Research and Innovation

The main pathogens studied at the laboratory are:

i) Ehrlichia ruminantium, an intra-cellular bacterium transmitted by ticks (Amblyomma variegatum also known as Tropical Bont Tick in the Caribbean) and responsible for transmission of Heartwater, a fatal disease of ruminants in Africa and the Caribbean. 

ii) West Nile Virus, a Flavivirus transmitted by mosquitoes among susceptible hosts, usually birds. The virus can also affect dead-end hosts, like humans and equines.

Recently, a new research field has been developed to study communities of micro-organisms (viruses, bacterias, protoozoa...) called "pathobiome" more especially transmitted by mosquitoes and ticks in the Caribbean region.

The objective of the research conducted in Microbiology is to better characterize pathogens, especially West Nile Virus which has never been isolated in the Caribbean, to better understand E. ruminantium biology, characterize pathogens communities in vectors and contribute to identify new generation vaccine candidates for heartwater

Molecular microbiology

Objective of the work is to develop transformation and mutagenesis techniques for E. ruminantium and most particularly to:

• Develop a transformation strategy to characterize the function of important proteins in vitro and then assess interesting mutants in vivo, by using a novel dynamic bio-imaging model in mouse
• Construct of a mutant library by random mutagenesis with firefly luciferase cassette
• Phenotypic analysis of the mutants (analysis of growth and development inside the host cell by microscopy and Q-PCR
• In vivo analysis in mice of E. ruminantium mutants tha present the strongest defects in growth and infectivity in mammalian cells

Proteomics

Activities in proteomics intend to investigate further the proteome of E. ruminantium at different stages of development and the proteome of host cells (infected vs. uninfected). Proteomic data will be integrated with transcriptomic data to better elucidate the pathogenesis of E. ruminantium. More specifically, the activities consist in the following:

• Characterization of E. ruminantium at reticulate body stage (intracellular stage) of virulent and attenuated Gardel Strains and differential proteom analysis of E. ruminantium between different development stages (intra and extra cellular forms) both for virulent & attenuated strains.
• Differential proteome of E. ruminantium between virulent strains (Senegal and Gardel) at extracellular stage
• Comparison of the proteome of uninfected and infected cells with Gardel virulent strain depending on the progresses of the previous tasks associated with E. ruminantim proteome.

Pathobiome study

Development of bioinformatics is essential for the analysis of important size of biological dataset such as those generated by previous research on E. ruminantium. It includes development and application of:

• Approaches for comparative genomic and transcriptomic studies to comprehend the dynamic biological process differentially involved between virulent and attenuated strains
• An algorithm integrating all the “omics” data (from genomic to proteomic) in order to understand the biological model E. ruminantium

Bioinformatics is also used to support other approaches developed in the team on the evolution of E. ruminantium in link with its tick vector using among others the metagenomic data generated locally.

West-Nile virus has been detected in the Caribbean since 2001, likely introduced from North America by wild birds stopping over the Caribbean islands during their migration southwards. WN regularly circulates in Guadeloupe since its first detection in 2002 on sentinel animals. Several epidemiological studies have been conducted and enable to identify risk areas, mainy in coastal humid areas (swamp forests, marshy areas and other back mangrove areas, ...). Actors of the epidemiological cycle in Guadeloupe have not yet been identified.

Objective of the entomologic study is to gain knowledge on mosquitoe communities, more specifically the bio-ecology of culicid populations in those ecosystems at risk of WNV circulation with a view to identify WNV vectors: identification of species communities; temporal population dynamics, seasonal variations related to environmental factors, host feeding preferences. Most specifically, the following activities are being undertaken:

• Longitudinal study: conducted in two WN hotspots: Mosquito communities are tracked fortnightly with CO₂-baited CDC traps all year round throughout humid and dry seasons. At each spot, simultaneous trappings are made across 3 ecosystems: sentinel farm surroundings, swamp forest and mangrove.
• Cross-sectional study: stratified random sampling over representative environment classes in urban, rural, natural, and coastal humid areas including swamp forests and mangroves

Entomological tools are being developed in order to fill the main gaps identified when planning development of entomological research such as lack of morphological diagnostic key for mosquitoes in the Caribbean. Other molecular tool may need to be developped according to the difficulty to distinguish two sibling species at the morphological level.

A number of surveillance data collected by the veterinary services in the Caribbean are not usable for research purpose or for early alert because of lack of accurate geographic data, delayed data entry compared to data collection, incomplete or sparse datasets. Series of evaluations of surveillance systems conducted in the Caribbean between 2008 and 2012 evidenced major gaps in data collection and management hence justifying the need for development of a regional geographic platform with a view to associate environmental, epidemiologic and economic data including animal movements in the Caribbean.

The main objective of the Caribbean Veterinary Information System (C-VIS) is to enhance the capacity of Caribbean countries/territories for spatial data collection, spatial data storage and spatial data analysis. Because of the use of standardized methods, it will enhance potential for data use at the Caribbean level, and ease communication among Caribbean countries/territories

Other aspects of the work understaken in Spatial epidemiology are:

• The collection of relevant geographic information of the whole Caribbean region: animal and human population data, health information, environmental information, socio-economical data
• Organization of database of geographic data with metadata
• Contribute to develop the capacities on GIS in the region and support CaribVET working groups in their studies and spatial analysis
• Data analysis of spatial dataset collected within the frame of national or regional surveillance activities

Economy is a brand new research field for the Research Unit. Priority research and development activities identified deal with: 

• Development of a method for the cost/benefit evaluation of supranational animal health network such as the Caribbean Animal Health Network (CaribVET) that would contribute to reinforce the political endorsement and advocacy of country and territory members and to sustain this network.
• Development of a tool for the evaluation of Costs of massive animal vaccination campaigns, in order to provide decision makers and organizations the necessary means to evaluate budget needed to achieve livestock disease control or eradication.

The activities are conducted in close collaboration with the CaribVET Network and with the members of the research team based in France such that the methods and tools developed are generica and applicable in both the Caribbean and African context and in future geographic regions.

Models at the population-average level are known to provide quite accurate descriptions of demographic parameters. Such approach ignore individual variability, which can be crucial when the aim is to describe individual-level parameters obtained from the collective dynamics. Concerning midges life cycle models, it is natural to inquire whether or not outputs are improved when including individual variation in responses to development. The approach here presented tempts to explore this question.

An integral projection-like approach is included within a stage structured population model (matrix population model) to give account of individual heterogeneity. Temperature is considered as the only environmental variable, but the model could be extended to other climatic/environmental variables. Model performance is tested with Culicoides (a genus of biting midges in the family Ceratopogonidaea) life cycle data from various published and unpublished laboratory studies. We explore how including individual heterogeneity impacts on the distribution of within-stage variation in maturation times by obtaining Bayesian estimates of development parameters. We find that including within-stage variability in dynamics allows for reproducing the observed minimum maturation times. Furthermore, we discuss the effects on posterior estimates of the associated basic reproductive number under different fixed temperatures and how this approach could help to obtain prior estimates for parameters of ecological state-space models that fit to observed time series data. Finally, general conclusions and suggestions related to improvements are presented.