Introduction to Parasites Flashcards
Define parasite
A parasite is an organism that lives in or on another organism (host) and derives its nutrients at the expense of this host
Where are parasites most commonly found?
Resource poor countries- developing countries.
Parasites may do two things relating to infection; what are they?
- Cause the infection themselves
- Be a vector for the infection
Define vector.
An organism which acts as an intermediate host for a parasite.
The vector transmits the parasite to the next host.
What is the World Health Organisation? (WHO)
A specialised agency of the United Nations concerned with international public health.
194 member states (countries) involved.
Where is the tropical region of the world?
Anywhere between the tropic of cancer and the tropic of Capricorn.
Name three subdivisions of parasite.
Protozoa, helminths and ectoparasites.
Name three types of protazoa.
Malaria, amoebae and flagellates.
Name three types of protozoa.
Malaria, amoeba and flagellates.
Name three types of helminth.
Roundworms, flatworms and flukes.
Name three types of ectoparasite.
Lice, ticks and mites.
Define protozoa.
Single celled organisms which can live within both the environment and humans and cause infection.
Define ectoparasites.
Parasites which live on the outside of the body.
Describe protozoa.
Microscopic, single-celled organisms
Can be free-living or parasitic in nature
Able to multiply in humans
Describe the two ways protozoa can transmit infection.
- Protozoa that live in a human’s intestine faecal-oral route
- Protozoa that live in the blood or tissue of humans insect vector
What is the most common cause of death related to parasites in the world?
Malaria.
What parasite causes malaria?
Plasmodium
What symtoms do patients with malaria experience?
Fever, chills, flu like illness.
What symptoms do patients with malaria experience?
Fever, chills, flu like illness.
What is the vector which causes malaria?
Mosquitos.
Throughout the world, how many species of plasmodium are there?
5
Name the ABCD for the prevention of malaria.
A- Awareness of the risk-> involves awareness of the area you’re travelling to.
B- Bite prevention ->e.g. wearing long sleeved clothing
C- Chemoprophylaxis (appropriate choice of antimalarial medication and compliance with theregime)
D- Diagnosis (prompt diagnosis and treatment without delay)
Okay now actually give a definition of malaria.
Mosquito-borne parasitic infection caused by Plasmodium species
Why is eradication of malaria difficult?
Because of the complex life cyle of the parasite.
What is Amoebic Dysentery?
Another type of protozoa infection which causes bloody diahorrea by the amoeba.
Where in the body is amoeba found?
In the gut.
How can you contract the amoeba infection?
By ingesting someone else’s faecal material in the form of contaminated food/water.
What do amoeba eat as a source of nutrients?
Red blood cells.
What is dysentery?
Bloody diahorrea.
What can happen if you have had Amoebic Dysentery for a long time?
Liver abscesses may form.
Where else can protozoa cause infection in the body?
Variety of body systems.
Name the three categories of worm.
Nematodes, cestodes and trematodes.
Give an example of the following-
1. Nematode
2. Cestode
3. Trematode
- Roundworm
- Tape worms
- Flatworms
What do we look for to diagnose worm infections?
Eggs of the worm in stool samples.
Enterobiasis is a type of??
Nematode.
Discuss Enterobiasis.
Sometimes referred to as the pinworm.
Often found in children.
Causes anal itch, especially at night.
Worm is approx 1cm long
Why does Enterobiasis cause anal itch?
At night, worm lays eggs around the anus.
How is Enterobiasis diagnosed?
Stick Sellotape on the child’s bottom and examine it under the microscope.
Describe Ascaris lumbricoides.
-The largest nematode in humans (Adults 15-35 cm)
-Often asymptomatic
What can ascaris lumbricoides result in in adults and children.
-May cause failure to thrive in children
-Mass of worms may obstruct small intestine or common bile duct
Describe the structure cestodes.
Long, segmented tapeworms.
How are cestodes transmitted?
By consuming raw or undercooked meat (beef or pork).
Name the intermediate hosts for cestodes.
Pigs and cows are the most common as have ingested larval cysts.
Name the definitive host for cestodes.
Humans.
Describe trematodes.
Also known as “flukes” or “flatworms”
Different species cause human infection in various body sites.
Name some of the various sites where you might find trematodes.
- Blood
- Lungs
- Liver
- Pancreas
- Intestine
What disease are trematodes associated with?
Schistosomiasis
What does Schistosomiasis need to be able to be transmitted.
Close to fresh water, snails important in lifecycle.
What can Schistosomiasis lead to if left untreated?
Complications such as liver failure and bladder cancer if left untreated
How do you get Schistosomiasis?
Swimming in fresh water where the snail (intermediate host) is present.
What are ectoparasites typically?
Insects or arachnids.
Ectoparasites are often vectors. What does this mean?
They cause infection as well as carrying other typesof infection.
For diagnosis of malaria, what kind of technique is used?
Blood microscopy using thick and thin blood films.
For diagnosis of ova, cysts and parasites, what technique is used?
Stoll microscopy.
Define ova.
Eggs
In what form do protozoa leave the body?
Cysts
Give two examples of indirect testing for parasites.
Serology (immune testing)
Rapid diagnostic tests
How do parasites get nutrients?
Get nutrients from their host at the expense of the organism.
