【bio-news】A Virus Moves North
A Virus Moves North
The sudden emergence of an insect-borne disease of livestock in northern Europe has plunged the agricultural sectors of three countries into crisis. At least 45 farms in the Netherlands, Germany, and Belgium have so far been affected by bluetongue disease, which infects ruminants such as cows, sheep, goats, and deer. Scientists are trying to find out how the disease, which had made inroads into southern Europe over the past 8 years, made the giant leap north, and what its potential for further spread is.
The disease was first discovered in sheep on a farm in the Netherlands on 14 August. On 21 August, the European Union announced a series of measures to contain it, including an export ban on ruminants--as well as their semen, ova, and embryos--in a 150-kilometer radius around stricken areas.
The Bluetongue Virus, carried by tiny insects called biting midges, causes severe and sometimes fatal disease--including a blue tongue, caused by bleeding--in sheep and goats; cows are reservoirs but usually don't get sick. The virus occurs in many parts of the world, including sub-Saharan Africa, Turkey, and the Middle-East. But until recently, it was rare in Europe. From 1998 on, however, different subtypes of the virus started spreading into Greece, Italy, Spain, Portugal, and the Balkan countries. Still, its sudden jump north--by some 10 degrees of latitude--is "very surprising," says Bethan Purse of the University of Oxford, who studies bluetongue epidemiology.
In southern Europe, bluetongue's main vector is a species called Culicoides imicola, which doesn't occur in the newly affected countries. A team led by medical and veterinary entomologist Willem Takken of Wageningen University in the Netherlands is trapping insects around Dutch farms to determine the most likely vector there. So far, the team has found predominantly C. obsoletus--which lab studies have shown to be a potential vector for bluetongue--as well as nine other Culicoides species, Takken says. Studies to determine whether they carry the virus are still underway.
在南欧国家，蓝舌病毒的主要载体是一种名为库蠓的昆虫，这种昆虫在新近发生感染的国家并没有发现。一个由荷兰Wageningen大学医学和兽医昆虫学家Willem Takken领导的研究小组诱捕了一些荷兰农场周围的一些昆虫想鉴定初在这里最有可能的载体是什么。Takken说到目前为止，研究小组已经发现主要是C. obsoletus（不显库蠓）以及其他9种Culicoides（库蠓）类可能具有携带蓝舌病毒的潜力。是否是它们携带了这种病毒，这项研究正在进行当中。
Meanwhile, virologists are trying to determine which of the 24 subtypes of the virus is involved. The fact that several cows in the Netherlands have fallen ill suggests that it may be an unusual one, Takken says.
Researchers aren't sure why bluetongue is moving north. In a paper published last year, Purse and colleagues suggested climate change might have triggered its recent spread into southern Europe. Other explanations, such as a more virulent strain or changes in land use, agriculture, or animal health systems, seemed implausible, they said, and the disease had struck primarily in those areas that had heated up the most.
作者:admin@医学,生命科学 2011-10-14 05:17