California Department of Food and Agriculture


Biosecurity is a series of management procedures designed to prevent or greatly reduce the risk of introducing new infectious agents to a farm. A related concept is biocontainment, management strategies directed at reducing the risk of spreading existing infectious agents between groups of animals or into the environment.  Key components to both concepts include: screening and testing, isolation and quarantine, immunization, selective purchasing and monitoring and evaluating.

Biosecurity is a whole farm approach to herd health management. The risks to herd health must be assessed, prioritized, and addressed. Risk can be categorized by source of possible infection, area of the farm or by susceptibility of animals.

(Definitions & concepts from Dr. John Thompson, AABP’96)



  1. Animal Density/Stocking Rate - Crowding of animals increases opportunities for aerosol and contact transmission. Crowded conditions also increases stress levels, affecting immune responses negatively.  This is situation is particularly critical for animals housed within barns or other enclosed environments.

    Solutions: Avoid overstocking, provide adequate air circulation.

  2. Introduction of sick or unknown status animals to the herd - Risk can be introduction of a disease the herd has not been exposed to (naïve population).

    Solutions: Maintain a closed herd (Raise your own replacements). If not feasible, isolate/quarantine new entries until you know they are healthy and try to buy animals from a known, disease free source. Isolation length depends on the incubation period of the disease(s) that concern you most.

  3. Shared water/feeding sites- Common feeding sites or water sources can be contaminated by infected animals. Animals that drink or eat from a common site then run the risk of becoming infected as well.

    Solutions: Provide individual feed/water sources. If not possible reduce the number of animals sharing sources and periodically clean and disinfect.

  4. Mixing of species – Some diseases can affect more than one species. In one species the diseases may have little to no health impact but by interacting with another susceptible species can result in devastating disease.

    Solutions: Use fencing and other management techniques to reduce contact between your animals and wildlife. If you raise multiple species, keep them separate and reduce disease transmission risks by having separate equipment and if keeping.

  5. Visitors- Domestic and international visitors can be a risk as they can be mechanical as well as biologic vectors (Mechanical: They can carry organisms on their clothing, shoes and even skin. Biologic: Some organisms can infect both people and animals meaning an infected person can be the source of disease for your animals.)

    Solutions: Don’t allow visitors. If not feasible then a) know where they come from and the potential risk for disease they present, b) provide clean clothing and footwear for them, and c) limit/ don’t allow access to animals.

  6. Vehicles- Vehicles can serve as mechanical vectors of organisms and therefore can be a source of transmission across farms and even within farms.

    Solutions:  Don’t allow vehicles that may enter other livestock premises onto your farm. If not feasible, limit their access to the periphery, non-animal areas of the farm. Requiring that any vehicles, including your own, be cleaned and disinfected entering and exiting also reduces risk of transmission.

  7. Health Monitoring/treatment- Undetected, untreated illnesses can put the rest of your animals at risk.

    Solutions:  Frequent monitoring (visual as the base tool) is essential.  Prompt isolation and appropriate treatment of sick animals can assist in reducing risk of transmission to others.

  8. Solutions: Be sure animals are getting the right nutrition for their species, age and physical activity and/or production level.

  9. Preventive measures (vaccines)-There are a variety of vaccines available that can assist in enhancing immune status. There are not vaccines available for all diseases.  It should be noted that some vaccines do not prevent disease but decrease the impact. Solution

    Solutions: Vaccines should never be considered as a sufficient solution for disease prevention/control.  They should be part of a broader biosecurity plan, one that addresses the various points made on this website.

  10. Animal handling/treatment practices- How you manage and treat animals can impact  the health of your herd or flock positively or negatively.

    Solutions: Treatments, including vaccination are usually thought of as a positive thing for herd health but don’t forget that good sanitation practices should be in place.  Some diseases can be spread when you are treating/ vaccinating for something else.  For example, repeated use of needles can introduce the risk of spread of blood borne diseases.  The person handling animals for treatment can become contaminated by sick animals and if appropriate sanitary measures are not in place they can introduce the organism to other animals.   To reduce risks of disease transmission within your herd or flock, you can consider grouping/housing animals by susceptibility and then planning management activities to protect the most susceptible animals.  The youngest animals generally are most susceptible so handling them before others helps to reduce risk.

  11. Engage your local veterinarian when developing a biosecurity plan.