Introduction To Parasites Flashcards
What is a parasite?
An organism that feeds itself at the expense of the organism it lives in (host).
What are the three classes of parasites?
Protozoa
Helminths
Arthropods
What are Protozoa and how are they transmitted?
Single cell microscopic organisms that can be free living or parasitic.
If they live in the intestine they are transmitted by the fecal oral route, if they live in the blood/tissue they are transmitted by arthropod vectors.
What species causes malaria and by what vector? How is it diagnosed?
Plasmodium species, P. Falciparum has the highest mortality.
Anopheles mosquito is the vector.
Diagnosed using a thick and thin blood film. Giemsa stained blood film shows infected red blood cells.
What is the life cycle of malaria?
Sporozites injected under the skin by mosquito where they travel through the blood and enter the liver. They mature in the liver and re-enter circulation as merozites. These invade red blood cells where they multiply and lyse cells. The sexual form is taken up by the mosquito.
Humans can blood transmit to each other.
What is amoebic dysentery, what is it caused by and how is it diagnosed?
Diarrhoea with blood and pus and can cause intestinal and extra intestinal infections and liver abscess in late stages.
Entamoeba histolytica.
Diagnose using ‘hot stool’ and the trophozite ingests red cells by throwing out pseudopodia.
What is leishmaniasis, what is it caused by and how is it diagnosed?
It is an infection by the bite of sandflies.
Leishmania species.
Cutaneous or mucocutaneous leishmaniasis can cause skin or mucosal ulcerations.
Visceral leishmaniasis can cause fever, weight loss and hepato-splenomegaly.
Diagnosed by histology it biopsy material.
What are three classes of helminths?
Nematodes (roundworms)
Cestodes (tapeworms)
Trematodes (flatworms)
What are enterobiasis and how are they diagnosed?
Roundworm found in children.
Diagnosed by sellotape against perianal region in the morning.
Ova can be seen on microscopy.
What are ascaris lumbricoides, what does it cause and how are they diagnosed?
Nematode whose eggs can hatch in the intestine and carry up to lungs then swallowed again to small intestine.
Often asymptotic but can have transient pulmonary symptoms (loefller’s syndrome) and mass of worms could obstruct small intestine or common bile duct.
What are taenia saginata and solium, what do they cause and how are they diagnosed?
Tapeworms found in beef and pork. Larval cysts ingested in meat then the adult tapeworm is in host.
Cause cysts by T. Solium.
What does echinococcus sp cause and what are they carried by?
Cestode carried by canines and vulpines and when humans ingest dog faeces the eggs hatch and hyatid cysts form in the liver. Surgical resection of the cyst is needed.
What is schistosomiasis, what is it caused by?
S. Haemotobium (bladder) can cause haemoruria and bladder cancer.
S. Mansoni and S. Japonicum (intestine)
They lay eggs that cause inflammation of bladder or intestine.
Have acute febrile episode one to two months later called katayama fever.
What is the life cycle of schistosomiasis?
Ova are excreted im urine or faeces.
Miracidia are released into fresh water.
Penetrate body of snail (intermediate host)
Cercaria emerge from snails a month later.
Penetrate humans skin and migrate from the lungs to the liver.
These mature into worms that migrate to mesenteric or bladder venules.
What is helminth infection accompanied by?
Eosinophilia
Elevated IgE
