Parasitology Introduction Flashcards
What is a parasite?
organism that lives in/on a host, getting its food at the expense of the host - can be obligate or facultative
What are three classes of parasites?
Helminths
Protozoa
Arthropods
What are the three classes of helminths?
Nematodes (round worms)
Trematodes (flat worms)
Cestodes (tape worms)
What are the three classes of protozoa?
Malaria
Flagellates
Amoebae
What are the three main classes of arthropods?
Lice
Ticks
Mites
Describe protozoa
Unicellular
Found on blood and tissue (arthropod vector) or intestines (faecal-oral route)
What parasite causes malaria?
Plasmodium falciparum
What is the vector for malaria transmission?
Anopheles mosquito
How can plasmodium falciparum be detected in the lab?
Using a Giemsa-stained blood film - think/thin
Describe how malaria is transmitted?
- sporozoites injected under the skin
- moves from blood to liver to mature
- merozoites re-enter circulation and invade RBCs
- sexual forms taken up by mosquitoes for further transmission
What parasite causes amoebic dysentery?
Entamoeba histolytica
Describe how amoebic dysentery presents clinically
- trophozoite ingests RBCs using pseudopodia
- causes cysts/intestinal infections/liver abscesses
What parasite causes leishmaniasis?
Leishmania species - cutaneous/muco-cutaneous/visceral
Describe the symptoms of leishmaniasis
- ulceration
- fever
- weight loss
- hepato-splenomegaly (liver and spleen swelling)
How is a leishmania species transmitted?
Using a sand fly vector
Give examples of infections caused by nematodes
Enterobiasis
Ascaris lumbricoides
How is ascaris lumbricoides transmitted?
- eggs hatch in intestines
- larvae move to the lungs where they are re-swallowed
- worms develop in the small intestine
Give examples of infections caused by cestodes
taenia saginata/solium
echinococcus
How is taenia saginata transmitted?
Beef; cysts (worm formed) or eggs (cysts formed) in humans
How is taenia solium transmitted?
Pork; cysts or eggs ingested
How is echinococcus transmitted?
- ingestion of dog faeces
- eggs hatch and enter circulation
- cysts firm in the liver
Give an example of an infection caused by a trematode
Schistosomiasis
Describe how a schistosomiasis species is transmitted
- ova excreted by humans into water
- miracidia released
- snail penetrated
- cercaria emerge
- human penetrated
- lung to liver to mature (on to bladder)
- eggs causing bladder/intestinal imflammation
- Katayama fever (acute febrile episode presents)
How are parasite infections diagnosed?
- helminths cause eosinophilia and elevated IgE levels
- microscopy of faeces/tissue
- serology to detect antibodies
