Ectoparasites and protozoa

Question 1

List some examples of Ectoparasites

Answer 1

Lice, mite and ticks

Question 2

List some examples of protozoa

Answer 2

Giadia lambia, Entamoeba histolytica, Toxoplasma gondii

Question 3

What is the difference in definitive host, intermediate host and parantenic host, and reservoir host?

Answer 3

Definitive: parasite reaches sexual maturity
Intermediate: Development but not sexual maturity
Parantenic: Parasite remains infective but no development
Reservoir: animal that is normally infected with the parasite and can infect others

Question 4

What is pediculosis? list symptoms and infectious organisms

Answer 4

Lice infections from Pediculus humanis (body), P.capitis (head) P.pubis (pubic hair). Symptoms include itch, macules

Question 5

Describe the lifecycle of lice and how you would intervene to treat infection.

Answer 5

32-35 day cycle.
Louse emerges from egg on hair, wihin 17 days the first/second/third moult is formed > adult lice (F larger than M). Female can lay 3-9 eggs per day.

Rx: topical insecticide

Question 6

Describe the lifecycle of scabies

Answer 6

Adult F lays eggs a borrows in epidermis > eggs hatch and release larvae > larvae molt into nymphs > mating > begin lifecycle again.
Causes itch and dermatitis

Question 7

Where does scabies infect and how would you dx. and Rx. it?

Answer 7

Finger webs of hands and other flexor surfaces.
Dx: skin scraping
Rx: Ivermectin topical

Question 8

Why are ticks important/dangerous?

Answer 8

They are commonly vectors for other bacterial, viral etc. infectious agents. They only need a short period of contact as the female gets the blood meal

Question 9

Describe how entamoeba histolytica causes disease

Answer 9

Faecal oral rout > infects colon tissue > causes large volume diarrhoea > dehydration and malnourishment

Haematogenous spread = liver and brain abscess

Question 10

How do you Dx and Rx entamoeba histolytica infection?

Answer 10

Dx: cysts in diarrhoea
Rx: Metronidazole + paromomycin

Question 11

Describe how giadia intestinalis causes disease.

Answer 11

Faecal oral spread > infect GIT > sub acute diarrhoea > chronic malabsorption > persistant nausea and abdominal pain

Question 12

How would you Dx and Rx giadia?

Answer 12

Dx: cysts in faeces
Rx: Single dose of Tindazole

Question 13

Describe how toxoplasma gondii causes disease

Answer 13

contaminated water or eating undercooked meat > obligate intracellular parasite > persistant usually asymptomatic infection > cysts stay for life

Can cause CNS lesions and Occular disease

Question 14

When is infection with toxoplasma gondii dangerous?

Answer 14

Immunocompromised
Pregnancy
neonate
HIV patients

Question 15

Give examples of roundworms, tapeworms, flukes

Answer 15

Roundworm: Pinworm, ascaris, Strongyloides
Tapeworm: Echinococcus, Taenia
Fluke: Schitsosoma

Question 16

Describe the lifecycle of pinworms (enterobius vermicularis

Answer 16

ingestion > larvae hatch in small intestine > mature in colon and migrate to perianal region > eggs on perianal folds > itch > female crawls out at night to lay eggs > transmission

Question 17

How would you Dx and Rx pinworm?

Answer 17

Dx: detection of eggs (stickytape test)
Rx: Antihelminthics

Question 18

Describe the lifecycle of ascaris lumbricoides?

Answer 18

Grow in plants > ingestion of cyst > small intestine hatch then mature > hepatic circulation > lungs > alveoli > trachea > re-swallow.

Also excrete in faeces unfertilised and fertilised cysts

Cause pneumonitis, intestinal obstruction (cholecystitis

Question 19

How would you Dx and Rx ascaris?

Answer 19

Dx: Eggs in faeces or imaging
Rx: Antihelminthics

Question 20

Describe the life cycle of strongyloides stercoralis

Answer 20

hatch in soil and borrow through skin > bronchotracheal migration > embryonisation in colon > can autoinfect and larvae excreted in faeces

If excreted > develop into mature free-living worms > eggs are produced and fertilised > infective form can penetrate skin again

Question 21

How would you Dx and Rx strongyloides?

Answer 21

Dx: eggs in faeces and serology
Rx: antihelminthics

Question 22

Describe the life cycle of schistosoma

Answer 22

swim in infected water or eat fresh water snails > Enters blood > portal vein > faeces > hatch in water > fresh water snail infection > become infectious

Can have acute infection of be a chroni carrier where the eggs lodge in skin or liver causing acute local inflammation

Question 23

How would you Dx and Rx Schistosoma?

Answer 23

Dx: eggs in faeces, serology
Rx: antihelminthics

Question 24

Describe the lifecycle of Echinococcus granulosus infection.

Answer 24

Definitive host = dog > dog ingests cysts > become adult in small intestine > fecal excretion of embryonated eggs > human or sheep (intermediate host) ingestion > penetration of intestine wall > in humans can cause hydalid cysts in heart, lung, liver, spleen, bone. In sheep they excrete cysts which are then ingested by dogs.

Humans are not necessary for lifecycle

Question 25

how would you Dx and Rx Echinococcus?

Answer 25

Dx: imagin and serology Rx: antihelminthics followed by surgery to remove cysts

Question 26

Describe the lifecycle of Taeniasis

Answer 26

eggs contaminate vegitation > pigs and cattle eat infected vegitation > hatch and migrate into musculature > develop cysts in muscle > Humans eat raw, undercooked infected meat > Adults attach to intestine wall > eggs in faeces

Question 27

How would you Dx and Rx tapeworm infections

Answer 27

Dx: imaging ans serology Rx: antihelminthic with caution because the immune response can lead to epileptic seizurea