Download Malaria parasites in the mosquito mid

TEACHER'S GUIDE:
Background Information (optional class content)
MALARIA AND ITS IMPACT
Malaria is one of the world’s most
devastating diseases. According to the World
Health
Organization (WHO), there are 300 to 500
million
clinical cases of malaria each year that result
in 1.5-2.7
million deaths.
Malaria is caused by tiny parasites that
are
transmitted from person to person through a
mosquito
bite, genus Anopheles. Plasmodium falciparum is
the most
virulent form of the parasite and causes the
majority
of infections. Although P. falciparum can
cause
serious and deadly diseases, not all infections
require
medical treatment. Individuals that are most
susceptible to severe infections are children
and
pregnant women, and travelers who have
not
previously experienced malaria. Whereas
most
malaria infections cause symptoms, such as a
fever,
tiredness, and headaches that have been
compared
to a very bad case of flu, the most serious
disease
complications include severe anemia
(excessive
loss of red blood cells) and cerebral malaria
(coma
from which one cannot be roused) and
placental
malaria (passed through placenta). These are
known as
complicated malaria. Cerebral and placental malaria can cause death if left untreated. Despite over a century of work
to control and eradicate this disease, malaria continues to take its devastating toll, largely in developing nations
where many parents are left childless. These deaths occur despite the fact that drugs exist to treat and cure
infections. However, the emergence of insecticide-resistant mosquitoes and drug-resistant malarial parasites has put
40% of the world’s population at risk. Therefore, new approaches to eradicate mosquitoes, and new anti-malarial
drugs, are desperately needed to prevent even more deaths. However, the ultimate malaria solution will require the
development of vaccines to
prevent infection
and disease
Liver
Human
Mosquito
Sporozoites
Life Cycle of the Malaria
RBC
P. falciparum parasites
Ring
the mosquito and the human.
transmitted to humans when
Life cycle of the Plasmodium parasite.
Merozoites
female anopheline mosquito
feeds on human blood in
Troph
nutrients to produce eggs.
sucking behavior is hardmosquitoes in order to ensure
survival. At the same time
Gametocytes
mosquito is acquiring its
Schizont
spitting factors into the
prevent blood clotting and
that would interfere with
mosquito thus acts as a syringe to deliver the parasite into the blood circulation.
Parasite
have two hosts,
The parasite is
a
order to acquire
Thus, bloodwired into
their specie’s
that the
blood meal, it is
human to
other activities
feeding. The
Once in the bloodstream, parasites travel to and invade liver cells where they multiply up to 30,000-fold,
eventually breaking out and infecting red blood cells (RBCs). Over 48 hours, the parasite in the RBC develops
through the ring, trophozoite (troph), and schizont stages. When the schizont matures, it ruptures and releases new
merozoites, which can then infect more RBCs, thus setting up a recurring cycle. It's these RBC stages that cause the
pathology connected with malaria. At a low frequency, some parasites will begin to differentiate into male and
female gametocytes shortly after entering RBCs. If ingested by an anopheline mosquito, the gametocytes fuse to form
a zygote and proceed through mosquito developmental stages, culminating in infectious sporozoites in the
mosquito’s salivary glands.
Source, WHO
Malaria parasites in the mosquito mid-gut.
TEACHER'S GUIDE
Key for Answers
Assigned Student Role
Tanzanian Doctor
Questions:
1. How would you describe access to medical care
in Tanzania? What role does the government
play? What role does the private sector play?
2.
How is malaria diagnosed?
3.
Tetanus and polio are two examples of diseases
that American children are vaccinated against.
What is the nature of these vaccines? How do
vaccines work, and how can malaria researchers
use knowledge about existing vaccines to develop
a malaria vaccine?
4.
The following information should be included in the
student answers.
1.
Medical care is available through public and
private facilities. The annual health budget of
Tanzania works out to between $4 –7 per person
per year. Medical care is available through a
referral system that ranges from Village Health
Services to Referral/Consultant Hospitals.
2.
Diagnosis includes evaluation of symptoms and
patient history, microscopic examination of
blood, ELISA, and PCR.
3.
Vaccines aim to prevent infection and disease by
inducing specific immunity (B and T
lymphocytes) that recognize the pathogen or its
disease-causing products. Vaccines take different
forms including 1) attenuated (weakened)
bacterial or viral vaccine (example polio), purified
antigens or “detoxified” toxins (example
Tetanus), synthetic antigens. The polio vaccine is
designed to induce an immune response against
the polio virus, while a tetanus shot generates
antibodies against the bacterial toxin that causes
disease.
4.
Students should consider impact on the doctor's
family as dependents and caregivers, as well as
lost income, and impact on health care system in
the doctor's absence.
If you were to contract malaria, what impact
would it have on all those who depend on you?
Health Care Worker
1.
Plasmodium falciparum – life threatening illness may
develop very rapidly, symptoms can include high
fever & coma, spleen, brain, liver & kidney
damage with a mortality rate of 4-20%.
Plasmodium vivax – fever and chills, recurring
fever, low mortality rate.
Plasmodium malariae and Plasmodium ovale – least
common, fever and chills, recurring fever, low
mortality rate.
2.
Treatment measures include rehydration, fever
management and specific antimalarial medicines.
Drug resistant strains of Plasmodium are common.
3.
Vaccines can be delivered orally or by injection.
SBRI is currently developing a genetically
attenuated malaria vaccine, with the goal of
injecting it through the bite of a mosquito! The
per capita income of most countries that deal
with malaria is extremely low. It is conceivable
that government and charity organizations would
need to assist in costs.
4.
Students should consider impact on the Health
Care Worker's family and his/her caregivers, lost
income, and impact on health care system in the
Health Care Worker's absence.
Questions:
1. What are the symptoms of each of the four types
of malaria?
2.
How is malaria treated?
3.
What are some ways that a malaria vaccine
could be administered? Who would pay for it?
4.
If you were to develop malaria, what impact
would it have on all those who depend on you?
Tanzanian Teacher
1.
Protective traits have evolved in individuals living
in parts of the world where malaria is endemic.
Many of these beneficial traits impact the red
blood cells in which the parasite lives. The Sickle
Cell Trait is perhaps the most famous example
and affects the type of hemoglobin that a person
inherits. Inheriting one such gene can confer
protection from malaria; inheriting two is actually
more deadly.
2.
From 1950-1972, a global effort to eradicate
malaria was launched by a new organization
called the Centers for Disease Control (CDC).
The centerpiece of the targeted mosquito control
utilized the pesticides such as DDT
(dichlorodiphenyltrichloroethane). The
application of this chemical on houses and
mosquito breeding grounds resulted in a
phenomenal drop in malaria cases in countries
such as India. Prior to this campaign, even
Seattleites battled malaria! In 1972 the US
government banned crop spraying with DDT,
and worldwide cases once again rose. Other
efforts include vaccine research, antimalarial
medications (including quinine, artemisinin,
doxycycline, mefloquine, sulfacoxinepyrimethamine (SP) and malarone), and
education. Thus far, none have been completely
successful. The greatest hopes lie with a vaccine.
(a,b). In 2007, the WHO has recommended the
return of judicious application of DDT in high
risk communities, and the implementation of
affordable combination therapies (such as
artemisinin & S-P).
3.
Use mosquito control techniques including
permethrin-impregnated bed nets, pesticides,
avoid being outside during the time that
mosquitoes are feeding. Education about control
and vaccine development is important for
society. Promote understanding that global health
scourges are everyone’s responsibilities, and not
merely the sufferers.
4.
Students should consider impact on the teacher's
family and his/her dependents, lost income, and
impact on the education system in the teacher's
absence.
Questions:
1. Why is it that some people can be bitten by
infected mosquitoes and never develop malaria,
yet others readily develop the disease?
2.
What efforts have been made to prevent the
incidence and spread of malaria? In what ways
have these efforts been successful? In what ways
have they not failed?
3.
What will be the most important things you can
teach students to help control the spread of
malaria?
4.
If you were to develop malaria, what impact
would it have on all those who depend on you?
Mosquito
1.
Female mosquitoes feed on blood to acquire
nutrients in order to produce eggs (male
mosquitoes have a “sweet tooth” and feed on
nectar). Mosquitoes have evolved to recognize
organisms that contain blood and have in-born
blood-seeking behavior. Signals include emission
of CO2, heat, and odors from bacteria that live
on humans (also attracted to limburger cheese for
the same reason). Anopheles mosquitoes transmit
malaria. While there are over 1,000 species of
Anopheles mosquitoes, only a handful of species
can transmit malaria to man. These species
inhabit different niches (i.e., some mosquitoes
like to breed in sun-lit water, others in clear
water, and some in cloudy water). Only some
species of anopheline mosquitoes are known to
transmit malaria to humans. In some, the parasite
may not survive. In others, they prefer to feed on
cattle blood rather than human. Some, like
Anopheles Gambia, take many small blood meals,
enhancing transmission, through the multiple
skin wounds.
2.
Although DDT is banned in many developed
nations, it is still used as a recommended vector
control method in some areas of the world that
are severely impacted by malaria. Judicious
amounts (< 0.5 kg) are now applied annually to
the inside of dwellings—in comparison, during
the 1950s, 100 hectare cotton fields used to
receive >1,100 kilograms of DDT over 4 weeks.
Some mosquitoes have developed resistance to
DDT and other pesticides. The risks include
dangers to other animal species and possible
birth defects. These concerns weigh heavily
upon the minds of policy makers—to the extent
that many NGOs and funders will not fund
multi-pronged malaria initiatives that include
DDT in the response (including the World Bank
and the International Monetary Fund agencies).
3.
The Anopheles mosquito harbors a parasite of
the Plasmodium genus. There are four species of
Plasmodium, each capable of causing malaria in
humans. The female anopheles mosquito must
drink blood in order to lay eggs. When she
injects her saliva into the host, to ensure a clogfree drink of blood, she will inject any parasites
that she might be harboring in her salivary
glands. The parasites in her salivary glands
arrived there, by way of the mosquito gut, when
she last took a blood meal from a person with
malaria parasites in their blood. See life cycle of
Plasmodium.
4.
Students should consider the impact of the
mosquito in the life cycle of other animals, such
as birds. What would be the consequence of total
eradication? This could affect bird species that
help abate mosquito infestation and lead them to
feed on an insect that is beneficial or plays a role
in supporting crops.
Questions:
1. What is the role of the mosquito in transmitting
malaria? Why types of mosquitoes are involved?
2.
Do the risks of DDT outweigh their benefit in
controlling the spread of malaria?
3.
What causes malaria? What role does the
mosquito play in spreading this disease?
4.
Is eradication the answer? How would this affect
the environment?
Mother
Questions:
1. What is the mortality rate associated with malaria
and which type has the highest mortality?
2.
What effect might a malarial infection have on a
developing fetus?
3.
What effect might a malarial infection have on a
woman while she is pregnant?
4.
1.
Nearly all malaria deaths are attributable to P.
falciparum. It has been estimated that nearly 20%
of infections result in severe diseases and 10% in
death. Malaria kills over 1 million people each
year, about 3,000 people a day. In sub-Saharan
Africa, malaria accounts for one in five of all
childhood deaths. Malaria kills an African child
every 30 seconds.
2.
May cause death of fetus. In pregnant women,
infected erythrocytes accumulate in the placenta.
The placenta is the site where nutrients are
passed between woman and fetus, and waste
products are returned from fetus to woman.
There may be direct effects of parasite
accumulation in the placenta or indirect effects
caused by immune abnormalities. Babies born to
malaria-infected women have lower than normal
birth weight. This is a risk factor for death
whenever a child is born. Malaria infections can
also cause miscarriages.
3.
Women may develop immunity to malaria.
Malaria infections can cause severe anemia (low
red blood cell numbers) in mothers. It has been
shown that pregnant women develop antibodies
that protect against malaria. This helps to protect
the fetus during subsequent pregnancies. SBRI
researchers are studying why this response occurs
in order to develop a vaccine that prevents
malaria during pregnancy.
4.
Students should consider impact on the woman’s
family and her dependents, lost income, and
social/economic impact of orphaned children.
1.
Avoid being outdoors at dawn and from 5- 9 pm,
use bed nets, use insect repellent, wear long
clothing, use antimalarial medications before,
during, and after visit, despite side effects. If you
have a fever within a few weeks after your visit,
see a doctor to rule out a malaria infection – be
sure to tell them you have recently traveled to a
malaria endemic area.
2.
Possibilities include educating others, including
peers, parents, and adults. Not-for-profit
research institutes welcome volunteers to assist
with community outreach and fund raising.
Future scientists are needed and a research career
could lead to future discoveries.
3.
Yes! Children under the age of five are the
population at highest risk for serious malaria.
The complications due to anemia, high fever and
poor digestions (recall that vomiting is malaria
symptom in children) make mild infectious,
deadly serious!
4.
Because malaria is not commonly seen in the US,
most people know very little about it. If not
covered by health insurance, your illness could
have a huge economic impact on your family.
What would you need to know about the
American doctors who are providing healthcare
to other women in the village before you would
consider participating in a malaria research study?
American Teenager Visiting Tanzania
Questions:
1.
What preventative measures will you take to
minimize the chances that you will contract
malaria?
2.
Even though you are a teenager, you are still
influential and powerful in many ways. What will
be your role in controlling the spread of malaria?
3.
Are children at higher risk than adults of
contracting malaria? Is the disease more severe
in children or adults?
4.
If you were to develop malaria, what impact
would it have on all those who care for you?
Researcher from SBRI
1.
Infectious diseases can be transmitted from one
person to another through contact (coughing,
saliva, blood, etc.). Non-infectious diseases are
not transmitted through contact (lung cancer).
2.
The malaria parasite is very complex. It has a
large genome; for example the human genome
has approximately 35,000 genes and the malaria
parasite 6,500. Malaria parasites have an
estimated 5,000 proteins that are potential targets
for a vaccine. The parasite has evolved very
complex strategies to evade the immune
response. These include extensive polymorphism
(assuming various forms) of proteins that are
exposed to the immune system. Thus, it is
difficult to find good vaccine candidates that are
conserved (the same) between different P.
falciparum parasites. The parasite spends most of
its life hidden from the immune system (known
as sequestration) within a red blood cell where T
and B lymphocytes cannot access it, but exposes
parasite proteins on RBC surface (the target).
3.
From the malaria genome project we got a
“blueprint” or how-to manual for building the
parasite. Just by examining the DNA sequence,
scientists can learn things. For instance, scientists
can discover which parasite proteins are different
from humans. Unique proteins or metabolic
pathways are potential drug targets. Different
proteins are discovered by knowing the parasite
DNA sequence, and these unique proteins and
genes can then be targeted for an ideal drug or
vaccine target—with less worry of harming the
human patient.
4.
There are many complicating factors in carrying
out research based on data being collected in
Tanzania. These include language barriers and the
ethics of working with humans in another
country. From a logistical standpoint there are
extreme challenges in shipping equipment and
time sensitive samples, problems with data
storage for 1,000 participants and travel safety
issues for the researchers traveling and working
in Tanzania.
Questions:
1. How would you define an infectious disease? A
non-infectious disease?
2.
Why is it so difficult to develop a vaccine for
malaria?
3.
How does knowing the genetic information (the
sequence of DNA nucleotides) within the
genome of Plasmodium help design a new
treatment, vaccine or healthcare response
(diagnosis)?
4.
What are specific challenges in carrying out
research based on participants in Tanzania?
Park Ranger
1.
The nature of the park ranger’s work, working
mostly outdoors increases their chances of
exposure, particularly when their work occurs
during prime mosquito feeding times.
2.
Factors include drug resistance of Plasmodium,
insecticide resistance of mosquitoes, increasing
poverty & malnutrition, political and social
upheaval causing displacement of large groups of
people, roads, dams, irrigation, and health budget
constraints.
3.
DDT was banned in the United States in 1972
and has been commonly banned since it was
linked to reproductive dysfunction such as thin
eggshells in birds. Also, some insects such as
mosquitoes have become resistant to DDT while
their natural predators were eradicated. Although
DDT is banned in many developed nations, it is
still used as a treatment of choice in some areas
of the world that are severely impacted by
malaria.
4.
Students should consider impact on the ranger’s
family and his/her caregivers, lost income, and
impact on environmental protection in the
ranger’s absence.
Questions:
1. Is your risk of contracting malaria any greater
than that of a teacher or doctor?
2.
Why has the incidence of malaria increased?
3.
What are the risks of DDT and do the risks
outweigh their benefit in controlling the spread
of malaria?
4.
If you were to develop malaria, what impact
would it have on all those who depend on you?
Conference/Town Meeting Notes and Learner’s Summary—Teacher’s Guide


Students take notes during class presentations in the Town Meeting. At the end of the Town Meeting, students should have a
comprehensive, “8-character” view of the social, environmental, economic and political impact of Malaria.
Students independently respond to questions 1-5, as homework.
Mosquito
What causes malaria? What role does the mosquito play in spreading this disease?
Doctor
Tetanus and polio are two examples of diseases that American children are vaccinated against. What
is the nature of these vaccines? How do vaccines work, and how can malaria researchers use
knowledge about existing vaccines to develop a malaria vaccine?
Health Care Worker
What are some ways that a malaria vaccine could be administered? Who would pay for it?
Teacher
What will be the most important things that your can teach students to help control the spread of
malaria?
Mother
What effect might a malarial infection have on a woman while she is pregnant?
American Teenager
Are children at higher risk than adults of contracting malaria? Is the disease more severe in children
or adults?
SBRI Researcher
How does knowing the genetic information (the sequence of DNA nucleotides) within the genome
of Plasmodium help design a new treatment, vaccine or healthcare response (diagnosis)?
Park Ranger
Do the risks of DDT outweigh their benefit in controlling the spread of malaria?