Protozoan Diseases

protozoan life cycle

trophozoite and cyst

Pathogenic properties of protozoa

-Protozoan waste products may cause symptoms
-Avoid host defenses by:
>Growing in phagocytes
>Antigenic variation

giardia lamblia

flagellate- causes GI symptoms from yucky water

Giardia lamblia transmission

cysts/fecal (human, beaver, muskrat, etc.), oral transmission

Giardia lamblia pathogenesis

protozoan's ventral sucking disk adheres to lining of duodenal wall => damage to enterocytes and loss of brush border of epithelial cells of the intestine

Giardia lamblia clinical presentation

malaise, nausea, bloating, flatulence, foul-smelling, fatty diarrhea

Giardia lamblia life cycle

1) Transmission via ingestion of food/water/fecal-oral contaminated with cysts. Cysts found in feces and are resistant forms that survive several months in cold water (individuals passed in feces cannot survive outside)
2) Trophozoites released from cyst in small intestine (2 per cyst) and they multiply by longitudinal binary fission.
3) Live in proximal small bowel, freely or attached to mucosa by a sucking disk
4) Encystation as they get near colon; pass out of body in cyst form

Giardia lamblia diagnosis

pear-shaped trophozoites with bilobed nuclei/cysts in stool, fecal antigen test

cryptosporidium

mild diarrhea from undercooked meat

cryptosporidium transmission

ingestion of oocysts in water

cryptosporidium pathogenesis

intracellular multiplication in the brush border

cryptosporidium clinical presentation

Severe diarrhea in immunocompromised AIDS patients
Mild watery diarrhea in immunocompetent host

cryptosporidium diagnosis

oocysts on acid fast stain, antigen detection

Entamoeba histolytica

amoebic dysentery from contaminated water

Entamoeba histolytica pathogenesis

trophozoites can invade the colonic mucosa and cause dysentery and through spreading through the bloodstream, gives rise to extraintestinal lesions (liver)

Entamoeba histolytica clinical presentation

blood and pus in stools, liver abscess, inverted flask shaped lesions in large intestine (peritoneum, liver, lungs, brains, heart)

Entamoeba histolytica diagnosis

trophozoites/cysts in stool

Entamoeba histolytica serology

nuclei have sharp central karyosome and fine chromatin "spokes"

Toxoplasma gondii

obligate intracellular parasitic protozoan

Toxoplasma gondii danger population

pregnant women, IC

Toxoplasma gondii transmission

cysts in meat, oocysts in cat feces, crosses placenta

Toxoplasma gondii disease

mononucleosis-like in IC
brain abscess in AIDS
congenital toxoplasmosis

congenital toxoplasmosis

chorioretinitis, hydrocephalus, and intracranial calcifications

Toxoplasma gondii pathogenesis

trophozoites infect brain, eyes, liver. CNS disease more common in immunocompromised patients

Naegleria fowleri

brain eating amoeba

Naegleria fowleri transmission

Swimming in freshwater lakes (think Nalgene bottle filled
with fresh water containing Naegleria); enters via cribriform plate

Naegleria fowleri disease

Rapidly fatal meningoencephalitis

Naegleria fowleri clinical presentation

severe purulent hemorrhagic inflammatory rxn
rapid onset of bifrontal headache

Naegleria fowleri pathogenesis

Trophozoite enters CNS through the cribriform plate leading to CNS infection

Naegleria fowleri diagnosis

Amoebas in spinal fluid (see picture)

Trypanosoma brucei

African sleeping sickness

Trypanosoma brucei transmission

Tsetse fly, a painful bite

Trypanosoma brucei disease

African sleeping sickness—enlarged lymph nodes, recurring fever (due to antigenic variation), somnolence, coma
-Two subspecies: Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense

Trypanosoma brucei pathogenesis

Often fatal if left untreated:
1. Localized inflammatory reaction near entry site
2. Invasion of lymph nodes- Winterbottom's sign
3. Invasion of CNS

Trypanosoma brucei clinical presentation

African Sleeping Sickness:

Cervical and axillary LAD
Recurring fevers (antigenic variation)
Somnolence and coma (parasitic involvement of CSF and CNS)

Trypanosoma brucei diagnosis

Trypomastigote in Blood smear (see picture)

Plasmodium

causes malaria

P. falciparum

species of Plasmodium that causes the most severe cases of malaria

P. malariae

Malarial organism characteristically has a band form trophozoite stretching across the red blood cell

P. vivax

benign tertian malaria
- persistent hypnozoites (relapse)

P. ovale

Malarial organism has large, coarse, red dots within a large, pale red blood cell with fimbriated edges
- persistent hyponozoites (relapse)

Plasmodium pathogenesis

- metabolism of hemoglobin and lysis of infected RBC => anemia/agglutination of infected cells

uncomplicated malaria

Symptomatic infection with the malaria parasite manifesting as fever, body aches, headache, diarrhea, and possibly other symptoms not associated with severe illness.

Severe malaria

symptomatic malaria infection that is complicated by coma or recurrent seizures, severe anemia, respiratory distress, kidney or liver failure, systemic acidosis, or other associated life-threatening conditions

P. falciparum pathology

causes greater parasitemia b/c organism can enter reticulocytes and mature RBC.
- secreted proteins that are concentrated in "knobs" in erythrocyte membranes- adhere to vascular epithelium, causing occlusion that can lead to thrombosis and ischemia of any organ

Babesia

tick bite leads to blood-borne dissiminated illness
(apicomplexa)

Babesia transmission

Ixodes tick (same as Borrelia burgdorferi)

Babesia pathogenesis

Massive destruction of erythrocytes during parasite development

Babesia clinical presentation

fever, hemolytic anemia, predominantly in northeastern US, (asplenia = danger)

Babesia diagnosis

Blood smear, ring form, Maltese cross, PCR

Trypanosoma cruzi

Chagas disease - blood disease from reduviid bugs (flagellates)

Trypanosoma cruzi transmission

Reduviid bug ("kissing bug") feces, deposited in a painless bite (much like a kiss)

Trypanosoma cruzi disease

-Chagas disease—dilated cardiomyopathy with
apical atrophy, megacolon, megaesophagus; predominantly in South America
-Unilateral periorbital swelling (Romaña sign) characteristic of acute stage

Trypanosoma cruzi pathogenesis

Extracellular pathogen in peripheral blood but intracellular in cardiac myocytes, smooth muscle cells and enteric neurons

Trypanosoma cruzi diagnosis

trypomastigote in blood smear

Leishmania

leishmaniasis from sand fly (volcano)

Leishmaniasis disease

cutaneous skin ulcer, spiking fever, hepatosplenomegaly, pancytopenia

Leishmaniasis pathogenesis

infective stage promastigotes reach puncture wound are phagocytized by macrophages - transform into tissue stage which divide/ infect others

Leishmaniasis diagnosis

Macrophages containing amastigotes in cutaneous lesions

Trichomonas vaginalis

exclusive human pathogen - flagellate
- STI

Trichomonas vaginalis transmission

Sexual (cannot exist outside human because it cannot form cysts)

Trichomonas vaginalis pathogenesis

adherence factors allow cervicovaginal epithelium colonization in women

Trichomonas vaginalis disease

Vaginitis—foul-smelling, greenish discharge; itching and burning; do not confuse with Gardnerella vaginalis, a gram-variable bacterium associated with bacterial vaginosis

Trichomonas vaginalis diagnosis

motile trichomonas trophozoites on a "wet prep"