Week 9: Neglected Tropical Diseases

Question 1

What are 3-4 reasons why NTD are neglected?

Answer 1

1. Visibility (they don’t cause high rates of mortality that make good headlines) 2. Competition 3. Silent (they don’t make explosive outbreaks that make good headlines) 4. Localised 5. Affect the poor (not very attractive to pharmaceutical companies) 6. Limited resources 7. Stigma

Question 2

What are some of the NTDs in Australia? (x5)

Answer 2

 Trachoma  Soil transmitted helminths (hookworm, roundworm)  Daintree / Buruli ulcer  Leprosy  Scabies

Question 3

What is trachoma and how is it transmitted?

Answer 3

Caused by a parasite which causes recurrent inflammation and injection of the eyes. THis leads to scarring of the conjunctiva. Transmitted through person to person or flies

Question 4

What is the treatment and prevention of trachoma? (SAFE)

Answer 4

Surgery Antibiotics Facewashing Environmental changes (controlling fly populations)

Question 5

What is the Daintree ulcer?

Answer 5

Ulcer caused by micro bacteria

Question 6

What are the 4 worms/parasites we are studying this week?

Answer 6

1. Roundworm (ascaris lumbricoides) 2. Hookworm (necator americanuys and ancylostoma duodenalis) 3. Strongyloides Stercoralis 4. Pinworm (not a STH, but is the most common helminth parasite)

Question 7

Explain the life cycle of a hook worm.

Answer 7

1. Somebody who has the worm defecates eggs on the ground 2. The eggs of the worm are then present on the ground, and therefore develop into larvae 3. After 2 – 3 weeks of development through larvae stages, the larvae then penetrate intact skin of a person walking by barefoot - This can cause a skin rash where they penetrate 4. The larvae then travel via the blood stream, mature in the liver and finish up in the capillary bed of the lungs 5. They then wiggle into the alveoli, and develop further - Whilst they are here, they can cause cough and a wheeze 6. Because of the cough that they cause, they are moved up the respiratory tract, and are then swallowed entering the intestine 7. The adults live in the duodenum and lay eggs, at which point the cycle continues

Question 8

Explain the lifecycle of a roundworm

Answer 8

1. Somebody who has the worm defecates eggs on the ground
2. The eggs are then swallowed orally
   - Can be done by contaminated water
   - Contaminated food
   - Scratching your bum
3. The eggs then go into the intestine, and the larvae hatch and penetrate the intestinal mucosa
4. These then travel through the blood stream into the liver where they develop and mature
5. These then travel to the lung, and are coughed up, and then swallowed
6. Once the adults are in the intestine they produce eggs, at which point the process starts again

Question 9

What are the clinical features of hook worm and prevention mechanisms for it (x3, x2)

Answer 9

Anaemia

cough

poor growth

prevented through shoes and building toilets

Question 10

What are (x3) clinical features of round worm and x2 prevents of round worm?

Answer 10

malnutrition

cough

abdominal pain

prevented through washing food and hands

building toilets

Question 11

What is characteristic about stronglyoides and which other worm do they have the same life cycle as?

Answer 11

this worm can reinfect you after only 1 exposure - due to auto infective larvae.

same life cycle as hook worm

Question 12

Explain what pin worm is and its life cycle

Answer 12

• Is neither a STH or NTD
• It is a very common infestation, especially in children
• These move through a faecal – oral route (no soil stage)
• Adults live in the colon; the females then emerge at night to lay eggs on the peri-anal skin (which causes an itchy bum)
• The only real clinical manifestation is a rectal itch