An Introduction to Parasites Flashcards
What is a parasite?
An organism that lives in another organism (host) and gets its food at the expense of the host
How does the complexity of parasites compare to bacteria?
They are simple organisms but more complex than bacteria
What do parasites cause?
Many diseases with malaria causing the most deaths globally
What are the 3 classes of parasites?
Protozoa
Helminths (worms)
Arthropods
What are examples of protozoa?
Malaria
Amoebae
Flagellate
Leishmaniasis
How is malaria spread?
By mosquito
What are symptoms of amoebae?
Diarrhoea with blood/pus and cysts formed in stool
What does leishmaniasis cause?
Skin or mucosal ulceration
Leads to fever and weight loss
How does leishmaniasis spread?
Bite by sandflies
How is leishmaniasis diagnoses?
Histology of biopsy material
What are examples of helminths?
Roundworms (nematodes)
Tapeworms (cestodes)
Flukes (trematodes)
What is the scientific name of roundworms?
Nematodes
How are nematodes diagnosed?
Pressing adhesive tape againt perianal region in the morning
Where are nematodes ova seen?
In microscopy
How are nematodes transmitted?
Faecal-oral route
What is a common nematode and what does it do?
Ascaris lumbricoides which is a mass of worms that may obstruct the intestine or bile duct
What are common cestodes?
Taenia saginata (beef)
Taenia solium (pork)
How do cestodes spread?
Larvae cysts ingested in meat
Where are cestodes ova seen?
In stool
What is a species of cestodes carried by dogs and transmitted by humans ingesting eggs?
Echinococcus spp
What is the scientific name of flukes?
Tramatodes
What is the scientific name of tapeworms?
Cestodes
What are common kinds of trematodes?
Schistosomes species:
S.haematobium (bladder)
S.mansoni (intestinal)
S.japonicum (intestinal)
Where are high rates of trematodes found?
Near fresh water
What is an important thing in the life cycle of trematodes?
Snails
What are examples of arthropods?
Lice
Ticks
Mites
What are protozoa?
Microscopic once celled organisms that can be free living or parasitic in nature
How are protozoa transmitted?
Faecal-oral route (live in human intestine)
Arthropod vector (live in blood or tissue)
Where do protozoa that are transmitted by the faecal-oral route live?
Human intestine
Where do protozoa that are trasmitted by a arthropod vector live?
Blood or tissue
What is the life cycle of malaria?
1) Sprozoites injected under skin by mosquito
2) Travels through blood and enters liver
3) Matures in liver and re-enters circulation at merozoites
4) Invade red cells, multiply and lyse cells
What is the life cycle of schistosomiasis?
1) Miracidia released in fresh water
2) Penetrate body of snail
3) Cercaria emerge from snail after 4-6 weeks
4) Penetrate human skin
5) Travel from lungs to liver
6) Mature in liver into worms (schistosomes) that migrate to the bladder venules
7) Lay eggs that cause inflammation
When does a definitive diagnosis of a parasite happen?
Once the parasite is identified in host tissue or excreta
What are the different stages present in microscopy?
Parasites
Cysts
Ova
What is rarely possible for parasites?
Culture
What is used to diagnose malaria?
Blood films
What is serology?
Detection of antibodies
Is serology used to detect parasites?
Yes it can be useful, especially for parasites in deep tissue
