Flashcards in Parasitology Deck (24):
-organisms that live on or within other living organisms (the host) for a significant period of its life and obtains nourishment from it
Give broad examples of parasite categories and be sure to name which 2 are the most common
-All viruses, some bacteria, some fungi
-arthropods: biting insects (lice, mites); important as vectors for other diseases
Compare protozoa and helminths
-P: unicellular, multiply in host, short life cycles, acute/chronic infections
-H: multicellular, do not multiple (lay eggs), long life cycles, chronic infections
4 main parasite portals of entry
2. arthopod bite
3. transplacental penetration
4. organism-directed penetration
Describe the structure and reproduction of protozoa
-single celled, eukaryotic organisms with NO CELL WALL
-usually reproduce by binary fission
-often produce cysts to survive harsh conditions--aid transmission
How do protozoa obtain nutrients from the host?
-via diffusion or pinocytosis
4 types of protozoa
4. Coccidia: non-motile
We covered 7 protozoa in lecture, belonging to 3 categories based off of location. Name them.
1. GI protozoa: entamoeba histolytica, Giardia lamblia, Cryptosporidium
2. GU protozoa: trichomonas vaginalis
3. Blood and tissue protozoa: toxoplasma gondii, falciparum (malaria), naegleria fowleri
How is Entamoeba histolytica spread?
-fecal oral route after ingestion of a cyst
What is the growing/active form of Entamoeba histolytica called?
What about the Entamoeba histolytica cysts make them useful in diagnosis?
-they have multiple (4) nuclei
Where to Entamoeba histolytica invade?
Both the Entamoeba histolytica cysts and trophozoites are excreted, but the _______ die quickly and it is the __________ that spread the infection.
-trophozoites die quickly
-cysts spread infection
What is the characteristic pattern associated with Entamoeba histolytica?
Describe the life cycle of Entamoeba histolytica
1. fecal oral transmission of cyst
2. acid in stomach converts to trophozoite
3. invasion and division in colon wall- lyses epithelial cells
4. forms flask-shaped ulcerations
5. division and excretion of cysts (and trophozoites) and spread of infection
Entamoeba histolytica epidemiology
-found world-wide, especially in areas with poor sanitation where attach rates can be 10-50% of the population
-many patients are asymptomatic and the infection is cleared
-symptoms will depend on level of infectious dose
-millions of cysts shed in stool per day
3 outcomes of Entamoeba histolytica infections
1. asymptomatic infection
2. intestinal amebiasis (amebic dysentery)
3. extraintestinal amebiasis
If carriers of E. histolyticas, how long do their infections usually last?
Clinical manifestations of intestinal amebiasis
- related to destruction of colonic epithelial cells
-cramping, diarrhea (not absorbing water well), pain, bloody stools with mucus
Clinical manifestations of extraintestinal amebiasis
-fever and rigors
-liver is primary target and can lead to abscess formation in liver
-immunosuppressed individuals are at greater risk of this
What are the 3 general factors that determine severity of E. histolytica
1. virulence of strain
3. immune status
How does one diagnose E. histolytica?
-detection of trophozoites and cysts (multiple nuclei) in stool
-serology can be useful, but not in endemic areas since most people will be seropositive
What is the treatment of E. histolytica?
-Metronidazole (flagyl) followed by iodoquinol