protozoa Flashcards
Protozoa as a group? related by? where they live? parasitic?
- 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
Encystation (many protozoa are capable of this)
• 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
Excystation
• 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
Locomotory Organelles
• some protozoa are nonmotile • motile species use one of following: – cilia – flagella – pseudopodia (s., pseudopodium) • cytoplasmic extensions
Reproduction
• asexual – usually by binary fission • mitosis followed by cytokinesis • sexual – usually by conjugation • exchange of gametic nuclei between paired protozoa of opposite mating types
Zooflagellates, spp
Motile due to one or more flagella
Giardia lamblia
Trichomonas vaginalis
Trypanosomes
Giardia lamblia disease
giardiasis - gastrointestinal disorder
Trichomonas vaginalis disease
trichomoniasis - sexually
transmitted disease
Trypanosomes, class/ disease
hemoflagellates
important blood pathogens
e.g., African sleeping sickness
Giardiasis
affects?
most common cause of?
gastrointestinal disorder
Most common cause of epidemic waterborne diarrheal disease
Giardiasis caused by? forms? transmission? reservoir? carriers?
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
Giardiasis clinical manifestations (acute and chronic)
– acute giardiasis - severe diarrhea, epigastric pain, cramps, voluminous flatulence,
and anorexia
– chronic gastritis - intermittent diarrhea with periodic appearance and remission of
symptom
giardasis tx, prevention
– antiprotozoal agents (metronidazole)
– avoiding contaminated water or purify it by boiling or filtering (cysts are resistant to chlorine treatment)
Trichomoniasis cause? transmission? form transmitted in?
Trichomonas vaginalis
• sexually transmitted
– One of the most common sexually transmitted diseases (found in 15% of women)
– No cyst stage (only trophozoites)
Trichomoniasis clinical manifestations
– accumulation of leukocytes at site of infection
– in females, results in yellow purulent vaginal discharge and itching
– in males, usually asymptomatic or burning urination
Trichomoniasis diagnosis and tx? (drug name)
observation of parasite in vaginal discharge, semen or urine
– antiparasite therapy (metrodiazole)
Trichomonas tenax
resides in mouth
Usually associated with poor oral hygiene
Aspiration associated with pneumonia
Hemoflagellate Diseases caused by? groups? transmitted how? what do these infect?
• caused by flagellated protozoa
– two major groups
• leishmanias
• trypanosomes
- transmitted by bites of infected arthropods
- infect blood and tissues of humans
Trypanosomes
flagellum?
pathogens of what?
hemoflagellates
important blood pathogens
african trypanosomiasis spp? common name? transmitted by? reservoirs? affected tissues?
Trypanosoma brucei
• 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
african trypanosomiasis 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
african trypanosomiasis diagnosis
diagnosed by observation of motile parasites in blood
african trypanosomiasis tx/ vax
drug therapy during systemic stage, but not as effective when CNS involved.
Vaccine not useful due to antigenic variation.
Chagas disease additonal name? transmitted by? resivoirs? infection age in endemic regions? early disease? % with later complications?
American trypanosomiasis
transmitted by kissing bug (= reduviid bug); 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
•
chagas disease leads to? how?
• 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)
chagas disease agent/ vector
Trypanosoma cruzi
• Parasite discharged in feces of kissing bug
• Enter human body through bite wound
chagas tx and vax
no treatment available for late complications
Vaccines not useful because of antigenic variation
- genetic switching
Leishmaniasis cause?
transmitted?
reservoirs?
macrophages?
• 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)
Leishmaniasis forms
three forms of infection
– mucocutaneous, cutaneous, and visceral
mucocutaneous Leishmaniasis
lesions of mouth, nose,
throat and skin that cause
extensive scarring and
disfigurement
cutaneous Leishmaniasis
•papules that develop into crustated ulcers •healing occurs with scarring and permanent immunity
visceral Leishmaniasis
involves?
clinical manifesations?
immunity?
•involves tissue macrophage disfunction
–intermittent fever and enlargement of spleen or liver
–recovery provides permanent immunity
treatment, prevention, and control of Leishmaniasis
– Several types of drugs available (including amphotericin B, the polyene anti-fungal agent)
– vector and reservoir control, and epidemiological surveillance
Amoebiasis cause
transmission
• amoebic dysentery
• caused by Entamoeba histolytica
• transmission by ingestion of cysts
l
Amoebiasis clinical manifestations
asymptomatic to fulminating dysentery, exhaustive diarrhea
and abscesses of liver, lungs, and brain
treatment, prevention, and control of Amoebiasis
stool? serological?
drug treatment?
water/food?
– observation of trophozoites in fresh warm stools or cysts in ordinary stools, and serological tests
– Metronidazole therapy
– avoiding contaminated water and food and hyperchlorination or iodination of water supplies to destroy waterborne cysts
Phylum Apicomplexa
lack?
all have?
• 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
Contains materials that are secreted and aid in penetration of host cell
Apicomplexan life cycles
• involves two different hosts (usually mammal and mosquito)
• involves both asexual and sexual phases
– schizogony
– oocyst
asexual phase of apicomplexans
undergoes? produces?
– schizogony
• rapid series of mitotic events producing infective organisms
sexual phase a apicomplexans
strucure? ploidy?
undergoes?
– oocyst
• produced during sexual phase
• thick-walled, diploid structure
• undergoes meiosis to produce haploid spores
Important sporozoan genera (sporozoan = apicomplexan) and diseases caused
- Plasmodium – malaria
- Cryptosporidium – cryptosporidiosis
- Toxoplasma – toxoplasmosis
Malaria
caused by? most virulent?
transmitted?
- caused by four species of Plasmodium (Plasmodium falciparum is most virulent; others are P. vivax, P. malariae, and P. ovale)
- transmitted by bite of an infected female Anopheles mosquito
malaria resivoir, host types
Reservoir: humans
Intermediate host: humans asexual reproduction
Definitive host: mosquito sexual reproduction
recurrent malaria
P. vivax and P. ovale form hypnozoites (dormant forms) within liver cells.
These cause recurrent malaria (months to years after initial disease).
malaira clinical manifestations
periodic attacks of chills and fever (coincides with RBC lysis and merozoite release, which stimulates cytokine production)
malaria cycle in humans
Hepatocellular cycle Released from liver as merozoities
8-14 days
erythocytic cyle in blood, 2-3 days, asexual reproduction
Small number of merozoites develop into gametocytes
malaria cycle in mosquitoes
Meiotic division generates sporozoites which can penetrate host cells
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 detox
– chemoprophylaxis for individuals traveling to endemic areas, netting, insect repellants
malaria early ring forms
Babesia
Endemic to USA
Caused by Babesia species transmitted by same Ixodes tick as Borrelia burgdorferi
(Lyme disease agent)
Babesia infections
severity? common name?
protozoa infect what? result?
subclinical to severe disease; “summer flu”
Protozoa infect red blood cells and cause fever upon release (like malaria, but no intermediate liver stage)
babesia resivoir
Humans are not the reservoir (white-footed mouse)
babesia diagnosis and treatment
Diagnosis: microscopy of Giemsa-stained blood samples, PCR, ring forms present
Treatment: clindamycin + quinine (different from malaria)
Toxoplasmosis
caused by?
transmission?
invades what cells?
- caused by Toxoplasma gondii
- transmission by ingestion of undercooked meat, congenital transfer, blood transfusion, tissue transplant and ingestion of cat feces
- Invades macrophages
Toxoplasmosis cycle
toxoplasmosis clinical manifestations
% symptomatic? can resemble?
fatal in what population? (how)
congenital?
usually asymptomatic (>99%) or resembles mononucleosis
– can be fatal in immunocompromised hosts (mass lesions in the brain)
– Congenital infections
Toxoplasmosis 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)
Cryptosporidiosis caused by? forms? parasitize what cells? resistant to? transmission?
- 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
– Public water system risks/ pools
Cryptosporidiosis
clinical manifestations
limited?
fatal in what populations?
– diarrhea, abdominal pain, nausea, fever, and fatigue
– usually self-limiting
– can be fatal in late stage AIDS patients and other immunocompromised individuals
Cryptosporidiosis diagnosis and treatment
– microscopic examination of stools
– symptomatic/supportive therapy
