African Swine Fever, or ASFV, is a viral disease with a significant impact on swine populations globally. It is caused by a large, double-stranded DNA virus from the Asfarviridae family. The disease affects all members of the pig family, including domestic pigs and wild boars. ASFV is not a threat to human health and cannot be transmitted to people. The virus is known for its high contagion and mortality rates in affected swine.
Virus Characteristics and Transmission
The African Swine Fever virus exhibits remarkable resilience in the environment. It can survive for extended periods in pig carcasses, contaminated feed, and various pork products, including both cured ham and sausages. This durability extends to contaminated surfaces, such as those found on farm equipment, vehicles, or even clothing, which can act as carriers for the pathogen.
Transmission of ASFV occurs through several primary pathways. Direct contact between healthy and infected pigs is a common route for the virus to spread within a herd. Indirect transmission is also a concern, where the virus is spread through fomites—inanimate objects that carry infectious agents. Contaminated boots, tools, or vehicles can introduce the virus to new, uninfected areas.
Another major transmission vector is the ingestion of contaminated materials. Feeding pigs uncooked garbage or swill that contains infected pork scraps is a high-risk practice that has been linked to numerous outbreaks. In some geographical regions, the virus is also maintained and spread through biological vectors. Soft ticks belonging to the Ornithodoros genus can act as reservoirs for the virus, transmitting it to pigs they feed on and perpetuating the disease cycle in the wild.
Clinical Signs in Swine
The clinical presentation of African Swine Fever in pigs can vary, with distinct differences between acute and subacute forms of the disease. In the highly virulent, acute form, infected animals display a rapid onset of severe symptoms. These include a high fever, with body temperatures reaching 40–42°C, profound lethargy, and a complete loss of appetite. Infected pigs often huddle together and may show signs of respiratory distress.
One of the most characteristic signs of acute ASFV is the appearance of reddened or blotchy skin, which is most visible on pale-skinned pigs. These hemorrhagic patches often appear on the ears, abdomen, and legs. Other severe signs include vomiting and bloody diarrhea. The disease progresses quickly, with mortality rates in acute cases often approaching 100%, typically within one to two weeks of the first signs of infection.
Less virulent strains of the virus can result in a subacute or chronic illness. In these cases, the symptoms are milder, and the mortality rate is lower, ranging from 30 to 70%. Pigs with subacute infections may still exhibit fever and lethargy but can survive the initial illness. These surviving animals may become carriers of the virus, capable of shedding it for weeks and spreading the disease to other susceptible pigs.
Global Spread and Economic Consequences
Originating in sub-Saharan Africa, where it is maintained in a cycle between warthogs and soft ticks, African Swine Fever has spread across multiple continents. A significant expansion of the virus began in 2007, leading to its establishment in parts of Europe and Asia. This geographic spread has resulted in devastating outbreaks, particularly in regions with large domestic pig populations.
The economic fallout from ASFV outbreaks is severe and multifaceted. Since there is no effective treatment, control of the disease relies on the culling of entire herds where infection is detected. This measure results in massive direct financial losses for pig farmers, from small-scale smallholders to large commercial operations.
Disruptions to the global pork supply chain are a major consequence of ASFV. Outbreaks lead to a reduction in the availability of pork, which can cause significant increases in consumer prices. Countries affected by the virus face long-lasting and economically damaging international trade bans on their pork and pork products. These restrictions can cripple a nation’s agricultural export market for years.
Biosecurity and Disease Management
With no commercially available vaccine or treatment, managing African Swine Fever relies on prevention through strict biosecurity and surveillance. On-farm biosecurity is the frontline defense against ASFV. This involves a multi-layered approach, starting with strict control over who and what enters a farm. Limiting access for people and vehicles and ensuring any essential visitors follow strict hygiene protocols is a fundamental practice.
Thorough and regular cleaning and disinfection of housing, transport vehicles, and equipment are necessary to eliminate potential sources of contamination. Sourcing pigs only from herds known to be free of disease is another important step in preventing introduction. Preventing any contact between domestic pigs and wild boars is also a measure to avoid transmission from wildlife reservoirs.
Proper management of food waste is important; the practice of feeding swill or untreated food scraps to pigs is a high-risk activity that is banned in many countries to prevent disease spread. Government veterinary services play a large role through surveillance, reporting, and the implementation of quarantine zones and eradication strategies when an outbreak occurs.