Cell fusing agent virus (Flavivirus) infection in Aedes aegypti in Texas: seasonality, comparison by trap type, and individual viral loads

Abstract

South Texas has experienced local transmission of Zika virus and of other mosquito-borne viruses such as chikungunya virus and dengue virus in the last decades. Using a mosquito surveillance program in the Lower Rio Grande Valley (LRGV) and San Antonio, TX, from 2016 to 2018, we detected the presence of an insect-specific virus, cell fusing agent virus (CFAV), in the Aedes aegypti mosquito population. We tested 6,326 females and 1,249 males from the LRGV and 659 females from San Antonio for CFAV by RT-PCR using specific primers. Infection rates varied from 0 to 261 per 1,000 mosquitoes in the LRGV and 115 to 208 per 1,000 in San Antonio depending on the month of collection. Infection rates per 1,000 individuals appeared higher in females collected from BG Sentinel 2 traps compared to Autocidal Gravid Ovitraps, but the ratio of the percentage of infected pools did not differ by trap type. The natural viral load in individual males ranged from 1.25 x 10² to 5.50 x 10⁶ RNA copies and in unfed females from 5.42 x 10³ to 8.70 x 10⁶ RNA copies. Gravid females were found to harbor fewer viral particles than males and unfed females.

Fig. 1

Study area and study sites for the collection of Ae. aegypti mosquitoes in the Lower Rio Grande Valley and San Antonio using AGO and BGS2 traps in 2017 to 2018. The map was made using QGIS 3.4.4 (https://qgis.org/en/site/). Map data: Google Maps, and with publicly available administrative boundaries (https://gadm.org/license.html)

Fig. 2

CFAV infection rates (IRs) per month of study in Ae. aegypti females from the LRGV collected using AGO traps in 2017 to 2018. The data points indicate the average CFAV IR per 1000 values observed, and the bars indicate the full range of CFAV IR per 1000 values observed

Fig. 3

Comparison of infection rates (IRs) in Ae. aegypti from the LRGV collected in BGS2 and AGO traps in 2018. The data points indicate the average CFAV IR per 1000 values observed, and the bars indicate the full range of CFAV IR per 1000 values observed

Fig. 4

Comparison of infection rates (IRs) in male and female Ae. aegypti of different physiological stages captured in BGS2 traps in 2018. The data points indicate the average CFAV IR per 1000 values observed, and the bars indicate the full range of CFAV IR per 1000 values observed

Fig. 5

Median with 95% CI of the CFAV load in individual male and female Ae. aegypti of different physiological stages captured in BGS2 traps in 2018