A new viral disease is sweeping across Europe, infecting cattle, sheep, goats, and bison.
Schmallenberg virus, which was discovered last fall, started with an unusual outbreak of disease in dairy cattle in Germany and the Netherlands. Infected cattle had fevers, diarrhea, decreased appetite, weight loss and reduced milk yields of up to 50 percent.
Illness lasted from weeks to days in affected animals. These signs of illness are not specific to a certain type of disease, so testing was performed to rule out other causes of illness. When none of the known diseases were confirmed, it was time to search for something new.
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Using sophisticated gene sequencing techniques, German researchers were able to determine that a new virus was causing the outbreak. It is named after a town in Germany where the outbreak was first identified and from which blood samples from infected cattle helped identify the virus.
Early this winter, deformed sheep infected with Schmallenberg virus were identified.
Pregnant ewes gave birth to lambs with unbendable joints (arthrogryposis), bent spines (scoliosis), short jaws and increased fluid in the brain cavity (hydrocephalus, also called water on the brain)
Infection in early gestation causes deformities and abortions. Most affected lambs were stillborn, and the rest died shortly after birth. Some herds have lost 25 percent of their lamb crop.
Biting midges and mosquitoes are suspected to carry the virus and inoculate susceptible animals when they feed. The virus does not survive well outside the body.
Researchers are working on vaccines and tests for detecting antibodies against the virus. No treatment is available.
Further research is necessary to determine if the virus has been circulating in Europe undetected or if it was introduced from elsewhere.
Infection in humans is possible, but viruses closely related to Schmallenberg virus do not typically infect people. It is too early to tell if the same will be true for this virus.
As of March 1, the virus had been detected in more than 1,000 farms in Belgium, the Netherlands, France, Italy, Luxembourg and the United Kingdom. It has remained a disease of ruminants, infecting bison, cattle, sheep and goats. It’s not known if other species, such as deer, moose, llamas and alpacas, are susceptible.
The economic impact of this disease is expected to grow in significance and will be further assessed following spring lambing.
Egypt, Ukraine, Russia and Mexico have already banned the importation of live cattle, semen and embryos from affected countries. German exports to Russia were valued at $78 million US last year.
The United States has increased import restrictions on European Union cattle, sheep and goat embryos and semen.
The significance of this outbreak to Canada remains undetermined.
The Canadian Food Inspection Agency says it is monitoring the outbreak. Live imported animals may harbour the virus, but it is suspected that semen and embryos are also at risk.
Even if the virus were inadvertently introduced to Canada, it would require a vector such as a mosquito, midge or tick that was capable of transmitting it between animals. It is possible that we do not have the appropriate hosts or that our weather is too severe.
On the other hand, it could sweep across the continent as we saw with West Nile Virus in the early 2000s.
In general, most infectious diseases in Canada are at their northern limit. However, with the shorter winters and longer summers that accompany climate change, mosquito populations are anticipated to grow.
As their season and range expands, mosquito-born viruses are also expected to become more of a health concern. Schmallenberg virus may be one of them.
