African Swine Fever (Update)

Barry Whitworth, DVM Area Food/Animal Quality and Health Specialist for Eastern Oklahoma

On July 28, 2021, the United States Department of Agriculture (USDA) confirmed African Swine Fever (ASF) in the Dominican Republic. The USDA is assisting the Dominican Republic with their efforts to contain and control this virus as well as offering help to Haiti which borders the Dominican Republic. The Dominican Republic is slightly over 200 miles from Puerto Rico. With Puerto Rico being a territory of the United States (US), any ASF found there would result in the World Organization for Animal Health (OIE) restricting the exportation of pork from the US. For this reason, the USDA is establishing a Foreign Animal Disease protection zone in Puerto Rico and the US Virgin Islands and is increasing efforts to keep ASF out of the continental US.

Loss of movement of pork from the US would have significant economic consequences in the US and Oklahoma. According to Kylee Deniz executive director of the Oklahoma Pork Council, Oklahoma pig farmers generate $5.7 billion in annual revenue. Loss of exports would not only affect pig producers but beef and poultry producers as well. All swine producers whether commercial, show pig producers, or kids with one 4H show pig must protect the Oklahoma pig industry. All pig producers should have a biosecurity protocol in place as well as be familiar with the symptoms of ASF.

The African Swine Fever virus is in the Asfarviridae family. The virus infects domestic and feral swine.  The virus is found in all pig secretions especially oronasal fluids of infected swine. The virulence of the virus varies considerably between strains with some strains resulting in large number of deaths and some with little sickness at all. The virus is resistant. Most common disinfectants will not destroy the virus. It will survive for long periods of time in blood, soil, and uncooked pork products.

The virus is easily transmitted by direct contact, indirect contact, and insect vectors. It may spread from pig to pig by inhaling the virus. Other ways that pigs may be directly infected are by ingesting the virus in uncooked pork products or by cannibalism. Fomites such as vehicles, footwear, clothing, equipment, and feed may serve as ways to introduce the virus to a farm. Feed and feed ingredients are especially worrisome. In simulated Trans-Atlantic and Trans-Pacific shipping models, ASF virus survived in feed ingredients (Dee et al.,2018). These experiments simulated shipping feed ingredients from Asia and Europe to the US. Lastly, the Ornithodoros ticks which are soft ticks are known to harbor the virus for long periods of time. These insects transmit the virus to pigs. 

Once a pig is infected with the virus, clinical signs will usually appear in 5 to 21 days. Sudden death may be the only clinical sign seen. Milder cases are often confused with other pig diseases. Clinical signs often observed are high fever, loss of appetite, weakness, and recumbency. Skin lesions sometimes seen are red blotchy areas or blackened areas. Infected pigs will have trouble breathing. Ocular and nasal discharges are seen in some pigs. Digestive signs include diarrhea, vomiting, and constipation. Pigs tend to have bleeding episodes such as nose bleeds or bloody diarrhea. Pregnant animals tend to abort. Abortion may be the first sign of the disease. Even though some strains of the virus cause minor clinical signs, most strains result in large numbers of sick pigs with several of them dying.

Treatment is not an option with ASF. Any swine operation that is found to have an ASF outbreak will be forced to depopulate and go through a rigorous cleaning and disinfecting of the farm. Vaccine research is ongoing, but no USDA licensed vaccine is available in the US at this time which means producers must rely on a good biosecurity plan to protect their premises. 

The USDA is working hard to keep ASF out of the US. However, many veterinarians would agree that if ASF were to be found in the US and the virus infected the feral pig populations, it would be very difficult to eradicate the virus from the US. For this reason, all swine producers need to focus on their disease prevention strategies to protect their animals. If producers would like more information about ASF, they should review the Foreign Animal Disease Prevention & Preparedness at www.pork.org/FAD  or contact their local veterinarian or local Oklahoma State University County Agriculture Extension Educator. 

References

Dee SA, Bauermann FV, Niederwerder MC, Singrey A, Clement T, de Lima M, Long C, Patterson G, Sheahan MA, Stoian AMM, Petrovan V, Jones CK, De Jong J, Ji J, Spronk GD1, Minion L, Christopher-Hennings J, Zimmerman JJ, Rowland RRR, Nelson E, Sundberg P, Diel DG . Survival of viral pathogens in animal feed ingredients under transboundary shipping models. PLoS One. 2018 Mar 20;13(3):e0194509.