David Cyranoski, Nature, in Tokyo reports:

Concerns over the presence of a dangerous strain of avian flu virus in Indonesia’s pigs are growing, as government tests confirm the existence of infection. In some areas, the H5N1 virus could be infecting up to half of the pig population, without causing any signs of disease.

The initial discovery was made earlier this year by an independent researcher working outside national and international surveillance systems. Chairul Nidom, a virologist at Airlangga University’s tropical-disease centre in Surabaya, Java, found the H5N1 virus in five of ten pigs tested from Banten in western Java.

The presence of the virus in pigs is a particular worry because the animals can harbour both bird and human flu viruses, and act as a ‘mixing vessel’ for the emergence of a strain of avian flu that can easily infect humans. There are now signs that the virus could be spreading unchecked through the pig population.

Nidom says that the pigs he tested showed no signs of illness, and the only reason he tested them was that they were kept near a chicken farm that was struck by avian flu last year. Nature has discovered that a government survey has since found similar results in the same region.

The virus was not found in 150 pigs tested from outside the area. Although the government says it has stepped up the surveillance of pigs in its seven satellite laboratories, it may fail to spot any spread of the virus because resources are short. “It’s a big country,” says Tri Satya Putri Naipospos, director of animal health at Indonesia’s agriculture ministry. “If you want to commit to eradicating a disease, you need more money.”

Nidom is also frustrated by a lack of resources. He says he has samples from another 90 pigs in Banten, but cannot afford to test them or to expand his survey to other areas.

Some health officials in Asia fear the presence of avian flu in pigs even more than in chickens or ducks. “I think pigs pose a much greater threat of spreading the disease to humans than poultry,” says Nidom.

The virus was found in pigs in China in 2001 and in 2003 (see Nature 430, 955; 2004). The country stepped up its surveillance, and two surveys in 2004 found that all 8,457 samples tested were free of H5N1.

Nidom’s discovery of H5N1 in pigs is a wake-up call for the Indonesian government. He says that when he first alerted the government to his findings in February, there was no reaction. “I don’t know why they are so passive,” he says. Nidom took his findings to a local newspaper, the Jakarta-based Kompas, which ran the story on 9 April. The news spread to international media earlier this month.

The government responded to the media attention by carrying out its own survey, and found H5N1 in three out of eight pigs it tested in Banten, Naipospos told Nature. Like those tested by Nidom, the pigs showed no outward signs of disease.

Despite this worrying result, communication has faltered between Indonesia and the international organizations charged with monitoring animal health, such as the United Nations’ Food and Agriculture Organization (FAO) and the World Organisation for Animal Health (OIE). When interviewed by Nature last week, the OIE’s regional representative for the Asia-Pacific region still referred to the presence of H5N1 in pigs as “a rumour”.

The FAO and OIE cannot act until they have received official government reports, says Carolyn Benigno, animal-health officer at the FAO’s regional headquarters in Bangkok. She hadn’t heard of Nidom’s work until Nature contacted her last week. However, Naipospos complains that although she is preparing an official report for the FAO, she cannot fast-track it because the FAO and the OIE do not classify the case as an emergency. “This is not an outbreak, it’s a finding,” she says, because the pigs are not ill or dying. As Nature went to press, the Indonesian government was preparing to send a report on the matter to the OIE. (See Box).

Nidom says he would like to expand his project, and to sample pigs from eastern Java. But he is not counting on being given the resources to do so. This is his second run-in with the government — in 2003 he caused a stir by releasing data showing that mass deaths of chickens at the time were caused by H5N1.

Nature 435, 390-391 (26 May 2005) | doi: 10.1038/435390a