Cattle abortions associated with modified-live viral vaccines to ‘red nose’
Veterinarians at the University of Wyoming and Colorado State University are noticing an increased number of abortions in heifers due to the virus responsible for infectious bovine rhinotracheitis (IBR), also known as “red nose.”
Some episodes occur after vaccination with specific USDA-approved modified-live viral vaccines. Multiple abortion episodes are being investigated in Wyoming and Colorado.
Donal O’Toole with the Wyoming State Veterinary Laboratory (WSLV) at the University of Wyoming and Hana Van Campen with the Veterinary Diagnostic Laboratory at Colorado State University in Fort Collins, CO, reported the abortion increase initially as a letter to the Journal of the American Medical Association.
“Often, there is a history of modified-live bovine herpesvirus-1 vaccine use some two- to eight-weeks prior to abortion,” they wrote. O’Toole and Van Campen suspect live vaccine strains of bovine rhinotracheitis virus are responsible for some abortion outbreaks.
Producers may be using modified-live bovine herpesvirus-1 vaccines in pregnant animals without realizing they must first use a specific group of vaccines within a defined time period before the pregnant cattle can be safely vaccinated, they wrote.
Since that letter was written in August 2010, both laboratories continued to see abortions in the wake of vaccinations with specific modified live products.
Losses range from 10-25 percent, said O’Toole, a pathologist with the WSVL.
“Typically, they occur 30- to 60-days after vaccination,” he said. “In almost all cases, pregnant heifers rather than pregnant cows are involved. Aborted fetuses have characteristic histological changes in livers and other major internal organs.”
He said it is unclear what proportion of abortions is due to off-label use of these vaccines and what proportion occurs in appropriately vaccinated animals.
“Producers who see a series of abortions one to two months after vaccination with IBR vaccines should submit fetuses and associated placental membranes to a diagnostic laboratory,” said O’Toole. “Typically, heifers recover quickly following abortion. There is little tendency for placental membranes to be retained.”
O’Toole and Van Campen suggested that vaccine companies should be required to provide genetic sequence information for modified-live vaccine viruses that are used in pregnant cattle. Currently, there is no simple way for diagnostic laboratories to distinguish vaccine from field strains of the IBR virus, even when they isolate virus from fetal tissues, they stated.
The two also recommended the warnings about abortion risks on product boxes be made larger and more explicit. Many producers may not realize that vaccines designed to prevent abortions may also cause them, they stated. They suggested that abortifacient (substance that induces abortion) vaccines should be sold only by veterinarians and in situations where a veterinarian-client relationship exists to minimize the risk of product-induced abortions.
Producers and veterinarians who think they experience problems with these vaccines should work with their diagnostic laboratories to document them, they advised. They should then report them to the vaccine manufacturer and to the Center for Veterinary Biologics (CVB) with the United States Department of Agriculture. The CVB can be contacted at 515-337-6203 or electronically through the USDA’s veterinary biologicals adverse reactions Web site by going to http://bit.ly/aphisadversereactions.
Many livestock producers are utilizing stockpiled pasture, hay regrowth and warm- or cool-season annuals to extend the grazing season this fall.