Lymphatic Filariasis Positive-Case Follow-up After TAS 2 in Haiti
To identify the sampling strategy for positive case follow-up after TAS 2 and TAS 3 that optimizes the chances of correctly identifying evidence of ongoing transmission, while saving program resources.
- Haiti's Nippes Department passed TAS 1 and TAS 2; however, the number of antigen-positive children identified increased from 2 in TAS 1 to 8 in TAS 2.
- In response, a household survey was conducted in Nippes using both purposive sampling of the 50 households nearest the index case and random sampling of households in the same enumeration area of the index case.
- Overall 29 of 1,936 (1.5%) of participants from 794 households were antigen positive.
- Higher positivity rates were identified in participants >10 years old; however two sampled children <10 years old were antigen-positive, suggesting recent transmission.
- Households selected using random sampling identified a smaller number of cases but a higher positivity rate (n=9, 2.5%) compared to households selected using purposive sampling (n=17, 1.4%).
- Antigen positivity was higher in the commune with four cases (2.4%) than in the other participating communes (0-1.8%) (P=0.002).
- Overall, a substantial number of LF cases were identified through both sampling methods indicating potential ongoing transmission in this area.
- These results demonstrate the need for systematic post-MDA surveillance and policy guidelines for responding to antigen-positive children identified in TAS.