African Swine Fever: A Global Menace In Swine Farming

African swine fever: a global menace in swine farming

In the past decade, African Swine Fever (ASF) has surfaced in several parts of Africa. As stated in the ASF report by the World Organization for Animal Health (OIE), 63 outbreaks were reported across the continent between 2016 and 2019, resulting in the deaths of 42,000 pigs.

The most recent outbreak in Nigeria is by far the worst that has been experienced in the country. As of May 2020, only in Nigeria’s Lagos state, more than 600,000 breeders and matured growers have been lost to ASF, excluding culled and sick animals.

“The rate of spread within and between farms is alarming and the death rate is higher than has been seen in the last 12 years. There are farms that have experienced the deaths of hundreds of pigs within 24 hours. The major reasons are weak farm biosecurity, disease surveillance and warning systems.” This was stated by Dr Oladipo Omotosho, a lecturer at the Department of Veterinary Medicine at the University of Ibadan, Nigeria, in an article published on The Conversation. He also confirmed that the outbreak is at ‘epidemic proportions’.

Also, UK-based newspaper The Guardian reported that farmers estimated that the local pig industry has lost up to 20 billion Nigerian naira (US$ 51.6 million), and that more than 20,000 jobs are at risk.

In all these, there seem to be a sort of relief in a statement recently made by Benjamin Oyedeji, the National Secretary of the Pig Farmers Association of Nigeria (PFAN). According to him, “the peak of the ASF outbreak has passed and the number of dead animals in the last 30 days has been decreasing”.

However, this does not understate the necessity of educating and enlightening the concerned stakeholders and even the general public about the disease, so as to ensure absolute control and prevention of re-occurrence. This is the essence of this article.

What is African Swine Fever (ASF)?

African swine fever (ASF) is a highly contagious haemorrhagic viral disease of domestic and wild pigs caused by a large, double-stranded DNA virus of the family Asfarviridae and genus Asfivirus. It affects pigs of all ages and has a high mortality rate, which may be up to 100%.

ASF was first discovered in Kenya in 1921 and was described as a highly lethal disease in recently imported European pigs. Since then, it has proceeded to become a disease of great concern worldwide, currently affecting four continents where more than 78% of the global swine population lives (Africa, Europe, Asia and Oceania).

YearSlaughtered domestic pigs
2007540,600
200846,700
200913,200
2010348,300
201173,700
2012195,600
201324,200
201439,200
201592,800
2016259,800
2017213,500
2018894,000
20195,870,000
Table 1 . Total number of domestic pigs slaughtered per year due to African swine fever (OIE, FAO)

It is currently the biggest challenge for the pig sector globally and arguably the biggest problem in animal health. Due to its important economic and animal health implications, it is on the list of notifiable diseases of the World Organization for Animal Health (OIE).

Does it affect humans?

The simple answer is NO. African swine fever does not affect humans or even other livestock. It is not a public-health threat or a food-safety concern. However, humans play a significant role in its transmission and this will be addressed shortly.

How is ASF transmitted?

The epidemiology of ASF is complex and varies depending on the environment, types of pig production systems, presence or absence of competent tick vectors, presence or absence of wild pigs and even human behaviour. The routes of transmission include:

  • direct contact with infected domestic or wild pig
  • contact with body fluids of infected animals (nasal, oral, feces, blood)
  • indirect contact  through ingestion of pork or other contaminated products containing the virus including swill, feed, waste, carcasses
  • contaminated fomites such as veterinary equipment, vehicles, tools, footwear, clothing and other contaminated objects.
  • biological vectors (soft ticks of the genus Ornithodoros)

The role of humans in transmission

Humans are recognized as the main cause of both long-distance transmission and virus introduction into domestic pig farms. They can carry the virus on their shoes or clothing from a farm or country that has African swine fever to one that does not, leading to new outbreaks if proper biosecurity practices are not in place. 

By considering only the biological particularities of the disease, contagiosity, tenacity and case fatality rate, but ignoring the human aspects, outbreaks of ASF cannot be controlled.

What are the signs of African swine fever?

The recognition and diagnosis of African swine fever can be difficult. Clinically, the disease looks identical to Classical swine fever and looks very similar to Erysipelas, Salmonellosis, Septicemic pasteurellosis and other septicemic diseases. Therefore, appropriate differential diagnoses must be observed to ascertain the aetiology.

Some of the signs of ASF are:

  • high fever
  • decreased appetite
  • abortion – it is common and may be the only sign of illness
  • weakness and difficulty in standing
  • vomiting, diarrhea (sometimes with bloody discharge)
  • red or blue blotches on the skin (especially on the ears, snout, tail, lower legs)
  • respiratory illness (nasal discharge, coughing, labored breathing)

Unusually high mortality rates among pigs of all ages can be a strong indicator of ASF. High proportions of the animals with the disease usually die within 10days while the ones that recover from the illness become carriers of the virus for several months.

Although, ASF may be suspected based on clinical signs, confirmation must be made through prescribed laboratory tests, particularly to differentiate this disease from other identical diseases.

If you suspect your pigs are infected with African swine fever, please contact your licensed veterinarian immediately.

The impact of ASF outbreak

African swine fever is known for its economic impact on smallholders and emerging commercial farmers. It negatively affects the livelihoods of numerous households that depend on pigs as a source of protein and income, as means to capitalise savings, and as ‘safety nets’ during times of hardship.

At the national level, one major consequence of ASF is the loss of status for international trade and the costs of implementing drastic measures to control the disease.

As revealed earlier, it has been estimated that the local pig industry in Nigeria has lost up to 20 billion Nigerian naira and that more than 20,000 jobs are at risk as a result of the outbreak.

Aside the economic impact, it appears that the effect of ASF outbreak has also left heavy psychological impact on farmers, especially the ones that are most hit. According to Pig Progress, the Oke Aro Farm Community, the area where the impact of the current ASF outbreak in Nigeria is most felt, has recorded at least 4 deaths among farmers. How unfortunate!

Also, in September 2019, it was reported that China alone had experienced direct economic losses of US$ 141 billion, no thanks to African swine fever.

All these reveal the devastating effect of ASF outbreaks and consolidate the necessity of taking a strong stance against it.

Prevention and control of ASF

There is currently no treatment or vaccine available for African swine fever. Therefore, the best strategy against it is a strong precautionary system to prevent entry of the virus. This includes; proper awareness and sensitization, implementation of strict importation measures for animals and animal products, strict quarantine protocol, strict on-farm biosecurity, efficient sterilization and disposal of garbage, controlled animal and human movement, effective disease surveillance and monitoring.

In case of an outbreak, effective management can be achieved by observing proper control measures such as:

  • efficient and early detection of virus
  • culling, slaughter and disposal of infected and exposed animals
  • thorough cleaning and disinfection
  • control of soft tick vectors
  • tightening of biosecurity measures
  • improved surveillance in the region

Progress in research of ASF vaccine

In the fight against ASF, efforts to produce a vaccine seem to have been producing promising results. Back in May, UK scientists appeared to have made a significant breakthrough in the research for ASF vaccine. According to their report, “All pigs that were immunized with the vaccine were protected from severe disease after challenge with an otherwise fatal strain of ASF virus, although some clinical signs of disease did develop.”

Dr Chris Netherton, head of Pirbright’s ASF vaccinology group, reportedly mentioned that “Although the pigs showed clinical signs of infection after challenge with the virus, our study has shown for the 1st time that a vectored vaccine against ASF is a realistic possibility”. He added that, “Our next step will be to uncover the mechanisms behind how the proteins produced by the virus genes stimulate the immune system so we can refine and add to those included in the vaccine to improve effectiveness”.

Finally, as we hope for a breakthrough in vaccine discovery, it is pertinent that we remain focused on the challenge staring us in the face and more importantly, rise to action by ensuring the implementation of necessary preventive and control measures set to rid our world of African swine fever and its devastating impact.

If you see any clinical signs in pigs on your farm that could be associated with ASF infection, kindly contact a licensed veterinarian immediately.

Please drop your thoughts and reactions in the comment box below. We would be glad to receive and respond to them.

References:

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