Saturday, June 26, 2010

Birds Of A Feather . . . .




# 4675



Yesterday Scott McPherson took a fascinating look at the role of of terrestrial wild birds (as opposed to waterfowl) in the spreading of various avian influenzas across the United States (see Songbirds, not just fowl, represent avian flu threat to US).


This morning, we’ve new research (that appeared yesterday) in PLoS One, suggesting that waterfowl may be acquiring and spreading avian flu viruses because their preening oils bind the virus to their feathers.


The persistence of avian flu viruses in bodies of water has been demonstrated in the past (Persistence of H5 and H7 avian influenza viruses in water  and  Persistence of avian influenza viruses in water).


Under the right conditions, the virus can remain viable for days or even weeks.


While avian influenza surveillance efforts among wild birds have concentrated on cloacal and tracheal samples, this research suggests that the additional step of sampling bird’s feathers might yield additional positives.


First, excerpts from the press release (slightly reparagraphed for readability), then a link to the PLoS One  Article.




Bird flu: In the plumage the secret of virus spread success

Today in PLoS ONE

International team of Italy-US scientists reports discovery of a new mechanism of avian influenza virus circulation and transmission in nature


A team of scientists, led by Mauro Delogu, virologist from the Veterinary Faculty of the Bologna University and researchers from the Istituto Superiore di Sanità, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia and St. Jude Children's Research Hospital (Memphis, Tennessee) have discovered a new way of avian influenza transmission.



The scientists actually discovered that the preen oil gland secretions, by which all aquatic birds make their feathers waterproof, support a natural mechanism that concentrates AIVs from water onto birds' bodies. They found that a progressive virus "sticking" on feathers occurs because AIV-contaminated waters interact with the preen oil gland secretion.


Since waterbirds use to spread preen oil over their own (self-preening) or other birds' (allo-preening) plumage, it is easily understandable how these preening activities could facilitate the diffusion of the viruses in nature.


The discovery, adds Delogu, has also important implications in the surveillance of avian influenza viruses.


In fact, virus on feathers could escape detection by the current surveillance strategies which assay the virus secreted in the cloacal and tracheal samples only. Lack of detection of these viruses may greatly complicate surveillance and rapid responses to new virus emergence and spread. For this reason, Delogu said, in routine surveillance programs, additional sampling methods could be necessary to detect AIVs on birds' bodies.

(Continue . . . )



The PLoS One  link and abstract follow:


Can Preening Contribute to Influenza A Virus Infection in Wild Waterbirds?


Mauro Delogu, Maria A. De Marco, Livia Di Trani, Elisabetta Raffini, Claudia Cotti, Simona Puzelli, Fabio Ostanello, Robert G. Webster, Antonio Cassone, Isabella Donatelli


Wild aquatic birds in the Orders Anseriformes and Charadriiformes are the main reservoir hosts perpetuating the genetic pool of all influenza A viruses, including pandemic viruses. High viral loads in feces of infected birds permit a fecal-oral route of transmission.


Numerous studies have reported the isolation of avian influenza viruses (AIVs) from surface water at aquatic bird habitats. These isolations indicate aquatic environments have an important role in the transmission of AIV among wild aquatic birds.


However, the progressive dilution of infectious feces in water could decrease the likelihood of virus/host interactions. To evaluate whether alternate mechanisms facilitate AIV transmission in aquatic bird populations, we investigated whether the preen oil gland secretions by which all aquatic birds make their feathers waterproof could support a natural mechanism that concentrates AIVs from water onto birds' bodies, thus, representing a possible source of infection by preening activity.


We consistently detected both viral RNA and infectious AIVs on swabs of preened feathers of 345 wild mallards by using reverse transcription–polymerase chain reaction (RT-PCR) and virus-isolation (VI) assays. Additionally, in two laboratory experiments using a quantitative real-time (qR) RT-PCR assay, we demonstrated that feather samples (n = 5) and cotton swabs (n = 24) experimentally impregnated with preen oil, when soaked in AIV-contaminated waters, attracted and concentrated AIVs on their surfaces. The data presented herein provide information that expands our understanding of AIV ecology in the wild bird reservoir system.