The spread of African Swine Fever in China and in Europe has been raising concerns in the US swine industry. To answer the need of updated and relevant information, we created the webpage: z.umn.edu/AfricanSwineFever.
Among other resources you will find recording of the session of the 2018 Allen D. Leman Swine Conference, a link to the Swine Disease Global Surveillance reports, and preparedness checklists from the Pork Checkoff.
The page is organized to answer the following questions:
What do we know about African Swine Fever virus?
What is the progression of African Swine Fever worldwide?
African Swine Fever in the field
What are the available diagnostic tests for African Swine Fever?
This report was published by the Swine Health Information Center and prepared by the University of Minnesota.
On September 14th, the OIE official report of the 1st ASF case in Belgium was released, confirming our previous report. On Saturday, 15th, the Federal Agriculture minister confirmed three new cases in the same area of the initial report, identified in wild boars found dead in the city of Etalle (Luxembourg province), near the border with France.
On Friday evening, a multisectoral meeting took place in Belgium, where the farming, meat and animal feed sectors asked for priority measures against the spread of African Swine Fever to be in place. In the joint statement coming from that meeting, they draw up five possible critical needs/measures to mitigate the disease spreading: a European plan to define and maintain the affected zone; the creation of a committee dedicated to the export of meat and pork products; a regulated slaughtering and butchering method for pigs in the area which is under tight surveillance; a realistic and feasible plan to reduce the boar population in the country; and finally the creation of a crisis communication committee.
Arrangements are being done to ban the movement, hunting and feeding of wild boars in the region to control the spread of the disease by human interaction. An investigation and monitoring program is being implemented, with the support of European experts.
With the reporting of two new outbreaks today (September 14th), unofficially, there have been 21 ASF outbreaks reported in China. The last two reported outbreaks included (a) 16 hogs with sudden death in the Inner Mongolian Province, and (b) a farm in Henan Province, with 148 infected pigs and 43% fatality rate. Officially, however, the OIE WAHIS platform still reports only 19 outbreaks in six provinces (Figures 1 and 2). Although the cause of ASF introduction into China remains unclear, in March, 2018, FAO alerted for the risk of introduction of ASF into the country by illegal introduction of animals or food. There are also concerns that, similarly to what has been reported in Europe, wild boars may play a role in the spread of the disease.
Approximately 40,500 pigs have been culled since the beginning of the epidemic, with mortality rates that varied between 0 and 23.17% (Figure 1). The Chinese government reported checking pigs in thousands of sites, which may have resulted in the increase of the identification of new outbreaks. In an attempt to contain the spread of the disease, all transport of live animals from infected provinces is restricted, feed policy is being adjusted to the current scenario, and the logistics of the industry and the Chinese market are being reviewed. On September 13th, the use of food waste and pig blood as feed for pigs in ASF-infected and neighboring provinces was banned. Also, testing pig feed to ASF will be required, and positive samples will trigger destruction of the whole batch of feed.
China is considering to import meat from other markets, including the European Union, that in 2017 faced an intense decline in pork exports. US hog market is also currently facing a low price market, however with expansion in number of sows and pork produced. International trade is at risk once ASF is spreading rapidly into consolidated markets like Europe and China, and concerns are growing around the globe.
In this first of a two part episode of At The Meeting Honoring Dr. Bob Morrison, we share a conversation on African Swine Fever or ASF.
Dr. Montse Torremorell joins Dr. Tom Wetzel and Dr. Gordon Spronk with special guest Dr. Liz Wagstrom, Chief Veterinarian for the National Pork Producers Council, to talk about ASF and how it is the most feared disease in pigs in the world.
Having ASF in the United States would impact trade
ASF is a hardy virus (hard to eradicate and lives in extreme conditions), and
there is no vaccine.
The U.S. pork industry is taking action now by making sure laboratory capacity is up to date, looking at identifying and categorizing higher risk transmission paths plus their mitigation plans, and improving the approach to surveillance and risk planning and implementation.
In this second of a two part episode of At The Meeting Honoring Dr. Bob Morrison, we continue our conversation on African Swine Fever or ASF. Dr. Montse Torremorell joins Dr. Tom Wetzel and Dr. Gordon Spronk with special guest Brad Heron, Director of Operations of Cherkizovo (pronounced “Chair-Kee-Zi-Vo”) in Russia. Brad offers a personal, boots on the ground perspective on ASF.
Brad shares several stories of how ASF was discovered and handled on the Russian farms he helps run. The early disease indicators were confusing due to other animal diseases also running its course so ASF was not discovered as early as they had thought they would.
Brad highlights what happened to the operations when ASF was discovered, actions they had to take, and the Russian regulations they had to work with requiring depopulations within a five mile radius. He also summarizes the biosecurity changes they made to defend against ASF, including transportation tracking, multiple testing points through out the operations, and physical farm and people security improvements.
The number one key take away from Brad: Have good testing; if you don’t test, you don’t have the ability discover outbreaks.
Remember that this afternoon a special session will be held at the Leman Conference regarding African Swine Fever.
Although it has not been officially reported to the OIE yet, preliminary reports indicate that ASF has been confirmed in two wild boars near the southern village of Étalle, in the province of Luxembourg, which is located 8 miles (12 km) from the border with France and 11 miles (17 km) from Luxembourg. It appears to have jumped a considerable distance from previously affected countries, about 300 miles (500 km) from the border with the Czech Republic, 500 miles from Hungary, and 750 miles (1,200 km) from the border with Romania (approximate distances). The Belgian authorities report they are working to prevent the possible spread of the disease among wild boar and onto pig farms.
In 2017, Belgium exported $1.4 billion of pork, making it the eighth largest pork exporter by country, and it is unclear how trade within the European Union will be affected. Following the report, the French Minister of Agriculture called for “an adequate response given the considerable economic interests at stake for the French agri-food chain” and warned about the impact of the Belgian outbreak, calling on officials to stop the disease from spreading across the border.
ASF has been spreading through Eastern Europe, mostly associated with transmission through wild boars, a population that has been growing in Europe over the last decade.This new outbreak represents the expansion of the disease, for the first time during the current pandemic, into Western Europe (Figure 1). This is also the first time ASF has been diagnosed in Belgium since 1985, when 12 farms were infected and 60 farms (34,041 animals) were eliminated. A recent modeling exercise on the potential spread of ASF in Belgium suggested that, in most of the cases, the disease would be controlled before any spread; however, if ASF virus was introduced into commercial farms, the median number of infected farms was predicted to be 6 (see Simons et al at the References section).
This new outbreak may represent a new change in the epidemiologic situation of ASF worldwide, suggesting that the disease may have reached pandemic proportions. “Pandemic” is a term that refers to “an outbreak of a disease that occurs over a wide geographic area”, which seems appropriate in this case, considering ASF expansion across Europe, and over considerable distances in China over the last year, in addition to the sustained occurrence of outbreaks in Africa and Russia.
New introductions of ASF to free areas of the disease are usually by uncooked pork fed to pigs.
Virus can be inactivated with temperature and low pH.
Survivor animals may play a role in the transmission and persistence of the disease.
Further outbreaks of African Swine Fever virus (ASFV) were reported last week in China several miles away from what is thought to be the first outbreak. This geographic dispersal leads us to think about dissemination mechanisms within the country and between countries.
Infected animals will go through a viremic phase and can shed the virus through nasal secretions, feces and urine. Therefore, the main transmission route is oral-nasal, as pigs can be exposed to ASF positive secretions or tissues (i.e. pork products). Indirect transmission can also occur by exposure to contaminated fomites. This virus can also be transmitted by ticks. This vector-borne route becomes relevant when the wild boar
population is present and moves across regions and countries. The common introduction route into ASF free regions is usually through positive pigs transported into the area, or contaminated pork products that are fed to other pigs. ASFV has also been detected in air samples; however, airborne transmission is considered a secondary route of transmission due to the high virus load needed.
Inactivation and persistence
Although ASFV is highly resistant, the virus can be inactivated at pH < 4 and pH >11. Survivability outside the host is heavily related to temperature. For instance, the infectious half-life in urine and feces can range from 3 to 15 days and 4 to 8 days at 37°C and 4°C, respectively. The virus may persist for several weeks or months in frozen, fresh, or uncooked pork, as well as in salted dried pork products. In contrast, ASFV is inactivated at high temperatures (i.e. 70°C cooked or canned hams) and in cured or processed products such as Spanish cured pork products after day 122–140 of curing. Pigs can become persistently infected and the virus can stay viable in their carcasses for up to six months. Therefore, infected carcasses represent a risk to other pigs. More recently, an investigation simulating a trans-Atlantic shipping of ASFV contaminated feed ingredients from Europe proved that viable virus can be recovered after 30 days.
The role of survivor pigs
ASFV recovered and sub-clinically infected pigs become a source of virus to other pigs. This plays an important role in disease transmission and persistence in endemic areas as well as becoming one of the most important routes of transmission into disease-free zones. In-vivo experiments have revealed an infectious period of moderately virulent virus isolates ranging from 20 to 40 days. In another in-vivo transmission study, pigs that had been exposed to ASFV 90 days prior were commingled with naive pigs and the virus was transmitted to naive pigs.
Serological field studies performed in positive regions of Brazil, the Iberian Peninsula, East Africa, Kenya and Uganda revealed that the there was a very low percentage of seropositive animals one year after the outbreak. It was hypothesized that those few seropositive pigs were still carriers and could have been responsible of some of the newer outbreaks.
ASF has a complex epidemiology with different routes of transmission that can involve animals and ticks as direct transmission, and contaminated clothes, tools, and surfaces as indirect transmission. Thus, early detection and intervention of the diseases are key to containing disease spread in absence of an effective vaccine.
Given the recent developments of African Swine Fever (ASF) in China, the Leman Conference is planning a special breakout session on Tuesday morning. The session will cover key aspects of the ASF virus as well as the spread of ASFV in Eastern Europe and China, important elements of ASFV transmission, and implications of the recent developments in China.
Not registered? No problem!
There is still time to register and join your colleagues at the annual educational event for the global swine industry.
African Swine Fever: an update as of September 3rd
Recent outbreak of African swine fever in china may have influence in the global trade market of pork during the following months.
Prevention focusing on imports and international movements is the best strategy in absence of a vaccine.
Rapid diagnostics and culling are key components of an effective eradication.
After the recent outbreak of African swine fever in China and the implications for international trade, swine health, and production we thought it would be a good idea to review the characteristics of the disease.
African swine fever (ASF) ranks third as a potential risk that could threaten the US swine industry in the swine disease matrix, from the Swine Health Information Center (SHIC). ASF is a highly contagious disease that causes hemorrhages in pigs. It is caused by a DNA virus from the Asfaviridae family. It affects pigs, warthogs, and European and American wild boars.
Clinical signs vary depending on the virulence of the virus. Severe infections can cause up to 100% mortality in 2Ͳ7 days with high fever as the main characteristic. Other relevant clinical signs are bleeding (nose or rectum), diarrhea, redness of ear, abdomen, or leg skin, respiratory disorder, loss of appetite and depression. Moderately virulent strains cause less intense symptoms as the beforehand mentioned but mortality can still range between 30-70%. ASF can also be found in a chronic form with loss of weight, discontinuous fever, respiratory signs, skin ulcers and arthritis.
Appearance of clinical signs and high mortality rates may trigger suspicion of ASF but confirmation has to be done through laboratory test. Differential diagnosis includes classical swine fever (CSF), high pathogenic porcine reproductive and respiratory syndrome (HPͲPRRS), swine erysipelas, septicemic salmonellosis and porcine dermatitis nephropathy syndrome (PDNS).
Diagnostic techniques include detection of antibodies in serum or the etiologic agent in different tissues (blood, spleen, lymph nodes, tonsil and kidney). Isolation, PCR,Haemadsorption test and Antigen detection by fluorescent antibody test are the techniques for the virus identification.
The warthog is the main reservoir of the disease and it transmits form pig to pig through a soft tick. Wild boars and other wild pigs can also carry and spread the disease. Domestic pigs usually become infected through direct contact with sick pigs or eating pig meat containing ASF virus. Also indirect spread can occur through contaminated vehicles, premises, equipment or clothes.
PREVENTION AND CONTROL
No treatment or vaccines are available at this point. Therefore the best strategies are implement strategies to avoid the introduction of the virus is to focus on import policies and movement of vehicles and people from infected countries. Rapid diagnosis and culling are the key features of a successful eradication program along with surveillance, movement controls, cleaning, and disinfection of the affected premises.
Since the disease landed in Georgia in 2007 ASF has made steady progress through Europe.Latvia, Lithuania, Poland and more recently Hungary are the last countries that reported the presence of the disease in Europe. The outbreak occurred in one of the most swine dense regions China, relatively close to the Korean peninsula. Three other cases have been reported to date. The effects of the outbreak will probably shape the global
trade of pork in the following months.