Intro to Parasites Flashcards
(39 cards)
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, very wide range of parasites globally, they can be vectors of infection or cause infection themselves, predominantly a problem of resource-poor countries
Vector
an organism which acts as an intermediate host for a parasite, the vector transmits the parasite to the next host
Classification of parsites
3 classes and examples
- protozoa e.g. malaria, amoebae, flagellates
- helminths (worms) e.g. roundworms, tapeworms, flukes
- ectoparasites e.g. lice, ticks, mites
How are parasites classified - broadly
- cellular structure
- life cycle
How are many parasites spread
by vectors
What are parasites predominantly a problem of
Resource - poor contries (equator/tropical regions)
what are protozoa
- microscopic, single-celled organisms
- can be free-living or parasitic in nature
- able to multiply in humans
how are protozoa transmitted
- protozoa that live in a human’s intestine => faecal-oral route
- protozoa that live in the blood or tissue of humans=> insect vector
Give an example of and explain protozoan infection
Malaria: mosquito-bourne disease caused by Plasmodium parasite
* patient often experiences fever, chills and flu-like illness
* Left untreated they may develop severe complications and die
How many plasmodium species are there and which is the deadliest
5 plasmodium species- P. falciparum has the highest mortality
Give some fun maleria facts :)
- causes the largest burden of death among all parasitic diseases
- present throughout the tropics and subtropics
- preventable disease
- recognition and appropriate treatment saves lives
- the complex life cycle of the parasite makes eradication very challenging
Lifecycle of maleria
- Sporozoites injected by mosquito
- Travel through blood and enter liver
- Mature in liver and re-enter circulation as merozoites
- Invade red cells, multiply and lyse cells - invade more red cells
- Sexual forms taken up by mosquito
What can show plasmodium infected red cells (parasitaemia)
Specially stained blood film
Is maleria a preventable disease
yes
What makes eradicating maleria very challenging
The complex lifecycle of the parasite
protozoal infections- amoebic dysentery
- causes bloody diarrhoea
- entamoeba histolytica invade gut wall
- microscopy: cysts in formed stool
- clinically= intestinal and extra-intestinal infections, liver abscess in late disease
- faecal-oral route of transmission for amoebae
- Causes infection in variety of body systems - can causes complications such as abscesses if left untreated
2 examples of protozoa
- Malaria (plasmodium)
- entamoeba histolytica
types of helminths
- nematodes- roundworms
- cestodes- tapeworms
- trematodes- flatworms
nematodes
enterobius vermicularis
- Cause enterobiasis (pinworm)- 1cm, threadlike, found in children
- Cause anal itch, especially at night
- Diagnosis= Press adhesive sellotape against perianal region in the morning
- Ova seen on microscopy
- faecal-oral route of transmission
Ascaris lumbricoides
neamatode
- ingested eggs hatch in the intestine - Ova seen in faeces by microscopy
- 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 the route of transmission for nematodes (roundworms)
fecal-oral
Explain ascaris infection (neamatode) further
- very common globally
- Leads to developmental delay in children
- Severe complications can arise as a result of bowel obstruction
cestodes (tapeworms)
type of helminth
- Long, segmented “tapeworms”
- Larval cysts ingested (intermediate host)-Eating raw or undercooked meat
- Adult tapeworms in human (definitive host)
- Ova in stools on microscopy
- Product of poor sanitisation/hygine
3 types of cestodes
- Taenia saginata (beef)
- Taenia solium (pork)
- Echinococcus
