Vector competence of Aedes vexans (Meigen), Culex poicilipes (Theobald) and Cx. quinquefasciatus Say from Senegal for West and East African lineages of Rift Valley fever virus

AbstractRift Valley fever virus (RVFV) is a mosquito-borne bunyavirus that is pathogenic to ruminants and humans. The virus is endemic to Africa and the Arabian Peninsula where outbreaks are characterized by abortion storms and mortality of newborns, particularly in sheep herds. Vector competence experiments in laboratory settings have suggested that over 50 mosquito species are capable of transmitting RVFV. Transmission of mosquito-borne viruses in the field is however influenced by numerous factors, including population densities, blood feeding behavior, extrinsic incubation period, longevity of vectors, and viremia levels in vertebrate hosts. Animal models to study these important aspects of RVFV transmission are currently lacking. In the present work, RVFV was transmitted to European (Texel-swifter cross-breed) lambs by laboratory-reared Aedes aegypti mosquitoes that were infected either by membrane feeding on a virus-spiked blood meal or by feeding on lambs that developed viremia after intravenous inoculation of RVFV. Feeding of mosquitoes on viremic lambs resulted in strikingly higher infection rates as compared to membrane feeding. Subsequent transmission of RVFV from lamb to lamb by infected mosquitoes was highly efficient in both models. The animal models described here can be used to study mosquito-mediated transmission of RVFV among the major natural target species and to evaluate the efficacy of vaccines against mosquito-mediated RVFV infection.

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Feeding behavior of Aedes (Aedimorphus) vexans arabiensis, a Rift valley fever virus vector in the Ferlo pastoral ecosystem of Senegal

10.1101/593491 ◽

2019 ◽

Author(s):

Biram Biteye ◽

Assane Gueye Fall ◽

Momar Talla Seck ◽

Mamadou Ciss ◽

Mariame Diop ◽

...

Keyword(s):

Feeding Behavior ◽

Blood Meal ◽

Rift Valley ◽

Rift Valley Fever ◽

Rift Valley Fever Virus ◽

Virus Transmission ◽

Fever Virus ◽

Host Feeding ◽

Aedes Vexans ◽

Valley Fever

AbstractHost-vector contact is a key factor in vectorial capacity assessment and thus the transmission of mosquito-borne viruses such as Rift Valley Fever (RVF), an emerging zoonotic disease of interest in West Africa. The knowledge of the host-feeding patterns of vector species constitutes a key element in the assessment of their epidemiological importance in a given environment. The aim of this work was to identify the blood meal origins of Aedes vexans arabiensis Patton (Diptera: Culicidae), the main vector of RVF virus in the Ferlo pastoral ecosystem of Senegal. Engorged female mosquitoes were collected in Younouféré in the pastoral ecosystem in the Ferlo region during the 2014 rainy season. CDC light CO2-baited traps were set at six sites for two consecutive nights every month from July to November. Domestic animals present around traps were identified and counted for each trapping session. Blood meal sources of engorged mosquitoes were identified using a vertebrate-specific multiplexed primer set based on cytochrome b. Blood meal sources were successfully identified for 319 out of 416 blood-fed females (76.68%), of which 163 (51.1%) were single meals, 146 (45.77%) mixed meals from two different hosts and 10 (3.13%) mixed meals from three different hosts. Aedes vexans arabiensis fed preferentially on mammals especially on horse compared to other hosts (P < 0.001). Proportions of single and mixed meals showed significant temporal (P < 0.001) and spatial variations (P < 0.001) according to hosts availability. Aedes vexans arabiensis shows an opportunistic feeding behavior depending on the host availability. Results were discussed in relation with the Rift valley fever virus transmission and vector involvement as well as its primary hosts.

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