Intestinal naematodes

Question 1

Pinworm life cycle

Answer 1

•	Eggs ingested
•	Larvae to ileum → molt x2
•	Adults in caecum 2-13 wks 
→ 11 000 eggs/d
•	Eggs perianal area
•	Egg maturation 4-6h in oxygen

Question 2

Pinworm organism

Answer 2

Enterobius vermicularis

Question 3

Trichuris trichiura life cycle

Answer 3

• Eggs ingested
• Larvae invade intestinal mucosa crypts → molt over 3/12
• Adults in caecum & colon 2-13 wks → 11 000 eggs/d
• Eggs in stool after 2-3 mths
• Egg maturation 2-4 wks moist soil

Question 4

Whipworm organism

Answer 4

Trichuris trichiura

Question 5

Causes of pulmonary eosinophilia

Answer 5

Schistosomiasis
Hookworm
Ascaris lumbricoides

Question 6

Acaris lumbricoides life cycle

Answer 6

• Eggs ingested
• Larvae hatch & moult in bowel → migrate over 4-7 d via bloodstream to lungs
= Loeffler’s syndrome (pulmonary eosinophilia)
• Larvae ascend airways to glottis → swallowed → dev into adults
• Adults live 1-2 yrs, lay up to 200 000 eggs/d
• Eggs in stool after 2 mths
• Egg maturation 2-4 wks moist soil; remain infective for many years

Question 7

Hookworm life cycle

Answer 7

• Filariform larvae penetrate skin
• Larvae migrate to lungs, ascend to pharynx, swallowed
• Adults live 1-0yrs in bowel, taking 0.03-0.2ml blood/d
• Eggs in stool 2 months after infection
• Rhabditiform larvae develop over 7d in soil → infective 3rd stage filariform larvae

Question 8

Hookworm organisms

Answer 8

Necator americanus

ancylostoma duodenale

Question 9

Measuring impact of antihelminths

Answer 9

1. Reduction in worm burden
   a) reduction in prevalence (CR - cure rate)
   b) reduction in eggs/gram (ERR - egg reduction rate)
2. reduction in proportion ‘heavily’ infected
   - reduces morbidity in community
   - reduces # eggs contaminating env to decrease transmission

Question 10

Major global helminthic disease control initiatives

Answer 10

LF - DEC & albendazole
    - ivermectin & albendazole
Onchocerciasis - ivermectin
Schistosomiasis - praziquantel
STH infections - albend & mebendazole
Ascariasis, trichuriasis, hookworm, schisto, LF, oncho & trachoma - Ivermectin/DEC, praziquantel, alb/meb & azithromycin

Question 11

Ascaris (key points)

Answer 11

large, physical obstruction, migration, malnutrition, many eggs

Question 12

Hookworm (key points)

Answer 12

penetrates skin, anaemia

Question 13

Trichurias (key points)

Answer 13

+/- rectal prolapse
failure to thrive
clubbing

Question 14

Strongyloides treatment

Answer 14

Ivermectin (1-2 doses)

Albendazole 800mg 7/7 clear second line

Question 15

Strongyloides infectious stage

Answer 15

Filariform larvae (L3) through skin penetration / autoinfection thru perianal skin/bowel mucosa)

Question 16

Strongyloides hyperinfection associations

Answer 16

CCSs, immunosuppressives
HTLV-1
Malnutrition (esp <10)
Malignancy

Question 17

Is strongyloides hyperinfection associated with HIV?

Answer 17

No