment with 300 mg oral-dose FILADEC, were prevalent. The antigenemia clearance in the concomitant infections (r=-0.732, p=0.039) as well as in the single W. bancrofti infection (r=-0.781, P=0.022) was correlated with time required to clear antigenemias. We reemphasize that W. bancrofti adult worm Ag loads in the sentinel population samples would be beneficial for the PELF's implementers at the provincial level to probe the disease burdens in target areas and to evaluate and monitor the DEC treatment efficacy and effectiveness in those sentinel populations, including those with concomitant HIV eligible for the DEC mass treatment phase in the PELF.