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Brucellosis exposure rates jump in Alpine elk
4/15/02
ALPINE, Wyo. (AP) - Brucellosis exposure rates among elk at a state feedground near the Idaho border have jumped six-fold, baffling wildlife researchers.
Testing of elk on the Greys River feedground indicated the number of elk exposed to the bacteria increased from about 8 percent to roughly 50 percent in the last two years, according to Dean Clause, Wyoming Game and Fish Department brucellosis biologist.
"It's got us kind of wondering what's going on," he said recently.
Two possible explanations are being offered: an ineffective dose of vaccine that Game and Fish used several years ago or mass exposure by elk to an aborted fetus carrying the bacteria.
Exposure to the bacteria does not mean the elk are infected. It means that they have been exposed enough to have formed antibodies to fight the bacteria, Clause said.
With the recent jump in exposure rates, Clause said he would expect to see a drop in the number of calves because more fetuses would have been aborted, but that hasn't happened. Instead, calf numbers are roughly the same.
Clause believes the increase in exposure is the result of a large number of previously vaccinated elk being exposed to an aborted fetus carrying the bacteria.
That exposure may have created antibodies that are masking vaccine antibodies, making it difficult to ascertain the presence of the vaccine in blood tests, he said.
The other cause could be a bad batch of vaccine used by Game and Fish in 1998.
After the vaccinations were done that year, researchers discovered the vaccine was old and had lost most of its potency, Clause said. Since then, batches are no longer kept for more than two years.
If either case is true, wildlife officials expect the exposure rate to return to lower levels over the next few years.
Meanwhile, tests are continuing on the vaccine.
State officials use a vaccine known as Strain 19, originally developed for cattle, to vaccinate elk on state feedgrounds. Federal officials, who manage the National Elk Refuge near Jackson, have refused to use the vaccine, saying it has not been proven safe and effective.
National Elk Refuge Manager Barry Reiswig said the jump in exposure rates on the state feedground will have no effect on what refuge officials do.
He said refuge officials are waiting for results from their own study of the effectiveness of the vaccine before making any decisions about using it on the federal site.
The refuge recorded a record low brucellosis exposure rate of 19 percent his winter, down from an average of about 30 percent in past years, Reiswig said.
Clause said the state will continue to use the vaccine.
"If we didn't think we were doing any good, we wouldn't be doing it," he said.
Brucellosis was first noted in the Greater Yellowstone Area in 1917 and no cure has been found. It causes abortions and infertility in elk, bison and cattle.
Although rare in humans, it can be passed to people through contact with infected animals or by ingesting their milk. Flulike symptoms can last for months or years.
Although the Yellowstone area is the last region in the nation where wildlife still have brucellosis, the scientific community is mixed on how easily it can spread from wild animals to livestock.
Still, biologists say a risk exists and are seeking ways to mitigate it.
----
On the Net:
Greater Yellowstone Interagency Brucellosis Committee:
http://www.nps.gov/gyibc/
4/15/02
ALPINE, Wyo. (AP) - Brucellosis exposure rates among elk at a state feedground near the Idaho border have jumped six-fold, baffling wildlife researchers.
Testing of elk on the Greys River feedground indicated the number of elk exposed to the bacteria increased from about 8 percent to roughly 50 percent in the last two years, according to Dean Clause, Wyoming Game and Fish Department brucellosis biologist.
"It's got us kind of wondering what's going on," he said recently.
Two possible explanations are being offered: an ineffective dose of vaccine that Game and Fish used several years ago or mass exposure by elk to an aborted fetus carrying the bacteria.
Exposure to the bacteria does not mean the elk are infected. It means that they have been exposed enough to have formed antibodies to fight the bacteria, Clause said.
With the recent jump in exposure rates, Clause said he would expect to see a drop in the number of calves because more fetuses would have been aborted, but that hasn't happened. Instead, calf numbers are roughly the same.
Clause believes the increase in exposure is the result of a large number of previously vaccinated elk being exposed to an aborted fetus carrying the bacteria.
That exposure may have created antibodies that are masking vaccine antibodies, making it difficult to ascertain the presence of the vaccine in blood tests, he said.
The other cause could be a bad batch of vaccine used by Game and Fish in 1998.
After the vaccinations were done that year, researchers discovered the vaccine was old and had lost most of its potency, Clause said. Since then, batches are no longer kept for more than two years.
If either case is true, wildlife officials expect the exposure rate to return to lower levels over the next few years.
Meanwhile, tests are continuing on the vaccine.
State officials use a vaccine known as Strain 19, originally developed for cattle, to vaccinate elk on state feedgrounds. Federal officials, who manage the National Elk Refuge near Jackson, have refused to use the vaccine, saying it has not been proven safe and effective.
National Elk Refuge Manager Barry Reiswig said the jump in exposure rates on the state feedground will have no effect on what refuge officials do.
He said refuge officials are waiting for results from their own study of the effectiveness of the vaccine before making any decisions about using it on the federal site.
The refuge recorded a record low brucellosis exposure rate of 19 percent his winter, down from an average of about 30 percent in past years, Reiswig said.
Clause said the state will continue to use the vaccine.
"If we didn't think we were doing any good, we wouldn't be doing it," he said.
Brucellosis was first noted in the Greater Yellowstone Area in 1917 and no cure has been found. It causes abortions and infertility in elk, bison and cattle.
Although rare in humans, it can be passed to people through contact with infected animals or by ingesting their milk. Flulike symptoms can last for months or years.
Although the Yellowstone area is the last region in the nation where wildlife still have brucellosis, the scientific community is mixed on how easily it can spread from wild animals to livestock.
Still, biologists say a risk exists and are seeking ways to mitigate it.
----
On the Net:
Greater Yellowstone Interagency Brucellosis Committee:
http://www.nps.gov/gyibc/
