Will African Swine Fever reach China? Its discovery in north-western Russia late last year, jumping 2,000 km to St Petersburg from southern Russia, and continued outbreaks into at least February 2010, mean that further eastward spread is a possibility.
Despite reports in 2007 that ASF had already entered China, they were never confirmed and vigorously denied by the Chinese authorities. The FAO, however, has warned that the virus could spread to other regions, including the EU, Eastern Europe, the Black Sea Basin countries and, in the worst case, scenario, central Asia and even China, which has the largest pig population in the world.
FAO chief veterinary officer Juan Lubroth, commenting on the St Petersburg outbreak, said that although the organization has known that the virus was circulating in the Caucasus – in Georgia, Armenia and Azerbaijan – for several years, spreading to southern Russia, its sudden appearance far away near the Baltic coast was worrying.
The virus shows both progressive spread and also that it can be transported over wider geographic areas through the movement of infected swine or contaminated pork products.
According to the Institute for Animal Health (IAH), ASF reference laboratory for the World Organisation for Animal Health, from Georgia, the virus spread into neighbouring Armenia, Azerbaijan and southern parts of the Russian Federation. In October 2009, the Russian Federation reported ASFV in St Petersburg, meaning that the spread is suspected as being via ASFV-containing recycled pig waste, derived from pork meat, imported from southern Russia.
The IAH has found that the first incursions of the virus into the Caucasus was by virus that originated in southeastern Africa and entered Georgia through the port of Poti, where garbage from the ship was taken to a local dump where pigs would come to feed.
When the disease emerged in Georgia, it is thought that its presence remained undetected for a long period, so increasing the risk of its spread.
ASF results in very high pig mortality. The disease has a catastrophic effect on commercial and smallholder pig production.
There is currently no vaccine against ASF, although a number of initiatives are underway.
Inactivated ASFV, often used successfully as a vaccine for other viruses, does not protect pigs. Strains of the virus that have been adapted to cell culture – in which large amounts of virus are produced – even when given to pigs as live virus, no longer induce immunity.
Naturally non-virulent strains, which in theory could form a starting point for vaccine development, only grow in cell preparations that are totally impractical for vaccine manufacture.
The IAH is carrying out fundamental research on ASFV, with funding coming from a number of sources. This includes identification of the factors that are required for the replication of ASFV, with the objective of developing a live vaccine against it.
In conjunction with the University of Liverpool, IAH has sequenced the complete gene set of the Georgian 2007 virus, which provides the basic information for the development of a vaccine using that strain.
Ultimately, the IAH is working to produce a live ASFV vaccine that is still able to grow sufficiently well in pigs to induce immunity, but which has been rendered incapable of causing disease by virtue of it having certain genes removed.
In another approach, the institute is collaborating with the Biodesign Institute of Arizona State University to test pools of ASFV genes for their potential to induce immunity. In February this year, the IAH won additional funding to look at exploiting ASF virus surface proteins to develop rapid diagnostic tests and to better understand virus host interactions.