Truth hard to find in pig virus debate

PUBLISHED : Sunday, 30 September, 2007, 12:00am
UPDATED : Sunday, 30 September, 2007, 12:00am

For the international scientists monitoring the declining pig stocks on the mainland, facts are hard to come by. And they say Beijing is not being upfront about the virus, which has swept the country for the past year.

The central authorities say it is a strain of blue-ear disease but have been reluctant to provide tissue samples to allow the scientists to classify it. The scientists do not believe blue-ear would cause so many pig deaths, and they do believe the numbers have been severely under-reported.

The central government says the disease is under control, but its effects are still being felt. Inflation shot up 6.5 per cent last month, primarily due to a 49.2 per cent year-on-year increase in the price of staple meats, in turn caused by a shortfall of pigs and higher feed prices.

Authorities have attributed the deaths to a new strain of blue-ear disease, officially known as porcine reproductive and respiratory syndrome (PRRS), which arrived on the mainland in 1996 via the US. Scientists, however, say PRRS is normally not fatal, and causes death in fewer than 5 per cent of cases.

'The types of blue-ear disease we see in North America and Europe do not have this type of mortality rate,' says Juan Lubroth, director of infectious diseases for the United Nations' Food and Agriculture Organisation (FAO) in Rome.

'It would not surprise me if there were some other microbes that are exacerbating the PRRS virus.'

Dozens of international experts say the disease - which has now spread to Vietnam and Myanmar - is most likely to be a combination of PRRS and classical swine fever, but until they see samples, no one will be able to say for sure.

For its part, Beijing vehemently denies that the disease has spread to neighbouring countries.

'The idea that blue-ear alone can cause a mortality of between 15 and 100 per cent is very new and unusual and is limited to the discussions about the current outbreaks in China,' says Steven McOrist, a professor of pig medicines at the University of Nottingham in Britain. 'To get these levels of mortality indicates that either China has a very severe new virus or has a more routine PRRS but [combined] with an additional severe virus such as classical swine fever.'

Dr McOrist says these two viruses tend to feed off each other and break down the pigs' defences. 'All the evidence points to there being two viruses involved,' he says.

If two different strains infect one pig, they can recombine, or exchange fragments of their genomes, says Tomasz Stadejek, of the National Veterinary Research Institute in Poland. 'This makes the generation of new virus variants likely but it needs to be proved that such mutations can make the virus so much more virulent. Until now no virulence markers are known.

'In my opinion there is an unknown additional, and probably infectious, factor contributing to the disease,' he says. 'There might be a more virulent PRRS virus in some Chinese herds, but I would not blame it for all the huge losses reported.'

According to Dr McOrist, pork is extremely important to the mainland, which is the world's fifth-largest exporter of pork. Pork also accounts for 70 per cent of mainland meat consumption and 4 per cent of consumer-price inflation.

The British pig expert says the global pig industry is concerned about the disease. He says that once mainland authorities turn over samples, the debate will come to an end.

'The global pig industry wants to know what's going on, and it wants independent verification,' he says.

The FAO's Dr Lubroth says that the cause of the deaths was still not clear. 'We've not yet got to the bottom of this,' he says.

'The FAO is now arranging with the mainland authorities to provide sample tissues to international laboratories. Samples from Vietnam have already been turned over to an international laboratory for investigation.

Dr Lubroth says there may have been a reluctance to share samples because in the past, mainland scientists have not received the recognition due them and there is concern about intellectual property issues.

Vincent Martin, an animal-health officer for the FAO in Beijing, says the FAO has been talking to the government about getting samples.

'There's a clear willingness to share the viruses,' he says.

According to the latest official figures, as of August 22, 257,000 pigs in 26 provinces and regions have been infected, with 68,000 deaths from the disease and 175,000 animals put down.

The figures do not add up, say the experts. They believe that, at best, the extent of the disease may be under-reported, and at worst that there could be a cover-up. Some scientists say the sharp increase in pork prices indicates a much higher rate of infection and death than the mortality numbers indicate, and that the actual figure for infected and dead pigs must be much higher.

'There are a lot of pigs in China, some 500 million,' says Dr McOrist, 'and a few hundred thousand infected pigs would not impact the supply and [bring about] the price rises we have been seeing.'

He says that the price rises are 'double to triple what one would expect' given the official estimates for infection and deaths, even if one factors in the rising cost of feed and other costs that have pushed up prices.

This idea was backed up by, the online arm of the Chinese Journal of Veterinary Medicine, which recently quoted commercial and industry sources as saying that government figures for the extent of the disease were too low.

The site said that the Ministry of Agriculture had reported a 2.1 per cent decrease in the survival rate of newborn pigs as of the end of June, compared with the same period a year ago.

But it quoted one industry source as saying that the survival rate of pigs was down 30 per cent for the same period, while one large feed company in Sichuan said the rate was down by as much as 60 to 70 per cent.

The same report claimed the disease had spread extensively in Gaogeng township in Sichuan despite government claims that it was not present in the province. The site quoted a veterinarian as saying that the disease there had reached a peak in the township in June, when farmers were lining up to buy medicine from 6am to 10pm.

One older villager said: 'In all my years I've never seen anything like this.'

Huang Yanzhong, director of the Centre for Global Health Studies at Seton Hall University's Whitehead School of Diplomacy and International Relations in the United States, says: 'The article makes it very clear that the disease had spread to Sichuan. But at the same time, the government is denying that Sichuan was affected. Obviously, there's something of a cover-up going on.'

Dr Huang attributes the lower reports to mainland fears about its export market and domestic concerns.

'It's probably because Sichuan is the largest producer of pork in China and the price rises have an impact on both economic and political stability,' he says. 'The government doesn't want to highlight the problem and provide ammunition for the international media to demonise China and its products.'

Dr Martin says that the problem may be more to do with under-reporting from far-flung localities than the result of a cover-up. 'We're dealing with a huge, huge country,' he says.

Dr McOrist tempers his criticism of the problem, saying it is, indeed, a large country with many problems.

To add to the woes, doubts have also been expressed about the efficacy of the vaccine that the government boasted was developed in record time, and which the Ministry of Agriculture claims has a proven 88 per cent success rate in preventing the virus.

'I would be very surprised if it works,' says Dr Stadejek. 'All the vaccines on the market are moderately effective at best.'

Dr Martin says: 'I think it's a bit early to say the vaccine is working.' While good results have been achieved in lab tests, more scientific testing needs to be done in the field, he says.

The government has adopted a number of far-reaching policies to rein in the problem. It has attempted to halt the disease by quarantining and slaughtering pigs. On August 30, the government passed laws laying down new penalties for animal owners who did not follow vaccination policies and who failed to report outbreaks.

In recent weeks it has taken steps to increase stock, releasing pigs from its pig bank, providing breeding pigs to farmers and offering them subsidies to raise sows.

Dr McOrist says that these steps will work only if the disease is halted.

Xinhua reported earlier this month that prices had begun to retreat from their August high. The state-run news agency said prices fell by 11.3 per cent from highs last month as a result of a rise in the supply of pork and a reduction in the disease.

However, there are anecdotal reports that the outbreak is not yet under control and may still be spreading.