Thursday, 6 June 2013

The H7N9 missing link: testing the wrong end?

Helen Branswell has an excellent piece detailing as yet unpublished work by the Southeast Poultry Research Laboratory in Georgia.

The researchers have found that influenza A(H7N9) virus can be detected from the nasal passages of chickens and quail - both animals implicated in transmission during the H7N9 outbreak in China. The "so what?" factor is that normally avian hosts shed influenza viruses from the gut reflecting that it is the primary site of influenza virus replication in birds.

As Helen writes, an implication is that if the thousands of birds that have been tested in China to date were only sampled at the cloaca and not from the upper respirator tract, H7N9 prevalence in these oft-blamed but seldom-positive hosts could have been grossly underestimated. However, Dr David Swayne, Director of SPRL notes that it is common practice to swab both ends of a bird when testing.

The research also plays down a major role in transmission for pigeons, ducks and geese.

The search for a definitive answer to what animal is the principal host for H7N9, goes on.