African Swine Fever Threat in US: Simulation Study Reveals the Challenges and Costs of Containing an Outbreak

African swine fever (ASF) is a devastating viral disease that affects domestic pigs and wild boars. It causes high fever, hemorrhages, and death in most infected animals, with a mortality rate that can reach 100%.

There is no vaccine or treatment for ASF, and the only way to control it is by culling infected and exposed animals and implementing strict biosecurity measures.

ASF does not affect humans or other animals, but it poses a serious threat to the pork industry and food security.

It is endemic in many parts of Africa and has spread to several countries in Europe and Asia in recent years, causing massive losses of pigs and economic damage.

In 2018, ASF reached China, the world's largest pork producer and consumer, and has since wiped out about half of its pig population.

It has also been detected in neighboring countries such as Mongolia, Vietnam, Cambodia, Laos, Myanmar, the Philippines, Indonesia, Timor-Leste, Papua New Guinea, and most recently, Malaysia.

The US is currently free of ASF, but the risk of introduction is high due to the global movement of people, animals, and products.

The US is the world's third-largest pork producer and exporter, with about 77 million pigs and a pork industry worth $20 billion.

An ASF outbreak in the US would have severe consequences for the pork sector, as well as for animal welfare, public health, trade, and national security.

How ASF could enter and spread in the US

(Photo : KHALED DESOUKI/AFP via Getty Images)

ASF could enter the US through various pathways, such as:

•  Illegal importation of infected or contaminated pork products or animal feed ingredients from ASF-affected countries. These products could be smuggled by travelers or shipped by mail or cargo. If these products are fed to pigs or discarded in areas accessible to pigs or wild boars, they could transmit the virus, as per Phys.org.
•  Legal importation of live pigs or pig products from ASF-affected countries that are not properly inspected or certified as ASF-free. These imports could introduce the virus into domestic pig farms or processing facilities.
•  Contact between domestic pigs and wild boars that are infected with ASF. Wild boars could become infected by consuming contaminated pork products or animal feed ingredients, or by interacting with other infected wild boars across borders. Wild boars could then transmit the virus to domestic pigs through direct contact or indirect contact via contaminated soil, water, or fomites (objects that can carry the virus).
•  Human-mediated transmission of ASF through contaminated clothing, footwear, equipment, vehicles, or other materials that come into contact with infected pigs or pig products. These materials could carry the virus from one farm to another or from one country to another.

Possible modes of ASF transmission 

Once ASF enters the US, it could spread rapidly among swine farms through various modes of transmission.

One possibility is between-farm movements of live pigs or pig products that are infected or contaminated with ASF. These movements could occur through trade, transport, slaughter, or disposal of pigs or pig products.

Vehicle movements that carry infected or contaminated pigs or pig products from one farm to another is one other possible transmission mode.

These vehicles could include trucks, trailers, cars, motorcycles, bicycles, or even drones.

There is also the possible local spread of ASF through direct or indirect contact between infected and susceptible pigs within a farm or between neighboring farms.

This contact could occur through nose-to-nose contact, biting, fighting, mating, nursing, aerosols, feces, urine, blood, saliva, or other bodily fluids.

Lastly, there's environmental spread of ASF through contaminated soil, water, vegetation, or wildlife that come into contact with infected pigs or pig products. The virus can survive for long periods in the environment under certain conditions.

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How the US is preparing for an ASF outbreak

The US has been taking various actions to prevent and prepare for an ASF outbreak, such as:

•  Enhancing border security and surveillance to detect and intercept illegal imports of pork products or animal feed ingredients from ASF-affected countries. The US Customs and Border Protection (CBP) has increased its inspections of travelers and cargo at airports and seaports using dogs, x-rays, and other technologies. The CBP has also increased its penalties for smuggling pork products or animal feed ingredients.
•  Strengthening biosecurity measures on swine farms and processing facilities to prevent the introduction and spread of ASF. The US Department of Agriculture (USDA) has issued guidelines and recommendations for biosecurity practices such as restricting access to pigs and pig products; cleaning and disinfecting clothing, footwear, equipment, and vehicles; disposing of dead animals and waste properly; reporting sick or dead animals promptly; and testing pigs for ASF regularly.
•  Developing contingency plans and response strategies for an ASF outbreak. The USDA has developed an African Swine Fever Response Plan that outlines the roles and responsibilities of federal, state, and local authorities; the goals and objectives of the response; the surveillance and diagnostic methods; the control and eradication measures; the communication and outreach activities; and the recovery and restoration plans. The USDA has also conducted exercises and simulations to test and improve the response plan.
•  Collaborating with international partners and stakeholders to share information and resources on ASF prevention and control. The US participates in various networks and initiatives such as the Global African Swine Fever Research Alliance, the World Organisation for Animal Health, the Food and Agriculture Organization of the United Nations, and the North American Animal Health Committee. The US also supports ASF research and capacity building in ASF-affected countries.

Despite these efforts, the US still faces many challenges and uncertainties in dealing with a potential ASF outbreak.

The lack of a vaccine or treatment for ASF. The development of an effective and safe vaccine or treatment for ASF is a high priority, but it is also a complex and difficult task that requires more research and funding.

The potential impact of wild boars on ASF transmission and control. The US has an estimated population of 6 million wild boars that are widely distributed across 39 states.

Wild boars could serve as reservoirs or vectors of ASF and complicate the detection and eradication of the disease.

Moreover, an ASF outbreak in the US could cause significant losses of pigs and pork products, as well as disruptions in trade, markets, prices, employment, income, food security, and public confidence.

An ASF outbreak could also affect other sectors such as tourism, transportation, energy, and health.

The US is not ready for an ASF outbreak, but it is working hard to prevent and prepare for one.

The country needs to continue its efforts to enhance its surveillance, biosecurity, response, research, and collaboration capabilities to protect its pork industry and food security from this devastating disease.

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