Parasites intro Flashcards
Describe the main groups of parasites and their life cycles.
Parasites:
Some live inside the body or some live on it
They are classified by:
Cellular structure
Life cycle
Many parasites are spread by vectors
Predominantly a problem of resource – poor countries
Nematodes (roundworms):
Faecal-oral route of transmission
In UK, pinworm very common in childhood
Ascaris infection very common globally
Can lead to developmental delay in children
Severe complications can arise as a result of bowel obstruction
Cestodes (tapeworms):
Eating raw/undercooked meat is route of transmission
Beef and pork tapeworms commonest
Pork tapeworm cysts can form outside of the gut and cause problems, especially in brain
Trematodes (flukes):
Commonest type globally is schistosomiasis
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
Helminths (worms):
Roundworms, flatworms and tapeworms
Cause a variety of diseases in a variety of body systems
Heavy burden of disease, especially in resource-poor settings
Most are transmitted by faecal-oral route but some use an intermediary host/vector
Describe the common diseases caused by enteric (in the intestines) and blood-borne parasites.
Malaria:
Mosquito-borne parasitic infection caused by Plasmodium species
Causes the largest burden of death among all parasitic diseases
Present throughout the tropics and subtropics
It is a preventable disease
Recognition and appropriate treatment saves lives
The complex life cycle of the parasite makes eradication very challenging
Protozoal Infections –
Amoebic Dysentery
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
Protozoa other than malaria:
Faecal-oral route of transmission for amoebae
Cause infection in a variety of body systems
Can cause complications such as abscesses if left untreated
How do you diagnose a parasitic infection?
Blood microscopy for parasites:
Thick and thin blood films for malaria
Stool microscopy for the following:
Ova, cysts and parasites
INDIRECT:
- Serology (immune testing)
- Rapid diagnostic tests
