In today's pork industry, perhaps no issue is as critical to protecting and maintaining the health and efficiency of swine herds as a scientifically based program of biosecurity.

Infection of susceptible swine with agents such as porcine reproductive and respiratory syndrome (PRRS) virus, Mycoplasmal pneumonia and swine influenza virus, in conjunction with pathogens such as Actinobacillus pleuropneumonia and Hemophilus parasuis, can lead to the formation of the porcine respiratory disease complex and result in reduced performance, elevated mortality and reduced profitability.

In addition, intestinal pathogens such as Lawsonia intracellularis, Transmissible gastroenteritis (TGE) virus and Escherichia coli negatively affect survivability, growth rate and feed efficiency. Preventing the introduction of these agents through a science-based biosecurity program is a critical component of a farm's disease control program.

Biosecurity Rationale

This article will summarize the rationale behind the protocols of swine herd biosecurity, review routes of pathogens spread between farms and provide data from scientific studies that support the application and practice of specific protocols.

These protocols continue to be tested and validated through an ongoing experiment at our Swine Disease Eradication Center (SDEC) production region model farm in west central Minnesota. This farm is using PRRS virus and Mycoplasmal pneumonia as model agents. It is well known that the cost of a PRRS break is anywhere from $5-15/pig or $250/sow.

Our hope is that swine veterinarians and their clients can work together to utilize this information for the development of effective biosecurity programs for sustainable disease control.

Direct Routes of Pathogen Spread

It is well known that infected animals and/or contaminated semen can introduce infectious agents to susceptible populations. Depending on the agent, once introduced to a herd, pathogens can be shed by carrier animals via blood, saliva, milk and colostrum; urine and feces; and by contaminated semen.

Purchasing genetic material from naÏve sources that are monitored on a regular basis is critical to a successful biosecurity program, as is proper use of scientifically validated quarantine and testing protocols.

Ideally, quarantine facilities for incoming breeding stock should be located on a separate site. Incoming stock should be kept separate from resident stock for a minimum of 30 days and farm personnel should monitor animals daily for clinical signs of disease. The herd veterinarian should remain in close communication with the seedstock supplier's veterinarian during this period, in case the onset of a disease is suspected in the source population or the animals in quarantine.

During the quarantine period, animals should be blood tested according to veterinary recommendations.

Indirect Routes of Pathogen Spread

Pathogens spread through indirect routes include contaminated facilities, fomites (i.e., needles, boots, coveralls), people, transport vehicles, pests and aerosols. Examples supporting these conclusions, as well as protocols to reduce the level of risk, are as follows:

Facilities — Swine facilities should be managed using all in-all out (AIAO) pig flow, thereby reducing the spread of PRRS virus from older, infected pigs to younger, naÏve animals.

In conjunction with AIAO flow, it is important to properly sanitize the facilities before introducing susceptible animals. All organic material (feces, urine, feed, bedding, body fluids) should be completely removed and the surfaces carefully washed.

Once clean, an efficacious disinfectant should be applied throughout the pen area. The application of disinfectants using a foamer allows for better visualization of where product has been applied and also prolongs the contact time between the chemicals and the surfaces. Allow adequate time to dry.

Fomites — For pathogens that replicate and/or circulate in the bloodstream, injection of consecutive animals using a contaminated needle can result in blood-borne spread of certain viruses, such as PRRS and possibly porcine circovirus Type 2 (PCV2).

To reduce this risk, it is recommended that producers change needles between sows during third trimester injections or utilize “needle-free” technology.

Contaminated containers, such as semen coolers, tool boxes and cartons of farm supplies, along with coveralls and boots, can serve as mechanical vehicles for PRRS virus spread.

Consequently, all incoming supplies should be disinfected and double-bagged prior to entry into a designated room on the farm. Barn-specific coveralls and boots should be available in all facilities and washed routinely. Disposable coveralls and boots are another option.

Use of footbaths can greatly reduce the risk of transfer of certain pathogens, such as PRRS virus, between groups of pigs. Footbaths should be changed daily to maintain disinfectant efficacy. Only disinfectants that have been validated as efficacious should be employed.

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