A newly identified disease is moving rapidly through livestock in Europe and has authorities both worried and puzzled. The disease, dubbed Schmallenberg virus for a town in west-central Germany where one of the first outbreaks occurred, makes adult animals only mildly ill, but causes lambs, kids and calves to be born dead or deformed.
The United Kingdom’s Animal Health and Veterinary Laboratories Agency (AVHLA) said today that the virus has been found on 29 farms in England; in the past few weeks they found it in sheep, but today announced that they have identified it in cattle as well. In mainland Europe, it has been identified on several hundred farms in the Netherlands, Germany and Belgium, and most recently in France. The European Center for Disease Prevention and Control has said that the new virus’s closest relatives do not cause disease in humans — but that other more distantly related viruses do:
The new virus belongs to the Bunyaviridae family, genus Orthobunyavirus, Simbu serogroup (preliminary information, based solely on genetic information)… Genetic characterisation has shown that the new virus is closest to the following Simbu serogroup viruses: Shamonda-, Aino- and Akabane-viruses, which do not cause disease in humans.
However, at least 30 orthobunyaviruses are zoonotic and may cause disease in humans, with symptoms ranging from mild to severe — e.g. La Crosse encephalitis virus, California Encephalitis virus, Cache Valley virus, Batai virus, Tahyna virus, Inkoo virus, Snowshoe Hare virus, Iquitos virus and Oropouche virus.
The viral vector — the thing which spreads it — is believed to be midges, small flying biting insects (Culicoides) and maybe also mosquitoes (Culicidae). The disease doesn’t pass from adult animal to another animal, but apparently does from a mother animal to its offspring in utero, and that is why it is showing up now: It’s lambing season. With Europe enduring its coldest winter in decades, there are no virus-carrying insects flying around now. Instead, the animals that are giving birth to deformed and dead offspring were infected last summer and fall. No one has been able to say so far whether the organism can survive in insects over the winter (the way West Nile virus, for instance, may).
The insect vector is also believed to be how the disease got to the UK. The seven counties where it has been found so far — Norfolk, Suffolk, Essex, Kent, East Sussex, West Sussex and Hertfordshire — are all in the southeast. They are the first places in the UK to catch winds from the Continent, and therefore the first where anything carried by the wind, including insects, might drop out.
The international disease-warning mailing list ProMED has collected links to all the maps of outbreaks published so far:
Agricultural media are starting to record the economic fallout, including a Russian ban on European livestock and the possibility of a ban on shipping live animals, including to livestock shows and sales.
And the CDC journal Emerging Infectious Diseases has just posted ahead of print the first paper on the new disease.
Meanwhile, the British Veterinary Record seizes on the outbreaks to make a larger point: Finding new diseases such as Schmallenberg depends on having good disease surveillance — but in the UK, funding is about to be sharply cut.
It is precisely this kind of emerging disease threat that scanning surveillance aims to detect – and it is also this kind of disease threat that might not be detected promptly if, for whatever reason, arrangements for surveillance fall short of the mark…
Schmallenberg virus is not the first new disease to be detected by scanning surveillance, nor will it be the last. It was scanning surveillance that identified the emergence of BSE in the late 1980s and, in more recent years, it has been responsible for, among other things, the early detection of pandemic H1N1 influenza in pigs, four notifiable avian disease outbreaks, bovine TB in non-bovine species, antimicrobial resistance in Salmonella and virulent psoroptic mange in cattle. The AHVLA has noted that the value of its surveillance programme has greatly exceeded the cost in recent years, with monetised benefits having been estimated at over £200 million a year.
(Hat tip to constant reader Pat Gardiner.)