Lecture 1 pages 1-15

symbiosis, especially in the form of parasitism

any two organisms living in close association

each of the individuals that live in close association with each other

1. phoresis
2. mutualism
3. commensalism
4. parasitism

two symbionts are traveling together mechanically, but not physiologically dependent on the other

bacteria on legs of fly
fungus spores on beetle feet

both benefit from the association, usually obligatory physiological dependence where one mutual can't survive without the other

termite and intestinal fauna that digests wood for them;
human and their gut bacteria

termite a nourished by fermentation products excreted by protozoa

lives in a stable environment and is constantly supplied with food

bacteria digest food for us, make vitamin K, and exclude pathogenic organisms from colonizing the gut

When one organism (the commensal) benefits from relationship with host and the host is not benefited or harmed by the other organism

amebic protozoans in human gut that do not cause diseases; protozoans derive nutrients from gut and a safe place to live in human hosts

symbiotic relationship where an organism actually harms the host or lives at the expense of the host

mechanical injury (boring hole), eating or digesting and absorbing host tissues, or poisoning host / robbing nutrition

ectoparasites
endoparasites
obligate parasites
facultative parasites
accidental / incidental parasites

a parasite that lives ON THE SURFACE of its host

a parasite that lives INSIDE its host

spend at least part of their lives as parasites to survive and complete its life cycles

not normally parasitic but can become so when they are accidentally eaten or enter a wound or body orifice

bot fly maggots

parasite enters or attaches to the body of a species of host different from its normal one

dog hookworm infects a human host

various stages of development that starts out on a particular host species and ends in another host of the same species, ending when the parasite reaches sexual maturity

definitive host
intermediate host

parasite reaches sexual maturity and reproduction

obligatory host in which some development of the parasite occurs but in which it does not reach sexual maturity;

if parasite doesn't get into the intermediate host, the lifecycle is not completed and the parasite usually dies

parasitic

protozoan

humans and other primates

one must swallow the cyst or trophozoite stage of parasite in fecally contaminated food or water

anal-oral sex

outside the host in water, soils, and foods
especially in moist conditions

when they are swallowed and excyst in digestive tract

emerge from the cyst

when cysts excyst

trophozoite stage

chromatin is in the center of the nucleus, creating a 'bulls-eye' appearance; can sometimes see RBC inside trophozoite

histo-lytic = tissue destroying
pathogenic!
Infection can lead to amebic dysentery or amebic liver abscess

bacillary dysentery caused by bacteria whereas
amebic dysentery is caused by amoebas

occurs when blood and mucus enter the stool

invasion of the bowel by a microbe

fulminating bloody diarrhea.
Weight loss,
fatigue,
abdominal pain

bores into the intestinal wall, causing lesions and intestinal symptoms;
can reach the blood stream

can reach diff vital organs of the human body (usually the liver) but sometimes lungs, brain, spleen, etc

liver abscess which can be fatal if left untreated

ingest red blood cells which are sometimes seen in amoeba cell cytoplasm

1. host ingest parasite
2. goes into the gut and then excysts
3. becomes trophozoite and causes disease
4. trophozoite replicates (binary fission)
5. host has diarrhea / dysentery; stimulates trophozoite to encyst
6. feces passes and lands on ground or water
7. ingested by another host

1. microscopy
2. antigen detection kits
3. real time PCR
4. Enzyme Linked Immunosorbent Assay (ELISA)

either the trophozoite or the cyst, or both

both the iodine concentration technique &
trichome stain
(trichome stain is easier)

iodine concentration technique

able to distinguish between E. histolytica and nonpathogenic members of entamoeba species (like E. dispar)

to distinguish E. histolytica from other nonpathogenic members of entamoeba

when diagnosing extra-intestinal disease (liver abscess); serum is used for detection of antibody

commensal

no (because commensal)

E. hartmanni looks the same but is smaller, also wont have presence of RBC in cytoplasm

through consuming fecally contaminated food or water

finding trophozoite and or cysts in fecal matter using trichome technique

genus of ameba that is found in the intestines of various animals

in the intestines humans

commensal (does not cause disease to host)

indicates consumption of fecally contaminated food or water, possibly indicating other pathogenic amoebas present

E. nana excysts in small intestine then migrates to large intestine where it lives

finding cysts and or trophozoites in fecal matter

commensal

humans, other primates, and PIGS!

worldwide

most commonly found in swine (the original host)

swine

in large intestine where it feeds on intestinal flora

cysts are swallowed from fecally contaminated food or water

in large intestine

by swallowing cyst-containing pig feces

finding trophozoites or cysts in fecal matter

opportunistic pathogen (causes disease under special circumstances)

not usually parasitic, disease is rare

Primary Amebic Meningoencephalitis (PAM)

acute, rapidly fatal illness usually affecting children or young adults who have been exposed to water harboring free-living N. fowleri

warm lakes, or via exposure to unchlorinated water;
patient goes swimming in water where this ameba lives

N. fowleri ameba is forced deep into nasal passages, migrates to olfactory nerves and into cranium

death from brain destruction (rapid, within 24 hours)

N fowleri divides rapidly

natural thermal pools or warm lakes / ponds

cyst
trophozoite (ameboid)
flagellate

biflagellate form when trophozoites are exposed to a change in ionic concentration such as placement in distilled water;
can transform from trophozoite to flagellates in minutes

reproductive stage of protozoan organisms, growing fastest at 42C and proliferates by binary fission

free-living trophozoites: feed on bacteria
in tissues: phagocytize RBC and WBC and destroy tissue

trophozoite encyst due to unfavorable conditions

food deprivation, crowding,
desiccation, accumulation of waste products, cold temps

at temps below 10C

1. culture
2. microscopy
3. antigen detection
4. molecular methods

several kinds of liquid axenic media or non-nutrient agar plates coated with bacteria

E. coli used to overlay the non-nutrient agar plate and a drop of CSF sediment added to it; plates inoculated at 37 and checked from thin tracks

trophozoites are present (and are eating the bacteria)

methylene blue

detected in CSF, tissue, or biopsy specimens using direct immunofluorescence (IIF) or immunohistochemistry (IHC) kits

PCR can be used to amplify DNA from the ameba in CSF or tissue

Giardia lamblia

2% of adults and 6-8% of kids in developed countries worldwide infect;
33% of people in developing countries have had giardiasis

flagellated protozoan parasite that colonizes and reproduces in the small intestine, causing giardiasis