Wildlife and Feral Animals

White tailed deer with antlersWildlife 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

Feral swine adults with piglets

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


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.

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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.

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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.

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