Avian Flu in Landfills?

Nature can be seen as a complex system of checks and balance and it is the biotic factors of life such as lack of food or predation that keep populations in check in order to ensure that this delicate balance is met. Humans have long tried to defy this fact of nature by building immense civilizations where food is plentiful and predators are no longer an issue, but despite our best attempts we cannot escape the ever present threat of disease. Throughout the history of human civilization, humans have been plagued by disease. In Europe during the Middle Ages it was the bubonic plague,with other notable examples such as The Spanish Flu of 1918and the cholera outbreaks during the 19th century. Even the briefest look through history reveals a disturbing trend of pestilence and fear. Ironically, the success of these plagues can be directly attributed to conditions that arose out of living in densely populated settlements, the biggest of which is poor sanitation. In the 21st century it seems we have learned from the past, and as a result we have much improved sanitation practises, but the modern day epidemics are arising from a very different source; agriculture. With the advent of the industrial revolution convenience and efficiency has dominated the way in which livestock and poultry farms are operated. With thousands of animals being crowded into cramped spaces and being fed growth hormones the farms of today resemble factories more than farms. With all these immunocompromised animals being cramped together in small confined spaces it’s really not much of a surprise that in these conditions it only takes one animal to get sick to start an epidemic. Avian influenza virus and the more recent H1N1 are the two pandemic potentials that continue to dominate the headlines.
To date hundreds of millions of birds have been killed by the Avian influenza virus or as a result of efforts to contain the virus (Bartelt-Hunt 2009). One of the issues that arise from this containment method is the disposal of a large number of carcasses. Currently, there are a number of different disposal methods that exist, but the three that are most recommended/economical for farmers are; on site burial, compositing or off site burial (landfills)(Bartelt –Hunt 2009). For disposal of large die-offs, off site burial at municipal solid waste landfills are a convenient option due to accessibility and capacity. However, a new study has revealed that even after disposal the virus can remain active in the dead host for up to two years. The study which was conducted by Bartelt-Hunt and colleagues from the University of Nebraska and was published in Environmental Science & Technology on April 30 2009. This study was unique in that it was the first one which set out to determine how long AIV remained infectious in leachate from landfills. The study compared how long AIV remained active in leachate versus water based on altering temperature, pH and conductivity (heavy metals). The results of the experiment showed that AIV had the potential to persist for up to two years at a low temperatures (4oC) and a neutral pH in both water and leachate. But, in leachate with non ideal conditions the AIV virus became inactive at either the same or two times faster than in water. This study was referred to in an article entitled Bird flu Survives in Landfills by Emily Sohn in Discovery News. The main differences between the two sources are:
1. Details of the study
2. Strength of claims
3. Extent of discussion of limitations
4. Language used/target audience
In the primary journal article all the details pertaining to the study such as materials, methods and raw experimental data are provided. Since the source is primary the extent of detail regarding the study needs to be provided in order for credibility of the experiment to be verified. However in the secondary source, some details regarding the basics of the experiment are provided but not to the extent provided in the primary source. One of the crucial reasons for the contrast in detail provided is also related to the differences in target audiences. The primary source article is indented for peers and other researchers as demonstrated by the language used and the extent of the detail. The secondary source is a news article that is directed at the public, as a result the language is much simpler and extensive detail of the study is omitted purely for the reason of making the article more comprehendible to individuals who do not have a research background. Another key difference is the strength of the claims made by both sources. In the primary article data was provided and conclusions were qualified based on the results. In contrast, the secondary source quoted the conclusions as fact without highlighting any uncertainty.
“AIV inactivation rates calculated in this study yield theoretical persistence times ranging from approximately 30 to >600 days (based on initial titer of 105 tissue culture infection dose50 (TCID50)). This indicates that AIV could remain infectious both during and after waste placement”(Bartelt-Hunt 2009).
The study also mentions that the AIV became inactive at the same or at a rate 2 times faster than that in water. In contrast the secondary article makes much more direct claims from the results of the study, the key difference again in the wording.
“After 60 days, the researchers were able to estimate how long the virus would remain infectious based on how quickly it was breaking down. At colder temperatures and neutral pH levels, the researchers reported in Environmental Science & Technology, the virus was likely to survive the longest -- sometimes for up to nearly two years. (Sohn 2009)”
Although no data is provided the same conclusion is made, but with more certainty. In addition the article does not mention the differing rates of inactivation between the leachate and water. Another key difference is the extent of the detail pertaining specifically to the limitations of the study.
In the primary source multiple acknowledgments are made regarding the limitations of the study such as, the exclusion of solid waste or microbials from the leachate and how that impacts virus survival. In contrast, in the secondary source the extent of the discussion of limitations is very simple. The article quotes David Stalknecht an epidemiologist who simply states “The lab experiment was a simplified version of what happens inside landfills, he said. In the real world, plenty of factors are likely to deactivate viruses more quickly”. (Sohn 2009)
The main reason for these differences is the target audiences: The primary source is intended for researchers and this is reflected in the language and extent of detail regarding the study. The secondary source is intended as a news article for the general public, therefore the language is much simpler and only final results of the study are included without any discussion of the study limitations.

References
Bartelt-Hunt, S.(2009) Survival of the Avian Influenza Virus (H6N2) After Land Disposal. Enviroment Science & Technology,43: 4063-4067. 30 April 2009. Retrieved October 1 2009 from, http://pubs.acs.org.subzero.lib.uoguelph.ca/doi/full/10.1021/es900370x
Sohn, E. (2009) Bird Flu Survives in Landfills. Discovery News, June 9 2009. Retrieved October 1 2009 from http://dsc.discovery.com/news/2009/06/09/bird-flu-landfills.html