Endemicity of leptospirosis in domestic and wild animal species from Reunion Island (Indian Ocean)

International audienceSUMMARY Leptospirosis is the major infectious disease on Reunion Island but little is known about the animal reservoir. We conducted a wide-ranging survey that included samples from 574 animals belonging to 12 species. The seroprevalence and prevalence of renal carriage varied greatly depending on the species, with the highest seroprevalence (79·5%) found in Norway rats, and the lowest (13·2%) in tenrecs. The renal carriage rate ranged from 84·6% in mice to 0% in tenrecs. Our results suggest that rodents are the most important reservoirs of leptospirosis on Reunion Island. The epidemiological role that animals play in human infection is discussed. For the first time, we quantified the renal concentration of leptospires in ten naturally infected mammals. The history of Reunion Island colonization probably explains why the circulating Leptospira serogroups were similar to those found in Europe. Our study provides evidence that will help implement preventive measures against this zoonosis

A predictive model based on a pluviothermic index for leathery pocket and fruitlet core rot of pineapple cv. ‘Queen’

International audienceLeathery pocket (LP) and fruitlet core rot (FCR) of pineapple (Ananas comosus L.) caused by Penicillium funiculosum Thom. and/or Fusarium moniliforme Sheld cause significant damage in all production areas, resulting in a major economic impact that affects both the fresh fruit market and the processing sector. The detection of Penicillium and Fusarium in the two main areas of pineapple production in Reunion Island, and representing a large range of climatic conditions, indicated that these fungi responsible for FCR and LP diseases were present throughout the pineapple cycle, whatever the climatic conditions. The proportion of fruits naturally infected by these pathogens was not related to climatic conditions during the infection period, suggesting that the inoculum level was not limiting. As these diseases cannot be reliably controlled, due in particular to the role of climatic conditions, an important research goal is to predict periods of higher disease risk using a model based on weather data. Taking advantage of the great diversity of environments on the tropical island of Reunion (Indian Ocean), we were able to establish a link between a pluviothermic index (PTi: ratio between total rainfall and the average temperature over the fruit development stages), and LP or FCR incidence. Disease incidence wasmodelled as a function of the pluviothermic index via a Weibull model. The most accurate model was obtained during the open heart to harvest stage. Lastly, the model output can be used by pineapple production stakeholders in farm management. (Résumé d’auteur) AD -; ; ; CIRAD-PERSYST-UMR Qualisud (REU); CIRAD-PERSYST-UPR HortSys (REU

Honeybee biomarkers as promising tools to monitor environmental quality

International audienceThe aim of this study was to distinguish the impacts of two different anthropogenic conditions using the honeybee Apis mellifera as a bioindicator associatedwith a battery of biomarkers previously validated in the laboratory. Both the urban (RAV, Ravine des Cabris) and semi-natural (CIL, Cilaos) sites in La Reunion Islandwere compared in order to assess the impacts of two types of local pollution using the discriminating potential of biomarkers. Hives were placed at the CIL and RAV sites and honeybees were collected from each hive every three months over one year. Honeybee responses were evaluated with respect to several biochemical biomarkers: glutathione-S-transferase (GST), acetylcholinesterase (AChE), alkaline phosphatase (ALP) and metallothioneins (MT). The results showed a significant difference between the localities in terms of GST, AChE and ALP activities, as regarding midgut MT tissue levels. Compared to the CIL site, ALP and MT tissue levels were higher at the RAV site, although AChE activity was lower. GST displayed more contrasted effects. These results strongly suggest that the honeybees based in the more anthropized area were subjected to sublethal stress involving both oxidative stress and detoxification processes with the occurrence of neurotoxic pollutants, amongst which metals were good candidates. A classification tree enabled defining a decision procedure to distinguish the sampling locations and enabled excellent classification accuracy (89%) for the data set. This field study constitutes a strong support in favour of the in situ assessment of environmental quality using honeybee biomarkers and validates the possibility of performing further ecotoxicological studies using honeybee biomarkers. (Résumé d'auteur

Mango-based orchards in Senegal: diversity of design and management patterns

Introduction. Mango-based orchards in Senegal occur in a large diversity of cropping systems, but few typologies of these systems exist and none are associated with their comprehensive and quantitative analysis. In this study we defined and characterized the typology of these systems based on a quantitative assessment of their planting design, management, vegetative state, hedgerow structure and infestation by a major pest of mango, the Bactrocera invadens fly. Materials and methods. Multivariate analysis and clustering methods were applied to data from 64 mango-based orchards and their surrounding hedgerows sampled in the Dakar and Thiès regions, in Senegal. Results and discussion. Four types of cropping systems were identified according to orchard design and management patterns: (1) ‘No-input mango diversified orchards’, (2) ‘Low-input mango orchards’, (3) ‘Medium-input citrus-predominant orchards’ and (4) ‘Medium-input large mango- or citrus-predominant orchards’. Orchard characteristics varied among these patterns. For instance, vegetation was dense and homogeneous in system 1, and the mortality rate of trees was high in system 2 but low in system 3. Orchards of systems 3 and 4 were mostly associated with hedgerows with, respectively, boundary-marking and defensive species. Lastly, the number of B. invadens flies was high in orchards of system 4, whereas it was low in those of system 2. Conclusion. The diversity of mango-based cropping systems in Senegal is now well described and quantified. This characterization is a preliminary step that is essential for further studies aiming to improve these systems