As the world swine population continues to grow domestically and internationally, this opens doors to producers and veterinarians to visit production locations away from home. In some cases, this may involve going to a location with diseases that aren’t present in the U.S.. Knowing this, it’s good to review biosecurity measures we can take to minimize risk of pathogen transmission and keep our borders safe.
On this topic, we all stand on common ground: to protect our national swine herd from four viruses we are free of: African swine fever virus, hog cholera, pseudorabies virus and foot-and-mouth disease.
1. Understand disease risk and transmission
The foreign animal disease (FADs) at the forefront of today’s news headlines is African swine fever, or ASF. In China, the first case of ASF was diagnosed in the beginning of August. Since then, the government has confirmed more than 50 cases, and more than 500,000 pigs have been euthanized.
Understanding the risks and transmission of this pathogen can help us keep this virus outside of our borders. Specifically, the risks from highest to lowest of harboring and transmitting ASF are blood, meat, direct pig contact and mechanical vectors such as shoes and clothing. Proof-of-concept investigations also indicate that we need to consider feed and feed ingredients as risks.
European Studies show ASF can survive and remain viable in blood for more than four months and, depending on the storage temperature of processed meats, up to 300 days. With this in mind, it’s incredibly important that any meat products imported from an ASF-positive nation are screened or entrance prohibited to minimize the risk of transmission to the United States. For example, it’s critical to prohibit international farm workers from consuming pork on site from a source other than the on-site farm to decrease the associated risk of transmission. All other food items entering farms should be sourced from grocery stores -- not wet markets that hold the potential of containing multiple species present from multiple sources that may be processed together.
On the perspective of blood, a single drop of blood from a pig infected with ASF can contain more than six logs of virus -- more than enough be the nidus of infection for a population of naive pigs. So using a disinfectant known to inactivate the ASF virus such as Virkon or 2% sodium hydroxide on contaminated surfaces will help reduce the risk of mechanical transmission through blood. When performing necropsies, take extra precautions to decrease bodily contamination and spread of this virus by using proper carcass clean up and disposal methods.
2. Use protocols for travel
There are many ways to decrease the risk of fomites during international travel. First, select clothing and shoes that you only use for (international) travel. When you return to the U.S., wash any clothing items you took overseas immediately in hot water and dry them with hot air to kill any pathogens that may be present. After cleaning, separate these clothes from the rest of a wardrobe as additional layer of biosecurity. In addition, use disinfectant wipes to wipe down all objects you’ve overseas locations. After items have dried, wipe them down a second time and let them dry fully. The National Pork Board recommends a minimum of 48 hours of downtime after international travel before returning to a farm in the U.S.
Many groups, including Pipestone Veterinary Services, would include a safety factor of additional nights – a protocol of a minimum of five nights of downtime after returning from a trip overseas that included visiting any swine farm.
3. Practice responsible importation
Based on research Scott Dee, DVM, and his colleagues completed in 2018 on the survival of feed ingredients in shipping models across the Atlantic and Pacific Oceans, we understand that a number of viruses, including ASF, are hearty enough to survive a transoceanic journey. With this information, we can generate an equation for imported feed ingredients to estimate the need of an additional storage period based on the necessity of the proposed import, the estimated contamination level at the source, the complete transport time from source to mill, and whether effective mitigants are available.
Fast facts About ASF
- European Studies show ASF can survive and remain viable in blood for more than four months and, depending on the storage temperature of processed meats, up to 300 days.
- A single drop of blood from a pig infected with ASF can contain more than six logs of virus -- more than enough be the nidus of infection for a population of naive pigs.
- Using a disinfectant known to inactivate the ASF virus such as Virkon or 2% sodium hydroxide on contaminated surfaces will help reduce the risk of mechanical transmission through blood.
The research also provides details on half-lives of various viruses in these different feed ingredients. With the knowledge that an ingredient sourced internationally could potentially be contaminated with virus, one of the main mechanisms for reducing the risk of entry into a U.S. herd would be to enact a voluntary downtime period to allow for the virus concentrations to decrease below the levels that would permit oral disease transmission.
Please see the Feed Ingredient Safety decision tree matrix below:
Only when everyone in the industry understands the risks and repercussions of a foreign animal disease in the United States and does practices prevention can we continue to keep our national swine herd free of ASF and other FADs.
For all producers, now would be a good time to confirm that you have the correct phone number and contact information of your state and local veterinarian, so you can launch an investigation immediately if you notice any alarming signs. This can speed the path to confirm a diagnosis.
Risks of Harboring and Transmitting ASF
Direct pig contact
Mechanical vectors, including shoes and clothing
* Proof-of-concept investigations indicate feed and feed ingredients may also pose as risks
Joseph Yaros, DVM, grew up in upstate New York with three twin brothers (a twin himself and younger twin brothers) on a 1,000-ewe sheep farm. Caring for livestock and understanding the management of the flock inspired Yaros to pursue a career in veterinary medicine, where he recently graduated from Cornell University. He spent the summer of 2014 and fall of 2015 with Pipestone Veterinary Services working as a swine veterinary intern.