Pupal Survey: An Epidemiologically Significant Surveillance Method for Aedes aegypti: An Example Using Data from Trinidad

This report documents the results of a country-wide pupal survey of Aedes aegypti (L.) conducted in Trinidad. The survey was designed to identify the important Ae. aegypti-producing containers, importance being a function of a container's abundance and its productivity. Results are summarized on a country-wide basis and by county: urban versus rural comparisons are also made. Numerically, the most common water-filled containers positive for the larvae or pupae of Ae. aegypti (foci) were outdoor drums, water storage tanks and buckets, laundry tubs, discarded tires, and small miscellaneous containers such as drink bottles and cans. The island-wide average number of foci per hectare was 287 and ranged between 65 and 499. The average standing crop per container of Ae. aegypti pupae was 9.5 and ranged 12-fold, the most and least productive being the flower pot (> 30) and the small indoor vase ( 90% of all Ae. aegypti pupae: the remaining seven types were responsible for 80% of Ae. aegypti production in the country. In our survey, the traditional Stegomyia indices used to document the density of Ae. aegypti and predict the threat of dengue transmission, the House, Container, and Breteau indices, were seen to have virtually no correspondence with the actual number of pupae per hectare or per person. We conclude that pupal survey is more appropriate for assessing risk and directing control operations.