Guinea Worm Infection Quiz

Study Notes

Distribution: Found in areas where communities use shallow ponds or open wells for drinking water
Adult Morphology: White, smooth surface; female is very long (up to one meter), male dies after fertilizing female
Habitat: Subcutaneous tissue of lower limbs
Larva: Large (500-700mm), rounded anterior end, pointed tail. Can be seen coiled or uncoiled in wet preparations.
Intermediate Host: Cyclops, live in water. Infection occurs when humans drink water containing these infected copepods.
Life Cycle: Larvae penetrate the host's stomach and intestinal wall, mature, and reproduce. Fertilized female worm emerges from skin after one year. L1 larvae are released into water from the emerging female.
Pathology and Symptoms:
- Inflammatory reaction (blister) at skin site when female emerges.
- Secondary infections (abscesses, ulceration, necrosis, cellulitis, septicemia) can occur when blisters contact cold water and rupture
- Other symptoms: urticaria, erythema, vomiting, fever
Diagnosis:
- Difficult: larvae often washed away into water
- Diagnosis is usually made when blister ruptures, exposing the anterior end of the female
- Can also use a few drops of water on ulcer to encourage larva discharge and examine it microscopically.
Treatment: Carefully roll the worm around a stick and slowly pull it out of the skin

Species:
- T. spiralis: Infects domestic pigs, rats, cats, and dogs
- T. nativa: Infects all carnivores
- T. nelsoni: Infects carnivores and wild pigs
Distribution: Africa, Asia, and America
Adult Morphology:
- Female: White, very small (4mm long), bluntly rounded posterior end, single ovary opening halfway down the body.
- Male: Small (1.5mm), curved posterior end, lobular appendages
Habitat: Small intestine
Larva: Coiled within lemon-shaped cysts, lie longitudinally along muscle fibres. Calcified larvae appear black.
Life Cycle:
- Direct life cycle: Definitive host is pigs; accidental host (dead end) is humans.
- Infective form: Encysted larvae in muscle
- Infection: Ingestion of raw or undercooked infected meat containing encysted larvae (L1).
Pathology and Symptoms: Typically mild; severe cases can cause: fever, chills, facial swelling, joint and muscle aches, rash
Diagnosis:
- Muscle biopsy (direct or digestion technique)
- Intra-dermal tests, Bachmann skin test
- Stool examination (adult presence in severe diarrhea)
- Xenodiagnosis
- Serology (ELISA, Latex agglutination test)