Biosecurity is Always Important for Your Farm or Ranch
Healthy livestock perform better—more growth and weight gain in young stock, better reproduction, etc.—and incur less expense in treatment or death loss. Cattle are vulnerable to many kinds of diseases and some of these can best be prevented by making sure your animals are never exposed to other cattle that might be harboring disease. Since some pathogens can remain in the environment for long periods of time, you also want to make sure your animals have a clean and uncontaminated environment.
Some spore-forming bacteria like those that cause clostridial diseases (blackleg, malignant edema, redwater, enterotoxemia in calves, etc.) can be spread via cattle feces and exist in the environment a long time. They “come to life” after they enter an animal via contaminated feed and water, or via wounds.
Blood-borne diseases are spread by insects biting an infected animal and carrying the pathogen to the next animal they bite. Other disease are spread by direct contact from animal to animal (including sexually- transmitted diseases like vibrio and trichomoniasis) or spread to cattle by wildlife or birds, or even by humans who came into contact with certain pathogens on one farm and carry it to another.
One of the best defenses against bovine diseases is to have a “closed” herd, with no new animals coming to your farm or ranch unless they are first tested for certain diseases (and found negative) or quarantined for several weeks (to make sure they are not incubating a disease upon arrival) before being added to your herd.
Some of the diseases commonly spread by direct contact include IBR, BVD, Mycoplasma bovis, and brucellosis. Others are spread by the fecal-oral route, like calf scours (including cryptosporidiosis and coccidiosis), Johnes disease, and some strains of Clostridia.
Biosecurity Depends on Clean Environment
Shannon Williams, Lemhi County Extension Educator (Salmon, Idaho) says it is wise to think about biosecurity, especially if you share hired help with another ranch, or have people coming to do your chores, help feed, or help during calving season. People may bring pathogens from one ranch to another, especially during calving or handling sick calves.
Megan Van Emon, PhD (Extension Beef Cattle Specialist, Montana State University), says that if you are helping at a neighbor’s place and they have sick calves and you simply go back to your own barn and pens because you are calving, too—you may bring disease home. “Switch boots every time (one set of boots at each place) or disinfect them, to minimize risk for spread of disease.”
She’s had numerous calls over the years from producers experiencing problems with coccidiosis. “This disease and several others can readily occur when cattle are confined and/or co-mingling. It helps if you can keep corrals and barns clean. If you are dealing with a sick animal, make sure you wash your boots afterward (before you go to another stall, barn, pen or lot) and not just with water. Use a good soap or disinfectant every time you leave that area,” says Van Emon.
Use of Virtual Fence to Create Buffer Zone
Donnell Brown is a Texas rancher who has been using virtual fence to facilitate biosecurity. He started using virtual fence in 2023 for pasture management, then found it useful for many other purposes, including biosecurity.
“We use virtual fence to keep neighbors’ bulls out of my cows by keeping my cows away from the property line. I can put a virtual fence 100 yards from the actual fence, to create a buffer zone and keep our cows away from neighbors’ cattle. Then our bulls are not as likely to want to fight their bulls and our cows are not tempting their bulls to come visit,” he explains.
“If a neighbor brings in new cattle without a good health history, or buys some cattle and has a disease outbreak, I can immediately put in a buffer zone to keep my cattle away from those cattle.”
Wildlife
It’s more challenging when diseases are transmitted between livestock and wildlife, because it’s harder to keep wildlife out of your cattle. For a pathogen to be transmitted between wildlife and cattle, both populations need to be susceptible to that particular disease and able to excrete the pathogen after infection. To share the same pathogen, there must also be interaction between them.
The type of interaction required may be different from one pathogen to another. With bovine tuberculosis in Michigan, for instance, it’s been shown that if deer and cattle eat at the same feed grounds there is possibility of transmission, yet there are many other pathogens that would never transmit in these conditions. They would either need much closer contact or a different situation.
If a certain pathogen is able to survive in the environment, it doesn’t need such close contact, however. It only requires overlap between the wildlife habitat and areas where cattle are grazed or fed. Wildlife may be attracted to areas where cattle are fed, or where ranchers put out salt and minerals, where cattle drink, where the haystacks are located, etc. Elk and deer often get into ranchers’ haystacks, especially in winter.
One of the diseases occasionally passed between wildlife and livestock is leptospirosis. There are many different strains of this pathogen, and many species of animals (including dogs, rodents, deer, etc.) that can be carriers. These bacteria are shed in body secretions, especially urine, which can contaminate feed and water—and can survive a long time in water. Contaminated water is often the route this disease is transmitted to cattle, and there are some strains that are not included in the lepto vaccine.
In the intermountain West, some ranchers must contend with brucellosis (spread to cattle from elk and wild bison leaving Yellowstone Park). Prevention measures for brucellosis include managing wildlife/cattle interactions and ensuring cattle are “bangs” vaccinated. It’s important to take note of any cows that are open and watch for abortions, or newborn weak calves—and possibly have them checked for brucellosis. This is a reportable disease; brucellosis must be reported by any veterinarian who diagnoses it. The same is true for bovine tuberculosis, which can be spread to cattle by wildlife.
Other problems shared by wildlife and livestock include liver flukes. Elk and deer are the source of fluke infections with Fascioloides magna, since they are the main hosts. This is a different type of fluke that is normally found in cattle, and the deer flukes are harder to control or treat inn cattle.
Neospora infections can also be a problem, causing abortion in cattle. Neospora caninum is a cyst-forming protozoan that infects the digestive tract of canines and is passed out with their feces. The immature forms of the protozoa contaminate forage plants and may be eaten by a grazing animal. Then the tiny protozoa penetrate the gut wall and enter the bloodstream. They travel around the body and end up in other body tissues where they form cysts. They remain there, dormant, until the animal dies or is killed by a predator. When the predator or a scavenging canine eats the dead animal, the ingested cysts begin the life cycle all over again.
Risks for this disease increase if carcasses are left out on pastures to be consumed by wild carnivores. If carcasses are burned, buried or removed from the ranch—to where carnivores don’t have access to them—there is not as much incidence of neospora infection. Domestic dogs can also be hosts for this protozoan, so they should not be allowed to feed on carcasses or placenta from cows that aborted, nor fed raw meat.
There are other pathogens that may infect both wildlife and cattle that are transmitted by mosquitoes or biting insects, rather than being transmitted by direct contact between wildlife and livestock. These are more difficult to control.
Birds can Spread Disease
Birds are often attracted to cattle feed (such as grain or grain-based feeds) and may spread disease via their droppings (contaminating feed and water). Salmonella is sometimes spread this way, if birds carry this pathogen in their intestines. Other diseases can be spread by birds walking in cattle feces or calf scours and taking pathogens on their feet to a neighboring farm or ranch.
One of the newest concerns is Highly Pathogenic Avian Influenza (HPAI) caused by avian influenza Type A virus. These viruses are readily spread among migratory birds and can also infect domestic poultry as well as other birds and animal species. On-farm bird populations can contract HPAI from migratory birds and spread it to cattle. Kevin Dill, PhD, director of dairy technical innovation at Purina’s research farm says an important aspect of biosecurity includes feed preparation and traffic patterns within a farm operation, to minimize potential spread of this pathogen as people and vehicles travel around the farm.
Waterers also need to be disinfected, not just cleaned. A disinfectant can knock down the pathogen load, since birds like to perch by the water and leave their droppings in it. Any new animals coming to the farm should be quarantined for at least 30 days, to make sure they are healthy before they are introduced to the farm.
Some of the aspects of biosecurity involve trying to reduce cow exposure to birds. In addition, it is important to closely monitor animal health. Any cattle you suspect might be sick should be isolated and checked by your veterinarian.
Sidebar: Reportable Diseases
Dr. Beth Thompson, South Dakota State Veterinarian, says her state agency is most concerned about foreign animal diseases that are reportable. “Foreign animal diseases are the ones we don’t have in this country (and want to make sure we don’t have). Other reportable diseases are the ones that cause economic concern to the cattle industry.
Reportable diseases include bovine tuberculosis. Many people think this is just a problem in dairy cattle, but since it is spread by wildlife it is also a concern for beef cattle. “Here in South Dakota, that’s where we’ve found most cases—in beef herds. These have all been TB strains that trace back to Mexico,” she says.
Bovine tuberculosis is a slow-growing disease. “Cattle sometimes don’t show signs. They might lose weight or look like they aren’t doing well, but it’s not a disease where a rancher goes out and finds several sick animals.” It’s a subtle disease that can sneak into a herd and you wouldn’t know it.
“Most of the South Dakota TB cases in the past have been found at slaughter; the producer didn’t know the animal was affected. Trained meat inspectors check carcasses at slaughter facilities and we then trace it back to the herd the animal came from. We haven’t had an established problem here in this state, in contrast to Michigan where it’s a serious challenge. In Michigan this disease became established in whitetail deer.”
There is public health concern with tuberculosis, primarily on the dairy side because of more human contact; dairy workers who handle the animals can be at risk. The main way to prevent this disease is to never import cattle that are not tested; don’t bring roping steers from Mexico and put them with your cow herd.
“It’s important to know the health of any animals coming into your herd, if you don’t have a closed herd. Even if you do, there might be some risk if your neighbor’s cattle are across the fence from yours. Traceability is important. You don’t always know when you might need to trace an animal to see where it came from. Have your animals individually identified, and keep records,” says Thompson.
Vesicular stomatitis (VS) is another reportable disease, because the ulcerations it causes on feet and mucous membranes of the mouth are similar to those of foot and mouth disease. VS sometimes moves into the U.S. from Mexico during summer and fall, spread by insect vectors. “It doesn’t always get very far north. If you see a blister on an animal, consult a veterinarian. We need to differentiate VS from foot and mouth disease, which was eradicated from the U.S. many decades ago,” says Thompson.
Johne’s is a reportable disease that can be carried silently for many years before animals show signs (weight loss and diarrhea). “We haven’t had as many cases in recent years as we did in the past. We may only have one or two herds with it in South Dakota, but people still test for it,” she says. Johne’s can be devastating once it gets into a herd and middle-aged cows start breaking with diarrhea.
One of the newest risk to the U.S. cattle industry is the New World Screwworm (NWS). This is a parasitic fly whose maggots burrow into the living flesh of cattle (and other warm-blooded animals, including humans), feeding on the living tissue, enlarging wounds, causing foul smell, and often leading to death if left untreated. This screwworm was eradicated from the U.S. in the 1960s but is now a threat again from Mexico and Central America, creeping north and not very far from our border. This threat has prompted new drug approvals like Dectomax-CA1 and strict biosecurity for U.S. ranchers to try to prevent reintroduction. Since 2023 here have been more than 140,000 cases in animals and over 1,000 in humans during this outbreak and the cases continue to appear closer and closer to our southern border.
Sidebar: Biosecurity is the Best Prevention
Monitor cattle closely so you know what’s going on, and know what you are buying and bringing into your herd. Dr. Lee Meyring (cow/calf veterinarian near Steamboat Springs, Colorado) says any new animals brought onto your place should always be quarantined for a few weeks before adding them to your herd—to make sure they are not harboring a disease you don’t want.
“Every year we get a reminder of this issue. For instance a rancher in this area recently brought home a 4-year-old bull and didn’t think anything about it. He hadn’t been vaccinating his cow herd consistently and within the first 2 weeks of putting that bull with the cows, he lost several adult animals. The only thing that had changed was the addition of this new bull that was carrying a disease–and the herd was naïve and had no immunity. It was surprising how quickly it spread,” says Meyring.
People often inadvertently bring something like BVD or IBR into their herd with a purchased animal. Many diseases will show up within a quarantine period, but a slowly incubating disease like Johne’s will not. Make sure you buy your new animals from disease-free herds.
“If your herd is naïve, meaning your cattle haven’t been exposed to or vaccinated against a certain disease, they are at risk,” says Thompson. The animal you bring in may look fine because it has some resistance, but can still spread the pathogens it carries.
Many diseases can be readily spread around the country with movement of cattle and wildlife. There may also be new diseases on the horizon that ranchers are unfamiliar with. “Keep good records, know your herd, and your neighbors, and stay in touch with your veterinarian,” she says. Your best resource for advice and help as it relates to biosecurity, animal health, animal movement and disease surveillance is usually your herd veterinarian.
It is always beneficial to have a good working relationship with your veterinarian, to assist in herd health management strategies and preventative medicine, rather than just emergencies. Many diseases and health issues are more successfully prevented than treated, so it’s best to be proactive and try to avoid them.
March 2026
By Heather Smith Thomas
Home – American Cattlemen
