Transcript Malaria and Evolution Case Student Version

Learning concepts in
evolution with malaria as
the case study
ADITI PAI
BIOLOGY DEPARTMENT
SPELMAN COLLEGE
[email protected]
What is
malaria?
http://www.flickr.com/photos/ajc1/3420714787/
http://www.flickr.com/photos/lamerie/407337286/
http://www.flickr.com/photos/atwj/3347071689/
10 facts on malaria
10 facts on malaria
WHO/S. Hollyman
March 2009 About 3.3 billion people - half of
the world's population - are at risk of malaria.
Every year, this leads to about 250 million
malaria cases and nearly one million deaths.
People living in the poorest countries are the
most vulnerable. Malaria is especially a serious
problem in Africa, where one in every five
(20%) childhood deaths is due to the effects of
the disease. An African child has on average
between 1.6 and 5.4 episodes of malaria fever
each year. And every 30 seconds a child dies
from malaria. This fact file presents the extent
and effects of malaria and how it can be
prevented and controlled.
http://www.who.int/features/factfiles/malaria/en/index.html
Facts about malaria
 Caused by a trypanosome: Plasmodium
 Transmitted by a vector: mosquito
 Prevalent in tropical and sub-tropical areas
 Symptoms: fever, chills, joint pain, vomitting etc.
Case study 1
A mutation story

http://www.pbs.org/
Objectives
 explain how mutations may be neutral, beneficial or
harmful depending on the environment
 list conditions for natural selection to take place
 discuss how natural selection acts on individuals but
evolution is seen at a population level
 predict whether the mutation will spread or not
when given the nature of a mutation and the nature
of the environment it is in
How is the gene that makes
hemoglobin relevant to the effect of
malaria on a patient?
A. Hb is a part of mosquito and malaria
affects mosquitoes
B. Hb is a disease like malaria
C. Hb is an essential part of the RBC and
malaria affects RBC
D. Hb is not relevant to the effect of
malaria
What is the adaptive
mutation described in the
video?
 Sickle Cell Anemia is
codominant
 AA = normal
AS = sickle cell trait
(few symptoms)
SS = sickle cell anemia
http://www.flickr.com/photos/wellcomeimages/4013247943/
The effect of mutations are______
A. Beneficial
B. Detrimental
C. Neutral
D. Dependent on the environment
http://www.mydochub.com/blog/index.php/2007/03/16/photo-project-sheds-light-on-sickle-cell-anemia/
What is the consequence if a person has
only 1 copy of sickle cell allele and 1
normal copy of Hb allele?
A. They could survive malaria
B. They could grow up and marry
C. They could have children
D. All of the above
What if a person has two copies of
sickle cell allele?
A. They could survive malaria
B. They could grow up and marry
C. They could have children
D. They had sickle cell anemia
What is the evolutionary
process described in the
video?
People in Africa have a high frequency of
sickle cell mutation because
A. They need it to survive malaria
B. The allele increased in frequency in the
population due to natural selection favoring
those who had one copy of the allele
C. Both of the above
Malaria has been a major
selective agent for human
populations in their
evolutionary history!
Diseases such as malaria have a strong
impact on evolution of organisms….
According to the video why is
genetic diversity important?
A. If a population is genetically identical,
B.
C.
D.
E.
an epidemic could wipe out the entire
population
Having genetic diversity improves the
chances that some are able to survive
future epidemics
Having genetic diversity guarantees
that the population survives future
epidemics
A and C
A and B
Case study 2
Who has sickle cell disease
and why?
 Reading from Bloom 1995
 Complete assignment in your group
Objectives
 list conditions for natural selection to take place
 discuss how natural selection acts on individuals but
evolution is seen at a population level
 predict whether the mutation will spread or not when
given the nature of a mutation and the nature of the
environment it is in
 explain how evolution is not goal oriented
 propose explanations for why people in different
parts of the world differ with respect to sickle cell
frequency
Sickle cell is allele common in
human populations
Do you know some one with sickle disease?
http://www.flickr.com/photos/exquisitur/2553768995/
http://www.flickr.com/photos/darienlibrary/2893149535/
Many famous people
have it!
End of Part 1
 What is common about the two
people with sickle cell disease I
just showed you?
Heterozygote advantage of the sickle-cell allele
 Causes mutations in hemoglobin but also confers
malaria resistance
 Exemplifies the heterozygote advantage
Comparison of the distribution of malaria (left) and sickle-cell trait (right).
Original work by Anthony Allison
http://commons.wikimedia.org/wiki/File:Malaria_versus_sickle-cell_trait_distributions.png
Sickle cell frequency is higher in Africa than America
because the mutation never arose in America but it
arose in Africa.
A. True
B. False
Sickle cell frequency is higher in Africa than America
because the mutation was advantageous in Africa but
disadvantageous in America.
A. True
B. False
Comparison of the distribution of malaria (left) and sickle-cell trait (right).
Original work by Anthony Allison
http://commons.wikimedia.org/wiki/File:Malaria_versus_sickle-cell_trait_distributions.png
Sickle cell frequency is higher in Africa than America
because the mutation did NOT cause sickle cell disease
in Africa but caused it in America
A. True
B. False
http://www.mydochub.com/blog/index.php/2007/03/16/photo-project-sheds-light-on-sickle-cell-anemia/
End of part 2
Case study 3
Malaria drug resistance warning
Read BBC article from 2005
Do assignment with group



Main point?
Implication for malaria control?
Drawing natural selection.
Objectives
 explain how drug resistance arises in malaria
parasites
 propose explanations for why different parts of the
world where malaria is prevalent, differ with respect
to malaria parasite drug resistance
 state the main point of an article in the context of the
class
WHO calls for an immediate halt to provision of single-drug
artemisinin malaria pills
New malaria treatment guidelines issued by WHO
19 JANUARY 2006 | WASHINGTON, DC -- The World Health
Organization (WHO) today requested pharmaceutical companies to
end the marketing and sale of “single-drug” artemisinin malaria
medicines, in order to prevent malaria parasites from developing
resistance to this drug.
The use of single-drug artemisinin treatment – or monotherapy –
hastens development of resistance by weakening but not killing the
parasite. When used correctly in combination with other anti-malarial
drugs in Artemisinin Combination Therapies (ACTs), artemisinin is
nearly 95% effective in curing malaria and the parasite is highly
unlikely to become drug resistant. ACTs are currently the most
effective medicine available to treat malaria.
"It is critical that artemisinins be used correctly," said Dr LEE Jongwook, WHO's Director-General. "We request pharmaceutical
companies to immediately stop marketing single-drug artemisinin
tablets and instead market artemisinin combination therapies only.
The new treatment guidelines we are releasing today provide
countries with clear and evidence-based direction on the best
treatment options for malaria."
According to the new WHO malaria treatment guidelines,
uncomplicated falciparum malaria must be treated with ACTs and not
by artemisinin alone or any other monotherapy.
www.who.int
The main point of the article was thatA. Artemesinin is a very strong drug
B. Malaria is a very bad disease
C. Malaria parasites are evolving resistance to anti-
malarial drugs
D. None of the above
The implications for malaria control from
this finding is that….
A. Malaria control will become harder if drug-
resistant parasites emerge
B. Scientists can easily control malaria with
artemesinin
C. None of the above
Drug resistance could set back malaria control success
US$ 22.5 million grant from Gates Foundation to contain malaria
parasites resistant to artemisinin
25 FEBRUARY 2009 | GENEVA -- WHO today said that the emergence of
parasites resistant to artemisinin at the Thai-Cambodia border could seriously
undermine the success of the global malaria control efforts.
Surveillance systems and research studies supported by WHO to monitor
antimalarial drug efficacy in countries are providing new evidence that
parasites resistant to artemisinin have emerged along the border between
Cambodia and Thailand. If local people, who walk for miles every day to clear
forests, were infected with a drug-resistant form of malaria, it could set back
recent successes to control the disease.
Huge strides have been made in the past 10 years to reduce the burden of
malaria, one of the world's major killer diseases. Strong malaria control
programmes have helped to lower infection rates in several countries. The
recent shift from failing drugs to the highly effective artemisinin-based
combination therapies (ACTs) has been a breakthrough. Appropriate treatment
with ACTs succeeds in more than 90% of cases. But malaria drug resistance
now emerging along the Thai-Cambodia border threatens these gains.
www.who.int
End of Part 3
Case study 4
WHO report.
 It shows whether or not malaria parasite in different
regions of the world are resistant to certain drugs
that are used to treat malaria.
 Study the table carefully and answer questions in
the assignment.
Objectives
 propose explanations for why different parts of the world




where malaria is prevalent, differ with respect to malaria
parasite drug resistance
predict what would happen if infected people or mosquitoes
moved from populations with drug resistant malaria, to
populations without drug resistant parasites
propose solutions to controlling malaria using evolutionary
thinking
state the main point of a table and a figure
give two examples of how evolutionary thinking is relevant
to human health and disease management
Drug resistance could set back malaria control success
US$ 22.5 million grant from Gates Foundation to contain malaria
parasites resistant to artemisinin
25 FEBRUARY 2009 | GENEVA -- WHO today said that the emergence of
parasites resistant to artemisinin at the Thai-Cambodia border could seriously
undermine the success of the global malaria control efforts.
Surveillance systems and research studies supported by WHO to monitor
antimalarial drug efficacy in countries are providing new evidence that
parasites resistant to artemisinin have emerged along the border between
Cambodia and Thailand. If local people, who walk for miles every day to clear
forests, were infected with a drug-resistant form of malaria, it could set back
recent successes to control the disease.
Huge strides have been made in the past 10 years to reduce the burden of
malaria, one of the world's major killer diseases. Strong malaria control
programmes have helped to lower infection rates in several countries. The
recent shift from failing drugs to the highly effective artemisinin-based
combination therapies (ACTs) has been a breakthrough. Appropriate treatment
with ACTs succeeds in more than 90% of cases. But malaria drug resistance
now emerging along the Thai-Cambodia border threatens these gains.
www.who.int
TABLE 3. DISTRIBUTION OF DRUG-RESISTANT PLASMODIUM FALCIPARUM MALARIA
Region
Resistance reported
Comments
CQ SP MQ Others
Central America
N
N
N
North-west of Panama Canal only
Caribbean
N
N
N
South America
Y
Y
Y
Western Africa
Y
Y
Y
Incidence of resistance to CQ variable, but
very common in most areas
Eastern Africa
Y
Y
N
Southern Africa
Y
Y
N
Incidence o f resistance to SP highly
variable, with some reports of focally high
incidence,
but generally uncommon
Resistance to SP, although reported, is
considered to be generally uncommon
Indian Subcontinent
Y
N
N
South-East Asia
and Oceania
Y
Y
Y
QN
HAL, QN
MQ and QN infrequently
Border areas of Thailand, Cambodia, and
Myanmar highest risk for multiple-drugresistant infections; in other areas,
incidence of resistance to SP and MQ
highly variable and absent in many areas
East Asia (China)
Y
Y
?
Resistance greatest problem in southern
China
CQ = chloroquine QN = quinine SP = sulfadoxine-pyrimethamine HAL = halofantrine MQ = mefloquine
Bloland 2001, www.who.int
www.who.int
Discuss in your group
 How does this relate to:
 Natural selection?
 Gene flow?
 Mutation?
If infected mosquitoes from areas with resistant
malaria parasite flew to areas with populations of
susceptible malaria parasite, this would be an
example of
A. Gene flow
B. Genetic drift
C. Mutation
D. All of the above
If malaria parasites in an area exposed to a certain
malaria drug suddenly show some individuals with
resistance to the malaria drug where none existed
before, this might be an example of
A. Genetic drift
B. Mutation
C. None of the above
Based on what you have learned about malaria..
How is evolutionary thinking relevant to
understanding and treating human disease?
End of part 4