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PostPosted: Fri Mar 20, 2015 6:53 pm 
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This is a class project on environmental issues and the topic involving emerging diseases. Please let me know what you think. Thank you.

Deforestation is defined as the permanent removal and destruction of forest lands due to agricultural, human colony expansion, and resource acquiring ventures. According to the United Nations’ Food and Agriculture Organization, roughly 18 million acres of forests are cut down every year, a section about the size of South Carolina. Some of the hardest hit areas are Brazil, the Republic of Congo and Southeast Asia. Deforestation brings with it numerous side effects: elevated levels of greenhouse gases spurring climate change, fragmentation of species habitats, soil erosion, and decreased ground water stores.

Besides these ecological influences caused by deforestation, another threat aimed at the populations nearest to those affected areas is developing: emerging diseases. The topic of this paper is deforestation in association with emerging diseases that have surfaced over recent years in tropical rainforest areas. Emerging diseases is defined by the World Health Organization (WHO) as a disease that is initially introduced to a society of people or an older disease which has reemerged with escalating occurrence in a population or geographic region. Two of the diseases that will be discussed are West Nile Virus and Malaria, their transmission patterns, accelerated infection rate due to deforestation, and possible remedies to this issue. Figure 1 shows major emerging diseases over the past 30 years globally (Morens).

http://ars.els-cdn.com.offcampus.lib.wa ... 61-gr1.jpg

Figure 1: Newly emerging, re-emerging/re-surging, and deliberately emerging diseases: (A) Selected emerging diseases of public-health importance in the past 30 years (1977–2007) with representative examples of where epidemics occurred. (B) Selected emerging diseases of public-health importance in previous centuries (430 BC to 1981).

MDR= multidrug-resistant.

SARS= severe acute respiratory syndrome.

vCJD= variant Creutzfeldt-Jakob disease.

XDR= extensively drug-resistant.





West Nile Virus (WNV) was discovered in Uganda’s West Nile district in 1937 and was first believed to be yellow fever but was later determined that it had similar properties to two other viral complexes, St. Louis encephalitis and Japanese B encephalitis viruses (Sejvar). This disease found the shores of the United States in New York in 1999 and spread to the west coast of the United States in under three years. Over the decades there have been multiple outbreaks in numerous countries, all with increasing intensity of symptoms with the most severe cases forming encephalitis or meningitis. These infections carry a mortality rate of 3-15% (CDC). The transmission of this disease is customarily by mosquitoes. Even though mosquitoes are believed to be the vector for the West Nile Virus, which in most cases they are, the mosquitoes themselves are infected when feeding on infected birds (WHO). The WNV cannot be contracted through normal human contact, but there have been cases where a person was infected by a blood transfusion or passed to a infant by way of breast feeding (CDC, WHO).

Malaria is an ancient disease whose symptoms have been described roughly since 2700 B.C. in ancient China (Sullivan). Malaria infections have been written about by the Mesopotamians, Hindus, Greeks, and countless societies throughout history (Cox, Sullivan). Even Greek doctors were known to attempt to cure the symptoms of malaria, and the father of medicine, Hippocrates himself, combated this sickness. Originally, this disease was thought to be transferred as an air-borne contagion. Only after scientific advancements in the field of bacterial studies by Robert Koch, Antoni van Leeewenhoek, Louis Pastuer, and many more, did the scientists of that era believe that this disease was caused by a microorganism and not what was once called “bad air” by the Italians (Cox, CDC). Malaria to this day infects over 300 million people with a mortality rate of more than one million people that are infected globally, according to a report performed in 1995 (Fauci). Malaria’s transmission was a mystery until 1897 when Ronald Ross, of the British Army serving in the Indian Medical Service, was able to prove that mosquitoes were able to be infected with a bird strain of malaria. This was later confirmed by Italian scientists lead by Giovanni Batista Grassi in 1899 with human testing (CDC).

Transmission of both of these diseases is similar in that the vector that transmission is carried out is a mosquito bite. Both diseases are known to be at the highest risk in tropical areas, where mosquito populations enjoy ideal breeding grounds and a dense population from which to feed upon. Two of the highest rates of infection are in Brazil and the Republic of Congo (Olson, Slutsker). Deforestation methods used in the rainforest provide the best possible habitat for mosquito populations. Typically with the slash and burn method, the technique mainly used when clearing areas of forest for agriculture usage, low laying trees and bushes are destroyed with taller trees being spared when possible. The combination of partial shade and the soil content becoming more alkaline, which is a side effect of the burning, increases the standing water to a pH level that mosquito larvae thrive in (Bradt). Increased usage of heavy industrial machinery to remove fallen trees leaves large indentations in the ground creating pools of standing, stagnant water in which mosquitoes lay more eggs.

Mosquito species can vary greatly from open farm or grasslands compared to rainforest populations. In a study done in Australia’s tropical rainforest near Queensland, researchers have noted up to 13 different species compared to the nearby grasslands (Steiger). Many of these species are known to carry both Malaria and WNV. A similar experiment was also performed in Africa with comparable results (Junglen).

Effects of human colonization, for both living habitats and agricultural farmlands, have been a major contributor to the deforestation efforts throughout much of South America and other tropical rainforests globally (Butler). Figure 2 demonstrates the amount of forest lost in the Amazon alone from 2001 to 2012. This amount of forest loss will terraform the land into a natural paradise for mosquito breeding areas. New species that were once contained within their own environment of the rainforest are now exposed to a new food supply in the farmers, settlers, and livestock present. A study carried out in Belgium showed larval habitats migrated from trees to unkempt livestock pens and areas of refuge (Dekoninck). These shifts in breeding grounds can cause an overall shift in mosquito populations and will increase the exposure of WNV and Malaria in the dense populations of expanding colonies.

http://mongabay-images.s3.amazonaws.com ... 1-2012.jpg

Figure 2: Forest loss trends in the Amazon.



Globally, Malaria and WNV are still a very prevalent disease in many countries. In 2012, there were a reported 207 million cases of Malaria resulting in about 627,000 deaths and WNV has been reported in numerous countries over the past 50 years (WHO). Trend maps show a decline of deforestation in many countries, Brazil being one with the greatest change, and this will assist in the efforts of fighting diseases by decreasing the areas where eggs are lain (Butler, Global Forest Watch). Though Brazil shows promise through their decrease in deforestation since 2002, other South American countries have been on a steady increase of both rainforest and overall forestland deforestation, as depicted in Figure 3 (Butler).

http://mongabay-images.s3.amazonaws.com ... trends.jpg

Figure 3: Forest loss trends in the Amazon.




Global Forest Watch and the University of Maryland have constructed incredible interactive maps that allow the user to see where in the world global deforestation is taking place and at what rate. This tool is a very enlightening and fun tool to show what areas are in great need of conservation efforts and possible hot zones of emerging diseases (Global Forest Watch, Global Forest Change).

Conservation efforts can be done on multiple levels to protect not only the forest land, but also the populations that are at risk in areas of heavy deforestation. Some solutions discussed by Gomez, et al., propose attacking the problem in three areas: conservation of single species, large area or eco-system level conservation, and engaging public awareness (Aguirre). All of these involved a small segment of planning that could help in the protection of large parcels of land that could best benefit species that are threatened most by deforestation. Whether this is accomplished by focusing on a selected species or an area of land that is deemed important through focus groups, all land that is procured would save habitats from agricultural and colonization efforts. One or all of these changes in ecology would directly affect interaction between parasite and host, causing a shift in disease transmissions that would normally be magnified by an increase of deforestation. Though these ideas are not widely accepted or have a particular recovery plan set aside for the parasites that are known for harboring the disease vectors, little is known of the part the parasite plays in the grand scheme of things in the biodiversity realm (Gomez). Yet, as history shows us, when the disease vectors are maintained within their own habitat with their typical hosts available, carte blanche, the spread of these diseases can be relatively contained.

With the continuous need to supply the population enough room and food to live comfortably, there comes a cost. Every year, deforestation encourages the release of new insect species that are vectors for viruses which can spread new diseases to the populous and create new emerging diseases. With the proper environmental conservation rules in place, along with a plan of optimizing the current farmlands to maximize yields, we can limit the amount of land getting stripped that creates the practical utopia for mosquito breeding and reduce the vector for these often deadly diseases.

























Work Cited

Aguirre, A. Alonso, Richard Ostfeld, and Peter Daszak, eds. New directions in conservation medicine: applied cases of ecological health. Oxford University Press, 2012.

Bradt, Steve. "Managing Malaria, Beating the Mosquito in the Amazon Jungle." Harvard University Center for the Environment. 15 Nov. 2011. Web. 3 Mar. 2015.

Butler, Rhett A. “Amazon Destruction.” Mongabay.com / A Place Out of Time: Tropical Rainforests and the Perils They Face. 9 January 2006. Web. 2 Mar. 2015

Cox, Francis EG. "History of the discovery of the malaria parasites and their vectors." Parasit Vectors 3.1 (2010): 5.

Dekoninck, Wauter, et al. "Human-induced expanded distribution of Anopheles plumbeus, experimental vector of West Nile virus and a potential vector of human malaria in Belgium." Journal of medical entomology 48.4 (2011): 924-928.

"Explore | Global Forest Watch." Explore | Global Forest Watch. Web. 4 Mar. 2015. <http://www.globalforestwatch.org/explore>.

Fauci, Anthony S., Nancy A. Touchette, and Gregory K. Folkers. "Emerging infectious diseases: a 10-year perspective from the National Institute of Allergy and Infectious Diseases." The International Journal of Risk and Safety in Medicine 17.3 (2005): 157-167.

"For 2003, a System for Web-based Reporting of Dead Birds Was Developed. This has Allowed for Rapid Reporting of Dead Bird Sightings, and Has Provided a Means of Collecting Appropriate Birds for WNV Testing.   In 2003 This Web Reporting Form Was Used over 5,000 times to Report Death and Illness in Nearly 7,000 Birds and Mammals, 1,800 of Which Were Corvid Species. On May 5, 2003 the First Positive Corvid Was Confirmed from Lenawee County.  A Total of 89 Corvids, from 75 Zip Codes, located In 33 Counties Tested Positive.  The First Human Case Occurred in Early September and Was Followed by 18 Additional Cases in Huron, Ingham, Macomb, Oakland and Wayne Counties. ." Emerging Disease Issues. Web. 3 Mar. 2015.

"Global Forest Change | Google Crisis Map." Google Crisis Map. Web. 4 Mar. 2015. <http://earthenginepartners.appspot.com/science-2013-global-forest>.

Gómez, Andrés, and Elizabeth Nichols. "Neglected wild life: parasitic biodiversity as a conservation target." International Journal for Parasitology: Parasites and Wildlife 2 (2013): 222-227.

Junglen, Sandra, et al. "Examining landscape factors influencing relative distribution of mosquito genera and frequency of virus infection." Ecohealth 6.2 (2009): 239-249.

"Malaria Worldwide." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 26 Mar. 2014. Web. 3 Mar. 2015.

Morens, David M., Gregory K. Folkers, and Anthony S. Fauci. "Emerging infections: a perpetual challenge." The Lancet infectious diseases 8.11 (2008): 710-719.
Olson, Sarah H., et al. "Deforestation and malaria in Mancio Lima county, Brazil." Emerg Infect Dis 16.7 (2010): 1108-1115.

Salinas Jr., Jess D., et al. "West Nile Virus ." West Nile Virus. Web. 3 Mar. 2015. <http://emedicine.medscape.com/article/312210-overview>.

Sejvar, James J. "West Nile virus: An historical overview." Ochsner Journal (2003) Summer-Autumn; 5(3): 6–10.

Slutsker, Laurence, et al. "In-hospital morbidity and mortality due to malaria-associated severe anaemia in two areas of Malawi with different patterns of malaria infection." Transactions of the Royal Society of Tropical Medicine and Hygiene 88.5 (1994): 548-551.

Steiger, Dagmar Meyer, et al. "Effects of landscape disturbance on mosquito community composition in tropical Australia." Journal of Vector Ecology 37.1 (2012): 69-76.

Sullivan, David. "Malariology Overview." The Johns Hopkins University , Bloomberg School of Public Health. 1 Jan. 2006. Web. 3 Mar. 2015.

"West Nile Virus." WHO. Web. 3 Mar. 2015. <http://www.who.int/mediacentre/factsheets/fs354/en/>.

"West Nile Virus Transmission." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 7 June 2013. Web. 3 Mar. 2015.

"Where Malaria Occurs." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention. Web. 3 Mar. 2015.

Wilcox, Bruce A., and Brett Ellis. "Forests and Emerging Infectious Diseases of Humans." Forests and Human Health. Web. 3 Mar. 2015.


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