New livestock virus rattles northern Europe

Jan 27, 2012

Animal health officials in Europe are scrambling for answers after a previously unknown virus cropped up in Germany this November. Provisionally called “Schmallenberg virus” after the German town in which it was first identified, the virus has also been found in the Netherlands, Belgium, and most recently in Great Britain. To date, it has been isolated in cattle, sheep and goats.

The virus is suspected of causing non-specific symptoms in adult animals including fever, diarrhea and significantly decreased milk production. More importantly, indications strongly suggest that the virus can be passed from pregnant females to unborn offspring, resulting in abortions, still births, and significant and often fatal malformations in fetuses.

According to the most recent count, the virus has been found on 32 farms in Germany. Sixty-six locations in the Netherlands, 30 farms in Belgium, and three farms in Great Britain are also known to have infected animals. Experts predict that as calving season picks up in February and March, significantly more cases will emerge. Yet because the virus is so new, there is currently no easily administered blood test that would aid in determining the disease’s spread.

According to a report issued Jan. 11 by the European Commission’s Standing Committee on Food Chain and Animal Health, the Schmallenberg virus belongs to the Orthobunyavirus genus of viruses typical to Asia and Oceana, but not commonly known in Europe. Similar viruses are transmitted by midges (tiny, blood-sucking flies) and mosquitoes, suggesting that animals do not catch the virus from one another.

“This virus belongs to a vector-transmitted group of viruses making direct transmission from animal to animal unlikely,” the report stated. “Although the congenital malformation in newborn animals has been detected recently … they are most likely caused by transmission of virus by insect vectors that occurred in summer and early autumn, during pregnancy.”

Many lambs and calves infected with the virus have been born dead, exhibiting extreme birth defects such as hydrancephaly, a condition where parts of the brain are replaced by sacs filled with fluid, or extreme scoliosis (curvature of the spine).

The epidemiological role of the aborted fetuses remains unknown.

At this point, authorities are skeptical that the Schmallenberg virus is transmittable to humans, but are unable to say definitively whether it poses a human health risk. According to a preliminary assessment carried out by the European Centre for Disease Prevention and Control on the zoonotic risks of the Schmallenberg virus, “It is unlikely that this virus can cause disease in humans, but it cannot be completely excluded at this stage.”

The assessment went on to emphasize that “[c]lose collaboration between animal and human health services is necessary to ensure rapid detection of any change in the epidemiology of animals and humans,” and that “the health of farmers and veterinarians in close contact with potentially infected animals should be carefully monitored.”

Researchers are trying to take advantage of cold winter temperatures to get a jump on the virus. With midges and mosquitoes currently dormant, a new round of infections is unlikely to begin until April.

“We are taking this very, very seriously,” Thomas Mettenleiter, head of the Friedrich-Loeffler-Institute (FLI)—the German federal animal health lab—told ScienceNOW. “[I]n some herds 20 percent to 50 percent of lambs show such malformations,” Mettenleiter added.

“And most of these animals are born dead.”

FLI, in conjunction with the Dutch Central Veterinary institute, has made significant strides over the past two months identifying the pathogen suspected of causing the birth defects. According to ScienceNOW, virologists have succeeded in isolating the Schmallenberg virus in the brains of affected lambs, and in culturing the virus in insect and hamster cells. FLI scientists have also sequenced the entire genome of the virus, giving them important insight into its functioning.

But at this point, the most important issue for producers is immunity. And with no vaccine available for the Schmallenberg virus, the coming spring and summer months when midges and mosquitoes hatch may foretell high livestock losses for European stockmen next year.

In a fact sheet on the virus distributed by FLI, experts indicated that for the coming season, the only means of preventing infection in livestock will be to protect animals from midges and mosquitoes. It is at best unclear how effective insect management will be in preventing new cases. “If the virus is newly introduced into naive ruminant populations with a high animal density, a rapid spread and malformed lambs and calves must be expected,” FLI warned.

To facilitate a rapid response to the outbreak, FLI has elected not to file patents on any discoveries relating to the Schmallenberg virus. “Our resources are limited,” Mettenleiter told ScienceNOW, “and we are happy to share our knowledge and materials with anyone interested in it for noncommercial or commercial reasons.”

According to the Food Chain and Animal Health Committee report, developing a guidance document on surveillance of the outbreak was “a matter of urgency.”

As the situation unfolds, many questions remain unanswered about the pathogen’s provenance and potential impact. FLI is at this time unable to say whether the virus is a new arrival, or whether it has been quietly present in Eu rope for years. It is also impossible to say what, if any, repercussions the outbreak will have in the U.S.

Although the disease has now been made reportable in the Netherlands, there are still no official controls or restrictions on trade that would prevent affected animals from being shipped to other regions or countries. Unhappy with the lack of containment, Russia has banned the import of all live sheep and goats from the Netherlands, and may extend their prohibition to include cattle, says Radio Netherlands Worldwide. According to the station, Dutch cattle exports to Russia are worth 30 million euros a year, a loss which could expand greatly if other countries follow Russia’s lead. Mexico, it seems, already has.

Dutch Deputy Minister Henk Bleker has been working aggressively to quell fears and reassure trade partners. Bleker told Radio Netherlands Worldwide that at present, he does not believe Dutch livestock pose any significant risk, and that trade bans are unreasonable.

“If people have a good reason to ban imports, then you have to make sure we do better here in the Netherlands,” Bleker stated.

“But if there’s no good reason for it, then I think you have to team up with the EC [European Commission] and take it up with the Russians straight away.” — Andy Rieber, WLJ Correspondent