Insects and Infectious Diseases  


  HEADPaul Reiter / paul.reiter@pasteur.fr
  MEMBERSAlain Boutonnier, Paban Dash, Irka Barkelowski, Catherine Lallemand, Marie Lemesle


  Annual Report

In recent years, mosquito-borne diseases have acquired high profile as “emerging” pathogens, particularly in discussion of climate change and other environmental concerns. IMI addresses three topics of importance in this context.

Genetic control ofAedes aegypti

The mosquito Aedes aegypti is the principal urban vector of dengue, chikungunya and yellow fever. Methods currently used to control this species have limited impact on transmission, so there is an urgent need for new and innovative approaches.

Bio-engineering is an active focus of research in public health entomology. We are collaborating with a British company, Oxitec (http://www.oxitec.com/) who have created strains of Ae. aegyptiwith a dominant gene that is repressed by tetracycline. The aim is to release transgenic males in the field and for these to mate with wild females (hence RIDL: Release of Insects carrying a Dominant Lethal gene). Female Ae. aegyptiare considered monogamous and tetracycline is unlikely to be present in breeding sites, so the progeny that result from these matings will die. We are studying mating behaviour and ‘fitness’ of several strains and are developing methods for quantitative assessment of fitness atributes. A strain with fluorescent spermatozoa (image below) is used in studies of monogamy. Our field studies in La Reunion have demonstrated greater dispersal range and much higher survival rates than anticipated. Field studies in the Cayman Islands confirm successful insemination of wild mosquitoes by the transgenic strain. We have initiated collaborative studies on this and other aspects of dengue epidemiology and control with research groups in Singapore.

Epidemiology of West Nile virus in Europe

West Nile virus (WNV) is a mosquito-borne flavivirus that is mainly transmitted between birds but can also infect mammals. A panzootic initiated by the accidental importation of WNV into the United States and recent circulation of new lineages of the virus in Europe have generated fears of the emergence of a new public health problem. IMI is co-directing an 11.4€ million EU-funded study (codename EDEN, Emerging Diseases in a Changing European Environment) and directing EDEN-WNV, a study of transmission at sites in Spain, France, Italy, Czech Republic and Romania http://www.eden-fp6-project.net/. Participants are committed to a common protocol to identify ornithophilic vectors, determine their vector competence, identify potential bridge vectors, determine seroprevalence in resident and migratory birds, assess the role of ectoparasites in viral maintenance, seek evidence of overwintering of virus in mosquitoes and monitor seasonal seroconversion in horses. A “horizontal” sub-project applies satellite-derived information and GIS (Geographic Information Systems) technology to our data to model present and future geographic distribution and transmission. Our work has provided evidence of significant circulation of virus between migrant warbler species (principally Acrocephalusspp.), several species of resident passerines, Coots (Fulica atra) and Cormorants (Phalacrocorax carbo), all of which cohabit in reedbeds with a super-abundant mosquito Culex modestus; in the laboratory we have demonstrated very high competence for the virus. We have also demonstrated presence of WNV in overwintering Culexspp. in Czech Republic and Romania, confirming that the virus survives the winter in Europe.

Vertical transmission of Yellow Fever and West Nile virus

Field studies indicate that “vertical” transmission of yellow fever virus via the egg stage may be more significant than is apparent in the laboratory. It is likely that overwintering Culexare also infected by this route because they do not feed on blood before entering diapause. We are exploring parameters that may promote this mode of transmission

Course: Arthropod Vectors and Human Health

This course on the biology and ecology of vectors and the dynamics and control of the pathogens they transmit is unique in the francophone world. It is approved as module of a Masters degree at Université de Versailles and a Graduate Degree at Paris Universities 6 and 7. The next course is scheduled for 2011.

Arthropod collection

We maintain a unique collection of ca. 300,000 specimens of arthropods, spanning nearly two centuries, and including many type specimens. This is consulted by specialists from around the world. Information on 200,000 mosquitoes and ticks have been incorporated in a data base that is available on the web.

Keywords: Vector, mosquito, dengue, chikungunya, West Nile, Yellow Fever, Aedes, Culex, genetic control, arthropod collection

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  Publications

Balanca, G., N. Gaidet, G. Savini, B. Vollot, A. Foucart, P. Reiter, A. Boutonnier, R. Lelli, and F. Monicat. 2009.Low West Nile Virus Circulation in Wild Birds in an Area of Recurring Outbreaks in Southern France. Vector Borne Zoonotic Dis.

Balenghien, T., M. Vazeille, M. Grandadam, F. Schaffner, H. Zeller, P. Reiter, P. Sabatier, F. Fouque, and D. J. Bicout. 2008. Vector competence of some French Culex and Aedes mosquitoes for West Nile virus. Vector Borne Zoonotic Dis 8: 589-95.

Lacroix, R., H. Delatte, T. Hue, and P. Reiter. 2009. Dispersal and survival of male and female Aedes albopictus (Diptera: Culicidae) on Reunion Island. J Med Entomol 46: 1117-24.

Reiter, P. 2007. Oviposition, dispersal, and survival in Aedes aegypti: implications for the efficacy of control strategies. Vector Borne Zoonotic Dis 7: 261-73.

Reiter, P. 2008. Global warming and malaria: knowing the horse before hitching the cart. Malar J 7 Suppl 1: S3.





Activity Reports 2009 - Institut Pasteur
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