EESA10 assignment 2.docx

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14 Apr 2012
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1
. A. What factors do yellow fever and malaria have in common? (1 points)
Yellow fever and malaria are both considered transmissible diseases, spread by a mosquito
vector. A vector is an organism that carries disease causing microorganisms from one host to
another. The disease causing microorganisms for both diseases are considered to be parasites and
cannot be spread from person to person directly. Yellow fever and malaria tend to be prevalent in
areas with tropical or subtropical climate because the weather favors an abundant vector
population, thus increasing the chances of transmission of the disease (WHO).
What factors are different in comparing the two diseases? (2 points)
The primary difference between the two diseases is that yellow fever is recognized as a viral
(Flavivirus genus) disease, whereas malaria is recognized as a protozoan (Plasmodium genus)
disease. Yellow fever is spread by a single type of mosquito vector, Aedes aegypti; however
malaria can be spread by several different types of Anopheles mosquito species. Vaccines are
available for immunization against yellow fever, yet there is no effective vaccine available
against malaria. Furthermore, treatments for both diseases are varied as well, malaria treatment
aims to cure a patient of the disease, conversely there is no cure for yellow fever and treatment
aims to alleviate the symptoms of the disease (WHO).
B. Why are yellow fever and malaria not threats at present in North America? (1 points)
Yellow fever and malaria are vector-borne diseases and an abundant vector population
contributes to high transmission rates. Heat and humidity are the main factors favorable to vector
population growth; fortunately the cooler North American climate does not provide optimal
conditions for vector population for long periods. As the vector population is reduced, the
presence of yellow fever and malaria are directly impacted and reduced. In Canada, malaria
disappeared at the end of the nineteenth century, although in 1998 cases of locally transmitted
malaria were reported in Toronto (McCally). Furthermore, the existence of effective
public health programs prevents any major issues relating to yellow fever and malaria.
C. Why is malaria such a significant hazard in Africa? (3 points)
As mentioned earlier, heat and humidity contribute to conditions conducive to outbreaks of
vector-borne diseases. The warm climate in Africa coupled with the humidity presents the
perfect conditions for mosquitoes to thrive in, increasing malaria transmission rates. Changes in
rainfall patterns create new bodies of standing water and mosquitoes only require a bit of water
to reproduce. Health costs associated with malaria include both personal and public expenditures
on prevention and treatment; however, in Africa, poverty and a poor health care system means
people lack access to treatment and as a result die from malaria more frequently. Finally, heavy
use of pesticides are increasing mosquito resistance to key insecticides such as DDT and
pyrethroids, particularly in Africa (WHO) coupled with a lack of alternative, effective
insecticides, compounding the problem.
D. Why does the number of West Nile virus cases in people increase in warmer weather? (1
points)
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