La fièvre du Nil occidental et la fièvre catarrhale ovine, deux viroses en progression inattendue

Abstract

This paper describes the spread of two arboviral diseases in Europe, and the control measures implemented by health authorities. Bluetongue, which affects only animals, occurred for the first time in Europe in 1998, and West Nile Fever, which affects horses and humans, re-emerged in 1996. Up until 1998, bluetongue was considered as an exotic disease. In 2006 and 2007, its unexpected explosion in Northern Europe highlighted the emergence and expansion capacities of vector-borne diseases. Surprisingly, the disease became perennial in Europe, rapidly spreading to eight European countries and crossing the English Channel and contaminating several herds in England. Its expansion resulted from vector movements carried over long distances by the wind (100 km), and followed a centrifugal pattern in 2006/2007. By 2008, the bluetongue virus (BTV) was occupying a wider European territory. The only control measure available is vaccination, which has been largely implemented in 2008. West Nile fever is a viral disease transmitted by mosquitoes, whose amplifying hosts are birds, whereas horses and humans are incidental but particularly sensitive hosts. West Nile fever appeared in Europe in the 60’s and 70’s, especially in the Camargue region of France, with sporadic foci. At the end of the 90’s, besides the introduction and expansion of the virus on the American continent, major epidemics affected several hundreds of people in Europe (Romania in 1996 and Russia in 1999). Since then, four distinct episodes of West Nile virus (WNV) circulation, associated with clinical cases in horses, were reported in France : in the Camargue region in 2000 and 2004, in the Var department in 2003 and in the Eastern Pyrenees in 2006. An increase in WNV activity was observed in Europe in 2008, with cases of infection reported in Italy, Romania, Hungary and Austria. An inactivated vaccine (Fort Dodge) has recently received a marketing agreement from the European commission. However, until now, control measures rely exclusively on a reinforced surveillance of neurological conditions in humans and animals (horses and birds generally), and on information of exposed people.

Seroprevalence of West Nile virus in horses in different Moroccan regions

“…Concomitant circulation of WNV and other flaviviruses can make the result interpretation difficult. The difficulty of interpretation attributed to cross-reactions among viruses from JE serocomplex has been encountered in India and Pakistan where WNV and Japanese encephalitis virus co-exist in humans with similar symptoms, and in North America where WNV co-exists with St. Louis encephalitis virus (Zientara et al 2009). In Morocco, circulation of other flaviviruses should also be taken in consideration as antibodies against Usutu virus were found in wild birds in Kenitra region in Z1 (Figuerola et al 2008).…”

Culicoides Species Communities Associated with Wild Ruminant Ecosystems in Spain: Tracking the Way to Determine Potential Bridge Vectors for Arboviruses

“…imicola and species belonging to the Obsoletus and Puliaris groups) at the different study sites (with wild ruminants) matched the known geographic pattern inferred from data obtained from the Spanish Bluetongue Entomological Surveillance Program ( Table 2 ). Culicoides imicola , which is the main BTV vector in the Mediterranean Basin [ 3 , 57 , 58 ], was detected in the 4 southern and central areas, i.e. the warmest parts of Spain, but absent from the northern ones ( Table 2 , Figs 3 and 4 ).…”

West Nile virus in Algeria: a comprehensive overview

“…1 ). In North Africa, the WNV strain isolated in Morocco belong to WNV lignage 1, clade 1a [17] . This strain is similar to mosquitoes of WNV Senegal/93 strain and equids of France/2000 strain [11] .…”