Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Bluetongue in Corsica: the SPOT satellite has revealed the vector midge's habitat

Until 1998, bluetongue was seen as an exotic disease in Europe. However, it is now firmly established around the Mediterranean and has also recently (since 2006) been affecting northern Europe.

It was first seen in France in 2000, and entered the country via Corsica. The sub-Saharan origin of Culicoides imicola, the main vector of the disease in the Mediterranean, prompted researchers to look into the environmental characteristics that favour its establishment and the appearance of the disease that it spreads within Mediterranean ecosystems.

They set out to study this issue in the case of Corsica, where diseased animals were seen in 2000, 2001 and again in 2003 and 2004. The virus is transmitted by female Culicoides imicola that feed on the blood of animals. These tiny midges (1 to 2 mm) are poor fliers, and thus have to establish themselves close to livestock farms if they are to find food. The researchers thus looked closely at the immediate surroundings of 80 sheep farms in the South of the island. To characterize these different environments, they used spatial images supplied by the French SPOT* satellite. The aim was to identify variables that could be used to distinguish between infected and healthy farms. The researchers studied various parameters linked to height above sea level, for instance slope or mean height, to hydrography, particularly the length of any rivers in the area, and to vegetation, through the abundance of the different types of land occupation or landscape structure. This last type of indicator was what made the study so original: "The high spatial resolution images from the SPOT satellite, with a resolution of around ten metres, provided us with landscape indicators, whereas previous studies, based on low-resolution images, only provided information on climatic factors", stresses Hélène Guis, who wrote a thesis on the subject. "This was a first in studies of bluetongue disease."

Sardinia, a transit zone for midges heading for Corsica

An analysis of the data provided two main results. Firstly, the number of farms affected was much higher in the far South of the study zone than elsewhere. Was this because of a higher temperature due to their geographical position? Apparently not: in Corsica, the temperature gradient varies according to altitude rather than latitude. According to the researchers, it is the proximity of Sardinia, which is just 12 kilometres from the Corsican coast in this area, that accounts for the preferential emergence of the disease there. "We know that midges can be blown long distances by the wind", Hélène Guis points out, "and the viral serotypes responsible for the epidemics in Corsica in 2000, 2003 and 2004 had all been seen in Sardinia a few months beforehand."

The results also show that landscape fragmentation, which increases the area of contact between different types of vegetation, also increases the risk of the disease. That risk is higher in the case of extensive transitional areas, particularly wooded zones (scrub, garrigue and broad-leaved trees), open prairies and bare soils. Zones with extensive transitional areas, with significant intermingling of different types of vegetation, may contain various essential elements of the midge's habitat, such as egg-laying and rest sites and host animals. To know more, it will be necessary to carry out entomological studies.

The study also produced a third result: mixed sheep-cattle-goat farms are more susceptible to the disease than farms with sheep alone. It was previously thought that cattle attracted more midges than sheep, and thus protected the sheep from midge bites. The results obtained here seem to suggest that cattle, which are healthy carriers of the disease in Corsica, may act as virus reservoirs and in fact increase the risk of the disease in the sheep alongside which they are reared. However, this result needs to be confirmed on a larger number of farms.

Still to come: a combined study of climatic and landscape factors

The model developed based on these results has been validated in Corsica on 134 farms around Ajaccio. However, it is not applicable to the problem in northern Europe, since while the disease is also found there, the viral serotype involved is different and, furthermore, the vectors, which are also different from those in Corsica, have yet to be categorically identified. In particular, Culicoides imicola is not found in the zone. Nevertheless, a similar modelling approach could be taken there so as to identify the environmental risk factors linked to the emergence of the disease in the region. As regards Corsica, a new study is due to begin in October 2007. It will be a combined study of climatic, environmental and landscape factors, and is to be conducted in partnership with the University of Liverpool, United Kingdom.

* Satellite Pour l’Observation de la Terre (Earth observation satellite)

Helen Burford | alfa
Further information:

More articles from Agricultural and Forestry Science:

nachricht Algorithm could streamline harvesting of hand-picked crops
13.03.2018 | University of Illinois College of Engineering

nachricht A global conflict: agricultural production vs. biodiversity
06.03.2018 | Georg-August-Universität Göttingen

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

A new kind of quantum bits in two dimensions

19.03.2018 | Physics and Astronomy

Scientists have a new way to gauge the growth of nanowires

19.03.2018 | Materials Sciences

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Science & Research
Overview of more VideoLinks >>>