Centre for Applied Entomology and Parasitology

I obtained my BSc in Biology from Lausanne University located on the Lake Geneva in Switzerland. This was followed by a PhD in Behavioural and Evolutionary Ecology of host-parasite interactions at Bern University in the same country. I then moved to the United States for 6 years of postdoctoral studies focusing on social insects at the University of California Los Angeles and on insect vectors of human diseases at the University of Texas Medical Branch and the University of California Davis . I have been a lecturer in Keele since January 2006.

ISTM research theme: Infection, Inflammation & Immunity

Arthropod-borne diseases are responsible for the death of millions of people per year. Research in my laboratory focuses on integrative biology of arthropods that transmit major human diseases. Our research projects combine studies in molecular ecology, ecological genomics, population genetics and behaviour in order to generate results of broad ecological importance that feed back on our understanding of vector population structure, pathogen transmission and vector control. We have ongoing projects and collaborations on Anopheles gambiae the vector of Malaria in Sub-Saharan Africa, Aedes aegypti and Aedes albopictus vectors of Dengue fever, Triatoma dimidiata vector of Chaga’s disease in Central America, and Sandflies vectors of Leishmaniasis in various parts of the world.

Above left: Female Lutzomia longipalpis vector of Leishmaniasis feeding (WHO/TDR/Stammers)

Above right:  Female Aedes albopictus vector of dengue feeding (WHO/TDR/LSTM)

Above left: A triatomine bug (Rhodnius prolixus) vector of Chaga’s disease feeding (WHO/TDR/Stammers)

Above right: Multiplication of Trypanosoma cruzii amastigotes and destruction of adjacent host heart tissue (WHO/TDR/Stammers)

Research projects

Population structure and speciation in the Anopheles gambiae complex

Past studies conducted in Greg Lanzaro’s laboratory at the Department of Entomology, University of California Davis, combined behavioural ecology, population biology and genetics to further our understanding of the complex population structure of An. gambiae. Molecular analyses of sperm extracted from mated mosquito females, revealed assortative mating between the recently speciated forms of An. gambiae, low levels of polyandry, and rare hybridization events (Tripet et al. 2001-03). Studying the movement of genes resulting from rare introgression events between the forms and sub-species of An. gambiae is critical for predicting the spread of genes responsible for pesticide resistance in many parts of Africa, and this aspect has been the focus of several other studies (Reimer et al. 2005, Tripet et al. 2006-07). Such knowledge is also necessary to assess the feasibility of the so-called malaria-fighting mosquito projects that aim at introducing genes of refractoriness to Plasmodia into natural vector populations.

We have showed through comparisons of levels of genetic differentiation in different parts of the An. gambiae genome how such rare hybridization events may prevent divergence of some areas of the genome but not others (Tripet et al. 2005). Unravelling the contrasted patterns of recombination and selection that lead to that mosaique-like pattern of differentiation during the process of speciation is important for understanding the extensive radiation observed in this and many other vector species complex. Recent advances have revealed several areas of the genome that exhibit strongly reduced recombination combined with selection. These so-called islands of speciation are likely to protect gene-complexes involved in ecological speciation including important mating behaviour gene.

Thanks to the support of UK’s National Environmental Research Council (NERC), we are currently re-sequencing areas of the genome involved in speciation in a large number of mosquitoes belonging to several forms of An. gambiae using 454GSflex ultra-sequencing technology. This project is expected to unravel numerous single-nucleotide polymorphisms, some of them potentially important for speciation. The data will next be used towards the development of a micro-array designed specifically for the detection of An. gambiae’s cryptic taxa and for describing patterns of gene flow in the field.

Evolutionary Ecology of mating behaviour in mosquitoes

Mosquito mating behaviour such as swarming and mate choice is particularly relevant to our understanding of speciation in mosquito species complex where pre-mating barriers to reproduction are often the only barrier to gene flow between recently diverged taxa. Ongoing research projects on the mating behaviour of An. gambiae focus on mate choice, sperm use, and sex-peptides (collaboration with Dr. Flaminia Catteruccia, Imperial College) as well as pheromones (collaboration with Dr. Gordon Hamilton, Keele University).

By affecting the genetic and phenotypic quality of mosquitoes, mass-rearing and genetic manipulations can affect the fitness of mosquito strains. As part of a large collaborative project sponsored by the Wellcome Trust and involving P. Eggleston’s (mosquito transgenesis), H. Hurd (mosquito/plasmodium interactions)(Keele University) and the Malaria Research Training Center in Bamako, Mali, we are studying the population dynamics of transgenes in experimental mosquito populations. We are particularly interested in detecting potential fitness costs associated either with transgenes and gene-drive systems themselves, or with the colonization, maintenance and mass rearing of transgenic mosquito strains. From a population biologist’s point-of-view understanding how the release of such strains could potentially drive behavioural shifts in natural populations is also fundamental. These aspects are being investigated through computer simulations, genetic studies and behavioural experiments.

Example of simulation models designed to study complex effects of male mating competitiveness on the rate of spread of a Medea-like gene drive construct. The distribution of mating phenotype of the target population is plotted in relation to time (generation). Left: In blue, the release at generation 0 of a large number of GM individuals with mating phenotype and variance comparable to the target population is simulated (conspicuous high peak at generation 0). Centre: In red, the build up of transgene carriers in the target population is shown, taking around 7 generations for all individuals to carry the transgene. Right: Simulated dynamics of the same transgene when released males have a phenotypic distribution slightly divergent from and less variable than that of the target population. In this case it may take up to 20 generations for the transgene to spread through the entire population.

Mating behaviour can sometimes also impact broad ecological processes such as competitive interactions between species that share a common habitat. In a project sponsored through the National Institute of Health, we recently assessed the role of mating behaviour in processes of competitive displacement of the Yellow fever mosquito Aedes aegypti by the Tiger mosquito Aedes albopictus in the Americas (Collaboration with Dr. Phil Lounibos, Florida Medical Entomology Laboratory).

Ecological Immunology of Anopheles/plasmodium interactions

Whether Plasmodium falciparum, the agent of human malaria responsible for over 2 million deaths per year, causes fitness costs in its mosquito vectors is a burning question that has not yet been adequately resolved but it has critical implications for the natural selection of parasite-resistance mechanisms. There is mounting evidence that susceptibility to the parasite may be determined by a limited number of loci. Thus, understanding the evolutionary forces that determine the frequency of susceptibility and refractory alleles is critical for understanding malaria transmission dynamics. This knowledge is particularly relevant for vector control strategies aiming at boosting naturally occurring refractoriness or spreading natural or foreign genes for refractoriness using genetic drive systems in vector populations. We are currently investigating the interactions between environmental factors such as variation in access to food and water and ambient humidity on fitness costs induced by Plasmodium falciparum infection in Anopheles gambiae.

Other collaborative projects

- Population genetics studies aimed at understanding the population structure and dispersal between the sylvatic, peri-domestic and domestic habitats of kissing bugs, Triatomina dimidiata, the vector of Trypanosoma cruzii in the Yucatan, Mexico (with Immunologist Dr. Eric Dumonteil, University of the Yucatan, Merida, Mexico).

- Population structure and taxonomy of phlebotominae in the Soudan (with Noteila Khalid, University of Khartoum and Dr. Dia Elnaiem, National Institutes of Health, USA)

- Population structure of Aedes caspius, vector of Rift valley fever in Saudi Arabia (with Drs Ashraf Ahmed, Mourad Aboul-Soud and Abdullaziz Alkedhairy, King Saud University, Saudi Arabia)

Further details

Year 1

• LSC-10032 Genetics and Evolution (also PHA-10008 Human genetics)
• LSC-10037 Diversity of Life

Year 2

• LSC-20010 Field course
• LSC-20007 IT for Life Sciences
• PTY-20020 Health and the Environment

Year 3

• LSC-30002 Parasitology
• LSC-30004 Experimental projects
• LSC-30007 Dissertations
• LSC-30013 Non-experimental Research Projects

Postgraduate

• MSC in Molecular Parasitology and Vector Biology (University of Salford, Keele and Manchester)

Current PhD students

• Fred Aboagyie-Antwi (2005-ongoing)
• Doug Patton (2008-ongoing)
• Rowida Baeshen (2008-ongoing)

Visiting PhD students

• Noteila Khalid (2008, University of Khartoum, Soudan)

Msc Students

• Dannielle Robins (2007)
• Simon Clegg (2007)
• Bamidele Alabi (2008)

Useful external links

Anopheles gambiae genome poster by Science magazine

EnsemblGenome exploration tools

Picture Gallery

Above left: Djenne, Mali - mosque and market (pict F. Tripet)
Above right:  Mango plantation, road to Guinea, Mali (pict F. Tripet)

Above left: Village on Niger near Mopti, Mali (pict F. Tripet)
Above right:  Dogon escarpment, Mali (pict F. Tripet)

Above left: Dogon village, Mali (pict F. Tripet)

Above right:  Mosquito breeding sites - pot holes, Mali (pict F. Tripet)

Above left: Mosquito breeding site - rice field, Mali (pict F. Tripet)

Above right:  Mosquito breeding sites - pool on edge of river, Mali (pict F. Tripet)

Above: Anopheles gambiae - 4th instar larvae (WHO/TDR/Stammers)