Honduras : use of cyclopoids for Aedes aegypti control in El Progreso -- October 1990-December 1992

The objective was to evaluate cyclopoid copepods (cyclopoids), which are tiny crustaceans that prey on first and second instar mosquito larvae. The study supplemented conventional methods of Aedes aegypti source reduction in the project. The study began in October 1990 and continued to December 1992. Eighteen species of cyclopoids were collected from aquatic habitats in the El Progreso area and placed in laboratory dishes with first instar Ae. aegypti larvae to see if they killed the larvae. The four largest species (Mesocyclops longisetus, Mesocyclops thermocyclopoides, Mesocyclops venezolanus, and Macrocyclops albidus) killed the most larvae and were selected to be evaluated for Ae. aegypti control. Laboratory colonies of the four species were established to provide animals for laboratory experiments and field trials. Methods were developed for mass production of these animals in small artificial ponds at the laboratory. The capacity of each of the four cyclopoids species to kill first instar Ae. aegypti larvae was evaluated in tires and 55-gallon drums at the laboratory. All four species killed approximately 20 larvae per day. Me. longisetus consistently killed the most larvae. Each of the four cyclopoid species was introduced to laundry tanks (pilas), 55-gallon metal drums, tires, animal drinking containers, cisterns, ornamental pools, and vases at people"s homes and monitored for 30 weeks. Me. thermocyclopoides, Me. venezolanus, and Ma. albidus did not survive in the containers for more than a few months, but Me. longisetus maintained large numbers in all containers as long as it was not dumped out or dried out. Me. longisetus was able to survive in drums and other water storage containers that were cleaned periodically only when the cyclopoid was removed from the container with a net before cleaning and returned afterwards. Me. longisetus was found to be effective for Ae. aegypti control in 55-gallon drums, tires, cement animal drinking containers, cisterns, ornamental pools, and plant vases. As long as Me. longisetus was in these containers, Ae. aegypti production was 98% to 99% less on average than in control containers without cyclopoids. Me. longisetus was selected for introduction to all appropriate containers in a barrio of approximately 160 houses. Distribution of the cyclopoids to the community and introduction to containers was easy, but Me. longisetus lasted only in containers such as cisterns and tires that were never cleaned and therefore required no special effort for maintaining the cyclopoids. Because the project team had many activities in addition to Me. longisetus, it did not devote sufficient attention to instructing people on preventing the loss of Me. longisetus when they cleaned containers such as drums and vases, and Me. longisetus disappeared from those containers within a few months. Newly organized, the barrio lacked the active participation of community volunteers necessary to maintain a comprehensive array of Ae. aegypti control activities. Me. longisetus did not receive much attention from the volunteers, and Me. longisetus usually was not replaced when lost from drums or vases. The Integrated Dengue Control project plans to employ Me. longisetus in other barrios where public motivation, community organization, and active participation by community volunteers are sufficiently developed to ensure that the necessary attention will be devoted to maintaining cyclopoids in containers after introduction. (Author abstract)