scholarly journals Modelling temporal dynamics of Culicoides Latreille (Diptera: Ceratopogonidae) populations on Reunion Island (Indian Ocean), vectors of viruses of veterinary importance

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Yannick Grimaud ◽  
Hélène Guis ◽  
Frédéric Chiroleu ◽  
Floriane Boucher ◽  
Annelise Tran ◽  
...  
Keyword(s):  
Vegetation Index ◽  
Temporal Dynamics ◽  
Control Strategies ◽  
Host Density ◽  
Environmental Drivers ◽  
Hurdle Model ◽  
Reunion Island ◽  
Annual Variations ◽  
Réunion Island ◽  
Set Up

Abstract Background Reunion Island regularly faces outbreaks of epizootic haemorrhagic disease (EHD) and bluetongue (BT), two viral diseases transmitted by haematophagous midges of the genus Culicoides (Diptera: Ceratopogonidae) to ruminants. To date, five species of Culicoides are recorded in Reunion Island in which the first two are proven vector species: Culicoides bolitinos, C. imicola, C. enderleini, C. grahamii and C. kibatiensis. Meteorological and environmental factors can severely constrain Culicoides populations and activities and thereby affect dispersion and intensity of transmission of Culicoides-borne viruses. The aim of this study was to describe and predict the temporal dynamics of all Culicoides species present in Reunion Island. Methods Between 2016 and 2018, 55 biweekly Culicoides catches using Onderstepoort Veterinary Institute traps were set up in 11 sites. A hurdle model (i.e. a presence/absence model combined with an abundance model) was developed for each species in order to determine meteorological and environmental drivers of presence and abundance of Culicoides. Results Abundance displayed very strong heterogeneity between sites. Average Culicoides catch per site per night ranged from 4 to 45,875 individuals. Culicoides imicola was dominant at low altitude and C. kibatiensis at high altitude. A marked seasonality was observed for the three other species with annual variations. Twelve groups of variables were tested. It was found that presence and/or abundance of all five Culicoides species were driven by common parameters: rain, temperature, vegetation index, forested environment and host density. Other parameters such as wind speed and farm building opening size governed abundance level of some species. In addition, Culicoides populations were also affected by meteorological parameters and/or vegetation index with different lags of time, suggesting an impact on immature stages. Taking into account all the parameters for the final hurdle model, the error rate by Normalized Root mean Square Error ranged from 4.4 to 8.5%. Conclusions To our knowledge, this is the first study to model Culicoides population dynamics in Reunion Island. In the absence of vaccination and vector control strategies, determining periods of high abundance of Culicoides is a crucial first step towards identifying periods at high risk of transmission for the two economically important viruses they transmit.

scholarly journals Percolation-Based Risk Index for Pathogen Invasion: Application to Soilborne Disease in Propagation Systems

2013 ◽  
Vol 103 (10) ◽  
pp. 1012-1019 ◽  
Author(s):  
S. Poggi ◽  
F. M. Neri ◽  
V. Deytieux ◽  
A. Bates ◽  
W. Otten ◽  
...  
Keyword(s):  
Plant Pathogens ◽  
Control Strategies ◽  
Risk Index ◽  
Host Density ◽  
Transmission Probability ◽  
Pathogen Transmission ◽  
Soilborne Disease ◽  
Pathogen Invasion ◽  
Fungal Plant Pathogens ◽  
Set Up

Propagation systems for seedling growth play a major role in agriculture, and in notable cases (such as organic systems), are under constant threat from soil and seedborne fungal plant pathogens such as Rhizoctonia solani or Pythium spp. Yet, to date little is known that links the risk of disease invasion to the host density, which is an agronomic characteristic that can be readily controlled. We introduce here, for the first time in an agronomic system, a percolation framework to analyze the link. We set up an experiment to study the spread of the ubiquitous fungus R. solani in replicated propagation systems with different planting densities, and fit a percolation-based epidemiological model to the data using Bayesian inference methods. The estimated probability of pathogen transmission between infected and susceptible plants is used to calculate the risk of invasion. By comparing the transmission probability and the risk values obtained for different planting densities, we are able to give evidence of a nonlinear relationship between disease invasion and the inter-plant spacing, hence to demonstrate the existence of a spatial threshold for epidemic invasion. The implications and potential use of our methods for the evaluation of disease control strategies are discussed.

scholarly journals Spatio-Temporal Modelling of Culicoides Latreille (Diptera: Ceratopogonidae) Populations on Reunion Island (Indian Ocean)

2020 ◽  
Author(s):  
Yannick René Pierre Grimaud ◽  
Annelise Tran ◽  
Samuel Benkimoun ◽  
Floriane Boucher ◽  
Olivier Esnault ◽  
...  
Keyword(s):  
Statistical Models ◽  
Large Scale ◽  
Control Strategies ◽  
Vector Competence ◽  
Meteorological Data ◽  
Environmental Data ◽  
Reunion Island ◽  
Sampling Campaign ◽  
Réunion Island ◽  
Mean Square Errors

Abstract Background: Reunion Island regularly faces outbreaks of bluetongue and epizootic hemorrhagic diseases, two insect-borne orbiviral diseases of ruminants. Hematophagous midges of the genus Culicoides (Diptera: Ceratopogonidae) are the vectors of bluetongue (BTV) and epizootic hemorrhagic diseases of deer (EHDV) viruses. In a previous study, statistical models based on environmental and meteorological data were developed for the five Culicoides species present in the island to provide a better understanding of their ecology and predict their presence and abundance. The purpose of this study was to couple these statistical models with a Geographic Information System (GIS) in order to produce dynamic maps of the distribution of Culicoides throughout the island. Methods: Based on meteorological data from ground weather stations and satellite-derived environmental data, the abundance of each Culicoides species was estimated for the 2,214 husbandry locations on the island for the period ranging from February 2016 to June 2018. A large-scale Culicoides sampling campaign including 100 farms was carried out in March 2018 to validate the model. Results: According to the model predictions, no husbandry location was free of Culicoides throughout the study period. The five Culicoides species were present on average in 57.0% of the husbandry locations for C. bolitinos, 40.7% for C. enderleini, 26.5% for C. grahamii, 87.1% for C. imicola and 91.8% for C. kibatiensis. The models also showed high seasonal variations in their distribution. During the validation process, predictions were acceptable for C. bolitinos, C. enderleini and C. kibatiensis, with normalized root mean square errors (NRMSE) of 15.4%, 13.6% and 16.5% respectively. The NRMSE was 27.4% for C. grahamii. For C. imicola, the NRMSE was acceptable (11.9%) considering all husbandry locations except in two specific areas, the Cirque de Salazie – an inner mountainous part of the island- and the sea edge, where the model overestimated its abundance. Conclusions: Our model provides, for the first time, an operational tool to better understand and predict the distribution of Culicoides in Reunion Island. As it predicts a wide spatial distribution of the five Culicoides species throughout the year and taking into consideration their vector competence, our results suggest that BTV and EHDV can circulate continuously on the island. It implies significant limitations for any preventive or control actions targeting vector populations. To assess other control strategies, our model could be coupled with an epidemiological model of BTV and EHDV transmission.

scholarly journals Strategic Approach, Advances, and Challenges in the Development and Application of the SIT for Area-Wide Control of Aedes albopictus Mosquitoes in Reunion Island

Insects ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 770
Author(s):  
Louis Clément Gouagna ◽  
David Damiens ◽  
Clélia F. Oliva ◽  
Sébastien Boyer ◽  
Gilbert Le Goff ◽  
...  
Keyword(s):  
Aedes Albopictus ◽  
Disease Transmission ◽  
Mosquito Control ◽  
Control Strategies ◽  
Specific Treatment ◽  
Public Understanding ◽  
Reunion Island ◽  
Additional Tool ◽  
Awareness Campaigns ◽  
Réunion Island

The global expansion of Aedes albopictus, together with the absence of specific treatment and vaccines for most of the arboviruses it transmits, has stimulated the development of more sustainable and ecologically acceptable methods for control of disease transmission through the suppression of natural vector populations. The sterile insect technique (SIT) is rapidly evolving as an additional tool for mosquito control, offering an efficient and more environment-friendly alternative to the use of insecticides. Following the devastating chikungunya outbreak, which affected 38% of the population on Reunion Island (a French overseas territory in the southwest of the Indian Ocean), there has been strong interest and political will to develop effective alternatives to the existing vector control strategies. Over the past 10 years, the French Research and Development Institute (IRD) has established an SIT feasibility program against Ae. albopictus on Reunion Island in collaboration with national and international partners. This program aimed to determine whether the SIT based on the release of radiation-sterilized males is scientifically and technically feasible, and socially acceptable as part of a control strategy targeting the local Ae. albopictus population. This paper provides a review of a multi-year and a particularly broad scoping process of establishing the scientific and technological feasibility of the SIT against Ae. albopictus on Reunion Island. It also draws attention to some prerequisites of the decision-making process, through awareness campaigns to enhance public understanding and support, social adoption, and regulatory validation of the SIT pilot tests.

scholarly journals From the threat to the large outbreak: dengue on Reunion Island, 2015 to 2018

2019 ◽  
Vol 24 (47) ◽  
Author(s):  
Muriel Vincent ◽  
Sophie Larrieu ◽  
Pascal Vilain ◽  
Aurélie Etienne ◽  
Jean-Louis Solet ◽  
...  
Keyword(s):  
Dengue Virus ◽  
Family Doctor ◽  
Austral Summer ◽  
Emergency Department Visits ◽  
Reunion Island ◽  
Large Outbreak ◽  
Mandatory Notification ◽  
Réunion Island ◽  
Sporadic Cases ◽  
Set Up

Background With more than 300 million infections estimated annually worldwide, dengue is the most prevalent arboviral infection. On Reunion Island, after a large outbreak in 1977–78, only limited episodes of viral circulation or sporadic cases were reported till 2015. Aim Our objective was to document and report on the circulation of dengue virus after the occurrence of a small outbreak during austral summer 2015/16 and until the large outbreak of 2018. Methods Beside the mandatory notification of biologically confirmed dengue cases, additional systems of surveillance were set up: estimation of dengue-like syndrome in people seeking care by their family doctor, surveillance of emergency department visits related to dengue, surveillance of hospitalised dengue patients and deaths classifications. Results After a moderate outbreak during summer 2015/16 with 231 cases, 2017 was characterised by limited viral circulation (97 cases) which, however, persisted during the austral winter. By February 2018, the number of cases had increased and led to a peak at the beginning of May 2018. More than 6,000 cases were reported this year (dengue virus type 2 only). In addition, six deaths of dengue patients were notified. Conclusion In 2017, the persistence of transmission during winter created favourable conditions for the emergence of an epidemic during summer 2018. After this moderate epidemic wave, the viral circulation persisted during winter 2018 for the second year, opening the door for the second wave in 2019 and for potential endemisation of the disease on Reunion Island in the near future.

scholarly journals Using an Emergency Department Syndromic Surveillance System to Assess the Impact of Cyclone Bejisa, Reunion Island

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Pascal Vilain ◽  
Frédéric Pagès ◽  
Katia Mougin-Damour ◽  
Xavier Combes ◽  
Pierre-Jean Marianne Dit Cassou ◽  
...  
Keyword(s):  
Surveillance System ◽  
Syndromic Surveillance ◽  
Health Impact ◽  
Epidemiological Surveillance ◽  
Reunion Island ◽  
Syndromic Surveillance System ◽  
Réunion Island ◽  
Ed Visits ◽  
Set Up ◽  
The Impact

On January 2, 2014 the cyclone Bejisa struck Reunion Island. In anticipation, an epidemiological surveillance was set up in order to assess the impact in the aftermath of the cyclone. Short-term health effects were assessed using a syndromic surveillance system based on data of EDs and EMS. A peak of calls to the EMS was observed the day of the cyclone and an increase of ED visits over the next two days. At the same time, a significant increase of visits for trauma, burns, conjunctivitis was detected. The reactivity and the flexibility of the syndromic surveillance system allowed to rapidly assess the health impact of the cyclone.

scholarly journals Cloud Radar Observations of Diurnal and Seasonal Cloudiness over Reunion Island

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 868
Author(s):  
Jonathan Durand ◽  
Edouard Lees ◽  
Olivier Bousquet ◽  
Julien Delanoë ◽  
François Bonnardot
Keyword(s):  
Sea Breeze ◽  
Satellite System ◽  
Research Infrastructure ◽  
Weather Data ◽  
Reunion Island ◽  
Wet Season ◽  
Trade Winds ◽  
Cloud Radar ◽  
Réunion Island ◽  
Global Navigation Satellite

In November 2016, a 95 GHz cloud radar was permanently deployed in Reunion Island to investigate the vertical distribution of tropical clouds and monitor the temporal variability of cloudiness in the frame of the pan-European research infrastructure Aerosol, Clouds and Trace gases Research InfraStructure (ACTRIS). In the present study, reflectivity observations collected during the two first years of operation (2016–2018) of this vertically pointing cloud radar are relied upon to investigate the diurnal and seasonal cycle of cloudiness in the northern part of this island. During the wet season (December–March), cloudiness is particularly pronounced between 1–3 km above sea level (with a frequency of cloud occurrence of 45% between 12:00–19:00 LST) and 8–12 km (with a frequency of cloud occurrence of 15% between 14:00–19:00 LST). During the dry season (June–September), this bimodal vertical mode is no longer observed and the vertical cloud extension is essentially limited to a height of 3 km due to both the drop-in humidity resulting from the northward migration of the ITCZ and the capping effect of the trade winds inversion. The frequency of cloud occurrence is at its maximum between 13:00–18:00 LST, with a probability of 35% at 15 LST near an altitude of 2 km. The analysis of global navigation satellite system (GNSS)-derived weather data also shows that the diurnal cycle of low- (1–3 km) and mid-to-high level (5–10 km) clouds is strongly correlated with the diurnal evolution of tropospheric humidity, suggesting that additional moisture is advected towards the island by the sea breeze regime. The detailed analysis of cloudiness observations collected during the four seasons sampled in 2017 and 2018 also shows substantial differences between the two years, possibly associated with a strong positive Indian Ocean Southern Dipole (IOSD) event extending throughout the year 2017.

Sign in / Sign up

Export Citation Format

Share Document