Agriculture

While waiting for vaccines, pig farmer focus should be heightened biosecurity in preventing the transmission and spread of African Swine fever (ASF)

African Swine fever (ASF) is a highly contagious viral disease affecting swine only. It is not a public health threat or a food safety concern, as it cannot be transmitted to humans through contact with pigs or consumption of pork products. 

The Minister of Agriculture, Land Reform and Rural Development, Thoko Didiza released a press statement on the 29 May 2020 on a new African Swine Fever outbreak in the Eastern Cape, with 16 out of 23 villages reporting pig deaths on 22 May, and a separate outbreak in the Free State, in the Mafube Local Municipality on 15 May, after 38 out of 70 pigs died on the same farm. 

Since the beginning of 2020, the Eastern Cape outbreak is the third ASF reported – a new outbreak was reported from a continuing event from 2019, in the Lekwa Local Municipality in Mpumalanga. It is a national imperative to have this disease controlled as soon as possible, as it has serious and catastrophic consequences for rural or small scale farmers and detrimental consequences on the loss of valuable animals and genetics, in South Africa’s commercial pig herds. Globally, the disease has recently spread extensively since 2016, with reports in China in 2018, Mongolia, Vietnam and Cambodia in 2019. By August 2019, five (5) million pigs had already been culled in Asia to prevent the spread of the disease – from this it is easy to understand why disease control of ASF is vital! 

What is African Swine Fever (ASF)?

ASF is a contagious virus that affects swine of all ages and origins, including warthogs, bush pigs, and other wild pigs. In South Africa, it is found in ASF-controlled areas of Limpopo, Mpumalanga and North West, the northern parts of Kwa-Zulu Natal and in other Southern African countries. This is a reportable disease by State Veterinary Services (Directorate: Animal Health) to the World Organisation for Animal Health (OIE). There is no medication that will cure this disease and currently, there is no vaccine available worldwide.

What are the clinical signs of pigs who have ASF?

These diseases can be acute or chronic. Affected pigs are dull and depressed – they have a high fever, loss of appetite, weight loss, pregnant sows may spontaneously abort, vomiting, diarrhea, and reddened or blotchy areas of skin (that may go blue) on the ears, abdomen and legs, coughing or difficulty breathing, arthritis and muscle weakness. Mortality rates can reach 100%.

How does ASF spread?

This deadly virus is spread in several ways:

  • Direct contact between warthogs, bush pigs and domestic pigs, especially when they are viraemic (when they have high fevers).
  • By feeding infectious food, like swill, to pigs.
  • From the bites of infected soft ticks (tampans) to pigs
  • Through contact with sick pigs and healthy pigs 
  • Through contact with any contaminated equipment, bedding, clothing, clothes, feed utensils, watering areas
The source is: https://www.wur.nl/en/Research-Results/Research-Institutes/Bioveterinary-Research/Animal-diseases/Virology/African-swine-fever-2.htm

How do I treat ASF?

ASF is not treatable and cannot be cured, as yet.

Is there a vaccine available for ASF?

Globally, there is no commercially available vaccine at the moment. Scientists from The Pirbright Institute in the UK are close to development of an effective ASF vaccine.The results of their recent trial has been published in the peer reviewed Vaccines (2020), showing that 100% of the trial pigs ,vaccinated with the new vaccine, survived a lethal dose of ASF – this initial work suggests that this vaccine provides protection against ASF. 

The other benefit of this type of vaccine, is that we will be enabled to differentiate between a field infected animal from an animal that has recently received a vaccine (DIVA). This is an important feature for disease control and international trade, as it allows vaccination programs to be established without having trade barriers between countries. This is an exciting and encouraging breakthrough in vaccine development, as ASF is a large and complex virus, making vaccine development challenging.

What biosecurity measures should I put in place with ASF in mind?

  • Stop all movement of pigs. If you have a sick pig, call your state veterinarian immediately for assistance. Do not transport to a veterinarian or transport for slaughter, as you increase the risk of spreading infectious viral particles. In accordance with the Animal Disease Act (Section 11, Act 35 of 1984), and Regulation 12, the responsible person must notify all neighbours of the presence of the disease, as well as buyers who have purchased animals from the producer/seller in the 30 days before disease was seen. Importantly, no farmer or livestock owner or purchaser may make an incision (cut or slaughter) in the carcass of an animal suspected to be infected with ASF.
  • Communicate with your State Veterinarian as soon as possible – If you notice any of the clinical signs, described above, in your pigs, please call your local state veterinarian immediately. Waiting will result in the death of animals. Work with State Veterinary Services to identify sick animals as early as possible and report it as soon as possible.
  • Never feed swill to your pigs. If you have no other option, you can either sterilise swill or cook swill for at least 60 minutes, cool down and then feed to pigs. This is a highly resistant virus, requiring  cooking above 65 degrees Celsius for at least 30 minutes to destroy it.
  • Separate sick animals immediately from healthy ones and isolate new animals for at least 2 weeks before bringing them in contact with your herd
  • Separate those animals that were in-contact with sick animals
  • Stop all animal movement immediately and limit/stop visitors to your farm
  • Restrict access of wild boar or feral pigs to your pigs – to break the cycle of infection
  • Control pests and pets – Do not allow other animals like pet dogs or cats near your pigs. While they cannot get ASF, they can act as mechanical fomites of the virus, the same can be said of rats and mice that may be attracted to your pigs’ food sources. The soft ticks are attracted to rodents. Manure removal and fly control go hand in hand – biting flies and Stomoxys calcitrans have been shown to transmit ASF to healthy swine. You will very rarely see soft ticks (tampans) on pigs as they have their blood feed and fall of the pigs thereafter – so getting rid of soft ticks is a little more challenging. They like damp cool places and you will find them in warthogs holes. Also, in pig pens, soft ticks like any cracks or fissures in cement, which should be your focus of any spraying.

What is biosecurity and how does it help farmers and livestock owners?

Biosecurity is a combination of measures taken by farmers and livestock owners to protect their livestock against harmful diseases or biochemical substances. These measures are aimed at preventing the introduction and/or spread of diseases and biochemical substances, in order to minimise the risk of transmitting these infectious diseases and substances between people, animals, plants and water.

Why is biosecurity important?

It is important for a number of reasons in agriculture: 

  • When talking about feeding the nation from ‘farm to fork’, we must remember that food safety does not start at the dinner table, it actually starts on the farm and biosecurity is an essential part of on-farm food safety. 
  • Biosecurity will also keep your animals healthy, and we all know that healthy animals are more productive animals. Productive animals benefit farmers and livestock owners which yields better margins to the operations.
  • Lastly, a reliable and robust livestock farming community has a positive effect on the South African economy, and is an essential resource that needs to be protected to maintain a healthy environment.

African Swine fever (ASF) does not affect humans and eating the meat is safe, so why do we need to control it?

  • Diseases like ASF are important to control as early as possible as they impact the availability of meat for domestic and pushes up the price of pork, making it less accessible to the average consumer, as well as affecting our domestic meat supply.
  • It affects South Africa’s reputation as a supplier of pork to international markets, as it places ASF-free countries at risk for infection, which can devastate entire pig populations in these free countries.
  • The death of breeding sows and boars in commercial herds, that have undergone genetic selection over decades, will result in the loss of valuable genetic characteristics – that may take decades to recover, if ever.
  • As a devastating pig disease, with many animals affected quickly and severely, it raises significant and concerning animal welfare issues of pain and suffering.
  • ASF has a serious environmental impact due to ‘cull-out the affected and in-contact animals’ policy. Carcass disposal requires incineration or burial. Both of these disposal methods have an impact on carbon emissions and the safety of our underground water tables, respectively.
  • ASF outbreaks have dire consequences to livestock owners who have few animals, as well as job losses in commercial herds, and negative effects on pork farmers and the industry.
  • Good biosecurity and disease prevention must be cheaper than controlling a disease that has occurred . Also, if you are treating animals within an outbreak, the meat may not be available for human consumption due to drug residue levels contained in the carcass.

A good basic biosecurity plan for your farm or smallholding is a necessary and cost effective defence, for disease prevention and control. Almost anything moved onto your property or near your animals can be a potential source of diseases for your animals. Quick and simple measures that are built into your daily farm activities, can help you protect your farm and the future reputation as a business provider of a constant supply of safe sources of meat. 

Healthy herds and flocks of livestock contribute to the health of the South African animal and agricultural landscape, as well as human and environmental health – livestock disease control in SA is everyone’s responsibility, let’s take it seriously.

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