Anthropophagic Florida mosquito species are poor vectors of prototype and emerging strains of oropouche virus

Abstract

Oropouche virus (OROV) is an emerging vector-borne pathogen in the American tropics that is a significant cause of human disease. Over 100 traveler imported cases of OROV were recorded in the continental USA in 2024 (103 in Florida), elevating the risk of local transmission of OROV should competent insect vectors feed upon viremic humans. The only confirmed natural vector of OROV is Culicoides paraensis (Goeldi), a biting midge species that occurs throughout forested areas of the New World, including the eastern USA, Central America and most of northern South America. Anthropophagic mosquito species, especially Culex quinquefasciatus Say and Aedes aegypti L. have been suspected of transmitting emerging lineages of OROV in areas where C. paraensis had not been reported (Cuba). Recent laboratory studies have shown that emerging strains of OROV replicate to higher titers in human cell lines than ancestral strains, raising the possibility that these strains may also be transmitted by select mosquito species that feed on humans. To assess the potential for anthropophagic mosquitoes in the southern USA to transmit OROV, we evaluated the vector competence (based on viral RNA detection) of lab-adapted Cx. quinquefasciatus and Ae. aegypti, along with an F1 generation of Ae. aegypti from field-collected mosquitoes in Florida, using prototype (TRVL9760, Trinidad 1955) and emerging (240023, Cuba 2024) OROV genotypes across two incubation periods in cell culture (5 and 7 days) and three extrinsic (7, 14, and 21 days) incubation periods. Both mosquito species exhibited moderate susceptibility to infection (24.2-43.2%) and disseminated infection (23.0-57.5%), but low competence to transmit OROV. Transmission was observed in Ae. aegypti (2.5% in the Lower Keys strain and 1.8% in the Orlando strain) and Cx. quinquefasciatus (0.7%). When the two viral genotypes (TRVL9760 vs 240023) were compared at the same incubation conditions (IP/EIP), the emergent genotype did not exceed the prototype in infection, dissemination, or transmission. Our data indicates that these two relatively anthropophagic mosquito species are unlikely to serve as competent vectors of OROV in Florida, attributable to substantial midgut and salivary gland barriers.