Email from Dr Ruth Watkins received May 2 2009

In response to the article in the New Scientist editorial on factory farming and swine flu Dr Watkins writes

I'd like to make 3 points about it:

If you test swine for influenza infection by serology you will only find what you are looking for. A molecular test for RNA would be the best way of finding what you do not know might be there, such as Dr Breeze's test. Especially in a virus as variable as influenza. The new H1N1 2009 human virus must have been in swine somewhere, it would seem from the sequencing and analysis of the genetic data that it is there somewhere.

I think the big commercial units with hundreds and thousands of pigs are essential to provide the immune driven mutation, and the mixing, the reassortment opportunities offered by dual or multiple infections and the onward transmission opportunity for newly reassorted viruses. Successful reassorted viruses do not occur as frequently as you might think. The newly reassorted virus must exit the pig in sufficient quantity to be infectious so that it has competed in the host with the original infecting virus to infect new cells, be competent to infect a new host, to compete with other prevalent influenza viruses. If successful in all these respects it must be spread to new populations and what better route than commercial and globalised trade of piglets. If one thinks of the small farm with animals outside where are the opportunities for this with influenza? Even if an interesting new virus does emerge it has a small number of animals to infect (influenza viruses give rise to acute infections so that virus is shed for a short period of time only) so where does it go next? It most likely comes to a dead end.

My third point is that however nasty the smells of the shit lagoons are they are not spreading a respiratory virus such as influenza in pigs and humans. One is going back to miasma theories of infectious disease. Influenza in birds is different where the norm is infection of the gut and faeco-oral transmission. However shit lagoons will spread diseases that have pathogens shed in the faeces to wildlife and to humans contaminated with the material, salmonella and E coli species and hepatitis E for instance. The most likely transmission route for influenza virus from pigs to humans is to those that work in the intensive pig farms and inspire or contaminate their respiratory tracts (eyes, nose and air passages) with the exhaled virus from infected pigs. We await the antigen prepared from this H1N1 2009 virus to do serological assays; the gold standard is the haemagglutinin inhibition test using red blood cells from 0 rhesus negative humans or other suitable cells. In this way we can go back and look for immunity to this particular H1 2009 indicating past infection. We need to look for this specific immunity in pig farm workers, and pigs, as well as a large population sample in Mexico.

with best wishes

Ruth