The United States pork industry is on high alert for a deadly virus sweeping through Asia and Europe — African Swine Fever virus (ASFv). Decimating domestic swine populations, this contagious and resilient virus has already affected thousands of pig farms. Although it doesn’t pose any threat to humans, this virus could be devastating for the pork industry at large.
While African Swine Fever virus has not yet been detected in the United States, the risk is high. The United States Department of Agriculture (USDA), industry organizations, producers, academics and allied partners — such as Kemin — have been working hard to keep it at bay. Education, awareness and preparedness are all key to protecting the industry from this emerging disease threat.
African Swine Fever virus is a contagious viral disease that affects swine of all ages and origins. Termed a hemorrhagic viral disease, African Swine Fever virus is frequently deadly to infected domestic pigs, causing a range of serious symptoms from fever and vomiting to extensive internal hemorrhaging.
African Swine Fever virus is the only member of the genus Asfivirus in the family Asfarviridae — the root “Asfar” in this case is an acronym, which when combined with the suffix for “viruses” literally means “African swine fever and related viruses.” One common mistake is to compare African Swine Fever virus with Classical Swine Fever (CSF) — although the symptoms of these two diseases are similar, the viruses are entirely unrelated.
African Swine Fever virus is a double-stranded DNA virus and replicates primarily in the lymphatic and vascular systems of infected pigs. The virus works by entering the bloodstream of pigs and infecting white blood cells. Once inside, the virus alters the DNA inside of the white blood cell, reprogramming the cell to start creating more of the virus. When the cell has reached the end of its usefulness, the virus destroys the cell and enters the bloodstream to infect more cells. Over time, the virus starts infiltrating cells in the spleen, lymph nodes, kidneys, gastrointestinal and respiratory tracts, resulting in widespread hemorrhages.
African Swine Fever virus is not a zoonotic disease, meaning that it does not transmit from animals to humans. African Swine Fever virus only affects the family Suidae, which includes domestic pigs, wild boars and warthogs. Because of this inability to affect humans, African Swine Fever virus is not a public health or food safety concern.
In domestic swine, the incubation period — the time between infection and onset of symptoms — can range from five to 15 days. Even more worrisome is the fact that infected animals can start shedding the virus more than 48 hours before their symptoms start appearing, and recovered pigs can continue shedding the virus for up to a month after their symptoms stop. These factors are just a few of the reasons that this disease is so difficult to contain with traditional farm biosecurity measures.
While a pig is contagious, it can spread the virus via three primary pathways, described below in detail:
· Direct contact: Direct contact with an infected animal, whether domestic or wild, can result in an infection. This occurs most often through swill feeding, where pigs are fed food scraps that contain meat or have come in contact with meat. Direct contact can also involve direct transmission of fluids, but this is less common.
· Indirect contact: Indirect contact with contaminated food or surface is another method of transmission. Food or surfaces may be contaminated with blood, feces, urine, saliva or semen, which can all carry the virus for a long time. Contamination can then spread to swine through the consumption of contaminated food or through contact with contaminated surfaces. African Swine Fever virus may also spread through indirect contact if a worker touches contaminated material before handling live swine.
· Vectoral transmission: African Swine Fever virus is the only known DNA arbovirus, meaning that it can be spread by arthropods, primarily ticks. The soft ticks from the genus Ornithodoros spread African Swine Fever virus by biting pigs and are also reservoir hosts for the ASF virus — this means that the virus can live within a tick host without negatively affecting its health, and can persist through the local tick population without needing to infect a primary host, in this case, a pig. Studies have also shown that pigs can become infected with African Swine Fever virus by ingesting blood-sucking stable flies, or Stomoxys calcitrans. Stable flies may carry African Swine Fever virus for up to three days after feeding on infected blood to transmit the virus to healthy swine.
Direct and indirect contact are the most common modes of transmission for African Swine Fever virus and are the focus of efforts for on-farm virus mitigation. Studies of 68 recent outbreaks in China found that 34 percent of the outbreaks were caused by swill feeding, 46 percent by contaminated equipment and handlers and 19 percent through transportation.
Domestic pigs can express a wide range of clinical symptoms — sometimes the symptoms are very obvious, while other times they can be challenging to detect, or easily mistaken with other conditions. Often, the severity of symptoms is based on the virulence of the virus and the type of pig affected. Generally speaking, the clinical signs of African Swine Fever virus come in two forms — acute and chronic.
Acute forms of African Swine Fever virus are more severe and more deadly, with mortality rates as high as 100 percent, especially in areas where the disease is not endemic. The symptoms will generally lead to death within 6 to 20 days of onset, depending on the conditions of the case. Acute African Swine Fever virus is characterized by the following symptoms:
· High fever
· Decreased appetite and weight loss
· Red, blotchy skin or skin lesions
· Muscle weakness
· Coughing and difficulty breathing
· Bluish discoloration of the skin from oxygen loss
· Spontaneous abortion in pregnant cows
· Diarrhea and vomiting
Chronic forms of African Swine Fever virus, also called subacute forms, are generally caused by less virulent forms of the virus, therefore causing less severe symptoms. This form is more common in areas where African Swine Fever virus is endemic and is also seen in wild boar populations. Animals with chronic African Swine Fever virus tend to express symptoms for a longer time, and it can take days for the symptoms to become recognizable. Though the mortality rate for chronic African Swine Fever virus is lower, it still tends to range from 30 to 70 percent. The most common symptoms of chronic African Swine Fever virus include the following:
· Intermittent fever
· Decreased appetite and weight loss
· Red, blotchy skin or skin lesions
· Coughing and difficulty breathing
If a producer or veterinarian notices any of the above-listed symptoms, they should immediately report to state or federal animal health officials for a thorough investigation. Even though African Swine Fever virus has not reached the United States yet, it is essential to report possible incidences promptly to help maximize response and prevent spread of the virus.
Currently, there is no African Swine Fever virus vaccine. Although previously infected pigs show immunity to subsequent infections, trial vaccines using a modified form of the virus have been unsuccessful at making pigs immune to the virus. One of the reasons for this is the fact that the ASF virus interferes with communication between cells, making the immune system less effective at creating antibodies.
While researchers continue working on a vaccine, African Swine Fever virus still poses a threat. Unfortunately, due to the high level of resilience of the virus, the only way to prevent African Swine Fever virus from spreading is to depopulate affected herds, disinfect all objects that came in contact with them and ensure strict biosecurity protocols are employed moving forward.
African Swine Fever virus has a long history, mostly affecting Europe, Asia and Africa. While the disease was originally identified in Kenya in the 1920s, African Swine Fever virus has spread through several countries, including several European countries, China, Cambodia and Vietnam.
African Swine Fever virus was restricted to Africa until 1957, when an outbreak was reported in Portugal. Though this initial outbreak was controlled and eradicated, a second outbreak in 1960 resulted in African Swine Fever virus becoming endemic to Portugal and Spain until 1995.
From Portugal and Spain, African Swine Fever virus spread to other European countries, including the Netherlands, Italy, France and Belgium. In the mid-1990s, there was a widespread effort to eradicate the disease outside of the African continent through pathogen control on farms, which was largely successful for all non-African countries. The exception was the isolated island of Sardinia, Italy, in which African Swine Fever virus has been continuously present since 1978.
A second transcontinental spread from Africa to the East European country of Georgia occurred in 2007. This highly virulent African Swine Fever virus strain, known as Georgia 2007/1 or ASFV-G, spread rapidly through the Caucasus region and to neighboring Eastern European countries. The Georgia 2007/1 strain has proven extremely difficult to eradicate and continues to impact the region today.
The Georgia 2007/1 spread was mostly attributed to the wild boars of the region — From 2015 to 2017 alone, studies found nearly 8,000 African Swine Fever virus -positive wild boars in Poland and the Baltic states. However, studies have also shown that ASFV-G can replicate in Ornithodoros erraticus ticks, meaning ticks may be partially responsible for the resilience of African Swine Fever virus in this region.
The Georgia 2007 outbreak has led to the current outbreaks of African Swine Fever virus, which affect a large portion of Eastern Europe and the eastern territory of the European Union, including Russia, Ukraine, Poland, Latvia, Lithuania, Estonia, Moldova, the Czech Republic and Romania. Between 2014 and 2017, almost 800,000 pigs have died as a result of the disease in these countries, either through infection or culling.
Recently, African Swine Fever virus has gained momentum and is starting to affect even more countries. In a major jump of the disease, likely carried by wild boar which were relocated for hunting, African Swine Fever virus traveled over 1,000 km from the Eastern European countries to Belgium in 2018. African Swine Fever virus is contained in an area around the Belgian/French border, and both countries are currently employing stringent African swine fever preparedness and prevention methods to keep the disease at bay, primarily using fencing and biosecurity solutions.
At present, plans for African Swine Fever virus in Europe rely on strict national and farm biosecurity — the hope is that the ASF virus will eventually die out from the wild boar population, slowing the spread of the disease. After this point, professionals can step in and use an intense hunting procedure to clear out the remaining wild boar population to reduce African Swine Fever virus and eventually eradicate it from the area.
The incidence of African Swine Fever virus in Asia started in August 2018, when an outbreak in China caused the death, directly or indirectly, of more than 1 million pigs. The China 2018 outbreak spread rapidly across the country, impacting backyard farms, mid-sized operations and large-scale commercial operations alike. As of July 2019, the outbreak has impacted 32 provinces and resulted in the culling of almost 1.2 million pigs.
From China, the disease spread to Vietnam, Cambodia, Mongolia and Laos. Infected products have also been found in South Korea, Japan, Taiwan and Australia. This outbreak hit Vietnam particularly hard, since pork accounts for three-quarters of Vietnam's meat consumption, and over 1.2 million pigs, accounting for 4 percent of the total population in Vietnam, have died as a result of the disease.
The first case of African Swine Fever virus was recently confirmed in North Korea on May 25, 2019, leading to the deaths of 70 pigs and the culling of another 20. Despite international efforts to control African Swine Fever virus in this region, the virus continues to spread in Southeast Asia.
As the number of international cases grows, the USDA is increasing its vigilance to protect against the disease and prevent African Swine Fever virus from spreading to the United States. This is due to the devastating effect that African Swine Fever virus could have on U.S. livestock producers and the economy.
While it's difficult to say how much of an impact African Swine Fever virus could have on the U.S. pork industry, we can look to the impact of African Swine Fever virus on Europe for an idea of what it could look like. Between 2014 and 2015, Poland, Lithuania, Latvia and Estonia experienced a reduction in the value of their pork and pork product exports totaling 961 million USD — with pork and pork products representing almost half of these countries' exports, this dealt a severe blow to these countries' economies.
With U.S. pork production value totaling an average $20 billion per year and supporting 550,000 jobs, African Swine Fever virus could have a severely detrimental impact on the U.S. agriculture economy. It would be particularly impactful in Iowa, which is the leading producer of hogs in the United States. If African Swine Fever virus were to come to the United States, U.S. pork exports would shut down entirely, resulting in a large oversupply of pork with no markets to sell it to. Combined with the costs of outbreak management, these consequences could negatively affect the pig farming industry for as long as it takes to wipe out the disease.
Biosecurity is the combination of all measures taken by producers and government agencies to reduce the risk of introducing and spreading diseases. Biosecurity takes place at every level, from herd to region to country, and it takes good biosecurity at every level to keep outbreaks at bay.
Biosecurity involves several principles, which should be the basis of any disease control program:
· Separation of infected animals: Infected and diseased animals should be quarantined to the best of your ability. All contact, both direct and indirect, between infected and non-infected animals should be avoided, and extra precautions should be taken to clean any equipment or clothing that comes in contact with infected individuals. Controlling pests like rats should also be a priority to help minimize any potential vector transmission.
· Ranking transmission routes: Assessing your herd, region or country, and prioritizing transmission routes should be done regularly. This type of assessment helps direct attention and effort to the right places so that high-risk areas are addressed over low-risk transmission routes. All risks should not be considered and treated in a homogenous way — doing so will spread resources too thin to effectively prevent new infections.
· Reduce infection pressure: Where possible, break the infection cycle in the diseased animal to help reduce the burden on their immune system. This may involve cleaning or disinfecting the animal or infection site or vaccinating the herd to help prevent new infections.
· Consider the numbers: Outbreak control on large operations requires greater measures, more effort and increased surveillance compared to smaller farms. Identifying and containing a biosecurity threat early when its reach is small may improve the success of outbreak control on large-scale operations.
· Never underestimate: Never take small numbers for granted. Even if there is a small chance that something may occur, multiplying that chance by an entire population — or by the number of exposures to a particular vector — increases that chance significantly.
These concepts are the basis of any program meant to improve virus mitigation on farms, but farm biosecurity measures like these can be extrapolated specifically for African Swine Fever virus.
Because of African Swine Fever virus’s specific biology and resilience, combined with the average pig herd size, it is a difficult disease to contain. Although it is fortunately not airborne, African Swine Fever virus is still easily transmissible in traditional pig farming setups. The following biosecurity measures, however, can help improve African Swine Fever virus preparedness as a whole in the event of an outbreak:
· Avoid buying-in animals: When possible, breed your own stock instead of buying animals from outside sources. Purchased animals may come from an unsafe source and potentially spread African Swine Fever virus to your herd. If you do need to buy-in animals, be sure to purchase from a known source with good biosecurity, and quarantine them from your operation before introducing them to the herd. The same holds true for semen — ensure that the semen comes from a good source and that the people transporting the semen are aware of and practice good biosecurity.
· Limit your visitors: Limit the number of visitors to your farm to an absolute minimum and keep a registry of them for future reference. All visitors should only wear thoroughly cleaned, farm-specific boots and clothing and should wash their hands before entering the operation. When possible, make sure to have some sort of entrance control to keep out unwanted visitors, and have a hygiene lock area where visitors can wash and change their outerwear.
· Transport carefully: Be very careful about every transport of animals and goods. Before transporting animals, thoroughly empty, clean and disinfect trucks, and handle food the same way. Do not allow trucks to park close to your operation, just in case they carry contaminated goods, and never allow truck drivers access to your animals. Whenever possible, dispose of animals and animal materials quickly and thoroughly — manure and carcasses are very high risk.
· Ward off boars: Feral swine have been significant vectors of African Swine Fever virus in Europe, and pose a similar potential danger in the U.S., where 6 million wild pigs are present across 35 states, with the largest populations present in California, Florida, Oklahoma and Texas. If you live in a region with wild pigs, be sure that your farm is fenced off and protected from infiltration by wild boars. Additionally, ensure that you do not come in contact with dead wild boars — even though the wild boar population poses a danger to swine farms, farmers should not get involved in population control efforts as this can increase the risk of exposure for their own pigs.
· Control pets and pests: Pets like dogs and cats, as well as wild rodents and birds, can carry the virus in their fur or feathers. To minimize risk, keep access to pig herds as controlled as possible, and closely monitor your farm to ensure there are no potential areas for vermin to find shelter.
· Never swill feed: Feeding food leftovers is an easy way to contaminate their food with infected pig products, which is why eliminating it is a primary farm and feed mill biosecurity measure. Swill feeding is a primary transmission factor in Asia, and Europe has even banned the practice in an effort to control the spread of the disease.
· Communicate with your vet: It is essential to notify your veterinarian of any suspicious symptoms as soon as they arise. Always be honest, and communicate with them promptly — any delays in communication could have disastrous effects on your herd and others in the area. You should also work with your veterinarian to assess your biosecurity plans and make improvements as needed.
These ideas don't just apply to the potential African Swine Fever virus outbreak — these are important measures to maintain for everyday farm biosecurity. Most of these measures aren't very expensive to implement — they simply take a shift in attitude and an investment of time. Together with your vet, suppliers, advisors, government and industry partners, we can prevent African Swine Fever virus and other diseases from developing and spreading in the United States.
Kemin understands the potential impact of African Swine Fever virus, and we are invested in doing everything we can to help keep the virus at bay. Since 1998, Kemin has worked toward a singular vision — to touch more than half of the people of the world every day with our products and services. That vision includes people working in and around the animal industry. We work in several areas, pushing research and spreading awareness to help the national effort against African Swine Fever virus.
Kemin continues its efforts to bring awareness about ASFV preparedness across the region through roadshows, webinars and social media platforms. Kemin organised seminars in Thailand and Vietnam since late 2018, introducing the concept of the “3D Approach to African Swine Fever Preparedness” that can help mitigate against the risks of the ASFV for the industry. The 3D Approach calls for the protection of the environment, feed and animals, and comprises the programs of environment biosecurity, pathogen load reduction with Sal CURB® and gut immunity priming with Aleta™.
Results suggest that the antimicrobial Sal CURB RM E Liquid may be a potential candidate as an antiviral feed additive for ASFV infection. Studies have demonstrated that the unique combination of formaldehyde in conjunction with organic acids disrupts the viral envelope of the ASFV, resulting in successful control of the virus, thus reducing potential infection in the animal via feed as a vector. The research was conducted in partnership with Professor Hoang Vu Dang, Department of Biochemistry and Immunology at the National Institute of Veterinary Research in Hanoi, Vietnam. A provisional patent application with the United States Patent and Trademark Office (USPTO) has been filed, with claims that the composition present in Sal CURB™ RM E Liquid can strongly inhibit the viricidal activity of ASFV when applied to animal feed. Together with increased biosecurity, Sal CURB RM E Liquid can help reduce the potential risk posed by ASFV.
Kemin Industries is a global ingredient manufacturer for over 50 years, dedicated to using applied science to improve the lives of as many people as possible. We've already achieved our vision of improving the lives of half the world's population, with 3.8 billion people each day using our hundreds of specialty ingredients made for human and animal health. We'll take this vision even further as we continue to work in the health, pet food, nutraceutical, food technology, crop technology and textile industries.
Established in 1961, Kemin is a privately-held, family-owned and operated, sustainability-centered company employing more than 2,500 employees globally and supporting operations in 90 countries. To learn more about our company and our efforts, you can browse our website for more information or reach out with questions.