Protazoa Flashcards
- Diverse group of eukaryotic microbes
- Related only by their simple organization: unicellular or multicellular without specialized tissues
- Most are free-living in aquatic environments or on decaying organic matter
- Some are parasitic
Protozoa
- formation of a cyst–resting state with a wall and low metabolic activity–function of cysts
- protection from changes in environment•sites for nuclear reorganization and cell division
- transfer from one host to another
- escape of vegetative form from cyst
- usually triggered by return to favorable environment
- trophozoite–vegetative form released by parasitic species–excystation often triggered by entry into new host
Encystation
–vegetative form of cyst released by parasitic species
trophozoite
•motile protozoa species use one of following 3 modes of locomotion:–cilia–flagella–pseudopodia (s., pseudopodium)•cytoplasmic extensions
–cilia
–flagella
–pseudopodia (s., pseudopodium)•cytoplasmic extensions
_____ reproduction of protozoa–usually by binary fission•mitosis followed by cytokinesis
•asexual
_____ reproduction of protozoa•–usually by conjugation•exchange of gametic nuclei between paired protozoa of opposite mating types
sexual
Motile due to one or more flagella (protozoa)
Zooflagellates
______: giardiasis -gastro-intestinal disorder
Giardia lamblia
______:trichomoniasis: -sexually transmitted disease
Trichomonas vaginalis
______: hemoflagellates important blood pathogense.g., African sleeping sickness
Trypanosomes
- African sleeping sickness
- transmitted by tsetse flies–reservoirs included domestic cattle and wild animals
- Chronic bloodstream infection with bouts of parasitemia
- CNS invasion after months to years•clinical manifestations–interstitial inflammation and necrosis within lymph nodes and small blood vessels of brain and heart, leading to lethargy and death within 1 to 3 years
- diagnosed by observation of motile parasites in blood
- drug therapy during systemic stage but not as effective when CNS involved. Vaccine not useful due to antigenic variation.
African trypanosomiasis
•American trypanosomiasis(Latin America; sporadic in southern USA)
•transmitted by kissing bug (= reduviidbug)
–reservoirs included domestic cattle and other animals
–In endemic regions most people in population infected in childhood
–Early disease mild; small % develop complications 10-20 years later
•heart disease and other disorders due to destruction of parasitized cells in the liver, spleen, lymph nodes, and central nervous system
–Megaesophagus, megacolon(due to damage to nerves in GI tract)
–Cardiomyopathy (due to damage to heart muscle)(sudden death from arrhythmia)
•no treatment available for late complications
Chagas disease
•caused by Leishmania species (several, with different tissue tropisms)
•transmitted by sand flies when they take a blood meal (usually tropical)
–animal reservoirs include canines and rodents
–Leishmania survives and differentiates in macrophages (superoxide dismutase)
•three forms of infection–mucocutaneous, cutaneous, and visceral
treatment, prevention, and control
–Several types of drugs available (including amphotericin B, the polyene anti-fungal agent)
–vector and reservoir control, and epidemiological surveillance
Leishmaniasis
GI disorder
Most common cause of epidemic waterborne diarrheal disease
•caused by Giardia lamblia–forms cysts and trophozoites–trophozoites attach to intestinal epithelium and interfere with nutrient absorption
•transmission usually by cyst-contaminated water–numerous animal reservoirs–asymptomatic human carriers are common (7% of US population)
•clinical manifestations
–acute giardiasis -severe diarrhea, epigastric pain, cramps, voluminous flatulence, and anorexia
–chronic gastritis -intermittent diarrhea with periodic appearance and remission of symptoms
•treatment, prevention, and control
antiprotozoal agents (metronidazole
avoiding contaminated water or purify it by boiling or filtering (cysts are resistant to chlorine treatment)
Giardiasis
______ giardiasis -severe diarrhea, epigastric pain, cramps, voluminous flatulence, and anorexia
–acute