Giuseppe
Emeritus
Environmental Contamination during Influenza A Virus (H5N1) Outbreaks, Cambodia, 2006
Sirenda Vong,* Sowath Ly,* Sek Mardy,*Davun Holl,† and Philippe Buchy*
To determine potential risk for bird-to-human transmission during influenza A virus (H5N1) outbreaks among backyard poultry in rural Cambodia, we collected environmental specimens.
Viral RNA was detected in 27 (35%) of 77 specimens of mud, pond water, water plants, and soil swabs.
Our results underscore the need for regular disinfection of poultry areas.
(...)
Conclusions
Our findings demonstrate that viral RNA was frequently present on various environmental surfaces or materials in the influenza (H5N1)–associated households and their surroundings.
The presence of viral genome in water and feces supports R. Webster’s finding (R. Webster, unpub. data) that the viruses could remain detectable in
water and wet feces up to 4–6 days at 37°C (6).
In addition, using regular techniques, we detected viral RNA in small volumes of unconcentrated water and in pond water plants, which suggests that levels of influenza A virus (H5N1) in these contaminated waters might have been relatively high (6).
Notably, mud collection and dry soil swabbing have been efficient in detecting viral RNA in a contaminated environment.
Nonetheless, the presence of RNA does not necessarily imply that the virus is alive or that transmission can occur; in addition, we were unable
to isolate the virus by culture.
This lack of culture growth may be related to a number of factors, including the fact that viruses could be short lived, whereas the decay of subtype H5N1 RNA may have been suffi ciently slow to enable detection by rRT-PCR.
Also, a live virus adsorbed on soil microparticles may have prevented viral binding onto MDCK cells, or these inoculated cell lines may have been damaged by bacteria or fungi present in the environmental specimens (7).
We used the interval between the last dead bird and the sample collection dates as a potential reflection of the survival of the virus in a natural setting.
However, this interval may be subject to some limitations.
First, we were not able to prove that infectious viruses were recovered after this interval.
Second, these viruses could have been shed by duck survivors a long time after the end of the outbreak.
Finally, interpretations were difficult because our analyses were limited by the modest number of flocks studied.
Notably, however, an interval of 12 days was reported in 1 household, although none of the remaining birds was infected or had markers of influenza (H5N1) infection; this suggests that the virus was shed by the last dead birds infected and detected 12 days later.
Bird-to-human transmission is believed to occur largely through direct contact between infected bird secretions and human respiratory mucosa by inhalation of infectious droplets or transfer with contaminated hands to the upper respiratory tract through the nose, mouth,or conjunctival mucosa; subtype H5N1 has been understood to replicate primarily in the human respiratory tract (7–9).
However, additional evidence suggests that influenza virus (H5N1) also replicates in the gastrointestinal tract, which indicates that ingestion of contaminated food (e.g., drinking duck blood) or water is not a negligible source of transmission (6,10–12). Most rural Cambodian households
possess small ponds (≈10–20 m2), which serve as water reservoirs for backyard animals and gardens.
Ducks gather and deposit large amounts of feces in these ponds, while at the same time children commonly bath and play in them.
Taken together, widespread dissemination of the virus in a subtype H5N1–infected household and high interaction between humans and poultry, the birds’ environment may be particularly worrisome (13).
On the other hand, current strains of subtype H5N1 may not yet easily be transmitted from poultry to humans; however, this transmission could increase as the virus continues to circulate and evolve (3,14).
In addition to illustrating the need for good poultry-handling practices, our results underscore the importance of the following for preventing disease transmission: general basic hygiene, fencing domestic birds, and regular environmental disinfection of poultry places (3,15).
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http://www.cdc.gov/eid/content/14/8/pdfs/1303.pdf
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Sirenda Vong,* Sowath Ly,* Sek Mardy,*Davun Holl,† and Philippe Buchy*
To determine potential risk for bird-to-human transmission during influenza A virus (H5N1) outbreaks among backyard poultry in rural Cambodia, we collected environmental specimens.
Viral RNA was detected in 27 (35%) of 77 specimens of mud, pond water, water plants, and soil swabs.
Our results underscore the need for regular disinfection of poultry areas.
(...)
Conclusions
Our findings demonstrate that viral RNA was frequently present on various environmental surfaces or materials in the influenza (H5N1)–associated households and their surroundings.
The presence of viral genome in water and feces supports R. Webster’s finding (R. Webster, unpub. data) that the viruses could remain detectable in
water and wet feces up to 4–6 days at 37°C (6).
In addition, using regular techniques, we detected viral RNA in small volumes of unconcentrated water and in pond water plants, which suggests that levels of influenza A virus (H5N1) in these contaminated waters might have been relatively high (6).
Notably, mud collection and dry soil swabbing have been efficient in detecting viral RNA in a contaminated environment.
Nonetheless, the presence of RNA does not necessarily imply that the virus is alive or that transmission can occur; in addition, we were unable
to isolate the virus by culture.
This lack of culture growth may be related to a number of factors, including the fact that viruses could be short lived, whereas the decay of subtype H5N1 RNA may have been suffi ciently slow to enable detection by rRT-PCR.
Also, a live virus adsorbed on soil microparticles may have prevented viral binding onto MDCK cells, or these inoculated cell lines may have been damaged by bacteria or fungi present in the environmental specimens (7).
We used the interval between the last dead bird and the sample collection dates as a potential reflection of the survival of the virus in a natural setting.
However, this interval may be subject to some limitations.
First, we were not able to prove that infectious viruses were recovered after this interval.
Second, these viruses could have been shed by duck survivors a long time after the end of the outbreak.
Finally, interpretations were difficult because our analyses were limited by the modest number of flocks studied.
Notably, however, an interval of 12 days was reported in 1 household, although none of the remaining birds was infected or had markers of influenza (H5N1) infection; this suggests that the virus was shed by the last dead birds infected and detected 12 days later.
Bird-to-human transmission is believed to occur largely through direct contact between infected bird secretions and human respiratory mucosa by inhalation of infectious droplets or transfer with contaminated hands to the upper respiratory tract through the nose, mouth,or conjunctival mucosa; subtype H5N1 has been understood to replicate primarily in the human respiratory tract (7–9).
However, additional evidence suggests that influenza virus (H5N1) also replicates in the gastrointestinal tract, which indicates that ingestion of contaminated food (e.g., drinking duck blood) or water is not a negligible source of transmission (6,10–12). Most rural Cambodian households
possess small ponds (≈10–20 m2), which serve as water reservoirs for backyard animals and gardens.
Ducks gather and deposit large amounts of feces in these ponds, while at the same time children commonly bath and play in them.
Taken together, widespread dissemination of the virus in a subtype H5N1–infected household and high interaction between humans and poultry, the birds’ environment may be particularly worrisome (13).
On the other hand, current strains of subtype H5N1 may not yet easily be transmitted from poultry to humans; however, this transmission could increase as the virus continues to circulate and evolve (3,14).
In addition to illustrating the need for good poultry-handling practices, our results underscore the importance of the following for preventing disease transmission: general basic hygiene, fencing domestic birds, and regular environmental disinfection of poultry places (3,15).
-
http://www.cdc.gov/eid/content/14/8/pdfs/1303.pdf
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