Laboratory demonstration of the vertical transmission of Rift Valley fever virus by Culex tarsalis mosquitoes

• Published in: PLoS neglected tropical diseases 2021-03, Vol.15 (3), p.e0009273-e0009273
• Main Authors: Bergren, Nicholas A, Borland, Erin M, Hartman, Daniel A, Kading, Rebekah C
• Format: Article
• Language: English
• Subjects: Amphotericin B; Animals; Antigens; Aquatic insects; Beads; Biology and Life Sciences; Blood; Blood meals; Coccidioidomycosis; Culex - virology; Culicidae; Detection; Development and progression; Disease transmission; Experiments; Female; Females; Gentamicin; Glass beads; Health aspects; Humans; Infections; Infectious Disease Transmission, Vertical; Instars; Laboratories; Larvae; Livestock; Male; Meals; Medicine and Health Sciences; Mortality; Mosquito Vectors - classification; Mosquito Vectors - virology; Mosquitoes; Offspring; Ova; Ovary - virology; Penicillin; Progeny; Rift Valley fever; Rift Valley Fever - transmission; Rift Valley fever virus - isolation & purification; Risk factors; Streptomycin; Transmission; Tropical diseases; Tubes; Vector-borne diseases; Viral Load; Virus research; Viruses; Wildlife sanctuaries
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0009273

Rift Valley fever virus (RVFV) is a mosquito-transmitted virus with proven ability to emerge into naïve geographic areas. Limited field evidence suggests that RVFV is transmitted vertically from parent mosquito to offspring, but until now this mechanism has not been confirmed in the laboratory. Furthermore, this transmission mechanism has allowed for the prediction of RVFV epizootics based on rainfall patterns collected from satellite information. However, in spite of the relevance to the initiation of epizootic events, laboratory confirmation of vertical transmission has remained an elusive research aim for thirty-five years. Herein we present preliminary evidence of the vertical transmission of RVFV by Culex tarsalis mosquitoes after oral exposure to RVFV. Progeny from three successive gonotrophic cycles were reared to adults, with infectious RVFV confirmed in each developmental stage. Virus was detected in ovarian tissues of parental mosquitoes 7 days after imbibing an infectious bloodmeal. Infection was confirmed in progeny as early as the first gonotrophic cycle, with infection rates ranging from 2.0-10.0%. Virus titers among progeny were low, which may indicate a host mechanism suppressing replication.