Wild Birds Could Spread Avian Flu

Wild ducks that are immune to the effects of H5N1 avian influenza could be spreading the virus far and wide, U.S. government researchers said on Monday.

Satellite tracking of migrating northern pintail ducks showed they flew from a bird flu-infected marsh in Japan to nesting areas in Russia, said the scientists from the U.S. Geological Survey and the University of Tokyo said.

The study does not prove the pintails carried the virus, but the species can be infected with H5N1 with no ill effects.

H5N1 bird flu has been circulating in Asia and the Middle East, with occasional outbreaks in Europe, since 2003. It rarely infects people but when it does it is deadly: the World Health Organization has documented 493 cases and 292 deaths.

It wipes out chickens, who have no immunity, and some other bird species and can seriously damage poultry farms. Experts fear it has the potential to cause a human flu pandemic that would be much worse than the H1N1 swine flu pandemic.

Experts have argued about whether wild birds, spread the virus, or the poultry trade, or both.

Writing in the journal Ibis, the researchers described how they attached satellite transmitters to 92 northern pintail ducks several months before the H5N1 virus was discovered in dead and dying whooper swans in a wetlands in Japan.

Twelve percent of marked pintails used the same wetlands as infected swans. Then some of them migrated more than 2,000 miles to nesting areas in eastern Russia.

Birds can spread flu viruses orally and in their droppings.

“Consequently, infected wild birds that do not become ill, or birds that shed the virus before they become ill, may contribute to the spread of H5N1,” said Jerry Hupp of the USGS.

USGS scientists have been testing birds in Alaska, considered a potential place where H5N1 could enter the Americas from Asia. So far, no case of highly pathogenic H5N1 has been found in either birds or people in the Americas.

Two cases with rapid development of drug-resistant 2009 H1N1 influenza reported

Scientists have reported two cases in which people with compromised immune systems who became ill with 2009 H1N1 influenza developed drug-resistant strains of virus after less than two weeks on therapy.

Doctors from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, have said that medics, who treat prolonged influenza infection should be aware that even a short course of antiviral treatment may lead to drug-resistant virus.

They also said that the authors, and clinicians should take into mind this possibility while developing initial treatment strategies for their patients who have impaired immune function.

Both patients in the new report developed resistance to the key influenza drug oseltamivir (Tamiflu), and one also demonstrated clinical resistance to another antiviral agent, now in experimental testing, intravenous peramivir, said senior authors Dr. Matthew J. Memoli and Dr. Jeffery K. Taubenberger.

This is the first reported case of clinically significant peramivir-resistant 2009 H1N1 illness, say the scientists.

The people in the current case report had immune limitations due to blood stem cell transplants that occurred several years previously. Both recovered from their influenza infections.

“While the emergence of drug-resistant influenza virus is not in itself surprising, these cases demonstrate that resistant strains can emerge after only a brief period of drug therapy. We have a limited number of drugs available for treating influenza and these findings provide additional urgency to efforts to develop antivirals that attack influenza virus in novel ways,” said NIAID Director Anthony S. Fauci.

The 2009 H1N1 influenza virus is susceptible to just one of the two available classes of anti-influenza drugs, the neuraminidase inhibitors. Besides oseltamivir, other neuraminidase inhibitors are zanamivir (Relenza), which is inhaled, and the intravenously administered investigational drug peramivir.

It was shown that some strains contained a genetic mutation (the H275Y mutation) that makes the virus less susceptible to some neuraminidase inhibitors.

The two people in the current case study had pre-existing medical conditions that impaired their immune system function before contracting 2009 H1N1 flu.

In the newly described cases, the mutation appeared after 14 days in one individual and after nine days in the second.

Protection from influenza virus

A University of Alberta-led research team has discovered the genetic detector that allows ducks to live, unharmed, as the host of influenza.

The duck’s virus detector gene, called retinoic acid inducible gene-I, or RIG-I, enables a duck’s immune system to contain the virus, which typically spreads from ducks to chickens, where it mutates and can evolve to be a human threat like the H5N1 influenza virus.

The first human H5N1 cases were in Hong Kong in 1997. Eighteen people with close contact to chickens became infected and six died.

The research by Katharine Magor, a U of A associate professor of biology, shows that chickens do not have a RIG-I gene.

A healthy chicken can die within 18 hours after infection, but researchers have successfully transferred the RIG-I gene from ducks to chicken cells.

The chicken’s defenses against influenza were augmented and RIG-I reduced viral replication by half.

One potential application of this research could affect the worldwide poultry industry by production of an influenza-resistant chicken created by transgenesis.

The study appears in the online, early edition of Proceedings from the National Academy of Sciences .