L36: Parasitic Protozoan Infections of the GI Tract Flashcards
4 classes of protozoa and their motility
- Amoeba – pseudopodia
- Flagellates – flagella
- Sporozoan – gliding
- Ciliates – cilia
How to most protozoans exist in the environment and why?
Produce cyst forms that protect them from drying out, etc. and aid in transmission (allows them to get through the stomach)
How to prozoa reproduce?
Normally by binary fission (asexual), can be with schizogony (asexual) or sporogoy (sexual)
What organism causes amebiasis?
Entamoeba histolytica
Life cycle of Entamoeba histolytica
Someone ingests the cyst and it breaks up so amoeboid form can come out – invades colon – can remain in lumen of colon and reproduce to cause dysentery or penetrate intestinal wall and go into circulation
Transmission of Entamoeba histolytica
Fecal-oral transmission due to ingestion of cysts – trophozoites will not survive in environment or gastric acidity – asymptomatic people tend to have more cysts in their stool and pass them more often
Intestinal disease of Entamoeba histolytica
Causes gastrointestinal distress, 95-100% of patients have blood in stool (dysentery) – fever is rare – gradual onset
Invasive disease of Entamoeba histolytica
Penetration of intestinal wall by trophozoites, leading to flask-shaped lesion – spread via bloodstream (liver abscess – abdominal pain, fever, WBC)
Diagnosis of Entamoeba histolytica
Stool examination (for eggs or cysts) or antigen detection, biopsy or serology
Control and prevention of Entamoeba histolytica
Sanitation and hygiene
How does type of stool affect presentation of Entamoeba histolytica?
Individuals with formed stool are more likely to have cysts
What organism causes giardiasis?
Giardia lamblia
Life cycle of Giardia lamblia
Exists as cysts, which enter the host and hang out on the mucosa but do not invade the cells
Transmission of Giardia lamblia
Fecal-oral transmission due to ingestion of cysts from contaminated water
Prevalence of Giardia lamblia
Seen often in very young children because kids are disgusting (many outbreaks occur in daycare centers), same prevalence in males and females, associated with water, occurs most often in summer
Characteristics of Giardia lamblia
Exists as a cyst outside of host and trophozoite inside host – has sucking disk like a plunger
Intestinal disease of Giardia lamblia
Sudden onset, causes foul-smelling, greasy, floating diarrhea; cramping, bloating, gas, NO dysentery (no blood) or fever
How long do the specific disease last for Giardia lamblia?
Acute = weeks Chronic = months to years (malnutrition due to malabsorption)
Diagnosis of Giardia lamblia
Observing cysts in formed stools or trophozoites in diarrheal stools (fecal antigen detection)
Control and prevention of Giardia lamblia
Sanitation and hygiene (water treatment/filtration)
What organism causes balantidiasis?
Balantidium coli
Life cycle of Balantidium coli
Ingested as a cyst, either stays in colon and multiples or invades wall of colon and multiplies
Transmission of Balantidium coli
Only ciliated organism to affect humans; fecal-oral transmission, frequently from pigs
Disease types of Balantidium coli
Chronic – diarrhea or constipation
Acute (invasion) – diarrhea with blood and mucus
What organism causes cryptosporidiosis?
Cryptosporidium parvum
Life cycle of Cryptosporidium parvum
Same as others but has oocysts (produced by sexual reproduction) – attaches to intestinal epithelial cells
Epidemiology of Cryptosporidium parvum
Not recognized as causing human disease until 70’s, now known to be relatively common – seen often in immunosuppressed patients
Transmission of Cryptosporidium parvum
Fecal-oral – ingestion of infectious oocysts, peaks in early summer to early fall
Intestinal disease of Cryptosporidium parvum
Causes profuse watery diarrhea accompanied by cramping, fatigue, and weight loss (no blood) – generally self-limiting but can be prolonged
Diagnosis of Cryptosporidium parvum
Detection of acid-fast oocyst in stool
Control and prevention of Cryptosporidium parvum
Proper sanitation and water treatment
Isospora belli
Elongated oocyst, fecal-oral, usually has to do with water, diagnosed more in immunocompromised individuals – causes fever, diarrhea, and weight loss
Isospora belli and AIDS
Causes severe disease in AIDS patients – watery diarrhea, malabsorption, weight loss, electrolyte imbalance, and potentially death
Cyclospora
Comes from oocysts in feces, outbreaks associated with water and produce (raspberries!) – disease is similar to cryptosporidiosis (watery diarrhea and cramping/fatigue/weight loss) – more severe in AIDS patients
Diagnosis of Cyclospora
Oocysts fluoresce under UV light
Microsporidia basics
Obligate intracellular parasites, primitive eukaryotes, distribution is worldwide
Infection of Microsporidia
Ingestion of spores
Intestinal disease from Microsporidia
Chronic debilitating diarrhea, anorexia, weight loss (10-20 stools/day)
Extraintestinal disease from Microsporidia
Keratoconunctivitis frequently seen, depends on organ system involved
