Field Efficacy and Persistence of Mermithid Nematodes for The Biological Control of Mosquito Larvae in Havana, Cuba

Abstract

Mosquito proliferation in natural aquatic habitats remains a public health concern, particularly where environmental impacts and insecticide resistance constrain conventional insecticide-based control. This study assessed the field infectivity and persistence of the mermithid nematodes Romanomermis iyengari and Strelkovimermis spiculatus in natural mosquito-breeding sites in two municipalities of Havana, Cuba. Field applications were conducted in three sites between 2018 and 2022: two ground pools inhabited by Anopheles albimanus and Culex nigripalpus, and one tree hole containing Aedes aegypti and Ae. albopictus. S. spiculatus was applied at a 5:1 parasite-to-larva ratio in the tree hole, whereas applications in ground pools were made with R. iyengari at 3,000 parasitic juveniles/m². Larvae were sampled before and after treatment and dissected to determine the prevalence of parasitism and infection intensity. High parasitism was detected after application, including 100% prevalence in Aedes larvae 72 h after treatment and 72% prevalence six weeks later, indicating persistence following a single application. In the ground pool treated with R. iyengari, the prevalence of parasitism reached 94% at 72 h and remained detectable during subsequent surveys. These findings provide field evidence that both mermithid species can infect mosquito larvae in natural urban breeding sites in Havana. Controlled and replicated field trials are required to quantify their comparative efficacy, persistence, effects on larval abundance, and feasibility for operational integrated mosquito management.