1
BIOLOGY INTERNAL ASSESSMENT
An investigation into the correlation between percentage rate of deforestation and the incidence of
malaria per 100,000 people in developing countries
Introduction
In light of the COVID-19 pandemic, I was interested in learning about global disease epidemiology and
factors that affect disease transmission. While studying ecology in my Biology classes, I remember
learning about climate change and was surprised to learn that climate change affects the transmission of
diseases. I had until then never considered the direct effect of ecological changes on human health and
this made me curious to see if this claim could be supported by a database investigation. Malaria is one
such infectious disease and was associated with 219 million cases and 409,000 deaths globally in 2019
alone (“Malaria Fact Sheet”), and is a substantial socio-economic and health burden in many
undeveloped and developing countries given the combination of the existing environmental,
demographic and socio-economic factors in these countries. This problem hit especially close to home
considering that in my country, India, infectious diseases account for almost half of the health burden
(Dikid et al.), the second most common of which is malaria. Thus, I decided to devote this investigation
to studying the correlates of malaria prevalence, in hopes of better understanding it in the larger picture.
In epidemiology, vectors are organisms that transmit infections by conveying pathogens from one host
to another. Malaria is one of the most
common vector-borne diseases globally,
and is caused by the protozoan
Plasmodium parasite that is transmitted to
humans via infected female Anopheles
mosquitoes. Mild symptoms consist of
fever, tiredness, sweating and chills, and
in severe cases it can cause anemia,
breathing problems, low blood sugar
and/or swelling of the brain (cerebral
malaria) (“Malaria ‒ Symptoms and
Causes”). A female Anopheles mosquito
gets infected with the Plasmodium
parasite when it takes a blood meal from
an already infected person. During a
subsequent feeding, the infected mosquito
injects the parasite into the bloodstream Figure 1: The life cycle of malaria (CDC)
of the human host, from where the parasite first infects the liver. It then re-enters the bloodstream to
grow successive broods inside red blood cells and then destroys them, releasing daughter parasites or
merozoites that in turn, continue the cycle by invading other red blood cells (“CDC - Malaria - About
Malaria – Biology”). Currently, no effective vaccine against malaria has been approved for use but
certain prevention measures are taken to reduce risk of transmission, which are mainly focused on
preventing contact between mosquitoes and humans for instance destroying adult mosquitoes by indoor
residual spraying and insecticide-treated nets or killing mosquito larvae using larvicides (Wangdi et al.).
, 2
The loss of natural forest cover, or deforestation, has been increasing at an unprecedented rate in recent
years; studies show that about 46% of all trees have been cut since humans started deforestation
activities (Crowther et al.). It is often followed by land use change for agricultural development,
urbanization or mining activities and impacts every component of an ecosystem including its
microclimate, soil and water conditions, and the ecology of local flora and fauna, including human
disease vectors (Rejmánková et al.). Some studies show that deforestation can increase malaria risk
factors in some settings (Kweka et al.), which implies that forest conservation could be a potential
preventive measure for malaria. However, additional research is required to establish the definite impact
of deforestation on malaria incidence in humans.
Understanding the factors that affect malaria transmission is essential to prevent further risk of
infectious diseases and protect public health. I specifically chose to investigate this research question
because as anthropogenic changes to the natural environment have only been increasing over time, it has
become all the more important to conduct research investigating how human activities may be changing
ecosystem conditions in ways that harm human life in the long run. Investigating this topic can have
important implications for formulating policies regarding forest conservation and the prevention of
infectious diseases; if deforestation amplifies risk of malaria for humans, forest conservation will then
reduce the transmission of malaria. Therefore, this investigation aims to answer the following research
question: What is the correlation between percentage rate of deforestation and the incidence of
malaria per 100,000 people in developing countries?
Variables
Independent variable: Percentage rate of deforestation.
Dependent variable: Incidence of malaria per 100,000 people.
Controlled Variables
To ensure that the results of this investigation are as accurate as possible, certain controls were
employed to reduce the effect of confounding variables.
Table 1: Variables that were controlled
Control Reason for control How it has been controlled
variable
Population Countries with relatively small populations Only countries with a minimum
may have higher variability in malaria population of 5 million were included
incidence that less closely approximates the in the sample.
true conditions of the country. This may give
results that are highly flawed and
unrepresentative.
Geographical Rates of the Plasmodium parasite and Only countries that are located in the
location Anopheles mosquito life cycles, the frequency Torrid Zone (23°27' N–23°27' S)
of mosquito blood meals and the rate at which were selected for analysis as they are
parasites are acquired by mosquitoes have all assumed to have similar climatic
shown to be influenced by changes in conditions. This region was chosen in
temperature (Siraj et al.; Beck-Johnson et al.). particular as most malaria-endemic
BIOLOGY INTERNAL ASSESSMENT
An investigation into the correlation between percentage rate of deforestation and the incidence of
malaria per 100,000 people in developing countries
Introduction
In light of the COVID-19 pandemic, I was interested in learning about global disease epidemiology and
factors that affect disease transmission. While studying ecology in my Biology classes, I remember
learning about climate change and was surprised to learn that climate change affects the transmission of
diseases. I had until then never considered the direct effect of ecological changes on human health and
this made me curious to see if this claim could be supported by a database investigation. Malaria is one
such infectious disease and was associated with 219 million cases and 409,000 deaths globally in 2019
alone (“Malaria Fact Sheet”), and is a substantial socio-economic and health burden in many
undeveloped and developing countries given the combination of the existing environmental,
demographic and socio-economic factors in these countries. This problem hit especially close to home
considering that in my country, India, infectious diseases account for almost half of the health burden
(Dikid et al.), the second most common of which is malaria. Thus, I decided to devote this investigation
to studying the correlates of malaria prevalence, in hopes of better understanding it in the larger picture.
In epidemiology, vectors are organisms that transmit infections by conveying pathogens from one host
to another. Malaria is one of the most
common vector-borne diseases globally,
and is caused by the protozoan
Plasmodium parasite that is transmitted to
humans via infected female Anopheles
mosquitoes. Mild symptoms consist of
fever, tiredness, sweating and chills, and
in severe cases it can cause anemia,
breathing problems, low blood sugar
and/or swelling of the brain (cerebral
malaria) (“Malaria ‒ Symptoms and
Causes”). A female Anopheles mosquito
gets infected with the Plasmodium
parasite when it takes a blood meal from
an already infected person. During a
subsequent feeding, the infected mosquito
injects the parasite into the bloodstream Figure 1: The life cycle of malaria (CDC)
of the human host, from where the parasite first infects the liver. It then re-enters the bloodstream to
grow successive broods inside red blood cells and then destroys them, releasing daughter parasites or
merozoites that in turn, continue the cycle by invading other red blood cells (“CDC - Malaria - About
Malaria – Biology”). Currently, no effective vaccine against malaria has been approved for use but
certain prevention measures are taken to reduce risk of transmission, which are mainly focused on
preventing contact between mosquitoes and humans for instance destroying adult mosquitoes by indoor
residual spraying and insecticide-treated nets or killing mosquito larvae using larvicides (Wangdi et al.).
, 2
The loss of natural forest cover, or deforestation, has been increasing at an unprecedented rate in recent
years; studies show that about 46% of all trees have been cut since humans started deforestation
activities (Crowther et al.). It is often followed by land use change for agricultural development,
urbanization or mining activities and impacts every component of an ecosystem including its
microclimate, soil and water conditions, and the ecology of local flora and fauna, including human
disease vectors (Rejmánková et al.). Some studies show that deforestation can increase malaria risk
factors in some settings (Kweka et al.), which implies that forest conservation could be a potential
preventive measure for malaria. However, additional research is required to establish the definite impact
of deforestation on malaria incidence in humans.
Understanding the factors that affect malaria transmission is essential to prevent further risk of
infectious diseases and protect public health. I specifically chose to investigate this research question
because as anthropogenic changes to the natural environment have only been increasing over time, it has
become all the more important to conduct research investigating how human activities may be changing
ecosystem conditions in ways that harm human life in the long run. Investigating this topic can have
important implications for formulating policies regarding forest conservation and the prevention of
infectious diseases; if deforestation amplifies risk of malaria for humans, forest conservation will then
reduce the transmission of malaria. Therefore, this investigation aims to answer the following research
question: What is the correlation between percentage rate of deforestation and the incidence of
malaria per 100,000 people in developing countries?
Variables
Independent variable: Percentage rate of deforestation.
Dependent variable: Incidence of malaria per 100,000 people.
Controlled Variables
To ensure that the results of this investigation are as accurate as possible, certain controls were
employed to reduce the effect of confounding variables.
Table 1: Variables that were controlled
Control Reason for control How it has been controlled
variable
Population Countries with relatively small populations Only countries with a minimum
may have higher variability in malaria population of 5 million were included
incidence that less closely approximates the in the sample.
true conditions of the country. This may give
results that are highly flawed and
unrepresentative.
Geographical Rates of the Plasmodium parasite and Only countries that are located in the
location Anopheles mosquito life cycles, the frequency Torrid Zone (23°27' N–23°27' S)
of mosquito blood meals and the rate at which were selected for analysis as they are
parasites are acquired by mosquitoes have all assumed to have similar climatic
shown to be influenced by changes in conditions. This region was chosen in
temperature (Siraj et al.; Beck-Johnson et al.). particular as most malaria-endemic
