Trematode - Paragonimus westermani (Lung Fluke)
Lung fluke: Paragonimus westermani
- Ingested with raw or undercooked crustaceans, such as crabs.
- Early infection can produce gastrointestinal symptoms and fever.
- Later, pulmonary symptoms can develop, and include cough with blood, chest pain, cavitation, bronchitis, fibrosis, and other compilations that impair respiration.
- These worms can also invade the central nervous system (cerebral paragonimiasis) and other organs.
Life Cycle:
1. Miracidia invade snail.
2. Miracidia give rise to cercariae, which exit the snail.
3. Cercariae invade crustaceans (crab or crayfish, the second intermediate host) and become encysted (metacercariae).
4. Human eats undercooked infected crab and metacercariae.
5. Metacercariae excyst in duodenum, moves through intestinal wall and migrates to lungs.
– In the lungs, they become adults and lay eggs via self-fertilization. They can also travel to other tissues, including the brain.
6. Eggs are coughed up in sputum or coughed, swallowed, and excreted in feces.
7. Eggs release miracidia.
Image Credits:
https://www.cdc.gov/dpdx/paragonimiasis/index.html