Malaria: From Mosquitoes to Microscopes
ColorColor-synthesized SEM (scanning electron microscope) Image from David Scharf www.ngm.com July 2007
Presented by Melissa Marzahn and Marsha Bush
What is malaria?
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Literally, “mal aria” or “bad air”
Mosquito-borne disease
Caused by a parasite
Mild infection causes fever, chills, and flu-like
illness
Severe infection spreads to brain, leading to
seizures, coma, and death if not treated rapidly.
Malaria affects most of the planet
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Approximately 40% of the world’s population
lives in areas where infection is likely to occur
Between 300 and 500 million cases of acute
illness occur every year
Malaria causes about one million deaths every
year, 75% of whom are children
Leading cause of death and disease in most
developing countries
http://www.cdc.gov/malaria/facts.htm
Three conditions for the spread of
malaria
Anopheles mosquitoes must be present
„ Humans must come in contact with Anopheles
mosquitoes
„ Malaria parasites (Plasmodium) must be present
* Rainfall, temperature, and humidity also play a
role in the spread of malaria
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Global Distribution of Malaria
Photos by John Stanmeyer; M. Finkel. (2007) “Bedlam in the Blood: Malaria” National Geographic July: 32-67. and
www.nationalgeographic.com/magazine
Plasmodium life cycle
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Protozoan
Parasite
Many species infect animals
Four species infect humans
P. falciparum is the most deadly
Completes life cycle in two hosts: Anopheles
mosquitoes and humans
Objectives
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Understand mosquito metamorphosis
How the malaria parasite spreads from
mosquitoes to humans
The effect of malaria on human cells
The impact of malaria on human populations
Activity One – Raise mosquitoes
http://www.enchantedlearning.com/subjects/insects/mo
squito/labellifecycle/labelanswers.shtml
Anopheles gambiae from www.cdc.gov/malaria
www.nwmadil.com/mosquito%20biology.htm
Activity Two – Malaria Infection
Supplies needed:
Eye droppers
Cups
Water
Starch
Iodine
Students carrying eye droppers
act as mosquitoes and feed
upon humans (cups of solution).
Use iodine to determine which
individuals are positive for malaria
infection (presence of starch).
Activity Two – Malaria Infection
Activity Three – Observe red blood cells
under microscope
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Compare normal RBCs
to infected RBCs
Could also look at sickle
cell anemia and other
blood diseases here
If slide set is not
available, students can
rotate through stations
to observe color images
A)
Electron micrograph of RBCs from
http://en.wikipedia.org/wiki/Red_blood_cell and
B)
B) light microscope
http://www.wadsworth.org/chemheme/heme/microscope/rbc.htm
C) Light microscope image with Giemsa stain of Plasmodium infected
RBCs http://en.wikipedia.org/wiki/Malaria and D) electron micrograph of
rupturing RBC
http://www.smccd.edu/accounts/case/malaria/malaria_rbc.jpg.htm
Expected Outcomes
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Diagram the life cycle of a mosquito
Demonstrate understanding of malarial parasite
life cycle and describe the spread of malaria
through populations in regions where malaria is
endemic
Demonstrate correct use of a light microscope
and identify one difference between normal and
malarial-infected RBCs
Further Outcomes
Significance of awareness and prevention of
malaria (and other mosquito-borne diseases)
How malaria can be prevented or treated
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Mosquito nets and pesticides
Chinese herbal medicines (artemisia plant)
Multi-drug cocktail
Researchers are trying to design a vaccine
Additional Resources
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http://www.cdc.gov/malaria Centers for
Disease Control and Prevention
http://www.ngm.com National Geographic
magazine
http://www.enchantedlearning.com
Additional resources are included in the
teacher’s guide segment of this module
Worksheets/Lab Reports
Malaria
Assignment 1
Mosquito life cycle
The stages of development for all mosquitoes are the same. Thus, the mosquitoes
grown in class are representative of the Anopheles mosquitoes that transmit malaria in
tropical and sub-tropical climates around the world.
Observe the mosquitoes as the larvae hatch from the egg raft and mature toward
adulthood. On each lab day, write your observations and draw what you see.
Worksheets/Lab Reports
Malaria
Worksheets/Lab Reports
Malaria
Worksheets/Lab Reports
Malaria
Assignment 2
Plasmodium life cycle:
Using an existing diagram of the Plasmodium lifecycle, draw your own version of the P.
falciparum lifecycle in humans and mosquitoes. Note which two cell types are infected
in the human body.
Source: http://www.smccd.edu/accounts/case/biol675/images/malaria.html
Worksheets/Lab Reports
Malaria
Assignment 3
Observe slides of normal red blood cells (erythrocytes) and compare to those of
malaria-infected individuals. Draw the cells you observed and note any differences.
Worksheets/Lab Reports
Malaria
Worksheets/Lab Reports
Malaria
Answer key:
Normal cells are red, round, and have “donut”
shaped appearance.
Infected cells are irregular in shape or ruptured, have
dark pigmentation. The parasites are stained dark blue.
Resources for Purchasing Supplies
Home Training Tools
Wright’s stain, blood smear (normal)
1 slide is $2.50
Individual blood test kit $6.90
http://www.hometrainingtools.com/product_categories/148/products/3481-human-bloodslide-wright-s-stain-smear
Microscopes and slide-making kits
http://www.hometrainingtools.com/catalog/cat_microscopes-accessories.html
Source for mosquitoes: http://www.carolina.com/ Enter “mosquito” as the search term.
From this company, you can purchase live mosquito egg rafts, larvae, and pupae. This
resource also has microscope slides, slide-making kits, and great information for science
teachers. There is a slide of normal human blood, but there is not one commercially
available for malaria-infected blood.
Teacher info for Experiment One
Mosquito life cycle from
http://www.leoncountyfl.gov/Mosquito/mceduc/mosquitobiology/mosquito_lifecycle.asp
http://www.enchantedlearning.com/subjects/insects/mosquito/labellifecycle/labelanswers.
shtml
Mosquito Biology (contains colorful pictures)
http://www.nwmadil.com/mosquito%20biology.htm
Great image of mosquito larvae located here: http://en.wikipedia.org/wiki/Mosquito
Mosquito species—most but not all—listed, described, and drawn in black and white
http://www.brunswickcountync.gov/Departments/MosquitoControl/MosquitoSpecies/tabi
d/424/Default.aspx
Some of the entomology students at UF may have access to a poster or slide with many
colorful images of multiple mosquito species, especially those with interesting stripes and
patterns on their tiny bodies.
As a result of rearing mosquito larvae in class, students will gain an understanding
of the mosquito lifecycle. They will observe mosquitoes growing in a confined water
source within the classroom, and they will be asked to draw what they see in the
container over the course of 3-4 weeks. From this experiment, they should become more
familiar with the stages of metamorphosis: egg, larva, pupa, and adult. Students should
also relate these stages of development to other insects such as fruit flies, grasshoppers,
butterflies, and beetles, among others.
More details about mosquito metamorphosis
Mosquitoes undergo complete metamorphosis; they go through four distinct stages of
development during a lifetime. The four stages are egg, larva, pupa, and adult. The full
life-cycle of a mosquito takes about a month.
Raft of Eggs: After drinking blood, adult females lay a raft of 40 to 400 tiny white eggs
in standing water or very slow-moving water.
Larva: Within a week, the eggs hatch into larvae (sometimes called wrigglers) that
breathe air through tubes which they poke above the surface of the water. Larvae eat bits
of floating organic matter and each other. Larvae molt four times as they grow; after the
fourth molt, they are called pupae. Larva = singular, larvae = plural.
Pupa: Pupae (also called tumblers) live near the surface of the water, breathing through
two horn-like tubes (called siphons) on their back. Pupae do not eat.
Adult: An adult emerges from a pupa when the skin splits after a few days. The adult
lives for only a few weeks.
Extensions of this experiment may include:
1. Observe images of various mosquito species to gain an understanding of the
variety of sizes, body shapes, and colors among mosquito species. Specifically,
identify pictures of Anopheles mosquitoes, the species that can carry the parasite
that causes malaria.
2. Things student can do to eliminate mosquito habitat around their homes. What
other practices can be established to prevent the spread of mosquito-borne
diseases?
3. Learn which insects and animals feed on mosquitoes at various stages (e.g. fish
fry eat mosquito larvae, dragonflies feed on adult mosquitoes, some species of
bats eat mosquitoes as part of their diet)
4. Study other mosquito-borne diseases (such as West Nile Virus, Eastern Equine
Encephalitis (EEE)) that could affect animals and people, especially focus on
those we could acquire in Florida and the southeastern United States.
Vocabulary words for students
Genus species (learn to use correct notation for scientific names)
Proboscis (what other insects have this mouthpart for feeding?) A: answers include flies,
butterflies, some moths, and several other insect species.
Anticoagulant (Or phrase this in the form of a question. How do mosquitoes keep blood
from clotting?) A: A compound in the female mosquito’s saliva is an anticoagulant
Teacher Info for Experiments Two and Three
Centers for Disease Control
http://www.cdc.gov/malaria/
Life cycle of malaria schematic diagram
http://www.cdc.gov/malaria/biology/life_cycle.htm
CDC webpage with malarial epidemiology
http://www.cdc.gov/malaria/distribution_epi/epidemiology.htm
Simplified plasmodium life cycle diagram
http://www.smccd.edu/accounts/case/malaria/
http://www.smccd.edu/accounts/case/biol675/images/malaria.html
National Geographic Magazine www.ngm.com type malaria into search box, look for
July 2007 issue along with links to field notes from two photographers. Entire article
from National Geographic July 2007 issue is available online.
http://ngm.nationalgeographic.com/2007/07/malaria/finkel-text
Background related to malarial infection and disease progression
From www.cdc.gov and National Geographic
Malaria is a mosquito-borne disease caused by a parasite, Plasmodium falciparum.
People with malaria often experience fever, chills, and flu-like illness. If left untreated,
severe complications can occur, resulting in death. Each year 300-500 million cases of
malaria occur worldwide, and over one million people die, most of them young children.
Malaria is endemic to 106 nations. Many of the hardest-hit counties are in sub-Saharan
Africa, especially Zambia and Tanzania. Name another major disease that is presently
wiping out populations in many African villages. (A: HIV/AIDS).
This sometimes fatal disease can be prevented and cured. Bed nets, insecticides, and
antimalarial drugs are effective tools to fight malaria in areas where it is transmitted.
Currently, bed nets are the best prevention, but it is difficult to persuade people to use
them in areas where it is hot and humid at night. Often the bed nets are used incorrectly,
as curtains or as fishing nets. Travelers to a malaria-risk area should avoid mosquito
bites and take a preventive antimalarial drug.
How P. falciparum spreads:
The malaria parasite spends a portion of its life cycle in female Anopheles mosquitoes.
Spread of the disease begins when a mosquito picks up the parasite during a blood meal.
Parasites at this stage are considered gametocytes. Over the course of 10-18 days, the
parasites mature in the mosquito and are found as sporozoites in the mosquito’s salivary
glands. The next time the mosquito feeds on a human, the sporozoites are injected with
the mosquito’s saliva and the parasites enter the bloodstream.
Mosquitoes are a vector for disease transmission. They carry the disease from human to
human but do not suffer from the presence of the parasite.
Once in the human, the parasites travel through the bloodstream (like a superhighway) to
the liver. The parasites sneak their way into liver cells unnoticed by the immune system.
After the parasites, P. falciparum, multiply for about a week, the liver cells explode. At
this stage, the parasites enter the bloodstream, burrowing into red blood cells. In the
blood, successive broods of parasites grow inside the red blood cells (erythrocytes) and
destroy them, releasing daughter parasites (merozoites) that continue the cycle by
invading other red blood cells. Each hijacked red blood cell is devoured as the parasites
proliferate. As the red blood cells rupture, symptoms develop for the first time, and the
body’s response is an attempt to “cook” away the parasite through a fever.
The blood stage parasites are those that cause the symptoms of malaria. When certain
forms of blood stage parasites (gametocytes) are picked up by a female Anopheles
mosquito during a blood meal, they start another cycle of growth and multiplication in
the mosquito.
Ancient methods of malaria treatment include Chinese herbal medicines. Old, but
effective, methods of prevention include hanging mosquito nets over beds. Ultramodern
methods involve the use of multidrug cocktails. In an effort to prevent parasite resistance
to one drug, antimalarial medication is delivered as part of a mixture.
Interestingly, an ancient Chinese herb, Artemisia annua, is the source of a compound that
is used to combat malaria and is the most effective drug currently available, artemisinin.
The goal sought by researchers is to design a vaccine that would slow down or possibly
eliminate the disease.
As a side note, in areas where malaria is endemic, people with the trait for sickle cell
anemia have some resistance against malaria. Those with full-blown sickle cell anemia
often die from the effects of the disease (sickle-shaped red blood cells that are deficient in
carrying oxygen throughout the body). The abnormal-shaped red blood cells are not as
flexible and therefore cannot travel through the bloodstream to nourish tissues as
effectively as healthy, round RBCs. People with one allele for sickle cell anemia and one
normal allele have an increased survival in areas where malaria is prevalent, specifically
sub-Saharan Africa. They receive adequate oxygen to all their cells; however, their
sickle-shaped RBCs are not desirable for the malaria parasite to enter.
After completing laboratory exercises two and three, students should possess a greater
understanding of how disease is spread throughout a community and what the effects of
the malaria parasite on red blood cells look like. They should be familiar with portions of
the life cycle of P. falciparum, especially the stages that occur in human liver and red
blood cells (RBCs). In addition, students should become aware of the impact malaria has
on communities, local economies, and the long-term health of individuals in Africa, Asia,
the South Pacific, and South and Central America.
Vocabulary words and questions for students
Parasite = an organism that lives in or on a host, obtains nutrients from the host, but
offers no benefit in return. Parasites are often harmful to their hosts, but in varying
degrees of severity, ranging from illness and disfigurement to death.
Plasmodium/plasmodia = parasite that causes malaria
Erythrocyte = red blood cell
Epidemiology = branch of science that studies the incidence, distribution, and
spread/control of a disease within a population
Endemic = infection maintained in a human population or restricted to a particular region
or locale
Pandemic = occurring over a wide geographic area and affecting a high proportion of the
population
Epidemic = an outbreak that occurs suddenly and spreads rapidly; affecting a
disproportionately large percentage of a population, community, or region at the same
time
Draw your own diagram of the malarial life cycle in mosquitoes and humans. Include in
your diagram transmission of the parasite from an adult mosquito to a human liver cell
and from liver cells to red blood cells.
What two types of cells in the human body does the malarial parasite attack? (A: liver
cells and red blood cells)
What does a normal red blood cell look like? (students should draw a donut or lifepreserver-shaped object).
What is one general function of red blood cells in the body? (A: to carry oxygen).
Extension question: How do red blood cells carry oxygen? A: through hemoglobin
(general biology textbook should have explanation about this oxygen-carrying protein
that gives RBCs their characteristic color).
What advantage do people with the trait for sickle-cell anemia have against malaria? (A:
People with sickle-cell anemia have some resistance to malaria. It is thought that their
misshapen red blood cells are not suitable for P. falciparum to invade).
Imagine you are traveling to a country where malaria is endemic. Name the continent
and country you would visit. What precautions can you take before and during your trip
to prevent catching malaria? Assume Anopheles mosquitoes will be present whether you
are indoors or outdoors.
Malaria is endemic to 106 nations. Many of the hardest-hit counties are in sub-Saharan
Africa, especially Zambia and Tanzania. Name another major disease that is presently
wiping out the populations in many African villages. (A: HIV/AIDS).