Porcine Epidemic Diarrhea (PED) is a highly contagious viral disease that affects pigs globally, posing a significant challenge to swine health and production. First identified in 1971, this disease has since been diagnosed in numerous countries. It impacts pigs of all ages, though its severity varies depending on the animal’s age.
The Porcine Epidemic Diarrhea Virus (PEDV)
PED is caused by the Porcine Epidemic Diarrhea Virus (PEDV), which belongs to the Alphacoronavirus genus within the Coronaviridae family. This enveloped RNA virus primarily targets and replicates within the epithelial cells lining the small intestine of pigs. The virus damages intestinal villi, reducing the absorptive surface area and resulting in fluid loss and dehydration.
Transmission of PEDV occurs primarily through the fecal-oral route, where pigs ingest virus-contaminated feces. The infectious dose is low, meaning a small amount of virus can cause infection. Indirect transmission is also a concern, with the virus spreading via contaminated vehicles, equipment, feed, and personnel who have been in contact with infected animals or their waste.
PEDV can persist in the environment on various surfaces, including styrofoam, rubber, plastic, and clothing, and can be transferred through contaminated fomites. Airborne transmission may also contribute to its spread between pigs and farms.
Identifying Symptoms in Swine
The clinical signs of PED in pigs vary in severity based on age, with younger animals experiencing more acute symptoms. In suckling piglets, especially those less than a week old, the disease manifests as severe, profuse watery diarrhea, often yellow-green, accompanied by vomiting and a loss of appetite. This rapid dehydration can lead to mortality rates up to 100% in this age group.
Older pigs, including weaners, growers, and finishers, exhibit milder symptoms. They may develop transient watery diarrhea without blood or mucus, experience a loss of appetite, and occasionally vomit. While mortality rates in these older age groups are low, 1% to 3% in post-weaned animals, they can still experience growth rate losses of 10%. Breeding sows may also show watery diarrhea and a temporary reduction in milk production.
Strategies for Disease Control and Prevention
Controlling and preventing PED outbreaks relies on strict biosecurity protocols. Comprehensive farm sanitation practices are essential, including regular cleaning and disinfection of facilities, pens, and equipment. Disinfectants like formalin, anhydrous sodium carbonate, and sodium hydroxide are effective against the PED virus.
Biosecurity Measures
Controlling the movement of vehicles, personnel, and animals. Vehicles entering and exiting farms should undergo thorough disinfection. Personnel should wear personal protective equipment, like disposable coveralls and boots, changing it between different animal housing areas or farms.
Quarantining new or returning animals for at least three weeks before introducing them to the main herd.
Feed ingredient testing to prevent virus introduction through contaminated feed.
Vaccination enhances herd immunity against PEDV. While vaccines are available, their efficacy varies depending on the specific virus strain. Proper animal nutrition and management practices, such as “all-in/all-out” systems, also limit disease spread. These systems involve moving groups of pigs together, then emptying, cleaning, and disinfecting facilities before the next group arrives. These strategies prevent the virus from entering a farm or mitigate its spread during an outbreak.
Broader Implications for Pork Production
PED outbreaks extend beyond immediate animal health concerns, imposing economic consequences on the global swine industry. High mortality rates, especially in suckling piglets, translate to production losses. For instance, during the first year of outbreaks in the United States, an estimated 7 million piglets died due to PED, contributing to economic losses between $0.9 billion and $1.8 billion.
Beyond direct pig losses, outbreaks lead to increased operational costs for producers, including expenses for enhanced biosecurity, diagnostics, and veterinary care. A reduced supply of pigs can lead to higher pork prices for consumers and impact the profitability of various segments of the pork supply chain. The presence of PED can also lead to trade restrictions, affecting international pork markets and disrupting global supply chains. Animal welfare concerns also arise due to the severe clinical signs experienced by infected pigs.