Mosquito vectors of the 1998–1999 outbreak of Rift Valley Fever and other arboviruses (Bagaza, Sanar, Wesselsbron and West Nile) in Mauritania and Senegal

Abstract

Following an outbreak of Rift Valley fever (RVF) in south-eastern Mauritania during 1998, entomological investigations were conducted for 2 years in the affected parts of Senegal and Mauritania, spanning the Sénégal River basin. A total of 92 787 mosquitoes (Diptera: Culicidae), belonging to 10 genera and 41 species, were captured in light traps. In Senegal, Culex poicilipes (41%) and Mansonia uniformis (39%) were the most abundant species caught, whereas Aedes vexans (77%) and Cx. poicilipes (15%) predominated in Mauritania. RVF virus was isolated from 63 pools of Cx. poicilipes: 36 from Senegal in 1998 and 27 from Mauritania in 1999. These results are the first field evidence of Cx. poicilipes naturally infected with RVFV, and the first isolations of this virus from mosquitoes in Mauritania - the main West African epidemic and epizootic area. Additional arbovirus isolates comprised 25 strains of Bagaza (BAG) from Aedes fowleri, Culex neavei and Cx. poicilipes; 67 Sanar (ArD 66707) from Cx. poicilipes; 51 Wesselsbron (WSL) from Ae. vexans and 30 strains of West Nile (WN) from Ma. uniformis, showing differential specific virus-vector associations in the circulation activity of these five arboviruses.

Vector Competence of Culex neavei and Culex quinquefasciatus (Diptera: Culicidae) from Senegal for Lineages 1, 2, Koutango and a Putative New Lineage of West Nile Virus

“…41 Indeed, numerous mosquitoes have been found naturally infected by WN virus in Africa, particularly in Senegal, mostly belonging to the genus Culex spp. 16,40,42 Among them, the Cx. neavei group, Culex poicilipes, and Culex antennatus were considered as the main potential vectors for WN virus transmission in Senegal regarding their bionomic and their regular infection during the virus amplification.…”

Mapping of zones potentially occupied by Aedes vexans and Culex poicilipes mosquitoes, the main vectors of Rift Valley fever in Senegal

“…With a rapidly increasing and migrating population and seasonal livestock movements, new epidemics occur in new areas. For example, with the appearance of the virus-carrying vectors Aedes (Aedimorphus) vexans Meigen and Culex poicilipes Theobald (Diptera: Culicidae) (Fontenille et al, 1998;Chevalier et al, 2005;Diallo et al, 2005), the Ferlo region south of the Senegal River became quite rapidly a RVF-prone area during the late 1980s. As already shown by Ndione et al (2003) and Lacaux et al (2007), discrete and intense rainfall events (such as squall-lines with 20 mm of rainfall and more) appear to be the confounding parameter for RVF mosquito abundance (Mondet et al, 2005a,b).…”

Virus isolations and high population density implicate Culex antennatus (Becker) (Diptera: Culicidae) as a vector of Rift Valley Fever virus during an outbreak in the Nile Delta of Egypt

“…The viral agent causing the disease is a single stranded RNA virus of the genus Phlebovirus, in the family Bunyaviridae. Periodic RVF outbreaks in livestock (goats, sheep, cattle, and camels) and acute febrile illness with hemorrhagic syndrome in humans have been reported widely throughout south and central Africa, from Kenya westward into Nigeria, Niger, Burkina Faso, Senegal, and Mauritania and northward into Egypt (Digoutte and Peters, 1989;Diallo et al, 2005 Saudi Arabia and Yemen during 1999 (Hoogstraal et al, 1979;Meegan et al, 1980;Arthur et al, 1993;Shoemaker et al, 2002). Egypt is the most northern, and populous nation to have suffered from RVF and the human illness and death experienced there during the 1977-1978 epizootic was of unprecedented severity (Laughlin et al, 1979).…”