Pigs as mixing vessels for novel pandemic influenza viruses

In an article to be published in the journal Microbial Pathogenesis, Chinese researchers report on a 4 year serological surveillance project of Influenza A on pigs farms in  Guangdong, Zhejiang, Fujian, and Yunnan Provinces in Southern China.[1] As the authors note, pigs are believe to be intermediate hosts or mixing vessels of pandemic influenza viruses. Influenza viruses can undergo reassortment in pigs, allowing the virus to adapted to humans and possibly cause a pandemic.

The serological study used haemagglutination inhibition (HI) tests to examine antibodies of H5 and H9 viruses among the samples from pigs. The good news is that the researchers failed to find H5 infections (Clade 2.3.2) within the pig samples. A ressortant H5N1 virus from pigs could easily start the next pandemic. H5 viruses have already infected more than 600 people from numerous countries in the last decade, so an H5N1 pandemic is a serious concern.

The bad news is that the authors found an infection rate of at least 3.7% among the samples from pigs for H9 viruses. H9 viruses also pose a pandemic threat for humans. Another serological study from 2009 in China found that a small percentage of farmers  from Xinjiang Uygur autonomous region and Liaoning province tested positive for H9 viruses.[2] A reassortant pandemic virus  does not have to originate in a pig, it could originate in a human infected with  H9 or H5 viruses.

  

[1] Serological surveillance of H5 and H9 avian influenza A viral infections among pigs in southern China

[2] Serological reports of human infections of H7 and H9 avian influenza viruses in northern China

H5N1 Poultry Vaccination in Egypt Will Not Stop the Spread of the Virus

Influenza A(H5N1) can still be considered a novel infectious disease even though it has been infecting people since 1999.  As of July, 2013,  more than 600 people around the world have been infected with H5N1.[1] Of these, more than half have died. If you are infected, it is a deadly disease.

A review of H5N1 case descriptions reported by the World Health Organization (WHO) almost always identifies the source of the infection as sick or dying poultry. In countries where H5N1 is endemic, vaccination of poultry is a strategy used to control the spread of H5N1.

In an article by El Masry and colleagues in Tropical Animal Health and Production published earlier this month, the authors  discusses the effectiveness of vaccinating poultry in Egypt against H5N1. [2]

The key observation by these researchers: 

Despite the enormous effort put into rural house-hold poultry AI vaccination by the Egyptian government, village CAFI [a measure of flock immunity] is unlikely to be maintained at the levels required to significantly reduce the virus load and restrict transmission. Reducing HPAI H5N1 viral load and transmission requires maintenance of high levels of flock immunity. This will require massive additional financial means, and it is questionable if it can be logistically feasible.

The authors conclude that current H5N1 poultry vaccination strategies in Egypt will be unsuccessful in controlling the virus load and transmission within local poultry flocks.  We can expected more human cases of H5N1 in Egypt from sick and dying poultry.

[1] http://www.who.int/influenza/human_animal_interface/Influenza_Summary_IRA_HA_interface_03July13.pdf

 

[2] Modelling influenza A H5N1 vaccination strategy scenarios in the household poultry sector in Egypt. http://link.springer.com/content/pdf/10.1007%2Fs11250-013-0446-8.pdf