Prevention only ‘cure’ for deadly, new swine virus
By Tracy Harper, Western Technical College
The first cases of a new swine disease, Porcine Endemic Diarrhea Virus (PEDv), were reported in the United States in May 2013. Deadly for over 90% of piglets infected in their first 10 days of life, it is estimated that up to 3 million pigs already have been lost to PEDv. Twenty-five states, including all in the Midwest, and over 4,100 farms have reported cases (National Animal Health Laboratory, March 2014). This very deadly and fast-moving disease is hitting conventional hog farms hard. Without a vaccine or other successful treatment, prevention currently is the only cure. Smaller-scale organic farms have not reported significant losses to the disease, but there is no guarantee the disease won’t hit here, too.
Maintaining overall health in any animal is dependent on two factors: the strength of the animal’s immune system and the amount of pathogens in the animal’s environment. The goal of every producer should be to find ways to build and support the animal’s immune system, while reducing the level of harmful bacteria, viruses and fungi in the animal’s environment.
Supporting the animal’s immune system starts with reducing stress in its environment. Pigs are highly social animals. Allowing for that fact, we need to maintain enough space at feeders, or create separation between feeding areas to prevent fighting over feed resources. It is important, for both social and health reasons, to avoid mixing groups of animals. Every time you introduce new pigs into an established herd they will fight to determine social status, cliques and dominance. This causes social stress, as well as stress over the availability of resources. This is especially true with young pigs—avoid mixing recently weaned pigs with pigs from other farms or even other pens on your farm.
Minimizing the environmental stresses of extreme heat and cold are also important to maintaining a healthy animal. All age groups require shelter with bedding. Heat lamps are needed to keep young pigs warm in the winter. Damp buildings with little ventilation will keep your pigs cold regardless of how much heat you add. A cold and dry pig will be less affected by temperatures than a warm and wet pig. Damp air will allow viruses and bacteria to more easily be shared among animals. In the heat of the summer, it is important to provide wallows of mud the pigs can use to keep cool, and well ventilated shelters or shade trees and shrubs to hide under. Keeping pigs comfortable year round will help to reduce your animals’ stress, and thus their vulnerability to disease.
Nutritional support also is essential for animal health. Pigs, by design, are omnivores. They will seek out and consume both roughages (hay, pasture) and concentrated sources of energy and protein such as berries, grubs, roots, grains and nuts. An adult sow can meet 50% to 70% of her needs for energy and protein from forages (SA Edwards, etal. Pro Nutri Soc, May 2003). However, pigs still will need an additional source of concentrated energy to maintain their body weight. This is especially true for lactating sows, whose energy needs will nearly double. This need for highly digestible energy sources is met most often by feeding grains.
A balanced diet for pigs includes both energy and protein, a vitamin-mineral source, free access to salt, and water (SA Edwards, etal. Pro Nutri Soc, May 2003). Growing pigs—50 pounds or more—also can utilize pasture and roughages in their diet. However, due to the limited size and design of their digestive system, only 30% of their diet should come from forages. Young pigs—less than 50 pounds—do not have the digestive capability to utilize roughages, and so will need a higher rate of concentrated sources of energy and protein in their diet.
The addition of probiotics, prebiotics and manno-oligosaccharides has been shown to improve the immune system response. Manno-oligosaccharides (MOS), found in yeast bacteria, can be made using organically certified methods. Current research indicates that MOS are capable of interfering with harmful bacteria that cause digestive illness (Wenner, etal. J Anim Sci, Oct 2013). MOS are additives in several organically certified probiotic and prebiotic products currently on the market.
Biosecurity is a cost-effective means of preventing infectious pathogens from overwhelming the pig’s immune system. Despite the fact that natural and organically raised pigs often have a stronger immune system, they are still susceptible to being overwhelmed by infectious pathogens. This is especially true of the PED virus. Since this pathogen is new to the United States, our animals do not yet have a natural immunity to it.
PEDv destroys the small villi, which are finger-like projections that line the small intestine. These villi are critical for the absorption of water and nutrients from the small intestine. The result is extreme diarrhea, dehydration, high fever and weakness. This disease is deadly to pigs under the age of 10 days, and pigs older than 10 days will have significantly reduced rate of gain and growth, but will most likely survive.
PEDv is highly contagious—it takes a very small amount to cause devastation in the herd. This hardy virus has been found to survive in fresh feces for seven or more days, and in manure slurry spread on fields for up to 28 days. It has been found to still be capable of infecting animals after being in water for up to seven days, and in feed 28 days (S Goyal, Univ of Minnesota, March 2014).
Eighty percent of the farms affected by PEDv reported that their farm had been visited by a live haul, dead haul or feed truck within the two weeks prior to the outbreak. Since it is not possible to keep these trucks off your farm indefinitely, you need to make plans to avoid direct contact of your farm equipment and boots with the area that these trucks visit. This virus travels far in small amounts of manure. A study of 50 convenience stores in Iowa found active PED virus on the floor in 100% of the stores!
A good biosecurity plan will help to keep this virus and other potentially harmful pathogens out of your herd. Consider all the ways pathogens can ‘walk’ onto your farm. Decrease these by having a pair of ‘farm-only’ boots and clothes, and requiring visitors to wear disposable boots and coveralls. Requiring new animals to be tested before coming to your farm will prevent the most common transfer of disease: animal to animal.
Happy hogs are healthy hogs. Keeping your animals stress-free and following simple bio-security guidelines will ensure your hogs stay healthy, and allow your herd the best chance of avoiding the deadly PED virus.
Tracy Harper has over 20 years’ experience in the swine industry. She teaches at Western Technical College in La Crosse. As a private consultant, she has worked primarily with producers of organic and natural pork.
From the May | June 2014 Issue