Photo Credit – FAO
A pair of related stories this morning that reinforce the notion that in some places the H5N1 virus may be hiding in the environment, or alternatively, in healthy looking chickens.
Neither of which are exactly new ideas, but thus far evidence for both scenarios has been less than overwhelming.
First, as study out of Cambodia (h/t Tetano on FluTrackers) that was published on Feb. 17th by the journal Influenza and Other Respiratory Viruses.
In this study, environmental samples were collected following outbreaks of bird flu in Cambodia between April 2007 and February 2010.
Srey V. Horm, Ramona A. Gutiérrez, San Sorn, Philippe Buchy
Article first published online: 17 FEB 2012
Results Of a total of 246 samples, 46 (19%) tested positive for H5N1 by qRT-PCRs. Viral RNA was frequently detected in dust, mud and soil samples from the farms’ environment (respectively, 46%, 31% and 15%).
Samples collected from ponds gave a lower proportion of positive samples (6%) as compared to those collected from the farms (24%). In only one sample, infectious virus particles were successfully isolated.
Conclusion During H5N1 virus outbreaks, numerous environmental samples surrounding outbreak areas are contaminated by the virus and may act as potential sources for human and/or animal contamination.
It should be noted that given the sensitivity of modern RT-PRC testing, the ability to detect a virus in the environment doesn’t always tell us if it is viable. That is . . . whether it remains capable of infecting a host.
This report reinforces similar research over the past few years that have expressed similar concerns.
During the summer of 2010, in a blog called Of Ducks, And Feathers, And H5N1 we looked at a study that determined that the H5N1 virus may persist on the dropped feathers from infected ducks and that they may spread the virus to the environment.
The surprising part of this study is how long these feathers retained some degree of viral contamination at various temperatures.
At 4°C (39F) the virus was detectable for 160 days, while at the higher temperature 20°C (68F), the virus was detected for 15 days.
The following month, in a study that appeared in Environmental Science and Technology titled:
Joseph P. Wood, Young W. Choi, Daniel J. Chappie, James V. Rogers, and Jonatha
n Z. Kaye
Copyright © 2010 American Chemical Society
Researchers conducted tests on four inanimate materials (glass, wood, galvanized metal, and top soil) to determine how long – and under what environmental conditions – the virus could survive.
They adjusted factors such as temperature, relative humidity, and simulated sunlight and checked the samples over a period of 13 days.
The virus was most persistent at lower temperatures, and on surfaces such as glass and steel. Their conclusion?: at these conditions, the virus would be expected to persist appreciably beyond 13 days.
And in November of 2010, we saw an EID Journal study that surveyed LBMs (Live Bird Markets) in Indonesia, and found traces of the H5N1 virus in nearly half of the environmental samples tested (see EID Journal: Indonesian Bird Markets Tested For H5N1).
He repeats a warning that he (and others) have given before; that ineffective or improperly dispensed poultry vaccines can mask H5N1 infection in poultry, allowing people to be exposed via `healthy looking’ chickens.
Wednesday, February 22, 2012 | 10:43 pm
TEMPO.CO, Jakarta - Head of Avian Influenza, Zoonosis Research Center University of Airlangga, CA Nidom, said that the bird flu virus (H5N1) can be found in healthy birds. Under these conditions because the vaccine is given to poultry.
He said the bird flu in poultry vaccine made antibodies to poultry so that the birds will stay healthy and not die even if hit by bird flu virus. As a result, signs of the virus has already infected, but not seen. So that public awareness is less because they think that their birds have in a healthy state.
"Our research states that avian flu has been vaccinated birds can still carry the virus even look healthy," he said by telephone on Wednesday, February 22, 2012.
If this sounds familiar, you may recall that Dr. Nidom has previously warned on using poultry vaccines to control Indonesia’s bird flu problem (see Indonesia: Debate Over Poultry Vaccination), as opposed to culling.
Similar warnings were expressed in early 2009 from Zhong Nanshan, a hero of the SARS outbreak and a highly respected respiratory disease specialist in China, who warned that vaccinated poultry can still become infected with the H5N1 virus.
www.chinaview.cn 2009-02-06 17:59:50
GUANGZHOU, Feb. 6 (Xinhua) -- A leading Chinese expert on respiratory diseases has warned the public to be aware that poultry can be infected with the bird flu virus but show no symptoms.
"Special attention should be paid to such animals, including those that have been vaccinated," said Zhong Nanshan.
"The existing vaccines can only reduce the amount of virus, rather than totally inactivating it," he said.
The OIE (World Organization For Animal Health) has been aware of the potential of vaccines to hide infection for many years, warning that vaccination of poultry cannot be considered a long-term solution to combating the avian flu virus.
In Avian influenza and vaccination: what is the scientific recommendation?, the OIE reiterates their strong recommendation that humane culling be employed to control avian influenza, and advising that vaccines should only be used as a temporary measure.
While the OIE concedes that some nations may require the use of vaccines for `several years', they strongly urge that countries move away from that program and towards the more conventional culling policy.
They call this shift away from vaccines an `Exit Strategy’, something which China, Indonesia, Vietnam, and have shown no move towards.
And the big news now out of Vietnam over the past year has been the failure of their poultry vaccine against the emerging 18.104.22.168 clade of the virus which is now widely circulating in the north.
Despite the growing concerns over asymptomatic poultry carrying the H5N1 virus, and evidence of environmental contamination by the virus, the limited number of human cases we have seen to date indicate that the virus still has a hard time infecting humans.
It is adapted to avian physiology – not human - and must mutate further if it is to become an imminent public health threat.
But with 20+ clades of the virus now circulating, and numerous opportunities to expose and infect other hosts (human, swine, mammal, and avian), the virus may one day succeed.
Which is why the world remains in pre-pandemic phase III on the H5N1 virus, and we watch its progress intently.