• giardiasis
• cryptosporidiosis
• dientamoeba infection
• blastocystis infection
• amebiasis

• epidemiology
  • most common cause of diarrhea of US
  • most common parasite worldwide
• structure
  • considered primative eukaryote
  • two nuclei
  • multiple flagellum
  • lacking mitochondria, so anaerobic
  • zoonotic host (for beavers)
  • pear shaped

1. human infection by water/food or person to person contact of cysts (esp. water)
2. trigges excystation when going through gastric acid and panceratic exocrine secretion
3. colonize prox. small intestines by trophozoite (actively swimming pathogenic form)
4. encystation in distal small and large intestines
5. excreted cysts in feces

• asymptomatic (higher possibility in children)
• acute giardiasis
  • 1-4 wk incubation
  • symptoms
    • loose foul smelling diarrhea
    • steatorrhea- fat malabsorption
    • cramping
    • bloating
    • nausea
    • anorexia, malaise, weight loss
    • NO BLOOD
    • fever early
• chronic giardiasis

• epidemiology: toddlers
  • second to CF as cause of steatorrhea
• symptoms
  • steatorrhea leading to increased fat excretion in stool
  • growth retardation
  • decreased serum carotene
  • abnormal xylose absorption

• fecal exam
  • enterotest
    • patient swallows a capsule at end of string
    • string moves to jejunum, where trophozoites attach
    • after 4-24 hrs, string withdrawn
    • scrape off mucus and look for trophozoites
  • duodenal aspiration biopsy
  • fecal ELISA
  • serum Ab
  • PCR (fecal inh.)

• metronidazole (remember, anaerobic protozoa is the hint)
• nitazoxanide (comes in suspension for pediatric use)
• tinidazole
• furazolidone
• albendazole

• epidemiology
  • transmission
    • water borne outbreaks in cyst form (oocyst)
    • person to person (day care centers and secondary spread from day care centers)
    • zoonotic transmission (farmers, animal handlers)
  • infects gastric and resp. epithelium
  • important pathogen in HIV/AIDS patients and children
  • peaks in late summer and early fall
  • even asymptomatic infection may cause failure to thrive in kids
• char.- obligate intracellular parasite

1. swallow oocyst
2. head toward microvilli surface of intestinal epithelium
3. replicate in and around the plasma membrane and apical surface of epithelial cells
4. make merozoites that can infect intestinal cells
5. another form (progametocyte) can go to other cells as macro amd microgametocytes to form new zygote and oocyst
6. oocyst passed in feces

• fecal exam and do acid fast stain
• monoclonal Ab staining (immunofluorescence)

• watery diarrhea and fatigue
• periods of remission and relapse

• ameboflagellate
  • ameboid morphology by light microscopy, but also has flagellum
  • electron microscopy and 16S rRNA (trichomonad)

• associated with Enterobius infection
• linked to chronic abdominal pain/ gastroenteritis

• clinical symptoms
  • vaginitis
  • foul smelling, greenish discharge
  • itching
  • burning
• epidemiology- higher infections in African American women
  • like Schistosoma hematobia, it increases risk of contracting HIV

• protozoan parasite poorly defined taxonomy and life cycle
• large glycogen like vacuoles
• pathogenicity is controversial

• low prevalance in US, but the majority of people who get it are in the Latino and Asian community
  • Latinos: males 20-40 yr olds
• seen mainly in tropical areas where crowded living conditions and poor sanitation (worldwide prevalance)
• major cause of morbidity in Central and South America, Indian subcontinent
• second leading cause of death by protozoa (number one is malaria)
• peak seropositivity in 5-9 yr old age group
• seen in all socioeconomic groups

• Entamoeba histolytica
• 5 or 6 cases that the agent could be E. dispar for every case caused by E. histolytica (non pathogenic deme)

MAKES IT HARD TO TREAT

• nucleus that looks like a bicycle wheel
• large size

• asymptomatic colonization
• amebic dysentery
• amebic colitis
• liver abscess

• gradual onset
• h/o symptoms for more than a week
• diarrhea
• dysentery
• abdominal pain
• weight loss
• fever
• heme + stools
• immigrant/traveler from endemic area

• burrows all the way down into the muscularis mucosa: flask shaped ulcer

• h/o symptoms for more than 4 weeks
• fever
• abdominal tenderness
• hepatomegally
• jaundice
• diarrhea
• weight loss
• more common in men
• cough
• immigrant/traveler from endemic area

1. cysts ingested in water, food
2. invade tissues of colon as trophozoites
   1. flask shaped ulcer
   2. liver abscess (went to portal circulation)
   3. brain abscess (systemic circulation
3. encyst in colon
4. cyst pass in feces

• microscopy
  • RBC's in cytoplasm of entamoeba
  • single stool sample and look for trophozoites (30-50% sensitive)
  • liver aspiration (20% sensitive)
• stool Ag detection
  • 67% sensitive
  • lectin in stool
• stool PCR
• serology
  • IHA
  • 99% sensitive for liver abscess
  • 88% sensitive for amebic colitis
  • remains positive for yrs
• colonoscopy and wet prep
• radiographic imating

• asymp. colonization could be wtih single luminal agent alone
• invasive amebiasis (colitis, liver agent)
  • metronidazole and luminal agent such as iodoquinol
  • percutaneous drainage usually not required

• adequate disposal of human stool
• safe and adequate water supply
• health education (hand washing, safe food prep, insect control)
• integrate surveillance programs ongoing sanitation and diarrhea control initiatives