In recent years the livestock industry has become more aware of wildlife transmitted diseases and the potential for increased risk to cattle through contacts with wildlife. Populations of some wildlife species (such as whitetail deer) have increased greatly in many parts of the country, creating more potential for transmission of certain diseases.
Dr. Sam Holland, South Dakota State Veterinarian, in discussing disease transmissions from wildlife, says that the ones he's dealt with that are really significant in this country are brucellosis and tuberculosis. "We've dealt with brucellosis in bison in private herds, and over the years eradicated brucellosis in those herds. We've dealt with the cervid (deer, elk, moose, etc.) species over the years and eradicated it in those species. We have dealt with brucellosis in state and national parks in South Dakota and eliminated it in our state park 40 years ago and the national park almost 30 years ago, with a good vaccination and testing program," he says.
"It takes a little more time in wildlife herds because you don't have access to these populations of animals as readily as you do a cattle herd, or even to bison that are privately owned. It takes effort and a lot of cooperation and patience by all parties, and you don't get results as rapidly as you do in domestic animals that are more confined and handled more," says Holland.
"We dealt with tuberculosis in elk and in bison that were privately owned 20 years ago in our state, and eliminated it. TB in captive elk was handled nationwide. We eradicated it from our state in the early 1980's and then we enacted a very stringent control program for TB and brucellosis in elk, much as we did for other animals, prior to the federal regulations that are now in place. There are now uniform methods and rules for elk and buffalo, in regard to TB and brucellosis, but there was a fairly significant amount of TB in elk in the late 1980's and early 1990's that was rapidly eliminated with cooperation from the owners and the animal health officials," he says.
"In Michigan now we're seeing TB (which has been in the deer population there for 20 years) spilling over into the state's cattle population. I think there are 17 cattle herds in Michigan affected with TB, from the wildlife. It's a lot more difficult to manage when you have the wildlife to deal with, because it takes more time to clean it up. To do that, they probably have to address some of the management practices that allowed the disease to become established in the wildlife. It's important that we have good wildlife managers in our fish and game departments that are responsible in attempting to manage the wildlife with concerns not only for the resource that's there for recreation and environment, but also for animal health. It's a big challenge," says Holland.
"It's one thing to manage livestock. It's a bigger challenge to manage wildlife to suit the needs of all stakeholders -- the various interests --because they don't always work together on these things. Some people would never be satisfied that we have enough wildlife of a given species, and others think we have too many. And sometimes we have too many in one place and not enough in other places," he points out.
"When they manage wildlife -- and the Michigan situation is an example --care must be taken in concentrating them, if they do become overpopulated. When animals are confined (and whether you are concentrating them by fences or by feeding, you are still confining them), you need to be really careful and do a lot of thinking before doing it -- such as what's happened in Michigan and also in the greater Yellowstone area. Whether it's by feeding in winter, or bait feeding for hunting (like in Michigan) or letting the numbers increase beyond what they should be, when we concentrate them that way we need to pay close attention to other husbandry practices, particularly animal health," he says.
We tend to get more disease problems when there are too many animals in a small area. "Sometimes the people who are responsible for managing wildlife don't put a high enough priority on health concerns. The wildlife interests certainly don't want disease in their animals, but sometimes management decisions are made that don't consider the risks, possibilities, and implications of diseases becoming established in populations of wildlife," he says.
"It isn't uncommon, for example, in the areas that have bluetongue virus or EHD (epizootic hemorrhagic disease, another virus disease that is primarily found in free-ranging deer), that when the populations of deer build up, we have problems. If other environmental conditions are right, such as temperature, stagnant water, vector populations, then we see a big dieoff of deer due to EHD. There are some states that have reported EHD signs and lesions in cattle populations, that have been related to the presence of EHD in deer in those areas. EHD could become a problem in cattle; it can cause lesions that are similar to those of VS (vesicular stomatitis) or FMD (foot and mouth disease). Whenever you get animals showing these signs, it becomes very crucial for proper diagnosis," explains Holland.
Deer can also harbor food-borne pathogens such as E. coli that can also occur in food animals. He says we need to manage the deer populations in terms of concentration and being careful where they are allowed to go. "Producers need to take precautions in terms of biosecurity to prevent wildlife from exposing their herds, such as mingling on feed grounds -- not only for diseases they might share, but also for food-borne pathogens that can be carried by either species and transmitted back and forth."
Another shared disease is cryptosporidiosis, caused by a parasite that can be carried by young cattle (causing diarrhea). "We know it can also be carried by free ranging cervids. Not only do producers need to be aware of these things, but this is another reason for maintaining separation and biosecurity for their operations. Deer could bring this into their herds, so it has to be considered. It can show up as disease in the livestock or may have the potential of polluting water sources," says Holland.
If we ever have a foreign animal disease come into this country, we not only must be concerned about the threat it would pose to our livestock but also to our wildlife, and it would be very difficult to halt it in the wildlife. This is another reason for properly managing population densities, says Holland.
"We see the artificial maintenance of wildlife populations, such as by seasonal feeding. Yellowstone elk are an example, being fed in the Jackson Hole area. A tremendous effort has gone on over the years to maintain what is no doubt an artificially high population of animals, which is unhealthy for both the habitat and the animals," he says.
This is also what happened with bison in the Yellowstone area in the past. The disease factor is mother nature's way of thinning an overly dense population--more animals than the habitat can support. So to manage for high numbers is asking for trouble.
"I think management practices for ranchers must be tailored to each producer's specific operation. For a confinement feeding situation, the big issue may be feed storage, and being careful that the stored feed is not accessible to contamination by wildlife (even rodents and canines, which can spread several diseases, including leptospirosis). For those who feed livestock in concentrated areas in winter, there's not only the problem of feed storage but also the intermingling of animals as wildlife are attracted to the feed. Each operation needs to be managed with consideration for biosecurity. The cattle industry in general is behind the swine and poultry industries in terms of attention and emphasis on biosecurity, but are becoming more aware."
"In our state's beef and dairy beef quality assurance critical management plan, biosecurity is one of the things mentioned, to assure quality and safety of the product. If we are going to do everything we can to minimize food-borne pathogens in an operation, we also need to minimize potential for wildlife to introduce those pathogens into a livestock operation," he points out.
"The subject of wildlife transmitted diseases is extremely important, and too often neglected. In addition to being aware of the immediate concerns and biosecurity, producers also need to make their concerns known to the appropriate animal health and wildlife authorities, not only at the state level, but at the federal level. It's important that there is cooperation. We're fortunate in our state that we have good cooperation and have effectively handled a number of diseases. At the federal level there needs to be (and it looks like now, with the new administration there is going to be) some cooperation. It looks like USDA and Interior have committed to cooperate to address animal health issues," he says.
"It's important for producers across the country to express their concerns to their political representatives also. There are a large number of other organizations out there that are not well informed in terms of husbandry and animal health. They are looking at numbers rather than the health of wildlife, and don't appreciate (probably because they are not fully informed) the significance of animal health issues. They are extremely vocal, and when their inputs are heard -- wanting to increase numbers and maintain artificial populations, not taking actions to control diseases, then it's very important that producers speak up to say, 'We've learned something about animals, and you need to be concerned about disease, and maintenance of animal health, or you will not have that wildlife resource forever.' Much of the general public is not aware of these things, and too often producers are too busy to go to the meetings." It's a difficult challenge, but one that is very important for the livestock industry to face.