Utility of screening easy-to-access population subgroups (EAG) as a surveillance tool in monitoring interruption of lymphatic filariasis transmission

This study aimed at understanding whether screening pregnant women at antenatal care clinics in Chikwawa and Nsanje districts, Malawi, might be a viable, easy to access population for post-validation surveillance. The study area included 12 health facility catchment areas divided into potential transmission risk zones (based on distance from water sources) in two districts. The team conducted concurrent surveys at 1) a health facility level to screen for LF infection at women's first antenatal clinic visit, and 2) a household survey in the same catchment area of the sampled health facilities. The antenatal clinic screening (ANC) included 1,085 pregnant women from 12 clinics (target sample 1005); high risk zone included five clinics and 291 (26.8%) women; the medium zone included four clinics and 470 (43.3%) women; and the low risk zone included three clinics and 324 (29.9%) women. One woman tested positive by FTS but negative for MF. Two villages near the clinic were sampled in the household survey (though not the village the woman was from). The household survey (HH) included 2,900 individuals from 53 villages (1,048 households) were included in the household survey; high risk zone included five health facilities, 21 villages, and 1,107 (38.2%) individuals; the medium zone included four health facilities, 17 villages, and 1,107 (34.0%) individuals; and the low risk zone included three clinics 15 villages, and 808 (27.9%) individuals. Five individuals were found to be FTS positive, but negative for night blood Mf (Table 3) from high and medium risk zones. The five individuals were men from four health facilities and nearby villages; aged between 12 – 70 years and had lived in the village for more than 10 years. Key findings from this study include: Combined LF antigenemia prevalence was found to be 0.14%, which indicates that the certification of WHO that Malawi has eliminated LF as a public health threat remains true. There was not a difference between the HH and ANC survey performance regarding the capturing of populations of different villages/areas though obviously gender balance was an issue. The study showed that it was feasible, acceptable, and certainly more cost-effective to conduct surveillance at ANCs but that the lack of male participants likely skewed the results of the survey (i.e. may have found more FTS positives) and therefore is not an acceptable easy to access group for PVS.