Geographical Factors in Asia Increase Epidemic Risk

Introduction

Based on the original broad claim, initial research was conducted to establish specific diseases that were common in Asian countries as well as certain geographic factors within Asia that affect infectious disease susceptibility; it was found that malaria cases notably increased in areas near deforestation. Thus, the original research question was formulated: “Does an increase in deforestation cause an increase in cases of Malaria?” Refinements to the research question were necessary to further developing the question, these refinements considered specific geographical factors as well as specific areas within Asia that were particularly affected by deforestation. There is a high occurrence of malaria cases within Southeast Asia as it is a tropical area with ideal climate a specific species of malaria – Plasmodium Knowlesi – has grown in prevalence.

Within Southeast Asia, specifically Malaysian Borneo, the spread of the malaria species Plasmodium Knowelsi has “...become the main cause of human malaria... Deforestation and associated environmental and population changes have been hypothesized as main drivers of this apparent emergence” (Grigg, M.J., 2016) Originally the P. Knowlesi parasite exclusively infected macaques that inhabited forests, but an increasing amount of human cases have emerged. As mosquitoes are common vectors for malaria, deforestation causes the displacement of mosquitoes, leading them to populate regions in closer proximity to humans. “Changes in vegetation, microclimate, and soil composition can affect the species composition and abundance of mosquito populations.” (Fornace, K.M., 2016) In Malaysian Borneo, the incidence of deforestation is increasingly high, a study found that “Eighty percent of the rainforests [in Malaysian Borneo] have been heavily impacted by logging...” (Butler, R., 2013) The rainforests are primarily cleared for the production of palm oil.

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There have been multitudes of research papers regarding the correlation between areas of high deforestation and cases of Plasmodium Knowlesi, these papers often corroborate with other research papers, amounting to the essentially the same conclusion.

Justified Arguments and Evidence

The number of hectares deforested in Borneo annually from 2001 to 2012. There is a prominent spike in deforestation in 2009 when there was a recorded amount of around 400,000 hectares deforested. This spike in deforestation can be correlated to the increase of P. Knowlesi incidents, in which there was a peak in cases of Plasmodium Knowlesi malaria in humans. Within the years of 2004 to 2008, the average rate of deforestation was 12,500 hectares per year. Whereas within the span of 1 year (from 2008 to 2009) there was an increase of 150,000 hectares per year. This increase in deforestation directly correlates to the increase in malaria cases as P. Knowlesi only became prevalent in 2008. The general positive trend of this graph indicates that the number of hectares deforested continues to increase beyond the labelled years.

The occurrence of human infections with different species of Malaria over the 14-year span decreased immensely from the initial recording in 1997. However, it is not until 2008 that the Plasmodium Knowlesi Malaria species is recorded. The occurrence of P. Knowlesi reached roughly 1000 cases in 2009, this peak can be related to the peak in deforestation in Malaysian Borneo in 2009 . This relationship can be further defined through the decrease in P. Knowlesi cases in 2010, reaching approximately 500, as a result of the decrease in hectares deforested in that same year. A contradiction to this correlation however is the number of cases in 2011 reaching almost the same number as in 2009, there was a decrease in deforestation in that year.

I is clear that the amount of forest cover in Malaysia is linked to the incidence rates of Plasmodium Knowlesi malaria. The recordings of high reported incidents (red) occur in areas of no forest cover. These results are likely due to an increase in macaque population density due to dwindling forest area to inhabit, forcing the population to relocate in regions closer to humans. In 2009 there was a recording of high incidence, this high recording in which there is a notably high spike in deforestation, as well as an increase in reported cases of P. Knowlesi malaria.

Conclusion

The conclusion that can be drawn from the data is that an increase in land degradation in the form of deforestation results in an increase of Plasmodium Knowlesi malaria cases in Malaysian Borneo. This conclusion is in support of the claim in that geographical factors in Asia do increase the susceptibility of infectious diseases. The evidence supports this conclusion as there is a positive relationship between the number of hectares deforested and the number of reported cases of Plasmodium Knowlesi malaria in Malaysian Borneo. This correlation is due to the fact that deforestation displaces carriers of the disease – the macaques that inhabit the forests – as well as the mosquito population, vectors of P. Knowlesi malaria. This displacement leads to an increase of human cases of malaria within regions close to deforestation.

Evaluation of the Claim and Recommendations

The data gathered definitively supports the claim that geographical factors in Asia make the region more susceptible to infectious disease. Research in regard to the relationship between deforestation and different strands of malaria has been well documented within the region of Malaysian Borneo by medical researchers specialised in the study of infectious disease. The data between different sources remained relatively consistent, supporting the reliability of the data. However, whilst the data sets maintain a high level of corroboration, some of the evidence displayed data from Malaysia, which is a larger region than Malaysian Borneo, this placed a limitation on the data as the research question focussed on a more precise region. Without data from the exact region in the research question, the claim can still be supported, but the research question cannot be answered with exact certainty. Further data concerning the specific area of Malaysian Borneo would be required to draw a valid conclusion. A further limitation on the data is that most of the cases of Plasmodium Knowlesi malaria were only the reported cases, there may be a much higher prevalence of the disease than displayed as the reported cases are representative of only a percentage of malaria cases. This limitation is based on the methods by which the data was collected. In most cases, the research was performed by medical researchers in the field of infectious diseases, the data was collected via hospital records of infected patients. However, the diagnosis of P. Knowlesi is commonly misdiagnosed as other species of human malaria, resulting in uncertainty of the true number of cases in that area.

This investigation has only considered the fact that there may be multitudes of other factors that affect the prevalence of P. Knowlesi cases such as population density of humans as well as mosquitoes and macaques, time of year, elevation of the land. These are all factors that limit the reliability of the data as deforestation is not the only independent variable.

Bibliography

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