Parasites Flashcards
What is a parasite?
Organism that lives in another organism
Gets it’s food at the expense of the host
What are the 3 classes of parasites?
Protozoa
Helminths
Arthropods
Give examples of helminths…
Roundworms
Tapeworms
Flukes
Give examples of protozoa…
Malaria (parasite that causes it)
Amoebae
Flagellates
Give examples of arthropods…
Lice
Ticks
Mites
Name 3 major illnesses caused by protozoa.
Malaria
Amoebic Dysentery
Leishmaniasis
How do protozoa tend to be transmitted?
Fecal-oral route or via an arthropod vector
What are the symptoms associated with malaria?
Fever
Chills
Other flu-like symptoms
Describe the life cycle of malarial parasites…
Sporozoites injected under skin by mosquito
Travel in blood to liver
Mature in liver to merozoites
Re-enter circulation
Invade RBC’s, multiply, lyse, invade more RBC’s
Merozoites produce gametocytes
Gametocytes form taken up by mosquito and sheg: leading to production of sporozoites
Process repeats
A patient has got amoebic dysentery. What symptoms/signs are they likely to present?
Diarrhoea with blood/pus
Intestinal and extra-intestinal infections
Possible liver abscess (in late disease)
How would you identify amoebic dysentery in a stool sample, under a microscope?
Cysts
2 nuclei + chromatoid body
How is leishmaniasis transmitted?
Bites of sandflies
What typical symptoms are there of cutaneous/muco-cutaneous leishmaniasis?
Skin/mucosal ulceration
What health affects are caused by visceral leishmaniasis?
Fever
Weight loss
Hepato-splenomegaly
What is the sellotape test used for?
Pinworm infestation (sellotape shows Ova when looked at under a microscope)
Type of roundworm
Lives up your bum
Tapeworms are transmitted through ingestion of beef or pork.
What form are they found as, in these meats?
Cyst
What are nematodes?
Round worms
What are cestodes?
Tape worms
What are trematodes?
Flat worms
What thread like, 1cm long hilminth is commonly found in children?
Enterobiasis (pinworm)
What are Ova?
Eggs of parasites
mature female reproductive cell
Which nematode is responsible for causing Loefller’s syndrome?
Briefly describe what the condition is.
Ascaris lumbricoides
Accumulation of eosinophils in lungs
Where do roundworms tend to inhabit when they infect a human?
Small intestine
Ascaris can also live in the common bile duct
Taenia saginata and taenia solium are both types of what?
Cestode - tapeworm
In the context of tapeworm transmission, describe what an intermediate and definitive host are.
Larval cysts ingested by animal (cow or pig) and then passed to humans when we eat beef/pork
Livestock ∴ intermediate host
Cyst only matures to adult tapeworm in human
Human ∴ definitive host
What is cysticercosis?
Parasitic infection of cysts of T.solium
Invade the brain, muscles or other tissues
What is the other main type of tapeworm, aside from solium and saginata?
Describe the main features of infection by this tapeworm.
Eichinococcus
Carried by dogs, foxes, wolves
Humans ingest eggs which hatch then enter circulation
Hydatid cyst forms in liver - must be surgically resected
Schistosomiasis (flukes) is an infection caused by what type of helminth?
Trematodes (flatworms)
What are the 3 major species of schistosomes, and organs does each affect?
S.haemotobium - bladder
S.mansoni - intestines
S.japonicum - intestines
What is the intermediate host, used by schistosomes?
Snails
Describe how schistosomes infect humans.
Ova excreted in urine/faeces near/in fresh water
Maricadia (swimming larvae) released into fresh water
Penetrate snail body
Cercaria emerge from snails after 4 - 6 weeks which penetrate human skin (swimmers itch)
Migrate from lungs to liver where they mature to schistosomes then migrate to mesenteric or bladder
Lay eggs that cause inflammation of organ wall
What fever is caused by schistosomes (bilharzia)?
Katayama fever
Which type of schistosome infection is most severe?
S.japonicum
Which schistosome is associated with causing haematuria and bladder cancer?
S. haematobium
If you suspected that a patient had been infected by a Helminth. What could you test for in the blood, and why?
Eisonophil levels
IgE levels
Infection if often accompanied by eosinophilia and elevated IgE levels
In diagnostics, what 3 things would you look for in a faeces sample, to look for evidence of parasitic infection?
PCO
Parasites
Cysts
Ova
How is malaria testes for?
Blood films: thick and thin
Summarise how a parasitic infection can be tested for.
Faeces microscopy
Serology
Thin+thick blood films
Tissue microscopy
