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

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

Le sérum de cobaye citraté peut-il être utilisé comme complément de l’épreuve de lyse

52 sérums de cobayes âgés de 3 semaines ont été étudiés comme source possible de « facteur accessoire » de l’épreuve de lyse (= dye-test) en toxoplasmose. 25 % des cobayes ont donné des résultats intéressants lorsqu’ils sont dilués en solution d’Alsever au 1/10e. La même solution d’Alsever diluée au 1/5e permet d’améliorer les premiers résultats en augmentant le pouvoir activateur des sérums. Sans l’addition de cette solution, le pouvoir lytique non spécifique de tous les sérums titrés engendrait une lyse totale des toxoplasmes. Il semble donc que la solution d’Alsever agit d’une part en augmentant le pouvoir activateur des sérums de cobaye, d’autre part, en diminuant la lyse non spécifique des sérums de cobaye permettant ainsi l’utilisation des sérums de ces rongeurs comme complément de l’épreuve de lyse en toxoplasmose