Parasitology I: Protozoans Flashcards
What is the distribution of Cryptosporidium hominis?
Global
What is the infectious and diagnostic stage of Cryptosporidium hominis?
Oocyst
What is the route of transmission of Cryptosporidium hominis?
Fecal-oral
What is the basic life cycle of Cryptosporidium hominis?
Oocysts in poop are ingested. Goes down GI tract and releases sporozoites. Trophozoites attach to microvilli of small intestine and wreck havoc.
Which stage of the life cycle causes all of the damage in Cryptosporidium hominis?
Trophozoites
What are the groups most at risk for Cryptosporidium hominis?
Elderly, young, immunocompromised, or pregnant
What is the incubation period of Cryptosporidium hominis?
2-10 days
What are the symptoms of Cryptosporidium hominis?
A week of watery diarrhea
Diagnosis of Cryptosporidium hominis
Test for Ova and Parasites
Modified acid-fast stain of stool samples (oocyst retains the dye)
Immunofluorescence using anti-C. hominis antibodies
Treatment for Cryptosporidium hominis
Nitrazoxanide (targets anaerobic metabolism)
What is the distribution of Cyclospora cayetanensis?
Global. Commonly found in tropical and subtropical regions.
What is the only host of Cyclospora cayetanensis?
Humans
What is the transmission of cyclospora cayetanensis?
Fecal-oral
What is the infectious and diagnostic stage of cyclospora cayetanensis?
Oocyst
What are the groups that are most at risk for an infection with Cyclospora cayetanensis?
People eating imported foods (human feces used as fertilizer in other countries)
People traveling to countries other than the U.S. or Canada
Diagnosis of Cyclospora cayetanensis
Stool acid-fast stain (Variably acid-fast!)
Symptoms of Cyclospora cayetanensis
Watery diarrhea (most common) Other GI symptoms
What are the major differences between Cyclospora and Cryptosporidium?
1) Cyclospora is variably acid fast wheras cryptosporidium is acid-fast
2) Cyclospora is twice the size of cryptosporidium
What is the treatment of Cyclospora cayetanensis?
Sulfa-Trimethoprim
What is the infectious stage of Toxoplasma gondii?
Oocyst
What is the diagnostic stage of Toxoplasma gondii?
Cysts in the tissues
Who gets Toxoplasma gondii?
Those who clean cat litter and those who eat raw/undercooked meat. Immunocompromised and preganant women at high risk
What are the symptoms of Toxoplasma gondii?
Immunocompetant: Asymptommatic
Immunocompromised: Fatigue, Sore throat, swollen lymph nodes, fever/headache, muscle aches, poor coordination/blurred vision, severe eye infections, and enlarge liver/spleen
Diagnosis of Toxoplasma Gondii
Primary method: Serology (look for antibodies)
PCR
Biopsied tissue
What are Toxoplasma gondii’s effects on the brain?
Causes multiple lesions that have a preference for the basal ganglia. In immunocompromised patients, toxoplasmosis is the most common cause of brain abscess
Treatment
Pyrimethamine + Sulfonamides +Leucovorin
**Pyrimethamine is teratogenic, so spiramycin should be used instead in the first trimester
Where does Babesia microti normally exist?
Northeast United States
What is the infectious stage of Babesia microti?
Sporozoite
What is the diagnostic stage of Babesia microti?
Trophozoite
What groups are at risk for infection with Babesia microti?
Individuals who spend time outdoors where ticks dwell
Splenectomized individuals
Immunodeficient individuals
Blood transfusion recipients
Symptoms of Babesia microti
Most are asymptomatic
Some develop flu-like symptoms, jaundice, hemolytic anemia
Diagnosis of Babesia microti
Look for the Maltese Cross on blood smears (tetrad while dividing)
Treatment of Babesia microti
Cominations of drugs:
Atovaquone+Azithromycin
Clindamycin+Quinine
What is the infectious stage of Plasmodium?
Sporozoite (via Anopheles mosquito)
What is the diagnostic stage of Plasmodium?
Trophozoite
What are the symptoms of Plasmodium?
Dark color urine (hemoglobin), enlarged spleen, anemia,jaundice
What can P. falciparum cause?
Cerebral malaria (high mortality)
Diagnosis of Plasmodium
Blood smears visualized with Wright’s stain or Giemsa
Card-based antigen detection: OptiMAL
Banana-shaped nucleus indicated P. falciparum
What does a banana-shaped nucleus indicate?
P. falciparum
Treatment of Plasmodium
Chloroquine, Mefloquine, Halofantrine
What kind of protozoan is Naegleria?
Rhizopod
Where is Naegleria most commonly found?
Southern States. Kids and young adults get in swimming in fresh water during heat waves.
What is the infective form of Naegleria?
Trophozoite
What is the diagnostic form of Naegleria?
Trophozoite in CSF
Is the cyst form of Naegleria transmissible?
No
What does Naegleria cause?
Primary Amoebic Meningocephalitis (eats brain tissue)
What is the the treatment for Naegleria?
Amphotericin B, Miconazole, Rifampin
What does Acanthamoeba cause?
Keratitis of the eye and Granulomatous Amoebic Encephalitis (focal lesions are common)
How is Acanthamoeba usually transmitted?
Through wounds on the skin/ contact lenses
Diagnosis for Acanthamoeba and Naegleria
Lumbar puncture
H&E Stain in Post-mortem tissue
Where does Entamoeba histolytica occur?
More common in tropical regions and areas of poor sanitation
How is Entamoeba histolytica transmitted?
Through human feces
What are the symptoms of Entamoeba histolytica?
Begin 2-4 weeks after infection and are usually minimal or asymptomatic
Mucosal ulceration is flask-shaped
Pathogen can go extra-intestinal and infect the liver
Abscesses can occur in the liver
What is the Diagnosis for E. histolytica?
ID of E. histolytica in the stool
E. histolytica antigen tests
What is the treatment for E. histolytica?
Metronidazole+diloxanide
Dehydroemetine for severe extra-intestinal infections
Does Trichomonas vaginalis have a cyst form?
No
How is Trichomonas vaginalis transmitted?
The trophozoite form is introduced during sexual intercourse, and it replicates within the genital tract
Symptoms of Trichomonas vaginalis
Women- persistant vaginitis, yellow-green discharge, foul odor
Men- Usually asymptomatic, painful urination, sterility
Diagnosis of Trichomonas vaginalis
Metronidazole or Tinidazole
What is the most commonly identified intestinal parasite in the United States?
Giardia intestinalis
Where is Giardia intestinalis usually found?
Warmer climates
What is the transmission of Giardia intestinalis?
Infectious cysts are introduced via fecal-oral route, trophozoites form in the small intestine
Who is at risk for Giardia intestinalis?
Children wearing diapers
People drinking contaminated water
Swallowing water while swimming
What are the symptoms of Giardia intestinalis?
Symptoms begin 1-3 days after infection
Diarrhea lasting up to 4 weeks (foul smelling, greasy stools)
Abdominal pain, nausea and vomiting
How do you diagnose Giardia intestinalis?
Identify cysts in the stool (Iodine stain) and ID trophozoites in diarrheal stools (Giemsa Stain)
What is the treatment for Giardia?
Tinidazole, Quinacrine, hydrochloride, Metronidazole
What is the distribution of Leischmania?
Mexico and the Middle East
What is the transmission of Leischmania?
Bitten by a sandfly which introduces a metacyclic promastigote into the host
Who is at risk for a Leischmania infection?
Travelers or military personnel going to the Middle East
What are the symptoms of Leischmania?
Cutaneous- Least severe. Crater on the forehead
Mucocutaneous- Painful metastatic mucosal lesions of the mouth and nose
Visceral- Most severe. Delayed onset for months to years. Enlarged lymph nodes and liver. Massively enlarged spleen, edema
Diagnosis for Leischmania?
Microscopic evaluation of parasites
Treatment for Leischmania?
Pentavalent antimonials (Glucantime and Pentostam)
Amphotericin B
Paromomycin
What is the distribution of Trypanosoma Cruzi (Chagas Disease)?
Central and South America
What is the transmission of Trypanosoma Cruzi?
A Triatome bug bites and defecates T. cruzi into you
What is the pathogenesis of T. cruzi?
Trypmastigotes transform into amastigotes, they transform back and trypmastigotes burst out of the cells and enter the bloodstream
What are the symptoms of Chagas Disease (T.cruzi)?
Acute phase: Periorbital swelling, myocarditis, encephalitis
Chronic form: Megacolon and megaesophagus
Diagnosis of Chagas Disease
Periorbital swelling (Romana’s sign), detection of parasites in a blood smear, serology
Treatment of Chagas Disease (T. cruzi)?
Nifurtimox
Benznidazole