Trucking/pig transportation protocols may need to be redone to develop successful regional eradication programs.
Editor’s note: This is the second in a two-part series of articles based on information presented during the Fourth International Swine Disease Eradication Seminar held in conjunction with last fall’s University of Minnesota Allen D. Leman Swine Conference in St. Paul.
In a previous article, Minnesota swine veterinarian Paul Yeske, DVM, MS, reviewed protocols in use today by the U.S. pork industry for eradicating swine disease (See Swine Practitioner, November-December 2004, page 16).
In this article, Yeske, with the Swine Vet Center, St. Peter, Minn., discusses disease control programs as opposed to disease eradication programs. He further discusses how eradication and control programs together might be used in regional efforts to eradicate swine disease, especially porcine reproductive and respiratory syndrome (PRRS).
“Disease control is a different matter than disease eradication,” he says. “The pathogen may still be present in the herd but is at a low enough level that there is no economical effect on the herd. Ideally the goal for commercial production is to have no clinical disease or suffer production losses. There are more options to control disease than eradication.”
Detailed, farm-specific biosecurity manuals need to be developed when embarking on disease elimination programs.
Multi-site production is one way of using animal flow to reduce the impact of the disease, according to Yeske. “This allows for a depopulation of the site with every group of pigs. However, this can be a double edged sword because the populations are vulnerable to more acute outbreaks of disease as well.”
Yeske says that the greatest risk is the stability of the source farms that determines the flow of the pigs, especially in multi‑sourced systems. “The flow is only as healthy as the weakest farm. Because the status of source farms is a dynamic thing, the flows must be evaluated on a weekly basis. The adjustments to the flow must be made when changes in health status occur. This requires good feedback from all stages of production. Many times the nursery can predict a PRRS outbreak before the sow farm is able to see it. With this information, you can go back to the sow farms and do more in depth diagnostics.”
Parity segregated farms are taking this to the next level, says Yeske. “Gilt offspring are most likely to have more problems. By separating this population from the mature sow herd, the increased disease pressure can be taken away from the older parity animals’ offspring. The gilt offspring can have more specialized treatments and vaccinations. We also know that these populations have more problems with Strep. suis, Haemophilus parasuis and Actinobacillus suis. This has worked well in some systems to control both PRRS and Mycoplasma. This technology can also work well for many other diseases.
Yeske says that vaccinations can be a a good method of disease control. “The use of swine influenza vaccine to sows is a good example of using a vaccination program to reduce disease in the nursery phase of production. Vaccination protocols are herd-specific and need to be customized.”
Minnesota swine veterinarian Paul Yeske believes that area and/or regional elimination of challenging swine diseases, such as PRRS, is possible with current control and eradication technology, but cooperation is needed from all involved.
Medication programs are also another good form of disease control, Yeske says. “These must be used prior to the onset of disease to really be effective. An example is using CTC (chlortetracycline) at 10 mg/lb on arrival of pigs into the finishing barn, to control Actinobacillus suis. This can keep the infection’s pressure at a low enough level to avoid the onset of disease. This approach can be used for a number of bacterial pathogens and depends on the farm’s timing of disease pressure and organisms present in the herd.”
Yeske says that combinations of medication and vaccination protocols can also be very effective for certain disease control situations. “An example of this is the use of feed grade antibiotics and vaccination to control Mycoplasma in problem finishing herds. The first dose of vaccine is given at 6 to 8 weeks of age and followed up with a second dose of vaccine at 9 to 11 weeks of age.
“In addition, you can feed Lincomycin the last two weeks of the nursery phase at 200gms/ton to help reduce the colonization of the Mycoplasma and again at eight weeks in the finishing phase to be ahead of the possible clinical outbreak. Timing of vaccination and medication protocols is best accomplished using serological profiling.”
Toward regional programs to control and eventually eradicat disease
Minnesota swine veterinarian Paul Yeske agrees that long-term regional disease eradication, especially for PRRS virus, will be the most effective means to reduce the risk of herd’s breaking back with diseases that have been eliminated.
In order to do this, however, “requires producers that are willing to share with other producers what they are doing and why they are doing it,” he says. “Communication and sharing are the most important factors in making these programs successful.”
Once an area has defined for eradication, you should map out all the herds in the area and define their status for the specific disease you are working with, according to Yeske. “There may need to be some changes in sourcing pigs for certain sites to help ensure success. An example is if there are positive finishing pigs in the area, they will need to be sourced from a negative source.
Vaccinations can be a good method of control for certain diseases.
“Sequencing of farms for eradication should be considered when there is cooperation in the area,” Yeske says. This allows for smaller areas to clean up and then expand out from the nucleus that starts the project.”
Yeske outlines the following additional considerations when attempting to develop area or regional disease eradication projects.
“Working with the drivers on routing of trucks is important so that trucks carrying positive pigs are routed around or away from herds that have been through the eradication process. This includes everything from piglets, feeder pigs, market hogs and culls from all stages of production.
“Truck-to-truck transfers may need to be done to accommodate the pig flow. Have a transfer chute.”
Washing of trucks is also important, Yeske says. “Designate positive and negative trucks and washes and make sure that there is no cross over. Servicing trucks also might be a challenge since both positive and negative trucks can be in the same service bay.
Yeske says that setting up detailed truck wash protocols is a must. “Have truck inspection forms to be filled out by the personnel washing trucks. Include third party inspections after the personnel have inspected the truck.”
Thorough drying of trucks appears to be the most important aspect after first getting the trucks clean, according to Yeske.
Yeske recommends developing detailed manuals with farm-specific guidelines that describe all biosecurity procedures. “Make sure that all supplies and suppliers are informed. Properly quarantine and in some cases fumigate all incoming supplies. Set up specific routes and schedules for suppliers.
“Set up feed systems so that once a week feed deliveries can be made on Monday mornings after clean up and disinfecting on the pervious Friday. Audit the processes and suppliers on a regular basis to ensure that the protocols are being followed and identify any new risks that may not have been previously recognized.
“Detail specific rules for employees on down time between clean and dirty, and rules for entry into the herd by service people. In larger systems, dedicate service personnel to the herds that have already been through the eradication procedure.”
Herd monitoring in the eradication area is just as important as the initial clean up, according to Yeske. “This needs to be done to ensure that if a herd’s status changes, it doesn’t affect other herds in the area.
He cites an example with PRRS eradication project: “All boars collected for semen use on farms that have been through an eradication procedure have been tested for PRRS by PCR before being shipped to farms.
“Routine serology doing statistical sampling in herds after eradication can help to pick up low-level infections before there may become significant clinical signs.” Further, adds Yeske, training farm personnel on what to expect for clinical signs and working up suspect cases as soon as possible is key to success.
Yeske believes that area eradication using currently available disease control and eradication protocols, is possible. “To set these types of programs up for success, work in areas with low prevalence – and usually low pig density – first. Make sure that producers understand the programs and what the benefits are.
He points to the successful national pseudorabies (PRV) eradication program as an example of what can be done. “The lessons learned from the PRV-eradication program are good and need to be implemented as we go forward with other diseases.”