protozoa 1
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Kingdom Protista▪ Subkingdom Protozoa▪ automonous unicellular eucaryotic organisms possessing various degrees of cellular specialization and some type of motility▪ Organelles specialize in nutrient storage, excretion, digestion, motility▪ Phylum = based upon motility
Size 2 - 100 micrometers Parasitic protozoa are most facultative
anaerobes; Mostly heterotrophic, chemoorganotrophs▪ Nutrients assimilated via phagocytosis,
pinocytosis, diffusion▪ Digestion may be both extracellular and
intracellular Two life stages
Trophozoiteactive pathogenic vegetative stage Cyst latent survival form
Sites of pathogenesis▪ Intestinal, Urogenital, Blood and Tissue
Phylum Sarcodina Motility via Pseudopoda▪ Extensions of the cell membrane into which
the cytoplasm flows▪ Cyclosis▪ No cell wall; thus, no uniform shape▪ Shape changes with movement
▪ Reproduce asexually by mitosis; sexually by meiosis
Trophozoite▪ Motile vegetative stage
Cyst▪ Latent survival stage
Phylum Ciliata Motility via cilia▪ Cilia surround the cell; their co-ordinated
movement▪ Uses energy from the cell membrane▪ Synchronized ciliary movement
Two nuclei per cell▪ Small micronucleus governs sexually
reproduction▪ Large macronucleus governs metabolism and
growth▪ Both nuclei divide during asexual mitosis
Intracellular organelles▪ Function in digestion and excretion
Only one ciliate pathogen affects humans
Phylum Mastigophora Motility via flagella▪ One or more whip-like filaments move in
counter-clockwise fashion creating rapid movement
▪ A flagellum is a complex organelle composed of many smaller tubules
▪ Flagella attach to the cell membrane and derive energy from movement from this membrane
Most numerous of the protozoan types▪ Several are pathogens of humans
All reproduce asexually; some reproduce sexually
Phylum Sporozoa No established means of movement▪ Thus, not motile
All are intracellular parasites in a variety of hosts▪ Several parasitic species affect humans▪ Most are in the Class Coccidia
All lack intracellular organelles All have three things in common▪ No motility▪ Sexual and Asexual mode of Reproduction▪ Intracellular parasites
Intestinal amebiasis Entamoeba histolytica giardiasis Giardia lamblia balantidiasis Balantidium coli crytosporidosis Cryptosporidium parvum
Urogenital trichomoniasis Trichomonas vaginalis
Blood and Tissue malaria Plasmodium spp meningoencephalitis Naegleria fowleri toxoplasmosis Toxoplasma gondii trypanosomiasis
▪ African Sleeping Sickness Trypanosoma brucei▪ Chagas Disease Trypanosoma cruzi
leishmaniasis▪ visceral leishmaniasis( Kala-azar) Leishmania
donovanii▪ cutaneous leishmaniasis Leishmania
topica/braziliensis
Amebiasis( Amebic dysentery) colitis with diarrhea(somtimes bloody)
accompanied by abdominal pain and cramping: numerous bloody stools per day extraintestinal amebiasis a complication of
intestinal amebiasis in which the trophozoites enter the blood and are carried to other
organs; most often the liver▪ these patients have fever, leukocytosis, rigors
Parasite Entamoeba histolytica trophozoite sarcodine protozoa which
slowly move among the crypts of the large intestine and are shed into the feces
cyst latent survival stage which is significant in transmission; spherical containing four characteristic nuclei; infective stage
Pathogenesis the trophozoites bind to colonic epithelial cells and secrete a cytotoxin which alters cell membrane permeability causing the cells to take in calcium and lyse; necrosis and inflammation also accompanies the lysis of neutrophils,
lymphocytes and monocytes
Diagnosis microscopic observation of cyst in the feces
▪ the trophozoite is seen occasionally▪ multiple concentrated stools specimens may be required since cysts are
distributed randomly▪ pathogenic ameba must be distinguished from commensal ameba
new test are designed to detect fecal antigen and trophozoite DNA extraintestinal complications can be confirmed via biopsy or
serological tests for antibody Epidemiology
reservior is infected humans, both asymptomatic and symptomatic▪ from 10 - 50 % of world population is infected▪ prevalence of infection in the U.S. is 1 - 2 %▪ asymptomatic individuals are chronic carriers
person -to - person, indirect, fecal-oral mode of transmission▪ food, water, fomites▪ fecal comtamination of fresh vegetables, water▪ flies and cockroaches also transmitt the cysts mostly to food and fomites
Amebiasis
Disease meningoencephalitis▪ destruction of the brain tissue causeing symptoms of frontal
headache, sore throat, fever, stiff neck, blocked nose with alter senses of taste and smell, and Kernig’s sign(a sign of meningitis in which the patient cannot flex the leg)
▪ cerebrospinal fluid is purulent and may contain erythrocytes▪ leads to rapid death in 4 - 5 days▪ Acanthomoeba can also enter the eye and cause keratitis and
corneal ulcers Parasite Naegleria fowleri or Acanthamoeba spp.
▪ trophozoite is a free living amoeba found in soil and water▪ cyst
Pathogenesis most infections occur when trophozoites in water enter the nasal passages when people
swim; they then envade the nasal mucosa and extend into the brain
Diagnosis trophozoites( in wet mounts or stained smears) in nasal discharge, cerebrospinal fluid, or corneal scrapings
Epidemiology - this organism is an envronmental opportunist acquired via contact with water, soil , or dust
Balantidiasis a dysentery (watery stools with blood and pus) accompanied by nausea, anorexia, tenesmus, and abdominal pain and tenderness
Parasite Balantidium coli trophozoite an actively motile ciliate; highly
specialized for reproduction and food intake (cytostome)
cyst a latent survival stage is significant in transmission; infective stage with one large nucleus
Pathogenesis ulceration of the intestinal mucosa especially in the large intestine sometimes compounded by bacterial infection no extraintestinal invasion as seen in amebiasis
Epidemiology reservoir is swine and humans fecal-oral transmission involving water and food
Diagnosis microscopic observation of cysts in the feces this trophozoite is very large and often seen also
Giardiasis mild diarrhea to severe malabsorption syndrome; sudden onset of watery diarrhea, often foul-smelling, with abdominal cramps, flatulence, and stearorrhea.
Blood and pus are rarely present. Parasite Giardia lamblia
Trophozoite - flagellate protozoan( 10 x 10 um) having two large nuclei, a large sucking disc, and many flagella; face - like appearance
cyst slightly smaller the trophozoite with four nuclei and parabasal body
Pathogenesis gastric acid stimulates excystation and releases trophozoite into small intestine where it attaches via the sucking disc to the intestinal villi; the alteration of the villi and inflammation of the mucous causes maladsorption, but not
obvious tissue necrosis; spontaneous recovery occurs in 10 -14 days, but relapse may occur; chronic infection is especially a problem in patients with IgA deficiency and diverticula
Diagnosis cyts and trophozoites in the feces with the onset of symptoms; cyts occur in”showers” and are not present every day, so stoo should be examined every three days
in the absence of observable cysts, new tests for fecal antigen are now available
Epidemiology sylvatic and domestic reservoirs, both human and animals(mostly those around lakes and streams; ▪ fecal - oral transmission via contaminated water is
most common mode of transmission; in U.S. domestic setting, fecal- oral fomites transmission is very common in day care settings; also uncooked contaminated vegetable and fruits may serve as a source of the cysts
▪ cyst are resistant to traditional chlorination methods▪ other than day-care centers, most recent outbreaks
have involved contaminated water from reservoirs
Giardiasis
Vaginitis and urethritis itching, burning, and painful urination sometime accompanied by scant watery vaginal discharge
Parasite Trichomomas vaginalis only a flagellate trophozoite with four flagella and
undulating membrane this flagellate has not cyst stage
Pathogenesis extensive inflammation and erosion of the vaginal or urethral epithelium causing itching, burning, and painful urination; also sometimes a scanty watery vaginal discharge
Epidemiology human reservoir with many asymptomatic carriers especially in males- females may also be asymtomatic trophozoite is sexually transmitted
Diagnosis microscope examination of vaginal or urethral discharge stained smear show trophozoites also parasite is detected in fluorescent antibody
stains and nucleic acid probes
Trichomoniasis
Cryptosporidosis enterocolitis characterized by water diarrhea without blood - self limiting in immunocompetent people
Parasite Cryptosporidium parvum Sporozoan(coccidian) parasite exhibits both
asexual(schizogony) and sexual(gametogony) in the brush border of the intestinal epithelium
Oocyts are released from the cells and transmitted Pathogenesis In immunocompromised patients, an
unremitting enterocolitis with as many as 50 water stools per day caused by the intracellular multiplication of the parasite
Epidemiology reservoir is a variety of mammals, fish, reptiles this host seed the environment especially water with
oocyts a-p, indirect, fecal-oral, contaminated water/fecal droplets p-p, indirect, fecal-oral/oral-anal - fomite/direct contact▪ high risk groups = homosexuals, day care
children/adults, animal handlers Diagnosis oocysts in the feces: concentrated and
stained also assay for fecal antigen
Cyclosporiasis -water diarrhea accompanied by nausea,anorexia, abdominal cramping: sometime bloating and flatulence
Parasite Cyclospora cayetanensis a sporozoan(coccidian) parasite of the small intestine asexual and sexual cycle similar to Cryptosporidium
but oocysts are larger Pathogenesis inflammatory changes in the
jejenum resulting from the intracellular multiplication of the parasite = villous atrophy
Epidemiology reservoir is a variety of mammals, birds, reptile source to humans is fecally contaminated water and
some fresh fruits like strawberries Diagnosis detection of oocysts in the stool:
concentrated and stained by a variety of methods including immunofluorescence
Cryptosporidiosis
Sporozoan(coccidian) malaria Plasmodium spp toxoplasmosis Toxoplasma gondii
Flagellates trypanosomiasis Trypanosoma cruzi African Sleeping Sicknes Tyrpanosoma
brucei leishmaniasis Leishmania spp
Malaria - influenza-like symptoms( fever, chills) with headache, muscle pain, photophobia, anorexia, nausea, vomiting
Parasites Plasmodium vivax - benign tertian malaria Plasmodium falciparum - malignant tertian malaria Plasmodium malariae - quartan malaria
Pathogenesis infection begins in the liver(exoerythocytic) but becomes a disease of RBC’s (erythrocytic) merozoites released every 48 hrs in benign tertian malaria merozoites released every 36-48 hrs in malignant tertian
malaria merozoite released ever 72 hrs in quartan malari
Epidemiology reservior in infecte humans and wild primates arthopod-borne transmission, via Anopheline mosquitos
where sporogamy produces infectious sporozoites Diagnosis trophozoites(schizonts) in blood
smears
Malaria
Toxoplasmosis infectious mononucleosis -like symptoms of fever, chills, headache, myalgia, lymphadenitis, and fatigue; chronic form = hepatitis, encephalomyelitis, mycocarditis
Parasite Toxoplasma gondii intracellular coccidian(sporozoan) parasite infecting various
tissues(systemic) but confined to intestines in felines infected tissues release pseudocysts containing bradyozoites feline intestines release oocyts containing tachyzoites
Pathogenesis cellular death due to intracellular muliplication of trophozoites especially severe in fetal and cerebral tissues
Epidemiology reservoir is a variety of mammals and birds including humans fecal-oral transmission of oocyst from felines common source transmission of pseudocyts in poorly cooked
meat esp beef Diagnosis serological detection of antibody: Elisa
test for IgM antibodies is most reliable Risk Groups Pregnant females and
immunocompromised
Toxoplasmosis
African Sleeping Sickness CNS infection progressing to lethargy, tremors, meningoencephalitis, convulsions, coma, and death
Parasites Trypanosoma gambiense- West/Central Africa Trypanosoma rhodesiense- East Africa
Pathogenesis - trypanomastigote multiplies in the blood, lymph, and cerebrospinal fluid; deprives the brain of amino acids
Epidemiology T. gambiense - human reservoir T. rhodesiense - cattle and wild game reservoir arthropod-borne transmission via the tsetse fly
Diagnosis trypanosomes in the blood, serological test for antigens in the blood
American Trypanosomiasis/Chagas Disease -systemic infection beginning with fever, chills, malaise, myalgia, fatigue, and chagoma; progressing to involve heart and brain
Parasite = Tryanosoma cruzi flagellate tryanosome exhibiting both the intracellular
amastigote(leishmanial) form and the extracellular trypanomastigote(tryupanosmal) form
Pathogenesis - the intracellular amastigote multiplies in cells and destroys the cells
Epidemiology- wild and domestic animal reservoirs arthropod-borne via the cone-nosed (reduviid) bugs which
live in the cracks of domestic dwellings Diagnosis trypanosomes in the blood;
amastigotes in biopsy; also xenodiagnosis and gene probes
Leishmaniasis ;Visceral - gradual onset of fever, chill, sweating, diarrhea, anemia which progresses to enlargement of liver and spleen with weight loss and emaciation: later kidney damage and granulomatous skin lesion = also called kala-azar cutaneous form -ulcerative skin lesions which contain parasite:
become infected with secondary bacteria and scar formation disfigures
Parasites Leishmania donovani - visceral- amastigote stage multiplies in visceral cells causing lysis Leishmania tropica - cutanous: Leishmania braziliensis -
mucocutaneous Pathogenesis - cells in infected visceral and cutaneous tissues
are destroyed by intracellular amastigote multiplication
Epidemiology - animal reservoirs including dogs and cats arthropod-borne via the bite of sandflies: the amastigote stage
becomes a motile promastigote in the sandfly gut Diagnosis - amastigote is observed in tissue biopsy, body
fluid aspirates, and in the blood: also serology for antibody presence