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
______ gastritis -intermittent diarrhea with periodic appearance and remission of symptoms
–chronic
sexually transmitted–One of the most common sexually transmitted diseases (found in 15% of women)
No cyst stage
–accumulation of leukocytes at site of infection
–in females, results in yellow purulent vaginal discharge and itching
–in males, usually asymptomatic or burning urination
•treatment, prevention, and control–observation of parasite in vaginal discharge, semen or urine–anti-parasite therapy (metrodiazole)
Trichomonas vaginalis
resides in mouth
Usually associated with poor oral hygiene
Aspiration associated with pneumonia
Trichomonas tenax
____ diseases:
•caused by flagellated protozoa–two major groups
•leishmanias and trypanosomes
•transmitted by bites of infected arthropods
•infect blood and tissues of humans
Hemoflagellate diseases
______ Leishmaniasis:
lesions of mouth, nose, throat and skin that cause extensive scarring and disfigurement
Mucocutaneous Leishmaniasis
______ Leishmaniasis:
•papules that develop into crustated ulcers•healing occurs with scarring and permanent immunity
Cutaneous Leishmaniasis
______ Leishmaniasis:
involves tissue macrophage dysfunction
•clinical manifestations–intermittent fever and enlargement of spleen or liver –recovery provides permanent immunity
Visceral Leishmaniasis
(amoeboid protozoa)•amoebic dysentery
•caused by Entamoeba histolytica
•transmission by ingestion of cysts
•clinical manifestations
–asymptomatic to fulminating dysentery, exhaustive diarrhea, and abscesses of liver, lungs, and brain
•treatment, prevention, and control
–observation of trophozoites in fresh warm stools or cysts in ordinary stools, and serological tests
–Metronidazole therapy (amoebas carry out anaerobic metabolism and drug penetrates tissue well to destroy invasive pathogens)
–avoiding contaminated water and food and hyperchlorination or iodination of water supplies to destroy waterborne cysts
Amoebiasis
Phylum \_\_\_\_\_: •lack locomotor organelles –except for male gametes and zygotes •all have apical complex –arrangement fibrils, tubules, vacuoles, and other organelles at one end of cell
Apicomplexa
______ life cycles
•involves two different hosts (usually mammal and mosquito)
•involves both asexual and sexual phases
–schizogony
•asexual phase
•rapid series of mitotic events producing infective organisms
–oocyst
•produced during sexual phase•thick-walled, diploid structure
•undergoes meiosis to produce haploid spores
Apicomplexan
_____ Apicomplexan life cycle:
–schizogony
•asexual phase
•rapid series of mitotic events producing infective organisms
–schizogony
_____ Apicomplexan life cycle:
•produced during sexual phase•thick-walled, diploid structure
•undergoes meiosis to produce haploid spores
–oocyst
Contains materials that are secreted and aid in penetration of host cell
Rhoptry
Apicomplexan ____ causes malaria
Plasmodium
Apicomplexan ____ causes cryptosporidiosis
Cryptosporidium
Apicomplexan ____ causes toxoplasmosis
Toxoplasma
______
caused by four species of Plasmodium (Plasmodium falciparumis most virulent; others are P. vivax, P. malariae, and P. ovale)
•transmitted by bite of an infected female Anopheles mosquito
Reservoir: humans
Intermediate host: humansasexual reproduction
Definitive host: mosquito sexual reproduction
P. vivax andP. ovale form hypnozoites(dormant forms) within liver cells.
These cause recurrent malaria(months to years after initial disease).clinical manifestations
periodic attacks of chills and fever(coincides with RBC lysis and merozoite release, which stimulates cytokine production)
Malaria
•Diagnosis, treatment, prevention, and control
–demonstration of parasites within Wright-or Giemsa-stained red blood cells and serological tests (but these of little value in acutely ill patient)
–antimalarial drugs (Classic drugs: chloroquine & other quinine based drugs -these block heme detoxification in Plasmodium
food vacuole)
(•Chloroquine resistance is widespread (drug pumped out of vacuole)
–chemoprophylaxis for individuals traveling to endemic areas, netting, insect repellants
Malaria
Endemic to USA
Caused by species transmitted by same Ixodes tick as Borrelia burgdorferi (Lyme disease agent)
Infections: subclinical to severe disease; “summer flu
Protozoa infect red blood cells and cause fever upon release(like malaria, but no intermediate liver stage)
Humans are not the reservoir (white-footed mouse)
Diagnosis: microscopy of Giemsa-stained blood samples, PCR
Treatment: clindamycin + quinine (different from malaria)
Babesia
•caused by Toxoplasma gondii
•transmission by ingestion of undercooked meat, congenital transfer, blood transfusion, tissue transplant and ingestion of cat feces
•Invades macrophages
This is the most common mode of transmission: undercooked meat containing tissue cysts
Cat is the definitive host (sexual cycle)
Toxoplasmosis
•clinical manifestations
–usually asymptomatic (>99%) or resembles mononucleosis
–can be fatal in immunocompromised hosts (mass lesions in the brain)
–Congenital infections
•treatment, prevention, and control
–antiparasite therapy for immunocompromised patients
–minimizing exposure by: avoidance of raw meat and eggs, washing hands after working in soil, and cat-handling practices
–Women screened for antitoxoplasma antibody at marriage or very early in pregnancy (if positive, fetus is protected)
Toxoplasmosis
•caused by Cryptosporidium parvum
–apicomplexan that forms cysts, sporozoites, and merozoites
•sporozoites parasitize intestinal epithelial cells
•chlorine-resistant
•transmitted from animal reservoirs in contaminated food or water
–many birds and mammals shed oocysts in feces
–Also spread from person-to-person in crowded urban environments (e.g. day care centers)
–Public water system risks
Cryptosporidiosis
•clinical manifestations
–diarrhea, abdominal pain, nausea, fever, and fatigue
–usually self-limiting
–can be fatal in late stage AIDS patients and other immunocompromised individuals
•treatment, prevention, and control
–microscopic examination of stools
–symptomatic/supportive therapy
Cryptosporidiosis
