Unusual Virus Identified In Aborted Calf

The findings by researchers in the College of Veterinary Medicine at Oregon State University were reported today in the Journal of the American Veterinary Medical Association. As one part of the larger viral family of caliciviruses, these "vesiviruses" are so named because they are indistinguishable from viruses of ocean origin that from the 1930s to 1950s caused repeated outbreaks in the United States of a disease in pigs called vesicular exanthema of swine, or VES.

The VES-like viral group is still classified as a "foreign animal disease agent" in the U.S., in part because some of the disease symptoms they can cause – blistering of the mouth, nose, and feet – mimic those of foot and mouth disease, a highly contagious and costly disease for many agricultural animal species.

The proven recurrence of this group of viruses in an aborted calf, along with the larger body of knowledge about how these viruses can spread, mutate, cross interspecies boundaries and occasionally cause major disease outbreaks, is a cause for concern, according to Dr. Alvin Smith, professor and head of the OSU Laboratory for Calicivirus Studies.

"We are well aware of the importance of reporting a possible new virus of bovine abortion," said Smith and other researchers in their study. "However, we assign much greater importance to the urgent need for differential diagnostic reagents for vesicular diseases." Foot and mouth disease, the researchers said, is not zoonotic, or able to be transmitted from other animals to humans. But some infections by vesiviruses do make that leap.

"The need for prompt and accurate diagnosis of vesicular diseases in livestock is not only important for the control of foot and mouth disease, but is also important because of the human health implications involving caliciviruses," the report said. "This public health issue is given even greater imputes by our recent reports of vesicular disease in humans, and possibly abortion and hepatitis, involving this pathogenic class of VESV-like caliciviruses, genus vesivirus, (which are) endemic in certain ocean species and U.S. livestock."

According to Smith, research has shown for 30 years that ocean mammals are a vast reservoir of different calicivirus strains, including the VESV group that caused a major animal health epidemic in the United States. For at least 15 years, he said, it's also been clear that these viruses are still endemic at high levels in the nation's livestock populations.

They should no longer be considered a foreign animal disease agent, Smith said, which by statute means they must be eradicated if they are diagnosed in U.S. animals.

Researchers at OSU, in collaboration with a private biotechnology company, have developed various assays and tests that can more accurately diagnose vesiviral infections. Those tests, if more widely used, could improve the diagnosis of diseases caused by this viral family and aid in their control, the scientists said. Caliciviruses are characterized by their ability to survive in a broad range of environments, from the deep ocean to family farms, infect a wide range of species, cross from one species to another, and cause disease symptoms that vary from mild to deadly.

Vesiviruses have been shown to infect swine, seals, cats, dogs, cattle, snakes, whales, primates and humans, among others. The diseases they have been associated with include blisters, hepatitis, diarrhea, abortion, pneumonia, encephalitis, myocarditis, and fatal hemorrhage. A single strain of calicivirus has been shown to have at least 21 animal hosts, ranging from oysters to sea lions, whales, horses and humans. One of the most deadly of the calicivirus strains, closely related to vesiviruses, causes rabbit hemorrhagic disease, a highly infectious and deadly disease that has killed hundreds of millions of rabbits around the world, in some cases up to 95 percent of local populations within 24-48 hours of exposure. That strain, Smith said, was one not known to exist prior to the 1980s. It probably evolved through mutation, he said, or was perhaps brought to rabbits through the most common reservoir for many caliciviral strains, marine animals.

Co-authors on the study just published include researchers from AVI BioPharma, a private company, and Dr. David Matson, a medical doctor at the Center for Pediatric Research in Norfolk, Va.