111 - Eukaryotic Parasites 2 Flashcards
(48 cards)
Three major types of worms
1) Roundworms
2) Tapeworms
3) Flukes
Similarities between all helminths
1
2
3
1) No lungs (extegument across which gasses exchange)
2) Sexual reproduction
3) Complex life-cycles, involving more than one host
Examples of human roundworms
1
2
3
1) Pinworms
2) Ascaris
3) Strongyloides
Examples of human tapeworms
1
2
1) Echinococcus
2) Taenia
Example of a human fluke
Schistosoma
Nematodes
1
2
3
1) Roundworms
2) Tube-like animal, covered with a cuticle
3) Most are free-living
Most clinically-important Nematode
Pinworm (enterobius vermicularis)
Features of pinworm infection 1 2 3 4
1) Most children infected at some time; highly contagious
2) 1cm long female crawls out of anus at night to release eggs
3) Fingers, sheets contaminated
4) Pre-patent period 4-6 weeks
Ringworm life-cycle 1 2 3 4 5
1) Embryonated eggs ingested
2) Larvae hatch in small intestine
3) Mate in caecum
4) Leave body through anus at night, lay eggs around anus
5) Transferred by scratching eggs
Symptoms of pinworm
Many asymptomatic infections.
Perianal/vaginal itch
Diagnosis of pinworm
Detection of eggs.
No serology, as never enters blood.
Treatment for pinworm
Antihelminth medication
Ascaris lumbricoides
Large intestinal roundworm
Number of eggs laid by Ascaris
200, 000 eggs per day (laid by female)
Size of Ascaris lumbricoides
Can be 30cm long
Ascaris lumbricoides life-cycle 1 2 3 4 5 6 7
1) Maturation in jejunum
2) Eggs passed in faeces, mature in damp soil over a few weeks
3) Eggs get into water, contaminate plant material.
4) Are ingested, infect jejunum
5) After maturation in jejunum are about 1/2mm long. Enter hepatic circulation, break through alveolar walls into alveolar space.
6) Migrate up the trachea, get swallowed again.
7) Attach to wall of jejunum, stay there for the rest of their lives
Distribution of Ascaris lumbricoides
Worldwide, but mostly in tropics (soil is too cold in many places, EG Melbourne)
Symptoms of Ascaris infection 1 2 3 4 5
1) Mainly asymptomatic.
2) Pneumonitis (from larval migration).
3) Intestinal obstruction (pancreatitis, cholangitis).
4) Because of repeated coinfections with different stages of 5) Ascaris lifecycle, have all symptoms at the same time (EG: asthma from larval migration irritating lungs)
Diagnosis of Ascaris
Eggs in faeces.
Imaging of large worms causing obstructions (EG ultrasound)
Number of Strongyloides infections worldwide
100 million
How do Strongyloides stercoralis infect host?
Penetrate skin of host.
Strongyloides stercoralis features of infection
1
2
3
1) Gram- co-infection (thought to be covered in G- bacteria, introduces these into the blood stream). Septicaemia.
2) Can come about if someone is immunosuppressed (EG: glucocorticoids prescribed)
3) Autoinfection. Entire life-cycle can occur within a human.
Strongyloides sterocoralis life-cycle 1 2 3 3 4 5 6 7 8 9
1) Rhabditiform larvae excreted in stool
2) Develop into free-living adult worms
3) Eggs produced by female worms
4) Rhabditiform larvae hatch from eggs.
5) Infective filariform larvae can penetrate intact skin of host
6) Filariform enters bloodstream, transported to lungs, enter alveolar spaces.
7) Carried into the trachea, are swallowed.
8) Female lays eggs
9) Autoinfection.
Example of a fluke
Schistosoma
