E&J Explains: Preventing African Swine Fever

E&J Official Veterinarians play a crucial role in public health, particularly in preventing and controlling diseases that can impact both animal and human populations. One of the significant threats currently facing the UK is the potential introduction of African Swine Fever.

In this article, Ester Benguerel, Food Safety and Animal Welfare Technical Lead at E&J, explains how African Swine Fever can be prevented, along with highlighting the signs and symptoms to look out for.

African Swine Fever is a highly contagious and severe haemorrhagic viral disease that affects domestic pigs and wild boars, causing severe economic and social impacts on the swine industry worldwide. Although African Swine Fever does not pose a threat to human health, its rapid transmission and high mortality rates in pigs make it a significant concern for animal health and food security. Understanding the transmission mechanisms and associated risks is crucial for effective prevention and control measures.

Transmission of African Swine Fever

African Swine Fever is caused by the African Swine Fever Virus (ASFV), which is highly resistant to environmental conditions, allowing it to survive for extended periods outside a host. The primary transmission pathways include:

Direct Contact:

• Infected Pigs: The most common transmission route is through direct contact between infected and healthy pigs. The primary route of infection by ASFV is the upper respiratory tract, where the virus replicates in the tonsils and lymph nodes draining the head and neck. Generalised infection is transmitted rapidly via the bloodstream, leading to high concentrations of the virus in all tissues. ASFV spreads mainly from the upper respiratory tract and saliva, and is present in all body fluids and excretions that contain blood.
• Wild Boars: Wild boars can also serve as a natural reservoir for the virus, transmitting it to domestic pigs through direct contact.

Indirect Contact:

• Contaminated Equipment and Vehicles: The virus can survive on farm equipment, clothing, footwear, and vehicles. Indirect transmission occurs when these contaminated items come into contact with susceptible pigs.
• Feed and Water: Contaminated feed and water sources can also facilitate virus transmission.

Passive Vector:

• Carcasses and Pork Products: The virus can persist in pig carcasses and pork products, leading to transmission when these materials are improperly disposed of or consumed.
• Processed Meat Products: ASFV can survive in processed meats such as sausages and hams, posing a risk if these products are transported across borders.

Vectors:

• Ticks: In some regions, soft ticks of the genus Ornithodoros can act as vectors for ASFV, transmitting the virus between animals.

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Signs and Symptoms

The disease can manifest in several forms, ranging from acute to chronic, each with distinct clinical signs and symptoms. The acute and peracute forms of ASF are characterised by a severe haemorrhagic disease that has an almost 100% mortality rate, making early detection and diagnosis critical for controlling outbreaks.

Forms of African Swine Fever

• Peracute Form: This form is characterised by sudden death, within 2-3 days of infection, with few or no visible clinical signs. It is the most severe form of ASF.
• Acute Form: The acute form is the most common and typically presents with severe symptoms. High fever, reddening or cyanosis of the ears and snout, loss of appetite, lethargy, weakness, respiratory and digestive symptoms, swollen lymph nodes. The acute form has high mortality rates.
• Subacute Form: The subacute form is less severe, with moderate fever, reduced appetite and growth rate, and milder skin lesions. This has lower mortality rates and prolonged clinical signs.
• Chronic Form: In chronic cases, symptoms may be milder and persist over time, making diagnosis more challenging.

Recognising the signs and symptoms of African Swine Fever is crucial for early detection and control of outbreaks. Since ASF can manifest in various forms with differing clinical presentations, veterinary professionals must be vigilant and prepared to implement appropriate biosecurity measures and diagnostic tests.

Any febrile disease in swine associated with disseminated haemorrhage and high mortality rates should raise suspicion of ASF.

Diagnosis of African Swine Fever requires laboratory confirmation, as the clinical signs can resemble other swine diseases: the major diagnostic problem is to distinguish ASF from classical swine fever.

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How African Swine Fever could enter the UK

The potential pathways for African Swine Fever to enter the UK include:

• Illegal Importation of Pork Products: Contaminated pork products from affected regions could introduce the virus if not detected and controlled at borders.
• Movement of Infected Animals: Importation of live pigs from affected areas could bring the virus into the UK.
• Human-Mediated Spread: People travelling from African Swine Fever affected countries could inadvertently carry the virus on clothing or equipment.

The work of all E&J veterinarians is essential to public health efforts, playing a vital role in preventing and controlling diseases at UK borders and beyond. By enhancing surveillance, implementing biosecurity measures, and raising awareness, veterinarians are fundamental in protecting the UK from the devastating impact of African Swine Fever.

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