Sheep studies could reduce spread of pneumonia |

Sheep studies could reduce spread of pneumonia

Sheep numbers have dropped from a 75 year high of 55 million head in the early 1940s to just over 5 million head today. Photo by Carrie Stadheim

Domestic sheep have historically been blamed by wildlife groups for infecting wild populations of bighorn sheep across the mountainous regions of the western U.S. with pneumonia.

Anti-grazing groups advocate removal of sheep from federal lands. But ranchers, as well as many researchers and land management agencies, say this is not a viable option. The forage needs to be managed. Additionally, ranchers say health problems in the bighorn sheep are not caused by interactions with domestic sheep but rather are due to weather, feed and general health, including persistent respiratory problems passed within bighorn herds.

Research has shown that bighorn sheep consistently harbor the respiratory bugs and are not “being infected” by domestic sheep, said South Dakota State University professor in pathology and bacteriology Dr. Larry Holler. But he and other scientists hope to find answers to help stop significant die-offs occurring in wild bighorn populations.

“Domestic sheep have them and the bighorns have them (bacterium), it is just a fact of life now,” Holler said. “The reality is these animals are already carrying the bugs. This research is trying to figure out how to improve the health of these existing sheep in the wild.”

Holler and several other SDSU scientists are teaming up with Idaho’s game and fish department and the University of Washington to perform a three year study on bighorn sheep from Idaho apparently infected with a new strain of Mycoplasma ovipneumoniae to determine just how the bighorns are passing the disease to one another. The researchers will compare “actively shedding” animals to those that are simply disease carriers to determine how and when the disease spreads from animal to animal.

“We are trying to find if it is just the shedders that are passing it on,” Frances Cassirer with the Idaho game and fish department explained. A shedder has the active pneumonia in its mucus while a carrier does not.

The ultimate goal, according to Cassirer, is to improve bighorn lamb survival rates. Cassirer believes it might be just the shedders – a relatively small number in the herd – that are passing the disease on to their young, but when the bighorn lambs interact they spread the disease to one another.

In general a bighorn sheep falls under one of three categories, said John Jenks, lead researcher at SDSU. “There are super-shedders who are always shedding pathogens, negatives that never shed, and then intermediates that shed when they come in contact with another shedder, but then stop shedding after a time,” said Jenks.

“We want to evaluate whether super shedders cause the diseases and then we can come up with management recommendation for dealing with it.”

Bighorn populations in the Black Hills experienced a 98 percent death rate in lambs in the past year, due in large part to Mycoplasma ovipneumoniae, SDSU researchers believe. Preliminary research at that college is indicating that the shedding theory may be validated but it is too early to know for sure, Jenks said.

If the theory proves correct, nobody is sure what the next step will be but wildlife managers may try removal of shedders from smaller populations of bighorn sheep to see if they can help slow passage of the disease.

It is possible that results from another study in another university on another group of animals could be helpful to the cause.

Sheridan Potter, a PhD student at Colorado State University is looking for a group of about 20 sheep free from another respiratory disease, Mannheimia haemolytica, as the university sheep are already infected. She will attempt to develop a vaccine for that pathogen and hopes to have her research completed by May of next year. It will depend upon availability of healthy sheep.

Potter said if her vaccine and an additional therapy she is pursuing prove successful, they could be used to prevent one strain of the pneumonia in cattle, domestic sheep and bighorn sheep.

Potter is aware of the political battles between the animal groups. Potter is testing some cull ewes from a western Wyoming ranch for the Mannheimia haemolytica. If those sheep are not free from the disease she will be on the lookout for healthy sheep and because of budget cuts she is hoping to find some relatively close to home and at a reasonable price.

“The ultimate goal with this vaccine and therapy that I’m developing is that it will help mitigate the issues of domestic sheep, cattle and bighorns grazing together.”

Her vaccine would be an oral one, she said, making it more feasible than a traditional immunization for broad dissemination for both wildlife and domestic sheep and cattle. But even in a perfect world, that is several years down the road, as she would need to conduct testing on bighorn sheep and cattle after the domestic sheep tests are completed.

The federally-funded U.S. Sheep Experiment Station, on the USDA Ag Research Service budget chopping block earlier this year, could be just the spot for continued pneumonia research, as well studies on a multitude of other sheep issues, said Idaho sheep rancher and state senator Jeff Siddoway. While the Clark County, Idaho research center is still in operation, earlier budget cuts have gradually whittled down the staff from 24 to just 14 employees and from six scientists in its heyday to just one today.

Siddoway is leading an effort to adjust the station’s focus away from traditional genetics and standard disease research. Siddoway says those studies on mastitis, footrot and different genotypes are critical but can be performed at any research facility. The U.S. Sheep Research Station’s location makes it the ideal location for studies on pressing issues that seriously challenge the domestic sheep industry, including bighorn interactions.

“The station is such a unique resource when it comes to research because in the western U.S. where our primary sheep populations are in the bigger ranches and the sheep are herded on the open range.” Siddoway said that the station operates on federal grazing land making it an ideal location for research to help western sheep ranchers including the bighorn interactions. “If they are going to do pneumonia research at these universities this could be the final testing place. They could see if it actually works.”

Other topics Siddoway hopes to see the station address are predator problems. “Through the experiment station the western sheep industry started to use guard dogs like Pyranees to protect our sheep from coyotes. Maybe there are other breeds that can help us with wolves and grizzlies. If we can find non-lethal ways to keep our sheep safe, I’m good with that.”

Siddoway said he also hopes the station can help with studies on alternative feeding concepts as well as wildlife co-habitation.

“The experiment station has 60 years worth of sage grouse, fire and livestock research and how those three interact.” Siddoway is hoping to gradually rebuild funding for the facility to enable it to employ more scientists and take on crucial research topics.

Sheep are easy prey. Just ask a coyote, fox, wolf, bear or a sheep producer. Sheep ranchers continue to watch for new methods of protection for their animals, from every kind of predator.

Easy prey to sharp-teethed animals, the shrunken domestic sheep industry has also become a target for anti-grazing groups as well as multinational companies importing lamb. In 2002, lamb and mutton imports were up 440 percent from 1975 numbers.

In about 30 years, U.S. sheep production has dropped from about 380 million pounds of meat in 1984 to just over 150 million pounds in 2011. Sheep numbers have dropped from a 75 year high of 55 million head in the early 1940s to just over 5 million head today.

Consumption is down too, with the average American eating an average of about 1.4 pounds per year in 1990 and a little less than a pound per year today. F


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