IPIL, Zamboanga Sibugayโ Freshwater crabs collected in Davao Oriental, Mindanao were recently found to carry DNA of a lung-fluke parasite (Paragonimus westermani), according to researchers with the Philippine Genome Center โ Mindanao.
The discovery raises concerns about a neglected foodborne infection that can affect humans who consume undercooked or raw freshwater crustaceans.
What is a Lung-Fluke Parasite?
Paragonimus species are parasitic flatworms commonly known as lung flukes. The most widespread species in Asia is Paragonimus westermani, which also occurs in the Philippines. Humans become infected when they eat freshwater crabs or crayfish carrying the parasiteโs infective larvae, called metacercariae.
Once ingested, these larvae excyst in the intestine, penetrate the gut wall, migrate through the diaphragm and settle in the lungs, where they mature into adult worms.
Why It Matters
The infection caused by these parasites is called paragonimiasis. Its hallmark signs often resemble tuberculosis (TB) โ including chronic cough, chest pain, and coughing up blood-tinged sputum. These symptoms can lead to misdiagnosis and inappropriate treatment.
Other symptoms may include fever, fatigue, abdominal pain, and difficulty breathing. In rare cases, the parasite can migrate to other organs like the brain, causing neurological symptoms.
Paragonimiasis is considered a neglected tropical disease (NTD). Meaning, it disproportionately affects rural and underserved communities where freshwater crustaceans form part of local diets and access to diagnostic services is limited.
How People Get the Infection
Transmission only occurs through ingestion of infected crustaceans that are raw, undercooked, pickled, or salted. It isย not through drinking water or casual contact. Cooking crabs and crayfish thoroughly kills the parasite and prevents infection.
Localized reports in parts of the country โ such as warnings issued by the Department of Health in Bicol โ have urged communities to avoid eating raw or undercooked crabs and crayfish. But public awareness remains uneven.
Health officials have highlighted that paragonimiasis is often mistaken for TB, delaying proper diagnosis and care.
The recent finding in Mindanao underscores the need for public education on safe food practices, improved surveillance, and better access to diagnostic and treatment services in rural areas.
Prevention and Treatment
โ๏ธ Cook freshwater crabs and crayfish thoroughly โ no raw or undercooked dishes.
โ๏ธ Seek medical care if symptoms like chronic cough or blood-tinged sputum develop, especially with a history of eating freshwater crabs.
โ๏ธ Diagnosis involves identifying parasite eggs in sputum or stool samples; serologic tests may assist in early detection.
โ๏ธ Treatment with antiparasitic medications such as praziquantel is effective when administered by a healthcare provider.
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