African swine fever is a highly contagious viral disease affecting domestic and wild pigs. It kills nearly 100% of the pigs it infects. The good news is that the African swine fever virus does not infect or harm humans. The bad news is that it devastates household and national economies. Particularly in Africa and now in China and Vietnam, it can destroy the livelihoods of poor pig farmers and others who trade pigs and pork, depleting their food as well as income.
The ongoing spread of the disease in China, the world’s largest producer of pigs (the country has some 440 million pigs, which is half the world’s swine population) and pork, is causing alarm. To date, more than a million pigs have been culled to try to stop the spread of the disease, the disease is badly hurting China’s pork industry.
The virus is endemic to sub-Saharan Africa, where it exists in the wild through a cycle of infection between ticks and wild pigs (bushpigs, and warthogs). Ticks infected with the virus can transmit the disease to domestic pigs. The disease was first described when European settlers brought pigs into areas endemic with the virus, they, too, became infected and spread the disease further, making this disease an example of an emerging infectious, or re-emerging, disease.
First described in 1921 in Kenya, the disease remained restricted to Africa until 1957, when it was reported in Lisbon, Portugal, afterward becoming established in the Iberian Peninsula. Sporadic outbreaks occurred in France, Belgium, and other European countries during the 1980s. Both Spain and Portugal managed to eradicate the disease by the mid-1990s, at great cost and through an extensive pig slaughter policy. It took Spain 35 years to eradicate the disease by 1995.
At the beginning of 2007, an outbreak occurred in Georgia and then spread to Armenia, Azerbaijan, Iran, Russia, and Belarus. By April 25 2019, the virus was reported to have spread to every region of China, as well as parts of Southeast Asia, including Cambodia, Laos, Thailand and Vietnam. Between 12-25-April 2019, 12 countries reported new or ongoing African swine fever outbreaks to the World Organisation for Animal Health (OIE).
In low- and middle-income countries in Africa and East and Southeast Asia, smallholder farmers produce and consume pork meat. In countries like Uganda, where ‘pork joints’ are increasingly popular, backyard pig production is a pathway out of poverty. And in countries like Kenya, sophisticated pork processing companies have emerged and produced a wide range of high-quality processed pork products for consumption targeted at different market segments with a strong focus on export. In many of these countries, small-scale pig production offers women and youth, in particular, new economic opportunities.
The disease not only significantly impacts household and national farm socio-economies, but it also affects the international trade of pigs and pig products. Canada, for example, which is free of the disease and the third-largest pork-exporting country in both value and volume, representing 20% of the world pork trade, could see significant improvement in export sales as a result of the African swine fever outbreak in China. The Canadian pork industry contributes to 103,000 direct and indirect jobs that, in turn, generate CAD 23.8 billion annually when farms, inputs, processing and pork exports are included. Today (30 Apr) the country will be hosting the inaugural African Swine Fever Forum, which will be attended by representatives from 15 countries to discuss how countries are responding to the disease.
No vaccine or therapy against African swine fever is currently available. A safe and effective vaccine against African swine fever, which can be used as an additional tool to reinforce control and eradication strategies currently in place, is urgently needed for both domestic and wild pigs. The challenge to develop a safe and effective vaccine will require effective partnerships to support long-term solutions at global, national and local levels.
At the International Livestock Research Institute (ILRI), African swine fever research began in early 2000 with a focus on the epidemiology and socio-economic impacts of the disease. Interdisciplinary teams of scientists, working with national veterinary officers and ministry staff in Uganda and Kenya, obtained an in-depth understanding of the prevalence and genetic diversity of the virus, its socio-economic impacts, and its modes of transmission and spread. In 2004, the Chinese Academy of Agricultural Science (CAAS) and ILRI established a joint laboratory in Beijing. ILRI-CAAS has been looking at the genetic basis of tolerance and or resistance of wild and locally adapted pigs to the virus and has been supporting work on diagnostic surveillance of African swine fever.
Over time, with several collaborative partners, the scope of research has expanded to develop a database of the virus genome sequences to lay the foundation for advancing our understanding of the differences among the many variants of the virus and to undertake the development of a vaccine against African swine fever. ILRI scientists and partners are currently working on developing vaccines for the disease using the CRISPR-cas genome editing system. With this method, the scientists hope to develop mutants as well as attenuated strains of the virus. By developing a synthetic viral genome and employing a ‘reverse genetics’ system, the scientists further aim to accelerate their ability to manipulate the viral genome.
This ILRI biosciences group is also conducting studies to identify the function of the genes of the virus, especially those that subvert the ability of pigs to fight the infection. The scientists are focusing on a Kenyan/Ugandan strain of the virus seen in outbreaks in eastern Africa. ILRI and partners are also researching the development of a ‘subunit vaccine’ based on components of the virus. Critical to these efforts is that ILRI has a well-established African swine fever infection model in pigs, which includes a scoring system and screening assays for monitoring the immune response of pigs to infection and the proliferation of the virus in pig blood. This permits the researchers to evaluate the efficacy of new methods for controlling the disease.
Read news about the recent spread of the disease in China by Raymond Zhong and Ailin Tang, A vicious, untreatable killer leaves China guessing, New York Times, 22 April 2019.
ILRI science papers
ILRI slide presentation
ILRI video (six minutes)
More ILRI news on African swine fever https://www.ilri.org/tags/asf