Deforestation and Malaria

Stephanie Saperstein ISB 201L 9. 24. 11 Deforestation and Malaria The changes in global environments is expected to affect the rate of malaria cases in humans. Malaria is a serious and at times fatal disease caused by an infectious parasite that can live within a mosquito that feeds on humans. These mosquitos breed in numerous areas and have affected many populations causing many people to suffer from its painful symptoms and effects of the disease. Researchers have been conducting tests on whether deforestation does in fact increase cases of malaria in hopes to increase the ability to control malaria’s outbreaks in certain areas.

The increase in population in many areas is causing there to be an increase in deforestation due to the needs for land for settlement, cultivating agriculture and extracting resources. Research has shown that deforestation does increase the rate of malaria because of the environmental changes of breeding sites and humans moving to and from forested areas. Malaria’s parasites most commonly and successfully infects the female Anopheles mosquitoes and those humans that are bitten by these mosquitos, however they are both affected by the parasite differently.

In humans the parasite begins by infecting the liver where it matures and begins to breed and multiply. After multiplying they begin infecting the blood stream and attacking the host’s red blood cells. These parasites continue this cycle by consistently infecting more and more red blood cells. Unlike humans the mosquito is not harmed when infected by the parasite. When a Anopheles female mosquito feeds on a human carrying this parasite a new cycle of growth and multiplication takes place in the mosquito. The parasite begins in the mosquitos stomach and then travels to the midgut wall of the mosquito where they breed and multiply.

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After 10-18 days, the parasites are found as "sporozoites" in the mosquito's salivary glands. (The Malaria Lifecycle 2006) When the Anopheles mosquito feeds on another human, the sporozoites are injected with the mosquito's saliva and start another human infection. The mosquito transfers the parasites to multiple people by biting them and therefore acts as a vector for the disease. In one study it is said that deforestation is the largest contributing factor to malaria out of the many environmental changes and its rates are expected to increase. Where malaria is found depends mainly on factors such as temperature, humidity, and rainfall.

Malaria is transmitted in tropical and subtropical areas, where Anopheles mosquitos can survive and multiply and where malaria parasites can complete their growth cycle in the mosquito. Research has recognized that deforestation increases malaria risk in Africa and the Americas and lessens it in South-east Asia. (Guerra, Snow, and Hay 2006) Malaria in the Amazon has been caused by ecosystem changes which were caused by human migration and opening of land for agricultural reasons, cattle, and natural resource extraction as well as deforestation and reforestation.

The change in the ecosystems relates to the promotion or suppression of Anopheles darlingi, or the number one malaria vector in the Amazon, is ultimately the most important factor. An. darlingi is the most important malaria vector in the Amazon region. The vector breeds in partly shaded pools found in flooded areas of forests, forest creeks, river edges and pools left after river-level recession during the dry season. When humans colonize forests or near-forest areas in the Amazon it causes an increase of An. arlingi populations by increasing human exposure to this species’ natural breeding habitats and by generating new breeding habitats on the forest fringes. When deforestation takes place there are less trees to shade the given area of land and the acidity and chemical composition of the soil changes. This environmental change often creates favorable conditions for the breeding of An. darlingi and therefore increases the local risk of human malaria. Government sponsored colonization projects and significant migration, which took place with the help of deforestation, have resulted in malaria outbreaks.

The “frontier malaria” phenomenon is exhibited in the Brazilian Amazon, among many other places, which increases the rate of malaria among humans. Frontier malaria is defined as a phenomenon operating at three spatial scales and with a distinctive time path. First at a micro/individual level, vector densities are high because of changes in the ecosystem that promote habitats for A. darlingi. This also occurs when human exposure is intense, such as at dusk or dawn. The second is at the community level where weak institutions, minimal community cohesion, and high rates of in and out migration characterize the frontier malaria.

Third, at the state and national level, there is unplanned development of new settlement areas where agriculture had failed and people avoided malaria. However, this only elevates the rate of transmission. This frontier malaria has a time path where at the opening of a settlement area malaria rates rise rapidly and after 6-8 years the unstable in and out human migration and the high level of ecosystem transformations such as land clearing is replaced by urbanization and community cohesion. This frontier malaria then consists of more stable and low rates of transmission of malaria. Singer and Caldas De Castro 2006) Malaria has recently struck in the Peruvian Amazon region and research has shown that deforestation was the main cause. This research states that the risk of being bitten by the primary malaria-carrying mosquito, A. darlingi, is nearly 300 times higher in cleared areas than in those that are largely undisturbed. (Meadows 2006) A study reported in the American Journal of Tropical Medicine and Hygiene shows how deforestation is a contributing factor to the increase in malaria outbreaks.

The study was conducted in the Loreto district of northeastern Peru, where malaria has risen from 600 cases in 1992 to 120,000 in 1997. Loreto’s population is increasing causing there to be increase is deforestation in order for more settlements such as roads for plantain, cassava, and other subsistence crops. As stated earlier, clearing forest for cropland also often creates better or more breeding sites for the A. darlingi mosquito by providing deep water and short vegetation. Researchers in Loreto experimented by measuring the rate of An. arlingi bites to test whether the population was the primary factor in the increase in malaria cases or whether deforestation was. They found that population size had no effect on the An. darlingi bite rate, but that deforestation had an enormous impact on it. The rate was 278 times higher in areas with the least forest and the most grass/crop land than in areas that were undisturbed. This study proves that areas of slash-and-burn agriculture provides a better environment for An. darlingi mosquitos to breed and increase in population, therefore causing more people to be at risk or in contact with the mosquitos that carry the disease.

As exhibited in the previous studies and research, deforestation is definitely a contributing factor to the rise of malaria infection. The increase of population and globalization increases the need for land to raise cattle, extract resources, cultivate agriculture, and areas to migrate to. This increase then leads to a need for deforestation which has proven to be a main factor in raising the cases of malaria. In these studies deforestation increased malaria in numerous ways. By destroying forests the climatic factors in areas affecting vector and parasite reproduction and development were significantly changed.

Deforestation changed ecological and landscape factors by increasing the amount of sunlight which in turn increases the temperatures of bodies of water, thereby changing the habitats for breeding areas. Overall deforestation is indeed one of the highest contributing factors to the rise in the insect vectored disease around the world. References Guerra, C. A. , R. W. Snow, and S. I. Hay. "A Global Assessment of Closed Forests, Deforestation and Malaria Risk. " American Journals of Tropical Medicine and Parasitology 100. 3 (2006): 189-204. Pub Med Central. U. S.

National Library of Medicine National Institutes of Health, Apr. 2006. Web. 24 Jan. 2011. . Meadows, Robin. "Malaria Linked to Deforestation. " Conservation Magazine. 2006. Web. Sept. 2011. . Singer, Burton, and Marcia Caldas De Castro. "ENHANCEMENT AND SUPPRESSION OF MALARIA IN THE AMAZON -- SINGER and DE CASTRO 74 (1): 1. " ENHANCEMENT AND SUPPRESSION OF MALARIA IN THE AMAZON 74. 1 (2006): 1-2. American Journal of Tropical Medicine "The Malaria Lifecycle. " TravelHealth. co. uk -- the UK Independent Travel Health Site. Travel Health Co, 21 Nov. 2006. Web. 14 Feb. 2011. .

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