Effects of Local Anthropogenic Changes on Potential Malaria VectorAnopheles hyrcanusand West Nile Virus VectorCulex modestus,Camargue, France

Using historical data, we highlight the consequences of anthropogenic ecosystem modifi cations on the abundance of mosquitoes implicated as the current most important potential malaria vector, Anopheles hyrcanus, and the most important West Nile virus (WNV) vector, Culex modestus, in the Camargue region, France.From World War II to 1971, populations of these species increased as rice cultivation expanded in the region in a political context that supported agriculture.They then fell, likely because of decreased cultivation and increased pesticide use to control a rice pest.The species increased again after 2000 with the advent of more targeted pest-management strategies, mainly the results of European regulations decisions.An intertwined infl uence of political context, environmental constraints, technical improvements, and social factors led to changes in mosquito abundance that had potential consequences on malaria and WNV transmission.These fi ndings suggest that anthropogenic changes should not be underestimated in vectorborne disease recrudescence.D uring the past 25 years, there has been a dramatic emergence and resurgence of epidemic vectorborne diseases affecting both humans and domestic animals (1).In most cases, sociodemographic changes, drug resistance, and anthropogenic environmental modifi cations appear to be the main factors responsible (1-4).The Camargue, the Rhone River Delta region in southeastern France, is an area relevant to the study of the infl uence of environmental changes on vector populations because 1) it has witnessed important anthropogenic ecosystem modifi cations in the past 60 years, 2) it contains a great abundance and diversity of mosquito-breeding sites and thus hosts large mosquito populations, and 3) it is a former zone of endemic malaria and a region of current and regular transmission of West Nile fever.Until the beginning of the 20th century, malaria, mainly transmitted by Anopheles (Anopheles) atroparvus Van Thiel, was endemic in the Camargue and constituted a major health issue there (5,6).The last Plasmodium vivax malaria epidemic occurred in 1943, with ≈400 cases (7).Malaria disappeared from this area after World War II because of improved housing and living conditions and the extensive use of quinine.Among 8 anopheline species recorded in the Camargue, An. atroparvus was recently found to be rare and An.(Anopheles) hyrcanus (Pallas) very abundant with a high human-biting rate (8), fi ndings that suggest that An. hyrcanus is currently the only Culicidae sp.likely to play a role in malaria transmission in the Camargue (8).Moreover, autochthonous transmission was recently suspected on the French Mediterranean Coast in 2006 (9), which also supports the idea that southern France remains suitable for malaria transmission.The fi rst description of West Nile virus (WNV) in France was in the 1960s, with human and equine outbreaks in the Camargue (10).After these episodes, the disease seemed to disappear from this region.However, WNV transmission apparently continued thereafter and Effects of Local Anthropogenic Changes on Potential Malaria Vector Anopheles hyrcanus and West Nile Virus Vector Culex modestus, Camargue, France