François Roger: "If African swine fever were to become established, the Chinese pig population would be an unprecedented reservoir!"

12/09/2018 - Article

African swine fever (ASF) has been seen in Chinese pigs since early August. The epidemic reeks of economic catastrophe, given that the country accounts for more than half the world's pigs and ASF is one of the most contagious animal diseases, albeit, of course, harmless to humans. Experts are afraid that the disease might become established in China and spread to neighbouring countries. A dramatic scenario for the entire supply chain in Asia. An update with François Roger, an epidemiologist with CIRAD.

In just a month, China has seen ASF outbreaks in six provinces. What should we be afraid of?
François Roger: China is already incapable of putting out the flames. Almost 50 000 pigs have been slaughtered in an attempt to contain the epidemic. The Chinese authorities have suspended movements and sales of live pigs from infected provinces. Unfortunately, the virus is spreading, and it is looking increasingly unlikely that the disease will be brought under control. China accounts for more than half the world's pigs, and if African swine fever became established, the Chinese pig population would be an unprecedented reservoir! This scenario would have a massive economic impact and would affect the pork supply chain worldwide. Chinese farmers could turn to other types of livestock, which would disrupt the current equilibria of several livestock supply chains. However, we are not there yet, and it is the spread of the virus to other Asian countries that is a more immediate threat. An AFS epidemic in more vulnerable countries such as Laos, Cambodia or Vietnam would have a substantial economic impact.
The risk of contaminationin Western Europe is growing as the disease spreads in the East of the continent. The virus can also be spread by wild boars or through contaminated meat imports. The virus is so contagious and resistant that the Americas are not safe either. It can survive for several weeks in meat, processed goods, food waste and agricultural effluent.

The disease is continuing to spread. How far has it got now?
F.R.: Since it was discovered in East Africa at the start of the 20th century, ASF has spread throughout the domestic pig population in sub-Saharan Africa. It has spread beyond the continent twice, reaching Europe, Brazil and several West Indian countries in the late 1950s. ASF was finally eradicated in these regions in the mid-1990s, except in Sardinia. However, it has never reached Corsica, where CIRAD has been working on the risk of its introduction and the efficacy of surveillance systems. It spread beyond Africa for the second time in 2007, to Georgia, then Russia and Eastern Europe, notably the Baltic states, and subsequently to countries in the EU (Bulgaria, Hungary, Poland and Romania), becoming a threat for Western Europe. The virus introduced into China in early August probably came from Russia.

In its capacity as an expert, CIRAD was invited to the emergency meeting convened by the FAO in Bangkok last week following the ASF outbreak in China. What can you tell us about the meeting?
F.R.: This is the first time the disease has been seen in Asia. The meeting was therefore intended to inform and raise awareness among veterinary services in East and Southeast Asia about the steps required to reduce the risks and prepare for emergencies on a regional and national level. The aim is to minimize the impact on the rural economy and more broadly on food security in the region.
During the meeting, the FAO also asked CIRAD to organize a special session on ASF at the upcoming International Symposium of Veterinary Epidemiology and Economics (ISVEE XV) from 12 to 16 November 2018 in Thailand.

What research is CIRAD doing on the disease?
F.R.: We have been studying the epidemiological and ecological aspects of ASF for several years, and have come up with appropriate risk analysis, surveillance and control approaches. This research is continuing to make progress, thanks to our links with partners in France (ANSES), in Europe, in particular with the Royal Veterinary College at the University of London, and overseas, with our partners in sub-Saharan Africa and the Indian Ocean.
We are therefore working on several "fronts". In Africa, pig farming is less intensive than in Asia, and farmers have sadly learned to live with the risk. The ongoing presence of ASF has significantly limited the development of livestock farming, and given that wildlife acts as a reservoir, it seems unlikely that the disease will be eradicated. In particular, we are providing support in terms of strengthening surveillance and control systems.
In Europe, we were involved in the ASForce project to try to eradicate ASF. As for Asia, we raised the alarm ten years ago about the likelihood of its introduction. Our fears are now being confirmed. However, China has for several years been preparing itself to cope with the ASF virus, by mobilizing scientists and veterinary structures in China and at the FAO (diagnosis capacity, emergency plans, training, vaccine trials, etc). It is probably this preparation that ensured the rapid detection of the first foci and relatively effective action on the part of the Chinese authorities.
We will be continuing to raise awareness among stakeholders in Southeast Asia via a platform in partnership for research and training (dP), GREASE. We are also pursuing our work in Africa, and are about to launch a major research project in South Africa, Mozambique and Madagascar, in collaboration with the University of California, Davis.

A violent haemorrhagic fever

ASF is directly transmissible from one animal to another (domestic pigs and wild boars), and also by ticks of the genus Ornithodoros. The natural reservoirs of the virus are ticks and African wild pigs (warthogs, bushpigs, etc). While the disease does not cause symptoms in these wild pigs, it triggers a violent haemorrhagic fever in domestic pigs and wild boars, with a mortality rate of virtually 100%. There are unfortunately no treatments or vaccines.

Interview by Caroline Dangléant