Download Disease_Spread_Simulation

Georgia Agriculture Education Curriculum
Course:
Unit 11:
02.42400 Veterinary Science
Principles of Disease
Lesson 3: Disease Transmission Lab Exercise (Who Done It?)
QCC: .................................................................................................................................................
Objectives:
1.
2.
3.
4.
Describe how disease organisms are spread
Determine the ease and speed of spread of diseases
Identify the original disease carrier
Follow the route of transmission
Teaching Time:
45 minutes
References:
Veterinary Science Teachers Guide, First Edition. Cornell University Agricultural
Resources Program,
Lawhead, James & Baker, MeeCee. Introduction to Veterinary Science. First
Edition. Thompson Delmar Learning, Inc. Clifton Park, NY.
Materials and Equipment:
EQUIPMENT
 One 250 ml Erlenmeyer Flask with cap or stopper
 One “dropper” bottle for the phenolphthalein
 One 50 ml plastic beaker for each student (3 oz. clear plastic or translucent
plastic disposable bathroom cups may also be used)
 One plastic test tube with stopper for each student
 Test tube rack
 One eye dropper for each student
 Safety glasses for each student
 Exam gloves for each student
Course: 02.42400
Veterinary Science
May 2007
Unit 11, Lesson 3
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Georgia Agriculture Education Curriculum
MATERIALS
NOTE: These materials are to be prepared and used by the teacher ONLY:
 Phenolphthalein indicator, premixed
o Order premixed from biological supply company or
o Obtain from your school’s chemistry teacher
 Sodium Hydroxide (NaOH), .1 Molar solution
o Obtain from chemistry teacher
o You also may use “Red Devil” lye (same thing) and mix it
yourself
o Mix by dissolving 1 gram of NaOH in 250 ml of distilled water
using the Erlenmeyer Flask.
 Distilled water
SAFETY
 Do not allow any of the liquid to come in contact with your skin, eyes, or
clothing
 Wash your hands thoroughly with soap after completing this exercise.
 Do not touch or drink any material in the lab exercise.
 Wear safety glasses and exam gloves.
 Dispose of solutions properly following exercise
 Wash all equipment thoroughly with soap following exercise
TEACHING PROCEDURE
Introduction and Mental Set
Preparation
Prior to class, prepare a beaker for each student in the class.
Number each beaker with a magic marker
Number each test tube with a magic marker the same as beakers
Place 20 ml of distilled water in each beaker, except one
Place 20 ml of NaOH in the remaining beaker
Place 20 ml of phenolphthalein indicator in the “dropper” bottle
Course: 02.42400
Veterinary Science
May 2007
Unit 11, Lesson 3
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Georgia Agriculture Education Curriculum
Mental Set
Ask students to imagine that they take their dog to a kennel and leave it for the
weekend. It comes home with Bordatella (kennel cough). Tell students kennel
cough is a highly contagious respiratory disease, similar to human colds. It is
spread through contact between dogs. It only takes one dog to spread the disease
to a large group of others. It is important to understand how disease is spread and
the role of “quarantining” and routine testing in preventing spread of infectious
disease.
In this exercise, tell students they will become “disease detectives”, much like
employees at the Center for Disease Control (CDC). Their job is to determine “who
done it” in the simulated spread of a highly contagious animal disease.
Discussion
1. Infectious diseases are caused primarily by bacteria, viruses, parasites,
and fungi. These disease-causing agents can enter an animal through the:
Skin (either broken or unbroken)
Mouth
Eyes
Mucous membranes
Lungs
Reproductive tract.
2. Infectious diseases can be spread by either direct or indirect means.
3. Direct transmission occurs by:
 Skin contact
 Direct exchange of body fluids such as blood, urine, feces, saliva, or
mucous through openings in the skin or body orifices.
 Ingestion of an infected animal or external parasite (ex. flea)
 Inhalation
 Sexual/reproductive contact.
4. Indirect transmission occurs through:
1. Vectors – mosquitoes, fleas, ticks, flies
2. Vehicles – equipment (brushes, buckets, tack), instruments and utensils
(needles, scissors), housing (cages, stalls, pet carriers)
3. Fomites – water, air, soil, food
Course: 02.42400
Veterinary Science
May 2007
Unit 11, Lesson 3
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Georgia Agriculture Education Curriculum
5. Spread of disease can be prevented or minimized by:
 Routine testing
 Quarantining - keeping an animal by itself to prevent the spread of
disease; isolation of animals known to be infected; isolation of animals for
a period of time to observe for possible infection.
Activity
 Give each student exam gloves and safety glasses. Have them put
on gloves and glasses before beginning.
 Discuss dangers in handling NaOH and go over safety precautions.
 Give each student a beaker containing 20 ml of distilled water. This
represents “simulated body fluid” of a healthy animal.
 Teacher record container numbers as they are given to students.
 Give one random student the beaker containing the NaOH. This
represents the simulated body fluid of an infected animal.
 Tell students that one of their animals is “infected” but only you know who
it is.
 Have all students remove one eye dropper of “fluid” from their beakers and
place in a numbered test tube. Place stoppers in the test tubes. These
samples will be used later for the final determination of “who done it.”
 Have them exchange “fluids” with 3 other random, different students. Do
not exchange with another student twice. NOTE: Do not let students
exchange only with others within small groups because this tends to
isolate the “disease.”
 Have students fill in the worksheet as they go, writing down whom they
exchanged “fluids” with.
 When all exchanges are complete, teacher add 5 – 7 drops of
phenolphthalein indicator to each student’s cup or beaker.
 The solution in the beaker will turn pink for students animals “infected” with
the NaOH.
 Draw a data table similar to the one on the following handout on the board.
Teacher fill in the names of persons with “infected” animals. Ask each
student with an “infected” animal to tell whom they swapped “fluids” with.
Place an asterisk beside each person in the table who has an "infected”
animal. NOTE: Some of the contacts with infected persons will not be
infected because they swapped “fluids” with them before they themselves
became infected.
Course: 02.42400
Veterinary Science
May 2007
Unit 11, Lesson 3
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Georgia Agriculture Education Curriculum
 Have students record on their worksheets the names of persons with
“infected” animals and whom they exchanged “fluids” with (copy complete
data table from the board, including asterisks).
NOTE: Note: Because the class is a closed system, you can only
trace the disease back to an original exchange (Round 1), but cannot
determine which one of the two individuals involved in the original
exchange had the disease. The only way that this can be
accomplished is to test the two individuals involved in the original
exchange, using the “Simulated Bodily Fluid” that was set aside in the
test tubes before ”fluid swapping” began.
 Once the entire class results have been recorded on the board and
individual data sheets ask students to identify the original exchange in the
class population (the original two persons’ animals who tested positive for
the disease).
 The owners of the two “infected” animals who were determined to be in the
original exchange will have to submit their test tubes for further evaluation.
Place one drop of phenolphthalein indicator in each test tube. The one
that turns pink is the guilty animal owner.
 Have students complete a flow chart from the data table tracing the route
of transmission of the disease through the population.
SUMMARY
Evaluation
Successful identification of original disease carrier through cooperative effort
among class members (group evaluation).
Completion of analysis questions on worksheet
Written test
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Veterinary Science
May 2007
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Georgia Agriculture Education Curriculum
Name:
Date:
Veterianary Science
Spread of Disease Lab Exercise
Names of persons with whom you
exchanged “simulated body fluids”.
Round 1
Round 2
Round 3
Color of your tube after test with “Disease Indicator Solution” (check one)
Clear _______ (Negative)
Pink _______ (Positive)
Class Results:
Fill in the names of owners of infected animals as well as their contacts. Place an asterisk
next to each name that is found to be positive for the simulated disease.
Class Data Table
Contacts of Owners with Infected Animals
Round 1
Round 2
Round 3
Owners of infected animals
Name of original carrier of disease:
Course: 02.42400
Veterinary Science
May 2007
Unit 11, Lesson 3
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Georgia Agriculture Education Curriculum
Route of Transmission Flow Chart
Draw a flow chart of the route of transmission to all infected animals. An example has been provided for you
below.
Round 1
Round 2
Round 3
(Example)
Round 1
Round 2
Jim
(original
carrier)
Round 3
Joe
Slim
John
Kim
Julian
Tim
Jesse
Analysis/Conclusions:
1. Were you surprised by the number of animals that acquired the disease? Explain your
answer.
2. How could the spread of this disease through the class population been prevented?
3. Select two names on the same line from the data table that tested negative (no asterisk)
in rounds 1 and 2, even though their animals exchanged “body fluids” with an infected
animal. Explain how this happened?
4. How many animals tested positive in your class? What was the percentage of positive to
negative?
5. Does there appear to be a mathematical relationship between the number of infected
animals in round 1 and the number of infected animals in round 3 in this closed system?
If fluids were exchanged with one more person, how many infected animals could you
expect there to be in round 4?
Course: 02.42400
Veterinary Science
May 2007
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