Culex pipiens, an Experimental Efficient Vector of West Nile and Rift Valley Fever Viruses in the Maghreb Region

Abstract

West Nile fever (WNF) and Rift Valley fever (RVF) are emerging diseases causing epidemics outside their natural range of distribution. West Nile virus (WNV) circulates widely and harmlessly in the old world among birds as amplifying hosts, and horses and humans as accidental dead-end hosts. Rift Valley fever virus (RVFV) re-emerges periodically in Africa causing massive outbreaks. In the Maghreb, eco-climatic and entomologic conditions are favourable for WNV and RVFV emergence. Both viruses are transmitted by mosquitoes belonging to the Culex pipiens complex. We evaluated the ability of different populations of Cx. pipiens from North Africa to transmit WNV and the avirulent RVFV Clone 13 strain. Mosquitoes collected in Algeria, Morocco, and Tunisia during the summer 2010 were experimentally infected with WNV and RVFV Clone 13 strain at titers of 107.8 and 108.5 plaque forming units/mL, respectively. Disseminated infection and transmission rates were estimated 14–21 days following the exposure to the infectious blood-meal. We show that 14 days after exposure to WNV, all mosquito st developed a high disseminated infection and were able to excrete infectious saliva. However, only 69.2% of mosquito strains developed a disseminated infection with RVFV Clone 13 strain, and among them, 77.8% were able to deliver virus through saliva. Thus, Cx. pipiens from the Maghreb are efficient experimental vectors to transmit WNV and to a lesser extent, RVFV Clone 13 strain. The epidemiologic importance of our findings should be considered in the light of other parameters related to mosquito ecology and biology.

Rift Valley fever virus: strategies for maintenance, survival and vertical transmission in mosquitoes

“…Using in vitro saliva collections it is calculated that mosquitoes inject around 50 p.f.u. ml À1 RVFV with each bite [48,49] although analysis of West Nile virus (WNV; Flavivirus), suggests these methods underestimate titres and vary between species [50].…”

First Nationwide Surveillance of Culex pipiens Complex and Culex torrentium Mosquitoes Demonstrated the Presence of Culex pipiens Biotype pipiens/molestus Hybrids in Germany

“…Accordingly, the spread of WNV is dependent on the presence of suitable mosquito vectors, and knowledge of the local mosquito species and their distribution are prerequisites for regional risk assessments of possible arbovirus-outbreaks. In Europe and other temperate regions, members of the Culex pipiens complex are the most ubiquitous mosquito species [1], [2] which serve as principal vectors for various arboviruses including WNV [3], [4], [5], [6], [7]. Culex pipiens pipiens (Linnaeus 1758) ( Cpp. )…”

Seasonal abundance and molecular identification of West Nile virus vectors, Culex pipens and Culex quinquefasciatus (diptera: culicidae) in Abeokuta, South-West, Nigeria

“…In Africa where climatic conditions and vegetation promotes abundant reproduction and distribution of diverse mosquito species, large epidemics of Arboviruses have occurred for instance the Yellow ever epidemic in Nigeria during the mid-1980 which ravaged thousands of lives 2 . West Nile virus is a highly virulent potentially lethal neurotropic virus widely distributed in the Americas and Europe 3,4 . In Nigeria, WNV infections have been reported 5,6 .…”