On top of record-setting sub-zero temperatures, depressed farm prices and lower crop yields, pork producers are facing another challenge that is testing their mettle: Pigs coming down with the highly contagious viral disease — Porcine Reproductive and Respiratory Syndrome.
PRRS causes reproductive failure in sows (abortions, weak and stillborn piglets, infertility) and in pigs, causing pneumonia and increased mortality. While a global problem, in the U.S. alone total costs to the swine industry hover around $580 million a year (2016 figure), down from $664 million in 2010.
There is no specific treatment or cure for this constantly mutating disease. It spreads via animal bodily fluids and can be transported by vehicles, people and wind. Feed also has been a suspected carrier.
Vaccination, monitoring, testing, early weaning, piglet isolation and extremely tight biosecurity protocols are helpful in controlling or minimizing the spread of PRRS. But that’s it, thus far. Farmers and their veterinarians do the best they can when PRRS strikes.
Pork producers Chuck and Wanda Patsche, Welcome, Minn., are managing another barn with some pigs infected with PRRS. They recently received 2,200 3-week-old pigs from their co-owned sow farm. Sows there had shown PRRS symptoms in December and January. Testing confirmed the disease.
“We had four veterinarians in four days looking at our pigs and working on a plan,” Wanda says. “It’s just really disheartening. There is nothing you can do. When we went through this a year ago, my husband says over his 40 years of farming, he had never seen pigs this sick.”
Their current barn of pigs will stay there until they are 5 1/2 to 6 months old, ready to market at around 280 pounds. Then, the Patsches will do the routine barn washing and disinfecting, then take another load of pigs.
CONTINUING CARE: The Patsches work with several veterinarians to formulate a treatment protocol for their pigs when the PRRS virus is detected.
Pigs sick with PRRS often show signs of fever, respiratory stress, pneumonia, lethargy and failure to thrive. With compromised immune systems, pigs also could contract strep, E. coli, rotavirus or salmonella, Chuck adds. They’ve seen mortality rates range from 10% to 20%.
Tracking ‘risky’ movements of workers
Current research at Ohio State University is looking at correlating “risky” movements of workers on swine farms to create an awareness of how such movements may impact PRRS spread and how they can be minimized. Movement data would also be analyzed and linked to its impact on production.
Andreia Arruda, a veterinarian at OSU’s Department of Preventative Veterinary Medicine, and her colleagues are working with three Midwest farms and recently shared preliminary data from one 4,400-sow farrow-to-wean swine farm with a history of PRRS.
A “risky” movement is defined as moving from a likely PRRS-infected location to a non-susceptible site, such as moving from a loading and shipping area to a farrowing or gestation room. Non-risky movements include going from farrow to farrow sites or moving from younger to older pigs.
Workers wore or carried coin-sized sensors that were detected via Bluetooth as they entered and left each room.
Preliminary data indicate a connection between movements and production data. A decrease in risky movements saw a slight increase in the number of pigs per litter, while an increase in risky movements saw a slight decrease, 0.37, in the number of pigs per litter. The increase in risky movements also resulted in a 3% increase in pre-weaning mortality.
The U.S. pork industry has set a goal for controlling PRRS. One of the National Pork Board’s strategic goals is to offer tools and programs to decrease the annual economic impact of PRRS by 20% by 2020, as adjusted for inflation and measured against a 2012 PRRS economic impact baseline study.
Managing PRRS in swine herds
A number of control strategies have developed over the past three decades since the PRRS virus was identified in the U.S.
In a recent news release, Andrew Bents, Hubbard Feeds, swine technical veterinarian, offered these vaccination and treatment strategies. Options can be mixed and matched to develop a program suited to each individual farm. Discuss options first with your veterinarian before implementation, he adds. Options include:
• Live virus inoculation, also known as “serum therapy” or “mass exposure.” This involves exposing the entire sow herd to a serum prepared from samples from infected animals and given intranasally or injected. One advantage: The serum is given to the whole herd simultaneously, minimizing rapid movement and mutation of the resident virus among sows. However, following exposure to the serum, some farms experience high reproductive losses and even increased sow mortality.
On the other hand, piglet quality seems to start to improve as the animals exposed in their second trimester of pregnancy begin farrowing. This varies, though, depending on the previous exposure of the virus to the herd and by controlling the virus’ movement throughout the farm
• Commercially produced modified live virus vaccines. These are readily available, have been prepared in a safe manner and can be safely implemented in multiple farms simultaneously.
Keep in mind that MLV vaccines are stimulating the body’s innate immunity. They will not be able to clear the infection nearly as effectively as acquired immunity, which includes antibody production. Think of MLV vaccines as a first responder, triaging the problem until the body has had time to identify and produce specific antibodies against the virus, which typically takes around two weeks.
These products work best when used in conjunction with a larger control strategy such as quarterly whole-herd vaccination with ongoing piglet vaccination, or vaccination of piglets post-weaning.
Five products are available in the U.S. market and each has its unique live viruses modified for use. Consult with your veterinarian to learn more about them.
• Killed virus vaccination with an autogenous product. These vaccines generally take two to three months to produce after identification of the virus. However, antibodies stimulated by this vaccine are exactly what is needed to fight off the existing infection in the herd. They are good for maintaining immunity within a herd against chronic infections, especially if there is reason to keep the live virus out of the control program. Ongoing surveillance is necessary to evaluate the herd’s PRRS status, however, since this vaccine type will give poor protection against a new strain of PRRS entering the farm.
• Antibiotics and ancillary therapy. Since PRRS is a virus, antibiotics are generally considered unsuccessful in treating the primary infection. However, using antibiotics correctly can reduce the presence of other pathogens in the herd. Recent research utilizing oral or injectable antibiotics from the Macrolide class has shown a reduction in the severity of a PRRS break, during either primary or serum exposure.
Adding anti-inflammatories like aspirin or ibuprofen in the drinking water carries some merit, given the high fevers that typically result from a PRRS break. However, they should be used judiciously.