Parasites: Protozoans Flashcards
Protozoans vs Metazoans
Protozoans:
- Single-celled eukaryotes
- Complex life cycle
- Flagellates
- Ameobas
- Sporozoea
- Ciliates
Metazoans:
- Multicellular
- “Helminths”
- Life cycles include: Egg, larval stages, adult stage
- Roundworms (e.g. Nematodes)
- Flatworms (e.g. Trematodes and Cestodes)
Trichomonas vaginalis
Epi: sexually transmitted
Morph: “twitching trophozite”, motile, symmetric with 4 anterior flagella
Path: replicates via binary fission
Clinic: ***Frothy greenish discharge that smells foul with STRAWBERRY CERVIX; presents with itching and burning
Dx: PCR + trophozoite discharge
Tx: Metronidazole for pt and partner (males are usually asymptomatic)
“GETGAP on the METRO”
Giardia, Entamoeba, Trichomonas, Gardneralla, Anaerobes, H. pylori all treated by METROnidazole
Entamoeba Histolytica
[Amebiasis]
Epi: major cause of amebic dysentery, due to poor hygiene
Morph: “Flask Shaped Ulcers”, trophozoite w/ single nucleus and ingested RBC
Path: transmitted by cysts in water–>mature cysts ingested via fecal-oral route–>excitation back to trophozoite in small intestine–>migrate to large intestine
Clinic: 3 possible presentations:
- Asymptomatic: trophozoites produce cysts–>pass in feces–>survive outside body
- Intestinal disease: acutely forms abscesses/”Flask shaped” in large intestine–>ACUTE DYSENTERY (frequent, small, bloody, painful stools)
- Liver disease: disseminates to portal circulation–>LIVER ABSCESSES WITH ANCHOVY PASTE ASPIRATE
Dx: AMEBA ANTIGEN +, cysts in stool, serology, PCR tests
Tx: Metronidazole
“GETGAP on the METRO”
Giardia, Entamoeba, Trichomonas, Gardneralla, Anaerobes, H. pylori all treated by METROnidazole
Giardia Lamblia
[Giardiasis]
Epi: mc protozoan intestinal disease in US, transmitted via cysts in water @ DAYCARES + CAMPERS (resistant to chlorine treatment)
Morph: trophozoite with 2 nuclei and symmetrical axostyles and suction disks. Cysts have 4 nuclei and a well-defined wall
Path: cysts in contaminated water ingested via fecal-oral route–>trophozoite multiply via binary fission–>excystation in colon–>cover and flatten intestinal epithelium (***NONINVASIVE)–>malabsorption
Clinic: Malabsorption and uncontrollable flatulence, bloating, foul-smelling fatty diarrhea (no blood/necrosis)
Dx: cysts/trophs in stool
Tx: Metronidazole
“GETGAP on the METRO”
Giardia, Entamoeba, Trichomonas, Gardneralla, Anaerobes, H. pylori all treated by METROnidazole
Cryptosporidium parvum
Epi: contaminated water source (even survives in chlorinated water), disease of immunocompromised (think: HIV and post-transplant pts)
Morph: oocysts are acid-fast +
Path: thick-walled OOCYST ingested (this is INFECTIOUS)–>sporozoites released and infect gastric epithelium–>asexually differentiate to merozoites–>differentiate into gametes–>gametes fuse to form zygotes–>reduction division forms oocysts–>repeat cycle
Clinic: In an immunocompetent host–>Diarrhea or nothing
MC HIV presentation–>Ascending cholangitis with watery diarrhea +/- dissemination to gallbladder, biliary tract, and lung
Dx: serology
Tx: Nitazoxanide
Toxoplasma gondii
Epi: HIV+ pts and pregnancy
Morph:
Path: ingestion of cysts from uncooked meats and cat feces-contaminated foods; also can be transmitted congenitally or via blood transfusion
Cat=DEFINITE host, humans=INTERMEDIATE hosts
Clinic: in HIV pts, mc CNS infections leads to ring-enhancing lesions representing BRAIN ABSCESSES
Congenital toxoplamsosis presents as a triad of CHORIORETINITIS, HYDROCEPHALUS, INTRACRANIAL CALCIFICATIONS
Dx: screen before pregnancy, so if you have a +serology in pregnancy, then you know it is an acute infection
Tx: Sulfadiazine + Pyrimethamine (give with Leucovorin because it inhibits folate)
Naegleria fowleri
Epi: swimming in contaminated water ~1 week prior…most rapidly fatal meningoencephalitis
Morph:
Path: swimming in contaminated water–>flagellated form enters via olfactory epithelium/cribriform plate
Clinic: primary amebic meningoencephalitis–>acute and rapid detioration ~1 week
CSF looks bacterial (low glucose, high protein, high PMNs), but does NOT gram stain
Dx: ameobas in CSF
Tx: Amphotericin B
Acanthamoabe keratitis
Epi: eye infection in CONTACT LENS WEARERS, associated w/ organism growth in certain solutions
Morph:
Path: amoeba feeds on bacteria
Clinic: suspect if chronic keratitis does not respond to antibiotics–>tell pt not to wear contacts with bacterial infection
Dx:
Tx: topical Rx + topical steroids
Trypanosoma brucei
[Sleeping sickness]
Epi: transmitted in salivary glands of Tsetse Fly
Gambiense–>West Africa
Rhodesiense–>East Africa
Morph: trypomastigote with kinetoplast and undulating membrane
Path: Bit from tsetse fly–>motile flagella form (trypomastigote) spread in blood to lymph nodes and CNS
Typanosomes have variable surface glycoproteins (VSGs) that change every time Abs develop [antigen variation]
Clinic: “Sleeping sickness”
- Bite reaction: chancre
- Parasitemia: fever, lymph node swelling
- CNS: coma and death–>encephalitis
Dx: card agglutination test (antigen in blood)
Tx: Blood stage–>Suramin
CNS stage–>Melarsoprol
Trypanosoma cruzi
[Chagas Disease]
Epi: transmitted via Reduviid bug–>South America
Morph: trypomastigote in blood, amastigote in tissue
Path: reduviid bug bites human while sleeping–>reduviid bug turns around 180 degrees–>reduviid bug shits in the wound–>trypomastigotes penetrates skin (chagoma)–>transform into amastigote–>replicate and infect tissue
Clinic: Chagoma–>UNILATERAL facial swelling, usually primary lesion where bite occurs
Acute parasitemia–>fever, pain, rash
Post-parasitemia–>damage to autonomic nerve ganglia–>DILATED CARDIOMYOPATHY, MEGACOLON, MEGAESOPHAGUS
Dx: Based upon clinical findings
Tx: No tx effective for reversing organ injury
Leishmania
[Leishmaniasis]
Epi: transmitted via sandfly bite from rodents, dogs, and foxes
L. Donovani–>visceral
L. Braziliensis–>mucocutaneous
L. Tropica–>cutaneous
Morph:
Path: sandfly bites human host–>promastigote invades macrophages–>transforms into non-motile amastigote in RES system
Clinic: -Cutaneous: ulcer develops at initial site
- Muccocutaneous: organisms in skin spread to mucoid tissue–>severe deformities (ulcers–>erosion of nasal septum, palate, lips)
- Visceral: severe invasion of RES–>hepatomegaly, MASSIVE splenomegaly with PANCYTOPENIA
Dx: serology + protozoa in liver/spleen
Tx: Sodium Sibogluconoate
Plasmodium
Epi: anopheles mosquito caries malaria in salivary glands
Morph:
Path: sporozoites injected from mosquito–>blood stream–>liver (begins PRE-ERYTHROCYTIC CYCLE)–>sporozoite forms trophozoite–>divides into thousands of nuclei (schizont)–>make membrane merozoites–>cell bursts
Vivax/Ovale/Mixed: forms ***hypnotize in liver (not targeted by Rx like Quinidine–>use PRIMAQUINE)
Rupture: basis for parasitemia (MC w/ Falciparum)
Go on to infect other hepatocytes
Can go infect RBCs (begins ERYTHROCYTIC CYCLE)–>bursts RBC all at same time
Clinic: ***CYCLIC FEVER & CHILLS WITH ANEMIA that may include headache, N/V/D, malaise, and splenomegaly–>cerebral disease–>ARDS–>hypoglycemia and lactic acidosis
- Vivix/Ovale=RBCs burst every 48 hrs–>fever on 1st and 3rd day
- Malariae=RBCs burst every 36 hrs–>fever on 1st and 4th day
- Falciparum=IRREGULAR pattern, RBCs burst between 36-48 hrs
Dx: Giesma smear + immunochromatography
Tx: Prophylaxis= Atavaquone-Proguanil>Doxy>Meflo
Quinine=RBC stage
Primaquine=Liver stage (Vivax/Ovale form)–>HEMOLYTIC ANEMIA WITH G6PD DEFICIENCY
Babesia
[Babesiosis]
Epi: Northeastern USA
Morph: MALTESE CROSS on peripheral smear
Path: Ixodes Tick (same as Lyme Disease, often co-infects humans)
Clinic: FEVER, HEMOLYTIC ANEMIA, ASPLENIA
Dx:
Tx: Quinine + Clindamycin
