Pest Management Science Pest Manag Sci 63:623–624 (2007)

In focus: Vector-borne diseaseEditorialThe holding of the one-day meeting ‘Vector-borne Exotic Diseases’ at the Society of Chemical IndustryInternational Headquarters was prescient for several reasons. Interest in this area in Europe had recentlybeen revived by well-publicised linking of changing distributions of vector insects and ticks with climatechange, and additionally by the emergence and re-emergence of several high-profile pathogens, includingzoonoses. One of the most notable of these has been the dramatic expansion in the range of bluetonguevirus (BTV), an arbovirus spread by Culicoides biting midges (Diptera: Ceratopogonidae), which causes ahaemorrhagic disease (bluetongue) in certain breeds of fine-wool and mutton sheep. From 1998 to 2005,multiple incursions of different strains and serotypes of BTV have moved northwards into the Europeancontinent with a frequency never before recorded, causing substantial disease-related costs through mortalityand morbidity and socioeconomic costs through implementation of control measures (including cessation ofanimal movements). In some of these areas, BTV has now reached some 800 km further north than everpreviously recorded in Europe (although the virus is sometimes found in more northern latitudes on othercontinents).

In 2006, however, BTV emerged again, this time from an as yet unknown source outside Europe and far furthernorth, spreading widely and rapidly across large areas of The Netherlands, Belgium, Germany, Luxembourg andnorthern France and reaching a maximum latitude of 53◦N. At this point, none of the affected countries (with theexception of France in its more southern regions) had any country-wide entomological or serological surveillancemechanisms in place for Culicoides, and had little experience with detecting the clinical signs associated with BTV(which can be difficult to diagnose). This problem was exacerbated by the logistic difficulties generated by theindex cases being identified near Maastricht, in areas bordering on three separate countries. For these reasons,it is likely that the virus was well established and had been spreading for some time before detection and hencethe design and implementation of an effective control strategy has proved very difficult. At the time of writing, nosafe and effective vaccine is available for control of the BTV-8 serotype responsible for this outbreak, and hencethe majority of control measures have focused upon reducing virus spread by limiting animal movements, and byattempting to reduce transmission by stabling of stock at vector activity times and by the application of insecticidesto animals and holdings.

The lessons to be learned from this outbreak are strikingly similar to those that have arisen with regard toWest Nile virus in the USA, as outlined here by Reisen and Brault1. First, it is clear that for effective surveillanceand prediction of exotic pathogen incursions, an appropriate infrastructure must already be in place that isbased upon comparable datasets containing detailed and recent information on the potential vectors and onhost abundance and distribution. At present, many risk assessments for arboviral incursions tend to rely heavilyupon historical datasets that take little or no account of land use or climate changes – and in some cases,datasets may be non-existent altogether. Datasets based upon recent and detailed information are vital to definethe threat posed by vectors across the EU and, additionally, can facilitate the detection and tracking of newintroductions of previously exotic vectors (e.g. in Europe, the ongoing spread of Aedes albopictus, the Asian tigermosquito).

Second, for many vectors the most basic information is still required on the efficacy and design of controlmethodologies. In addition to assessing the financial costs of eliminating or controlling vector populations viainsecticide treatment, information is also required on the potential for the development of resistance, as describedby Nauen2, and the possible effects of intervention on public health and the environment. In livestock production,this is particularly relevant, given the ongoing environmental issues surrounding the use of pyrethroid-basedproducts on livestock in the UK, and this area is also further complicated by the special problems facing theorganic farming sector. Pyrethroids have also come under scrutiny for possible carcinogenicity in humans inthe US, where they are used to control West Nile virus vectors, as described by Gammon3. It is thereforevital that we examine alternative methods of control, some of which are described by Logan and Birkett4,and also, for the long term, consider methods for insect control based around genetics, reviewed here byCatteruccia5.

While the impact of insect- and tick-borne pathogens in the UK will never reach the scale of importanceexperienced in tropical regions, it is likely that with the advent of climate change these areas willincrease significantly in importance in the coming years. To combat this threat we will require notonly increasing multinational collaboration and multidisciplinary approaches to detection, monitoring andcontrol, but also the availability of comprehensive and up-to-date datasets which are vital in predictingDOI: 10.1002/ps.1412

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Editorial

such incursions and in reacting appropriately to them. Time is not on our side in achieving theseobjectives.

Simon CarpenterArbovirology Research Group Institute for Animal Health Woking UK

REFERENCES1 Reisen WK and Brault AC, West Nile virus in North America: observations and commentary. Pest Manag Sci 63:641–646.2 Nauen R, Insecticide resistance in disease vectors of public health importance. Pest Manag Sci 63:628–633.3 Gammon DW, Public safety aspects of pyrethroid insecticides used in West Nile Virus-carrying mosquito control. Pest Manag Sci

63:625–627.4 Logan JG and Birkett MA, Semiochemicals for biting fly control: their identification and exploitation. Pest Manag Sci 63:647–657.5 Catteruccia F, Malaria vector control in the third millennium: progress and perspectives of molecular approaches. Pest Manag Sci

63:634–640.

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