By Greg Cima
A newly identified virus is thought to have caused illnesses, stillbirths, and congenital malformations among ruminants in at least five Western European countries.
The novel orthobunyavirus, which is currently identified as Schmallenberg virus, has been linked with disease in sheep, cattle, bison, and goats in Belgium, England, France, Germany, and the Netherlands. It is not likely zoonotic, and it is believed to be transmitted through mosquitoes, biting midges, or both, as well as passed to offspring in utero, according to the World Organisation for Animal Health (OIE).
Clinical signs in adult cattle have included fever, anorexia, reduced milk production, and diarrhea, and animals have typically recovered within a few days. The disease has also been connected with stillbirths and malformations among calves, lambs, and kids.
The European Centre for Disease Prevention and Control reported that the virus was detected and isolated in November 2011 from cattle near Schmallenberg, a city in Germany. Detection followed an unusually high incidence of illnesses during the summer. Cattle herds in the Netherlands had similar signs of illness during August and September 2011, and PCR tests showed 18 of 50 serum samples from affected herds were positive for the orthobunyavirus.
Lambs in the Netherlands were also infected with the virus in utero, resulting in congenital malformations, according to the European disease prevention agency.
"Based on current evidence, it is not possible to confirm or exclude a causal relationship between detection of the new orthobunyavirus and the observed clinical symptoms in cattle and small livestock," the ECDC reported in December 2011.
The ECDC predicted at the time that, because the virus was likely spread by midges, infections would decrease during winter and potentially increase during the next vector season.
An Emerging Infectious Diseases journal article (Emerg Infect Dis 2012;18:469-472) indicated humans' risk of harm from the orthobunyavirus was believed to be low or negligible, because the virus is closely related to Shamonda virus, which is not zoonotic, and no human illnesses have been linked with that virus. But risk assessments should be updated with clinical and serologic surveillance of humans and animals, according to the article.
The OIE similarly called for collaboration among public and animal health services to detect possible human infections, particularly among farmers and veterinarians.
A report from the U.S. Department of Agriculture's Foreign Agricultural Service indicates Russia responded to the disease reports with bans on importation of German and Dutch sheep, goats, and related products. Mexico banned importation of reproductive tissues from sheep, goats, and cattle from the Netherlands. |