5.51 Flashcards
Protozoa
• Diverse group of
eukaryotic microbes
Protozoa
• Related only by their
simple organization: unicellular or
multicellular without specialized tissues
Protozoa
• Most are
• Some are
free-living in aquatic environments or on decaying organic matter
parasitic
Encystation (many protozoa are capable of this)
• formation of a cyst
• formation of a cyst
– (2)
resting state with a wall and low metabolic
activity
function of cysts (3)
- 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
Excystation
• usually triggered by
return to favorable
environment
Excystation
trophozoite (2)
– vegetative form released by parasitic species
– excystation often triggered by entry into new
host
some protozoa are —
nonmotile
• motile species use one
of following: (3)
– cilia – flagella – pseudopodia (s., pseudopodium) • cytoplasmic extensions
Zooflagellates
Motile due to
one or
more flagella
Giardia lamblia
giardiasis -
gastrointestinal disorder
Trichomonas vaginalis
trichomoniasis -
sexually
transmitted disease
Trypanosomes
3
hemoflagellates
important blood pathogens
e.g., African sleeping sickness
Giardiasis
— disorder
Most common cause of
gastrointestinal
epidemic waterborne diarrheal disease
Giardiasis
caused by
Giardia lamblia
– forms cysts and trophozoites
– trophozoites attach to intestinal epithelium and interfere with nutrient absorption
Giardiasis
transmission usually by (3)
cyst-contaminated water
– numerous animal reservoirs
– asymptomatic human carriers are common
Giardiasis
• clinical manifestations
– acute giardiasis - (5)
– chronic gastritis -(2)
severe diarrhea, epigastric pain, cramps, voluminous flatulence,
and anorexia
intermittent diarrhea with periodic appearance and remission of
symptoms
Giardiasis
• treatment, prevention, and control (2)
– antiprotozoal agents (metronidazole)
– avoiding contaminated water or purify it by boiling or filtering (cysts are resistant
to chlorine treatment)
Trichomonas vaginalis sexually transmitted (2)
– One of the most common sexually transmitted
diseases (found in 15% of women)
– No cyst stage (only trophozoites)
Trichomonas vaginalis clinical manifestations (3)
– accumulation of leukocytes at site of infection
– in females, results in yellow purulent vaginal discharge and itching
– in males, usually asymptomatic or burning urination
Trichomonas vaginalis
treatment, prevention, and control (2)
– observation of parasite in vaginal discharge, semen or urine
– antiparasite therapy (metrodiazole)
Trichomonas tenax resides in —
Usually associated with —
Aspiration associated with —
mouth
poor oral hygiene
pneumonia
Hemoflagellate Diseases
• caused by
flagellated protozoa
Hemoflagellate Diseases
– two major groups (2)
- leishmanias
* trypanosomes
Hemoflagellate Diseases
• transmitted by bites of
infected arthropods
• infect blood and tissues of humans
Trypanosomes
hemoflagellates
important — pathogens
blood
African trypanosomiasis
• African sleeping sickness
• transmitted by
tsetse flies
– reservoirs included domestic cattle and wild animals
African trypanosomiasis
• Chronic bloodstream infection with
bouts of parasitemia
African trypanosomiasis
• 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
• diagnosed by
observation of motile parasites in blood
African trypanosomiasis
• drug therapy during systemic stage but not as effective when
CNS
involved. Vaccine not useful due to antigenic variation.
tsetse fly
2
• Intermediate host
between animal reservoir &
humans
• Determines disease range
Chagas disease
• American trypanosomiasis (Latin America; sporadic in southern USA)
• 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
heart disease and other disorders due to destruction of parasitized cells in the liver, spleen, lymph nodes, and central nervous system
(2)
– Megaesophagus, megacolon (due to damage to nerves in GI tract)
– Cardiomyopathy (due to damage to heart muscle)(sudden death from arrhythmia)
Chagas disease
tx (2)
• no treatment available for late complications
Vaccines not useful because of
antigenic variation- genetic switching
Chagas disease
Vector
(2)
• Parasite discharged in feces
• Enter human body through
bite wound
Leishmaniasis
• caused by
Leishmania species (several, with different tissue tropisms)
Leishmaniasis
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
three forms of infection
– mucocutaneous, cutaneous, and visceral
visceral
•involves
•clinical manifestations (2)
tissue macrophage disfunction
–intermittent fever and enlargement of
spleen or liver
–recovery provides permanent immunity
mucocutaneous
lesions of mouth, nose,
throat and skin that cause
extensive scarring and
disfigurement
cutaneous (2)
•papules that develop into crustated ulcers •healing occurs with scarring and permanent immunity
Leishmaniasis
treatment, prevention, and control (2)
Several types of drugs available (including amphotericin B, the polyene anti-fungal agent) – vector and reservoir control, and epidemiological surveillance
Amoebiasis (amoeboid protozoa)
• amoebic —
• caused by
dysentery
Entamoeba histolytica
Amoebiasis
• transmission by
ingestion of cysts
Amoebiasis
clinical manifestations
– asymptomatic to fulminating dysentery,
exhaustive diarrhea, and abscesses of
liver, lungs, and brain
Amoebiasis
treatment, prevention, and control
(3)
– 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
Phylum Apicomplexa
• lack — organelles
• all have — complex
locomotor
apical
Phylum Apicomplexa
lack locomotor organelles
– except for (2)
male gametes and
zygotes
Phylum Apicomplexa
all have apical complex
– arrangement (3) at
one end of cell
fibrils, tubules,
vacuoles, and other organelles
Apicomplexan life cycles
involves (2)
• involves two different hosts (usually mammal and
mosquito)
• involves both asexual and sexual phases
Apicomplexan life cycles
– schizogony
(2)
• asexual phase
• rapid series of mitotic events producing
infective organisms
Apicomplexan life cycles
– oocyst (3)
• produced during sexual phase
• thick-walled, diploid structure
• undergoes meiosis to produce haploid
spores
Important sporozoan genera (sporozoan = apicomplexan) • Plasmodium – • Cryptosporidium – • Toxoplasma –
malaria
cryptosporidiosis
toxoplasmosis
Malaria
• caused by four species of
Plasmodium (Plasmodium falciparum is
most virulent; others are P. vivax, P. malariae, and P. ovale)
Malaria
• transmitted by
bite of an infected female Anopheles mosquito
Malaria
Reservoir:
humans
Malaria
Intermediate host:
humans
asexual reproduction
Malaria
Definitive host:
mosquito
sexual reproduction
Malaria P. vivax and P. ovale form --- (dormant forms) within liver cells. These cause --- (months to years after initial disease).
hypnozoites
recurrent malaria
Malaria
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
(3)
– 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)
– chemoprophylaxis for individuals traveling to endemic areas, netting, insect repellants
Babesia
— to USA
Caused by — species
transmitted by
Endemic
Babesia
same Ixodes tick as Borrelia burgdorferi
(Lyme disease agent)
Babesia
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)
Babesia
Diagnosis:
microscopy of Giemsa-stained blood samples, PCR
Babesia
Treatment:
clindamycin + quinine (different from malaria)
Toxoplasmosis
• caused by —
• transmission by (5)
• Invades —
Toxoplasma gondii
ingestion of undercooked meat, congenital transfer, blood transfusion, tissue transplant and ingestion of cat feces
macrophages
Toxoplasmosis
— is the definitive
host (sexual cycle)
Cat
Toxoplasmosis This is the most common mode of transmission: undercooked meat containing
tissue cysts
Toxoplasmosis clinical manifestations (3)
– usually asymptomatic (>99%) or resembles mononucleosis
– can be fatal in immunocompromised hosts (mass lesions in the brain)
– Congenital infections
Toxoplasmosis
• treatment, prevention, and control (3)
– antiparasite therapy for immunocompromised patients (pyrimethamine and
– 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
Cryptosporidium parvum – apicomplexan that forms cysts, sporozoites, and merozoites • sporozoites parasitize intestinal epithelial cells
Cryptosporidiosis
• —resistant
chlorine
Cryptosporidiosis
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 – Swimming pools
Cryptosporidiosis
clinical manifestations
(3)
– diarrhea, abdominal pain, nausea, fever, and fatigue
– usually self-limiting
– can be fatal in late stage AIDS patients and other immunocompromised
individuals
Cryptosporidiosis
treatment, prevention, and control
(2)
– microscopic examination of stools
– symptomatic/supportive therapy
