Parasitology of Guinea Worm and Trichinella

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Study Notes

Distribution: Found in areas where people use shallow ponds or open wells for drinking water.
Adult Morphology: White, smooth-surfaced. Females are very long (up to 1 meter), males die after fertilizing.
Adult Habitat: Subcutaneous tissue of lower limbs.
Larva Morphology: Large (500-700 mm), rounded anterior end, pointed tail. Can be seen coiled or uncoiled in wet preparations.
Intermediate Host: Cyclops, live in water. Humans become infected by drinking water containing infected Cyclops.

Hosts: 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: White, very small. Female: 4mm, bluntly rounded posterior end, single ovary, vulva in body half. Male: 1.5mm, curved posterior end with two lobular caudal appendages.
Adult Habitat: Small intestine.
Larva Morphology: Coiled inside lemon-shaped cysts, lie longitudinally along muscle fibers. Calcified larvae appear black.
Life Cycle: Direct life cycle. Definitive host: Pigs. Accidental host: Humans (dead end). Infective form: encysted larva in muscle, ingestion of raw or undercooked meat.

Pathology: When the female reaches the surface of the body, it releases toxic substances causing local inflammatory reaction (blister formation).
Symptoms: Blister formation, urticaria (hives), erythema (redness), vomiting, fever, secondary infections, abscesses, ulceration, necrosis, cellulitis, septicemia.

Diagnosis: Primarily during blister rupture. Larvae are usually washed into water, so lab identification is difficult.
Method: Placing water on ulcer to encourage discharge of larvae, collecting on slide for microscope examination.

Treatment: Slow process of daily gently rolling the worm around a small stick and slowly pulling it out from the skin while taking precaution not to pull apart the worm.

Symptoms: Trichinellosis. Symptoms are often mild, Severe trichinellosis cases can result in fever, chills, facial swelling, joint and muscle aches, and rash.

Methods: Muscle biopsy (direct or digestion technique), intradermal test (e.g., Bachman skin test), stool examination (to detect adult worms in diarrhea) Xenodiagnosis, serology (e.g., ELISA, Latex agglutination test).