Le moustique Culex pipiens, vecteur potentiel des virus ... - Toubkal
Le moustique Culex pipiens, vecteur potentiel des virus ... - Toubkal
Le moustique Culex pipiens, vecteur potentiel des virus ... - Toubkal
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Abstract<br />
West Nile <strong>virus</strong> (WNV) and Rift Valley fever <strong>virus</strong> (RVFV) are two emerging<br />
arbo<strong>virus</strong>es causing epidemics outside their natural range of distribution.<br />
WNV (Flaviviridae, Flavi<strong>virus</strong>) is one of the most broadly distributed arbo<strong>virus</strong>es in<br />
the world, being found on all continents. Recent outbreaks of WNV were recorded all<br />
over the Mediterranean region. WNV has been isolated from horses and birds in<br />
Algeria, Morocco and Tunisia, indicating an active circulation of the <strong>virus</strong> in this<br />
region. Emergences may occur when adequate vector and susceptible vertebrate<br />
host populations intersect under permissive climatic conditions. Moreover, RVFV<br />
(Bunyaviridae, Phlebo<strong>virus</strong>) is endemic to countries bordering the Maghreb region.<br />
Illegal importations of viremic livestocks along trade routes have been suspected to<br />
introduce the <strong>virus</strong> and initiate local viral transmission.<br />
<strong>Culex</strong> <strong>pipiens</strong> is widely found in North Africa. This species has been incriminated in<br />
the transmission of different arbo<strong>virus</strong>es including WNV and RVFV. In this context,<br />
we define the importance of Cx. <strong>pipiens</strong> as vector of both <strong>virus</strong>es in the Maghreb<br />
region. For such, we experimentally infected field collected populations of Cx. <strong>pipiens</strong><br />
from North Africa with WNV and RVFV at titers of 10 7,8 and 10 8,5 plaque forming<br />
units/mL. Disseminated infection and transmission rates were estimated 14-21 days<br />
following the exposure to the infectious blood-meal. We show that 14 days after<br />
exposure to WNV, all mosquito strains developed a high disseminated infection and<br />
were able to excrete infectious saliva. However, only 69.2% of mosquito strains<br />
developed a disseminated infection with RVFV Clone 13 strain, and among them,<br />
77.8% were able to deliver <strong>virus</strong> through saliva. We showed that Cx. <strong>pipiens</strong> from the<br />
Maghreb are efficient experimental vectors to transmit WNV and to a lesser extent,<br />
RVFV.<br />
Cx <strong>pipiens</strong> has two recognized forms ‘‘<strong>pipiens</strong>’’ and ‘‘molestus’’ which are<br />
morphologically indistinguishable with distinct behaviors and physiologies that may<br />
influence their vectorial status. In this study, we prospected for these forms in<br />
Morocco by using diagnostic primers <strong>des</strong>igned for the flanking region of microsatellite<br />
CQ11. We established the presence of both forms of Cx. <strong>pipiens</strong> and their hybrids in<br />
Morocco.<br />
Our findings should be confronted to parameters <strong>des</strong>cribing mosquito ecology and<br />
biology. Thus, North Africa should be considered as a bridge region between the<br />
Sub-Saharan region where both <strong>virus</strong>es are endemic circulating within a selvatic<br />
cycle and the northern latitu<strong>des</strong> such as Europe for emergence of vector borne<br />
pathogens. Unintentional introductions of birds or animals may have set the stage for<br />
the emergence of WNV and RVFV in Europe.<br />
Key words: <strong>Culex</strong> <strong>pipiens</strong>, West Nile <strong>virus</strong>, Rift valley fever <strong>virus</strong>, vector<br />
competence, molecular identification, Maghreb region.