I. Introduction
A. Question
1. Are the parasites Taenia solium, Toxoplasma gondii, and Naegleria fowleri using the same mechanism to invade the host’s brain?
B. Hypothesis
1. Null hypothesis
a. The parasite Taenia solium, Toxoplasma gondii, and Naegleria fowleri use the same mechanism to invade the host’s brain
2. Alternative hypothesis
a. The parasites Taenia solium, Toxoplasma gondii, and Naegleria fowleri do not use the same mechanism to invade the host’s brain
C. Definition of parasitism
1. Categories
a. Ectoparasite vs endoparasite
b. Microparasite vs macroparasite
c. Facultative parasite
d. Obligate parasite
D. Parasite adaptations
1. Behavioral
a. Adaptive advantage of parasite behavior
b. Parasite may alter host behavior
2. Immunological adaptations
a. Absorption of host antigen
b. Antigen variation
c. Molecular mimicry
d. Loss or masking of surface antigens
e. Disruption of the host’s immune response
3. Life cycle adaptation
a. Changing behavior of the infected intermediate host
b. Infections of secondary and tertiary hosts
4. Reproduction
a. Asexual reproduction
b. Hermaphroditism
c. Self-fertilization
E. Species Categories
1. Phylum Platyhelminthes
a. Class Cestoidea
b. Form and function
2. Phylum Apicomplexa
a. Class Conoidasida
b. Form and function
3. Phylum Percolozoa
a. Class Heterolobosea
b. Form and function
II. Comparison/Contrast
A. Taenia solium
1. Discovery
a. One of the earliest parasites discovered
b. Friedrich Kuchenmeister
2. Hosts
a. Pigs
b. Rats
c. Humans
3. Mechanism of parasitism
a. Autoinfection
b. Enters bloodstream to reach brain
c. Consuming undercooked/raw pork meat
d. Ingestion of eggs
4. Pathology
a. Cysticerci found in any organ and tissue
b. Epilepsy, blindness, paralysis, etc.
5. Epidemiology
a. Poor sanitation
b. Contamination of food
c. Orthodox Jewish community in NYC infected.
B. Toxoplasma gondii
1. Discovery
a. Charles Nicole and Louis Manceaux
2. Hosts
a. Family Felidae
b. Rodents and birds
c. Humans
d. Changed behavior of hosts
3. Mechanism of parasitism
a. Ingesting oocyst with sporozoites
b. Enters bloodstream to reach brain
c. Undercooked beef
d. Blood transfusion
e. Litter box
f. Contaminated food and water
4. Pathology
a. Asymptomatic
b. Toxoplasmosis
c. Congenital toxoplasmosis
5. Epidemiology
a. Blood transfusion
b. Transplacentally from mother to fetus
C. Naegleria fowleri
1. Discovery
a. Dr.’s Fowler and Cutler
2. Hosts
a. Low host specificity
3. Mechanism of parasitism
a. Free-living amoeba
b. Migration through olfactory nerve to brain
c. Releases enzymes that dissolve tissues in brain
d. Destruction of neurons
4. Pathology
a. Primary amebic meningoencephalitis
b. Fatal disease
5. Epidemiology
a. Found in warm freshwater environment
b. Sensitive to chlorine
c. No infection from drinking water
III. Discussion
A. Evidence fails to support the null hypothesis
1. Parasites don’t use the same mechanism
a. Blood-brain barrier penetration
b. Olfactory nerve passage
c. Bloodstream
d. Different diseases
e. Invasion of different areas of the brain
2. Greater behavioral change in rodents and birds
a. Mice are attracted to cats
b. Experiment with mice and cat urine attractant
3. Greater fatal rate for Naegleria fowleri
a. Rapid invasion
b. Poor immune response
c. Rare disease
4. Most common disease-causing brain parasite
a. Neurocysitecosis
B. Cost/ Benefit of parasitic relationship
1. Red Queen Hypothesis
a. Parasite-Host Coevolution
b. Immune response evolution for host and parasite
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