Visit with a Vet: Monitoring for Porcine Epidemic Diarrhea Virus to Begin This Month

Originally published in the April 30, 2014, issue

 

Visit with a Georgia veterinarian in this monthly feature. This edition comes from State Veterinarian Dr. Robert Cobb in Atlanta, Ga., and follows up on a previous Visit with a Vet story on Porcine Epidemic Diarrhea virus from the Oct. 30, 2013, issue.

Porcine Epidemic Diarrhea virus is highly contagious in swine.
It has not yet been found in Georgia, but producers are
encouraged to take biosecurity and other measures to prevent
PEDv from making its way to their farms. File photo

The US Department of Agriculture recently announced it will be instituting a monitoring and control program to prevent the spread of Porcine Epidemic Diarrhea virus, a viral disease of swine associated with fever, severe diarrhea and vomiting. Right now, PEDv is considered a production disease, and is not regulated by the World Health Organization or the Department. However, USDA Animal and Plant Health Inspection Service will issue a federal order in May that requires mandatory reporting of all herds diagnosed with PEDv. Herds will be required to identify themselves and provide location information. In addition, animal health laboratories that receive diagnostic samples will be required to provide positive tests and location information to USDA.

The disease is highly contagious and is caused by a coronavirus. PEDv mimics a common pig disease called transmissible gastroenteritis, or TGE, which is also a coronavirus. Only lab tests can tell the difference between the two. PEDv is not a zoonotic disease, meaning it does not affect people. It does not affect other domestic species and is not a food safety concern. 

The disease is most severe in young piglets, but can affect pigs of any age. The disease can cause death and loss of production. Introduction of PEDv into a swine herd with no previous exposure to the virus typically results in acute outbreaks of abortion, severe diarrhea, vomiting, high morbidity – often 100 percent – and variable mortality, as high as 100 percent in pigs younger than 3 weeks of age. The incubation period is short, three to four days, and natural immunity develops. Pregnant sows often abort due to fever; however, older pigs usually recover from the disease within seven to 10 days.

PEDv exists in many parts of the world. The disease is very common in China, Korea and other Asian countries. In May 2013, the disease was first diagnosed and confirmed in the US, in Iowa.  It is unknown how the virus entered the US. There is some concern that feed products, such as porcine plasma products sprayed on pellets in certain rations, was responsible for introduction or spread of the disease. PEDv is not a listed disease of the World Organization for Animal Health, or OIE; is not considered a foreign animal disease in the US; and there are no international or interstate trade restrictions pertaining to PEDv in US swine.

The disease has spread to 28 states and to Canada, causing millions of dollars of damage due to losses from abortions, mortality and poor feed conversion. The number of confirmed cases is more than 5,500. In the Southeast, only Georgia, Florida, Alabama, Louisiana and Arkansas have not had a reported case of PEDv.

There is no specific treatment or commercially available vaccine for the disease. Supportive therapy is useful in the treatment of older animals, and sows that have recovered from the disease pass immunity to their offspring. Recovered animals can shed the virus for up to a month after recovery. 

PEDv can be spread in several ways. The fecal-oral route involves healthy animals ingesting the fecal matter of infected pigs. Fomites, which are inanimate objects such as trailers, chutes, buckets and waterers, clothing, boots and contaminated feed have all been shown to spread the virus as well. The virus is hardy and can survive for long periods of time, especially in cold, damp weather.

A strict biosecurity program is the only way to prevent introduction of the virus. Thorough cleaning and disinfecting of trailers and equipment are essential to keeping the virus out. Be diligent about personnel and visitors, but also consider supplies, feed ingredients, food items, etc. that might be of international origin. To check the origin of a product or ingredients, contact the supplier and request that information. The creation of a “clean crossing line” will help to prevent contaminated personnel or products from entering the farm. 

Additional biosecurity recommendations include thoroughly cleaning and disinfecting anything coming onto the farm; enforcing downtime requirements and maintaining a log of visitors; properly disposing of dead livestock; isolating new animals; continue vet-to-vet discussion about animal health at the herd of origin; and showering into the facility and changing into clean boots and overalls. Veterinarians should also be careful not to transport the virus between herds on their person, equipment or vehicles.

All hog farmers are encouraged to monitor the Department website for news and updates on PEDv.

Some information in this column comes from the National Pork Board, American Association of SwineVeterinarians and USDA-APHIS. For more information on PEDv, visit www.agr.georgia.gov, www.pork.org/pedv or contact the State Veterinarian’s Office at 404-656-3671. Veterinarians can send samples to the two state diagnostic labs for confirmation of PEDv. The Athens lab can be reached at 706-542-5568 and the Tifton lab at 229-386-3340.

Visit with a Vet: Porcine Epidemic Diarrhea Virus

Originally published in the Oct. 30, 2013, issue

 

Visit with a Georgia veterinarian in this monthly feature. This edition comes from Dr. Jeremiah Saliki, director of the Athens, Ga., Veterinary Diagnostic Lab.

 

In April and May 2013, multiple Midwestern American pig farms were simultaneously hit with a disease characterized by diarrhea and vomiting. These symptoms led clinicians and diagnosticians to suspect the coronavirus transmissible gastroenteritis virus, or TGEV, as the cause. Testing fecal samples from sick piglets using standard laboratory techniques failed to confirm these suspicions.

 

However, when the same samples were examined under an electron microscope, coronavirus particles were detected. The unexpected discovery of coronavirus particles that were negative for both US swine coronaviruses – TGEV and porcine respiratory coronavirus – prompted further testing. Tests done at Iowa State University and the Federal Laboratory at Ames were done for exotic coronaviruses, and resulted in the confirmation of porcine epidemic diarrhea virus for the first time in the US.

 

Geographic distribution, transmission and clinical signs

 

Coronaviruses are highly contagious, and the outbreaks in the US spread rapidly. Within six weeks the virus had been confirmed in about 200 hog facilities in 14 states including Arkansas, Iowa, Illinois, Indiana, Kansas, Michigan, Minnesota, Missouri, North Carolina, New York, Ohio, Oklahoma, Pennsylvania and South Dakota.

 

Sporadic outbreaks of porcine epidemic diarrhea were first identified in the United Kingdom in 1971, and this infection has become endemic in most Asian countries since 1982. There was one incursion into Canada in 1980, but it has not been reported in North America since then.

 

The virus is transmitted by the oral-fecal route, with an incubation period of three to four days. Contaminated personnel, equipment, or other fomites may introduce PEDV into a susceptible herd. The disease is difficult to distinguish from TGEV, with the main clinical sign being watery feces that may resemble tufts of wool and have an unpleasant smell. Vomiting may occur and dehydration is a secondary sign.

 

Morbidity and mortality can surpass 90 percent in suckling piglets fewer than 14 days old, but gradually decreases with age. During necropsy, histological examinations – where thin pieces of tissue are mounted on slides and viewed under a microscope – show the small intestine is inflamed with shortened villi, which indicates nutrients are not being properly absorbed, causing diarrhea.

 

Diagnosis

 

The most useful diagnostic specimen is feces or a loop of small intestine. A variety of diagnostic tests, including negative-staining electron microscopy, fluorescent antibody staining, immunohistochemical staining and virus isolation, commonly used for TGEV diagnosis are available in our laboratory for presumptive PEDV diagnosis. However, a test known as polymerase chain reaction is the only technique that can differentiate between TGEV and PEDV. The diagnostic labs in Tifton and Athens, Ga., offer a PCR technique that can detect both viruses, and  a positive result is followed by an additional test – sequencing – for definitive diagnosis.

 

PED and Georgia

 

The rapid spread of PED across the US and its occurrence in neighboring North Carolina raise concern for its possible introduction into Georgia. Fortunately, we are poised to rapidly detect the virus if it was to enter the state. The vigilance of swine practitioners and animal owners is key to detecting its incursion into our state. We recommend that PEDV testing be requested for all cases in which an acute TGEV-like disease is observed with high morbidity.

 

Some information in this column comes from the USDA Porcine Epidemic Diarrhea Technical Note and the 2012 publication “Porcine epidemic diarrhea virus: a comprehensive review of molecular epidemiology, diagnosis, and vaccines.”