Wednesday, June 21, 2017

Appl Environ Microbiol: Survival of HPAI H5N1 In Infected Poultry Tissues

Credit Rosselkhoznadzor


Between the recent discovery of tons of H5N8 contaminated poultry products distributed, and sold to the public, across Russia (see Rosselkhoznador: HPAI Contaminated Poultry Shipped To At Least 9 Regions Of Russia), and the need to dispose of (often by onsite burial) of tens of millions of infected birds, there is an obvious need to determine just how long HPAI viruses can remain viable in the tissues of infected poultry.

Long time readers will recall we've visited this subject several times before (including 2010's Of Ducks, And Feathers, And H5N1), but avian viruses continue to evolve, new AI subtypes have emerged, better test methods continue to be developed, and scientists always look to build on earlier discoveries.
Meaning that the results obtained only a few years ago may not hold true across the board today. 

In the 2010 study mentioned above, we looked at a study conducted by researchers at the  National Institute of Animal Health, Tsukuba, Ibaraki, Japan. They determined that the H5N1 virus may persist on the dropped feathers from infected ducks and may therefore spread to the environment.  
Applied and Environmental Microbiology, August 2010, p. 5496-5499, Vol. 76, No. 16
0099-2240/10/$12.00+0 doi:10.1128/AEM.00563-10
Persistence of Avian Influenza Virus (H5N1) in Feathers Detached from Bodies of Infected Domestic Ducks
Yu Yamamoto, Kikuyasu Nakamura, Manabu Yamada, and Masaji Mase

At 4°C (39F) the the H5N1 virus was detectable in feathers for 160 days, while at the higher temperature 20°C (68F), the virus was detected for 15 days.

Three of these same authors are back with a new study, this time expanding their tests to include the viability (via viral isolation) of H5N1 in experimentally infected chicken's feathers, muscle tissue, and liver at various temperatures ( +4°C or +20°C).

Appl Environ Microbiol. 2017 Jun 16. pii: AEM.00604-17. doi: 10.1128/AEM.00604-17. [Epub ahead of print]
Survival of H5N1 Highly Pathogenic Avian Influenza Virus in Tissues Derived from Experimentally Infected Chickens.

Yamamoto Y1, Nakamura K2, Mase M2.

The tissues were stored at +4°C or +20°C and viral isolation was performed at different times for 360 days. The maximum period for viral survival was observed in samples stored at +4°C in all tissue types, i.e., 240 days in feather tissues, 160 days in muscle, and 20 days in liver. 

The viral infectivity at +20°C was maintained for a maximum of 30 days in the feather tissues, 20 days in muscle, and 3 days in liver

(Continue . . . )

Interestingly, viable H5N1 was detected at both temperatures in feathers for considerably longer periods than in the 2010 study. The persistence of H5N1 in refrigerated chicken for up to 160 days is another important finding, particularly given the vulnerability of the food chain in some countries.

But even at the higher temperature (68F), the virus remained viable for a month in feathers, and just under 3 weeks in muscle tissue. This provides opportunities for dead birds in the wild to infect scavengers,and reinforces the need for people in contact with dead birds to take safety precautions.
We would need to see similar tests run on H5N8, H5N8, and H7N9 to know just how their results compared.  
The reported viability of the virus in feathers, in particular, may to help explain why exposure to, or even living near, live bird markets in China is considered a risk factor for avian flu infection (see Detection Of Airborne H9 Nucleic Acid In Chinese Live Poultry Market).

We've also seen some evidence that avian viruses can be spread from farm to farm - at least over short distances - by prevailing winds (see Bird Flu’s Airborne `Division).  The suspected culprit: `dust’ (desiccated chicken manure, feathers, etc.).
In 2012's EID Journal: Persistence Of H5N1 In Soil, we looked at several studies that found H5N1 could remain viable on various surfaces, and in different types of soil, for up to 13 days (depending upon temperature, relative humidity, and  UV exposure).
Any way you slice it, H5N1 virus continues to prove itself to be much hardier than one might first suspect.

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