Wildlife may be considered all free-ranging animals, including native and exotic wildlife species, as well as feral domestic animals. Where their paths cross, livestock can be exposed to disease-causing agents carried by wildlife. This may happen at a water source that livestock share with Canada geese or a feed manger that also happens to be home to a family of mice. These are just two examples of where contact and transfer of disease can take place. You need to be aware of the risks posed by wildlife.
The three main areas targeted as wildlife biosecurity concerns are:
- Feed (particularly feed storage).
- Water sources.
- Livestock living areas.
Birds, rodents, coyotes, pet dogs and cats, insects such as mosquitoes, and deer can be carriers of diseases that affect other animals or humans. Deer carry a worm, Parelaphostrongylus tenuis, or P. tenuis, that can cause fatal meningitis in sheep, goats, or llamas. There are also emerging diseases that have been found in wildlife and may spread to livestock. Chronic Wasting Disease (CWD) is being monitored for this potential.
In addition, there are bacteria and other microbial pathogens that live on the farm that do not need wildlife as a host, but can easily be introduced to the herd by way of a contaminated water source. Intestinal diseases such as cryptosporidiosis, Johne's Disease, and campylobacteriosis can all be spread in this way.
Transmission of disease between wildlife and livestock, can occur directly (such as from nose-to-nose contact or exposure to body fluids/tissues, such as feces, urine or blood) or it can occur indirectly through contaminated environments (e.g., soil) or shared feed and water sources.
Farm managers and maintenance personnel can reduce the risk of domestic animal exposure to these and other harmful diseases. Periodic maintenance of feed storage areas, watering systems, and animal facilities will reduce wildlife biosecurity risks. Regular maintenance will ensure a low risk of exposure to wildlife or other disease vectors and optimize herd health and productivity.
Eliminating or reducing interactions between humans, domestic animals, and infected wildlife is a key point because controlling disease in wildlife is difficult and expensive. Some methods to discourage wildlife and protect livestock include:
- Vaccination for diseases such as rabies.
- Create areas unattractive to wildlife and barriers between wildlife and susceptible livestock. Fencing is one option.
Feral Animals

Image source: USDA APHIS
Depending on the disease of concern, wildlife species may become infected and ill with the disease, spreading it to other species; or they may become infected, without illness, but serve as a source (or a reservoir) to spread the disease agent to other locations and animals, including livestock or poultry. However, in other diseases, wildlife may simply be a reflection that the disease is already occurring in domestic livestock or poultry in the area.
For example, feral swine are susceptible to and can serve as a reservoir of diseases such as classical swine fever and African swine fever viruses that can also infect domestic swine. Feral swine can transmit pathogens to livestock, which may result in financial losses to livestock producers due to lower productivity, veterinary costs, or even mortality.
They are also capable of killing young calves and lambs, and vulnerable adult animals during the birthing process. Feral swine may also eat or contaminate livestock feed, mineral supplements, and/or water sources. Feral swine are also a risk for the reintroduction of pseudorabies into domestic swine populations.
Wildlife Biosecurity Recommendations
House sparrows, starlings, pigeons, and swallows commonly inhabit barns on livestock farms. Geese and wild turkeys often share ponds or pastures with livestock. Birds can spread salmonellosis and avian tuberculosis (which cross-reacts with bovine tuberculosis tests). They also can carry the organisms that cause enteric bacterial diseases, fungal diseases, Q fever and other diseases associated with mastitis and abortion, tapeworms and other parasites.
Most of these diseases are also transmittable to humans. Not only can birds spread disease onto healthy farms, but they can also be an expensive nuisance. A starling will eat 50 percent of its body weight in grain each day. Nests that are made in barns close to the heat of a light fixture or bad wiring can be a fire hazard.
To reduce the exposure of livestock to birds and their droppings, first evaluate the current presence of birds on the farm:
- Identify places on the farm where birds like to nest, bathe, and perch.
- Inspect the farm for places where there are lots of bird droppings.
- Observe whether birds perch on or above livestock.
- Observe whether birds bathe in livestock water troughs.
- Where birds are a problem, bird detractors should be considered.
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- Options include recordings of distress calls, whistles that make an irritating sound, as well as visual detractors, bird netting, and reflectors.
- Use of these methods is still no guarantee that all birds will stay off the farm.
- Attracting raptors like red-tailed hawks may help.
Additional maintenance procedures should be followed to keep birds and droppings away from the herd’s feed and water:
- Clean out water troughs and feed bunks daily.
- Keep livestock away from ponds where birds congregate.
- Keep stored feed well-covered.
- Install screening to prevent birds from accessing barns.
- Destroy nests and eggs of nuisance birds.
- Thin stands of trees where starlings would roost.
- Discourage migrating flocks of birds from stopping at your farm.
Rodents, like birds, are found on most farms. Rats and mice live in farm buildings, feed storage areas, and woodpiles. They eat grain intended for the herd and potentially spread bacteria like Salmonella and E. coli by contaminating feed with their droppings. They may also chew the insulation off of wires, causing a fire hazard.
To control these risks to the herd’s health:
- Identify and routinely bait places where rodents could den in storage areas or barns.
- Inspect buildings and feed storage areas for evidence of rodents, such as droppings and nests.
- Identify their source of food and prevent access to it.
- Destroy their denning places and block off any small holes to prevent reentry.
- Eliminate hiding areas around barns and storage facilities. Consider paving right up to buildings and removing all vegetation close to building entrances. Rodents do not like crossing wide open areas.
- Use traps or bait to catch rodents. Place 10 to 20 feet apart.
- Use tamper-resistant bait stations to protect farm pets, especially dogs, from rodent poison.
- Search for dead rodents and dispose of them appropriately. Do not touch them with bare hands.
- Prevent more rodents from coming on the farm by maintaining a clean and regularly inspected facility.
Coyotes
Coyotes are wild canines with dog-like features. They are well-adapted to populated areas and are no strangers to farms, fields, and woods. Coyotes are less likely to attack livestock where wild game such as rabbits, squirrels, and mice are plentiful. They will also kill deer and eat carrion.
How deadstock are handled may enhance a farm’s coyote population and encourage depredation of livestock. Coyotes may carry disease-causing agents and should be kept out of areas where livestock are pastured or housed.
Dogs
Dogs may be used on farms to help move or guard animals. Unfortunately, dogs tend to eat just about everything from Rocky Mountain or prairie oysters and afterbirth to horse manure.
Unless dogs are kept out of animal feed and housing areas, they may spread any of a number of disease-causing agents that can be spread through fecal-oral contamination. Of particular concern is data suggesting that dogs play a role in completing the life cycle of the protozoan parasite Neospora. Neospora causes abortion in cattle.
Dogs should, therefore, not be able to access pastures during calving, lambing or kidding season, or maternity areas of barns.
Cats
Cats may be part of a farm’s rodent control program. Like dogs, they can spread a number of disease-causing agents and may carry Neospora as well.
It is best to prevent cats from living in hay mows or other areas where feedstuffs are accessible. Farm cats and dogs should be routinely vaccinated against rabies.
Deer can also introduce disease onto a farm. Deer can carry Bovine Tuberculosis, Johne’s Disease, and Chronic Wasting Disease. Pastures and water sources shared between deer and livestock should be avoided.
To evaluate your farm and decrease the risk of your livestock contracting diseases from deer, do the following:
- Look for droppings, deer beds, and signs of deer around the perimeter of the farm and pastures.
- Evaluate the water sources on the farm to ensure that deer cannot contaminate the herd’s drinking water (e.g., brooks, streams, etc., that pass through grazing pastures).
- Prevent the herd from drinking out of these types of water sources.
- Secure fences along the perimeter of pastures.
- Wind socks may be used on fence posts to deter deer from coming close to the fence where transfer of disease or bacteria would occur.

Deer Tick
While a vector is technically defined as any living organism that can carry disease causing agents between animals, disease carrying vectors are most commonly thought of as arthropods (members of the insect and spider families), such as mosquitoes, fleas, biting midges, flies, ticks and mites.
Arthropods can transfer disease causing organisms through a bite while feeding on an animal, or sometimes simply by carrying the disease agent on their body, such as on the legs of certain fly species. Many animal diseases that are spread by arthropod vectors affect domestic livestock, as well as wildlife species.
Vector control and elimination measures are an important consideration and component for many animal disease outbreak responses. Vector control begins with an understanding of the arthropod’s life cycle and the transmission potential. Insect life stages vary in their habitat and ability to transmit disease. Specific control measures will be needed based on the life stage.
For instance the egg laying grounds for flies are different than that of mosquitoes and midges; one control method may not work of all.
Limiting livestock and poultry exposure to arthropod vectors or their habitats can reduce infection risk. Excluding access of livestock (or wildlife) to vector habitat areas or avoiding exposure during peak vector activity times are examples.
Eliminate Breeding Habitat
Reducing the source of the arthropod vectors consists of eliminating potential insect breeding areas and larval habitats. Generally, this involves:
- Removing standing water sources, such as tree holes or old tires.
- Agitating any standing water sources, such as stock tanks or water troughs, or mowing vegetation to reduce habitat.
Some insects require manure or organic material for development, so cleaning animal feeding areas, yards and barns can minimize these vectors.
Sometimes biological agents or natural predators for a particular arthropod vector may be used to control the larval stages of other insects. Examples include bacterial toxins such as Bacillus thuringiensis, parasitic wasps or dung beetles that feed on arthropod larvae.
Control of Adult Insects
Control for adult insects often involves the use of chemical insecticides. Some products are used in vector habitat areas, while others may be applied directly to animals.
- Fogging or knockdowns products may work to a limited extent.
- Baits and fly traps may also aid efforts.
However, none of these should be used as the sole method of control, only as a supplemental measure.
Controlling the egg and larval stages of the arthropod vector is generally more efficient than controlling adults. When using chemical pesticides, proper precautions must be taken when handling or applying them. It is a violation of State and Federal Law to use a pesticide in a manner that differs from the product label. Use only according to label directions.
Vector Content Source: Just in Time Training, Center for Food Security and Public Health at Iowa State University.
Mosquitoes

Mosquito
These annoying, biting insects can carry diseases such as West Nile virus and other encephalitis viruses that affect humans and horses, and they carry heartworm of dogs.
One of the best ways to minimize the risk of these diseases on your farm is to control the number of mosquitoes. Destroying their habitats and breeding grounds will reduce their numbers.
Most mosquitoes lay their eggs on the surface of shallow water. Eggs take about 48 hours to hatch, and then the larvae (the immature stage of the mosquito) live in the water for about a day, eating organic material and breathing through a tube that reaches the surface.
The larvae then molt into pupae (similar to the cocoon stage of butterflies) where they develop for about two days, still in the shallow water.
Finally, the adult emerges and leaves the water. Adult females bite a host animal to get a blood meal before breeding. The saliva that transmits diseases during a bite also causes swelling and itchy irritation. Males, on the other hand, feed on nectar and do not bite.
There are simple measures that can be taken to reduce their numbers:
- Prevent standing water as much as possible.
- Clean out gutters, birdbaths, and troughs regularly.
- If you have a pond, stock it with fish that eat mosquitoes like goldfish. Also, damselflies and dragonflies eat mosquitoes.
- Make your pond with steep sides to minimize shallow water and allow fish to get to the edge to eat the larvae.
- Note that mosquito fish are considered a non-native invasive species, and may be illegal to stock in your state.
Wildlife Biosecurity Resources

Livestock Management in the Mountains
This downloadable PDF covers several topics including wildlife management, fencing, managing small pastures & more. A publication from the Colorado State University Extension service.

Wildlife Management and Vector Control
Although this document is for emergency response, it has useful information for wildlife control and management. From the Center for Food Security and Public Health, & USDA.

Feral Swine Management
Feral swine cause tremendous damage to agriculture, including row crops, forestry, livestock, and pasture. A website with information about the USDA APHIS feral swine program, and contact info for Wildlife Services.