Two Texas researchers have published findings supporting claims by Montana agricultural officials that buffalo migrating from Yellowstone National Park should be killed because they carry a disease that could infect domestic cattle herds.
The disease is brucellosis, which causes cattle to abort their calves. Buffalo in the park have the disease. They are shot and killed when they move northward from the park onto private lands to keep them from infecting cattle.State veterinarian Donald Ferlicka said the brucellosis bacteria kills tissue in the placenta, cutting off the oxygen supply to the fetus. After two or three aborted fetuses, the mother can build up immunities to the disease and once again deliver healthy young.
The disease is spread when animals eat the hay or grass that infected fetuses have lain on.
Until the findings were published by Garry Adams and Donald Davis of the Texas Agricultural Experiment Station, there was no scientific proof that buffalo could actually transmit brucellosis to cattle.
The Texas researchers published a report in the "Journal of Wildlife Diseases" in 1988 on an experiment they performed twice. They said the research showed brucellosis can be passed between buffalo and cattle in a laboratory setting.
Adams and Davis put six pregnant buffalo and six domestic cattle together in small paddocks.
The researchers dropped a solution containing the brucellosis bacteria into the eyes of each healthy, pregnant buffalo. The animals contracted brucellosis, and eventually aborted their fetuses.
The bacteria in the fluids from the aborted fetuses mixed with the cattle's feed, and the cattle contracted brucellosis and eventually aborted their fetuses, Adams said in a telephone interview with the Bozeman Chronicle.
The scientists first conducted the experiment in 1987 and repeated it in 1988.
"If you can do it in two replications, the probability is that it would repeat results at least 95 percent of the time under these laboratory conditions," Adams said. "We had a higher concentration of both bison and cattle than would normally occur where you have extensive cattle ranches," he noted.
Ferlicka, who is responsible for protecting the state's cattle from disease, said the hunts, approved four years ago by the Legislature, are necessary because the buffalo could spread brucellosis to cattle on ranches near Yellowstone's borders.
"I think it's extremely unfortunate that it had to come to hunts," Ferlicka said. "We've been working with the Park Service since 1968, since their natural population control plan. We worried about what would happen if the herd grew in size.
"It's not a good answer, but right now I'm afraid it's the only answer."
A total of 201 buffalo that wandered outside of Yellowstone have been shot by hunters in Montana in the past four months.
About 2,700 buffalo now inhabit Yellowstone, officials estimate. Approximately 800 are in the park's northern herd, and they have been leaving the park in great numbers this winter because of heavy snow and damage to forage from last summer's wildfires.
Last Friday, Montana Department of Fish, Wildlife and Parks officials used a helicopter to run 41 buffalo headed toward cattle ranches in Paradise Valley back into the park, said FWP spokesman Don Bianchi.
Yellowstone Park officials say there are no documented cases of wild buffalo giving brucellosis to cattle.
"There are no proven cases of wild bison infecting domestic cattle with brucellosis although certainly the bison are carriers of brucellosis," park spokeswoman Joan Anzelmo said.
Bozeman veterinarian John McIlhattan noted Yellowstone Park buffalo mixed with cattle prior to the state hunting season without an outbreak of brucellosis.
Ferlicka said he's never seen an aborted buffalo fetus in Yellowstone Park but is convinced that buffalo abortions have taken place.