Introduction to parasites Flashcards
What is a parasite?
A parasite is an organism that lives in or on another organism (host) and derives its nutrients at the expense of this host
What is a vector?
An organism which acts as an intermediate host for a parasite
The vector transmits the parasite to the next host
What are the classifications of parasites?
Ectoparasites- parasites that live on top of the body
Endoparasites- live inside the host
What are the sub classes of endoparasites?
protozoa
helminths (worms)
Describe protozoa?
Microscopic, single-celled organisms
Can be free-living or parasitic in nature
Able to multiply in humans
Transmission:
Protozoa that live in a human’s intestine - faecal-oral route
Protozoa that live in the blood or tissue of humans - insect vector
Describe malaria?
it is a protozoan infection
Malaria is a mosquito-borne disease caused by a parasite called Plasmodium
Patient often experience fever, chills, and flu-like illness
Left untreated, they may develop severe complications and die
5 Plasmodium species
P. falciparum has the highest mortality
Mosquito vector (Anopheles mosquito)
Specially stained blood film shows infected red cells (parasitaemia)
What is amoebic dysentery (protozoa infection) ?
Approx. 50 million cases annually
Causes bloody diarrhoea
Entamoeba histolytica invade gut wall
Microscopy: cysts in formed stool
Clinically:
Intestinal and extra-intestinal infections
Liver abscess in late disease
What are the three sub classifications of helminths/ worms?
nematodes- round worms
cestodes- tape worms
trematodes- flatworms
What is enterobiasis? (nematode)
Enterobiasis (pinworm)
1cm, threadlike, found in children
Cause anal itch, especially at night
Diagnosis:
Visual confirmation of adult worms in perianal region
Ova (eggs) seen on microscopy
What is Ascaris Lumbricoides? (nematode)
The largest nematode in humans
Adults 15-35 cm
Often asymptomatic
May cause failure to thrive in children
Mass of worms may obstruct small intestine or common bile duct
What is name of beef tapeworm?
Taenia saginata (beef)
How do humans contract tapeworm infection?
Tapeworms migrate into muscle tissue of animal - where they form a cyst and go to dormant.
They wait for animal to be eaten.
Cysts wake up once eaten and develop into adult worms.
Mature and start to produce eggs -which can infect animals as they eat eggs in human stool
What is name of pork tapeworm?
Taenia solium
How do we differentiate between beef and pork tapeworm?
Neurocysticerosis -
Pork tapeworm cysts can form outside of the gut and cause problems, especially in brain
What is schistosomiasis (trematodes)?
Three major species of Schistosomes:
S. haematobium (bladder)
S. mansoni (intestinal)
S. japonicum (intestinal)
This is transmitted by contact with freshwater where the snail intermediary host is present
“Swimmer’s itch” common sign
Can lead to complications such as liver failure and bladder cancer if left untreated
