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58 Cards in this Set

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Parasite
Eukaryotic micro-organisms
Includes two kingdoms: Protozoa (protozoans) and Animalia (helminths)
Parasites
(general routes of transmission)
Fecal-oral
Insect vectors
Penetration of intact skin
Kingdom Protozoa
Microscopic
Single cell
ASEXUAL reproduction WITHIN host
Classified by how they move/spread
Phylum Sarcomastigophora
Oranisms use flagella/pseudopods for locomotion
Includes amebas and flagellates
Amebas
Simple lifecycles
Two forms: trophozoite and cyst
Trophozoite
Tropho = growth
Growing, motile form of amebas
Divides by binary fission
Cyst
Dominant form (of ameba life cycle)
Tough chitin shell
Excreted in environment and functions in transmission
Flagellates
(taxonomy)
Kinetoplasts, Diplomonads, Trichomonads
Kinetoplasts
(general)
Contain a unique, specialized mitochrondrion (kinetoplast)
Binary fission @ all stages of life cycle
Trypanosoma and Leishmania
Diplomonads
Ex: Giardia
Flagellate
Cyst and Trophozoite form
Trichomonads
Flagellate
Only trophozoite form
Phylum Acomplexia
"Sporozoans"
Apical complex facilitates cellular invasions
Complicated life cycles with multiple host
Sexual and asexual reproduction
Organisms that fall under "Acomplexia"
Think: complex
Then think: "PlasTIC Crying Babe"
Plasmodim
Toxoplasma
Isospora
Cyclospora
Cryptosporidium
Babesia
Life Cycle Stages (Sporozoans)
Oocyst (2N) -> Sporozoite (1N) -> Merozoite (1N, motile) -> Trophozoite (1N, intracellular, non-motile) -> Gamete (1N)
Helminths
Kingdom Animalia
Multicellular
Sexual reproduction outside host
Therefore, if disease will result from HEAVY infection
Eosinophilia
Helminths
(Taxonomy)
Roundworms (nematodes)
Flukes (trematodes)
Tapeworms (cestodes)
Roundworms
a.k.a. nematodes
Tubular gut
Intestinal and tissue worms
Intestinal: HATES (lil' Emily HATES pinworms!)
Flatworms
1) Flukes
2) Tapeworms
Flukes
a.k.a. trematodes
Blind gut, hermaphroditic
"____ flukes" (i.e. Schizosomes are called "blood flukes")
*SNAILS*
Tapeworms
a.k.a. Cestodes
Flatworms = flukes + tapeworms
Scolex = intestinal form; adult, segmented
Proglottids = segment w/eggs; shed to environment and ingested by intermediate host
Tapeworms
(general lifecycle)
Human: scolex and sheds proglottids (segments + eggs)
Intermediate host: ingests eggs --> tissue cyst
Human: ingesets cyst (when eats meat); cyst becomes scolex
Scolex
Adult, segmented, intestinal tapeworm
Proglottids
Of Tapeworm
Segment filled w/eggs that is shed to the environment. The eggs in turn will be ingested by the intermediate host.
Definitive Host
Where organism undergoes sexual reproduction/maturation
Intermediate Host
Animal where larval or aesexual stage develops
Resevoir Host
The animal which harbors a parasite dangerous to other animals
Incidental Host
Due to accidental infection; not required for parasite survival
Zoonoses
Man = incidental host
Vectors
Move parasite from one host ot the other
NOTE: these vectors may/may not be essential to the parasites lifecycle
Parasites
(routes of transmission)
1) Fecal-oral (including food-borne)
2) Skin
3) Vectors
Entamoeba histolytica
Amoeba (of Sarcomastigophora, a protozoan)
Fecal-oral spread
Ingest cyst, trophozoite @ intestines
Trophozoites: 1) form cysts or 2) invade (munch of red blood cells)
Intestinal Amebiasis
E. histolytica burrow through intestinal wall (of colon)
May lead to frank dysentery
Extraintestinal Amebiasis
Invading histolytica may spread to liver and form liver abscesses
Diagnosis: Entamoeba histolytica?
Serology: generally positive in intestinal and extraintestinal amebiasis)
Antigen-detection tests and microscopy of stool
Trichomonaas Vaginalis
Flagellate
Causes vaginitis/urethritis
Treat both partners
Giardia lamblia
(general)
Flagellate (diplomonads)
MOST COMMONLY DIAGNOSED PARASITE IN STOOL SAMPLES
(Beaver Fever - drinking from cold mountain streams)
Giardia lamblia
(pathogenesis)
Fecal-oral route
Cyst ingested
Trophozoite latches onto intestinal mucosa
Malabsorption - loose, foul smelling stool
Giardia lamblia
(Diagnosis)
Identification/antigen test of stool
NOTE: may need to do multiple tests (
Kinetoplasts
Flagellates w/unique mitochonodrion: kinetoplast
(note: flagellum can have various locations on organism)
Includes Leishmania and Trypanosoma
Think: "KTL"
Trypanosoma cruzi
Think: Cruz (hispanic) . . . Chagas Disease!
Chagas Disease
(pathogenesis)
Reduviid bug bites and defecates in wound
Stages (similar to syphilis): primary chancre; secondary resh; tertiary CV/GI complications
Chagas Disease
(primary diagnosis?)
Serology
African Trypanosomiasis
"African Sleeping Sickness"
Vector: Tsetse fly
Hallmark illness: fever, lymphadenopathy, hepatosplenomegaly. Late stages: may spread to CNS and cause "sleeping sickness"
Variable Surface Glycoprotein
African Trypanosomiasis has multiple VSG genes, but only expresses one at a time
Underlying reason for "waves" of parasitemia (enables parasite to escape host response for a period of time)
Leishmania
KTL (It's a kinetoblast)
Vector: sandfly
NOTE: 4 complexes (or groups of species, generally old vs. new world)
Invades macrophages
Cutaneouos infections. May spread to mucous membranes (granulomas) and even viscera (often fatal if left untreated!)
Sporozoa
Phylum Acomplexia
Includes: Cryptosporidium; Plasmodium (malaria); Toxoplasma; Isospora; Cyclospora; Babesia
Malaria
(general points)
MOST COMMON CAUSE OF DEATH among parasitic countries
If someone presents with a febrile illness after traveling to an endemic country, you must include malaria in the differential!
What are the four Plasmodium species that cause malaria?
Malaria
Vivax
Falciparum
Ovale
Plasmodium
(life cycle)
Human: only haploid stage
Mosquito: fertilization and sporogony
Mosquito bites: sporozoite (to liver), trophozoite (RBCs), merozoite (between cells)/gametocyte
Gametes are taken up w/blood meal, fertilization, oocyst and sporogony to make additional sporozoites
Malaria
(pathogenesis)
RBC destrucotion: lysis and phagocytosis (by macrophages, note: RBCs may/may not be infected!)
Inflammatory response (due to lysed RBCs)
Malaria: Blood Sludge
(Etiology)
Falciparum "knobs" (antigens) on RBC surface bind to vascular endothelium w/localized blood sludge (and obvious consequences)
Malaria
(Symptoms)
Recurrent fever (chills, fever, headahce then resolution)
Every 2-3 days
Corresponds w/parasites life cycle (I guess when they lyse RBCs?)
Vivax/Ovale - 2 days
Malariae - 3 days
Malaria
(Complications)
Falciparum ONLY
Why? These cause BLOOD SLUDGE (re: parasitic antigen on surface of RBC)
Complications include: hemolytic anemia; ceebral malaria (due to blood sludge); renal/pulmonary failure; hypoglycemia
Why does Falciparum present with serious complications vs. other species?
Falciparum causes "blood sludge"
Knobs (parasitic antigens) on RBC surface - stick to vessel walls and cause sludging
Malaria
(Diagnosis)
Thick/thin blood smears
MUST BE LOOKED AT BY A TECHNICIAN (the automated counters will not pick up the parasites)
Distinguishing falciparum from other species? % RBCs infected w/falciparum >>> others
Toxoplasma
Normal life cycle between cats (definitive host, shed oocysts) and herd animals (tissue cysts)
Humans: incidental hosts
Infection: asymptomatic or mono-like
Can cause birth defects if congenital infection
REACTIVATION in immunocompromized hosts
Toxoplasma
(diagnosis)
Serology but use imaging w/immunocompromized hosts (b/c they have a shit immune system and will not seroconvert)
Toxoplasma
(how are they distinguished from the typical protozoan life cycle?)
These guys undergo sexual reproducotion w/in the host! (Most protozoans don't)