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