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AVIAN INFLUENZA, POULTRY VS MIGRATORY BIRDS (05): PREENING
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[1]
Date: 25 Jun 2010
Source: PLoSone [edited]
<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011315>
"Can Preening Contribute to Influenza A Virus Infection in Wild Waterbirds?"
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Abstract
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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 2 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.
[Byline: Mauro Delogu et al]
--
Communicated by:
Mauro Delogu
<mauro.delogu@unibo.it>
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[2]
Date: Thu 1 Jul 2010
From: Mauro Delogu
<mauro.delogu@unibo.it>
Subject: R: Discovery on avian influenza virus ecology
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We are referring to the content of our paper titled: "Can Preening
Contribute to Influenza A Virus Infection in Wild Waterbirds?" which
was published in PLoS ONE on Fri 25 June 25 2010:
<http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0011315>,
reporting data from both field and experimental investigations.
In the above study 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. Hence, we consistently detected both viral RNA and
infectious avian influenza viruses (AIVs) on swabs obtained by rubbing
preened feather's surface of wild mallards.
We showed that a progressive virus "sticking" may occur because
AIV-contaminated waters interact with the preen oil gland secretion.
Our results indicate there may be a previously unrecognized
concentration mechanism of AIVs by which virus particles are captured
by preened feathers and concentrated from the aquatic environment to
birds' bodies. In such a context, the natural preening behaviour, by
which waterbirds spread preen oil all over their plumage
(self-preenig) or other birds' plumage (allo-preening), could
facilitate the ingestion of AIV particles stuck on birds' feathers,
thus promoting a preening-mediated infection route.
There are some potentially important public health consequences of our
discovery. In fact, if the proposed preening-mediated mechanism of
infection is at play in nature, birds carrying viruses on their
feathers but testing negative for virus in the cloaca and trachea by
current surveillance programs might still play an active role in
spreading AIV infection. These "false-negative" birds could include
susceptible birds that are naïve to AIV infection, as well as
unsusceptible [resistant] birds that are naturally immunized to AIV
infection. In the 2nd case, this novel infection mechanism might
escape the birds' immune system such that unsusceptible hosts might
infect susceptible birds by allopreening.
Results from our field studies indicate that AIVs can be carried on
the feather surface of infected ducks (i.e., those virus
isolation-positive from both cloacal and feather swabs) and uninfected
ones (i.e., those virus isolation-positive from feathers only). For
this reason, in routine surveillance programs, additional sampling
methods could be necessary to detect AIVs on birds' bodies. Our field
and experimental results also suggest that during the time period
between the virus adhesion to the bird's body and the infection
(possibly due to self-preening and/or allopreening), the virus could
move in nature with the host by an undescribed circulation mechanism.
With particular regard to the geographical spread of the Eurasian H5N1
HPAI virus in wild birds, the uninfected carrier hosts could have
facilitated, by preening behavior, the circulation of a virus able to
kill the natural reservoir. Our results also suggest that a preened
body surface could be the common denominator that explains how AIV
infection occurs in different taxonomic groups of aquatic birds.
Further study to reproduce the preening-mediated AIV infection
mechanism in the animal model are in progress.
Overall, our discovery may contribute to explain H5N1 HPAI circulation
and persistence in Eurasia and the only recorded human case of fatal
infection passed from wild birds in February 2006. All infected humans
were involved in defeathering of dead wild swans after a massive
die-off of these aquatic birds occurred in Azerbaijan.
--
Dr. Mauro Delogu D.V.M., Ph.D.
Lab of Pathogens' Ecology
Department of Veterinary Public Health and Animal Pathology (D.S.P.V.P.A.)
Bologna University, Via Tolara di Sopra 50
40064 Ozzano Emilia (Bologna) Italy
<mauro.delogu@unibo.it>
[This research goes a fair way to explain why so many different
aquatic wild species are seen with this infection. - Mod.MHJ]
[see also:
Avian influenza, poultry vs migratory birds (04) 20100410.1160
Avian influenza, poultry vs migratory birds (03) 20100409.1150
Avian influenza, poultry vs migratory birds (02) 20100402.1063
Avian influenza, poultry vs migratory birds - Bulgaria 20100331.1022
2009
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Avian influenza, poultry vs migratory birds (03): Russia (TU) 20090701.2377
Avian influenza, poultry vs migratory birds (02): environ trans 20090414.1418
Avian influenza, poultry vs migratory birds: China (HK) 20090308.0958
And postings back to 07 Sep 2005]
...........................jw/mhj/ejp/jw
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