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ADITI PAIBIOLOGY DEPARTMENT
SPELMAN [email protected]
Learning concepts in evolution with malaria as
the case study
What is malaria?
http://www.flickr.com/photos/ajc1/3420714787/
http://www.flickr.com/photos/atwj/3347071689/
http://www.flickr.com/photos/lamerie/407337286/
10 facts on malariaWHO/S. HollymanMarch 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.
10 facts on malaria
http://www.who.int/features/factfiles/malaria/en/index.html
Facts about malaria
Caused by a trypanosome: PlasmodiumTransmitted by a vector: mosquitoPrevalent in tropical and sub-tropical areasSymptoms: 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 malariaC. Hb is an essential part of the RBC
and malaria affects RBCD. Hb is not relevant to the effect of
malaria
What is the adaptive mutation described in
the video?
Sickle Cell Anemia is codominant
AA = normalAS = sickle cell trait (few symptoms)SS = sickle cell anemiahttp://www.flickr.com/photos/wellcomeimages/4013247943/
The effect of mutations are______
A. BeneficialB. DetrimentalC. NeutralD. 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 malariaB. They could grow up and marryC. They could have childrenD. All of the above
What if a person has two copies of sickle cell allele?
A. They could survive malariaB. They could grow up and marryC. They could have childrenD. 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 malariaB. 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, an epidemic could wipe out the entire population
B. Having genetic diversity improves the chances that some are able to survive future epidemics
C. Having genetic diversity guarantees that the population survives future epidemics
D. A and CE. A and B
Case study 2
Who has sickle cell disease and why?
Reading from Bloom 1995Complete 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 orientedpropose 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?
Many famous people have it!
http://www.flickr.com/photos/exquisitur/2553768995/
http://www.flickr.com/photos/darienlibrary/2893149535/
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 Allisonhttp://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. TrueB. 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 Allisonhttp://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. TrueB. 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 2005Do 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 Jong-wook, 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 that-
A. Artemesinin is a very strong drugB. Malaria is a very bad diseaseC. Malaria parasites are evolving resistance to
anti-malarial drugsD. 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 successUS$ 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 figuregive two examples of how evolutionary thinking is
relevant to human health and disease management
Drug resistance could set back malaria control successUS$ 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 MALARIARegion Resistance reported Comments
CQ SP MQ OthersCentral America N N N North-west of Panama Canal only
Caribbean N N N
South America Y Y Y QN MQ and QN infrequently
Western Africa Y Y Y Incidence of resistance to CQ variable, but very common in most areas
Eastern Africa Y Y N Incidence o f resistance to SP highly variable, with some reports of focally
high incidence,but generally uncommon
Southern Africa Y Y N Resistance to SP, although reported, is considered to be generally uncommon
Indian Subcontinent Y N N
South-East Asia and Oceania Y Y Y HAL, QN Border areas of Thailand, Cambodia, and
Myanmar highest risk for multiple-drug-resistant 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 flowB. Genetic driftC. MutationD. 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 driftB. MutationC. 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
