Paragonimus species, a parasitic lung fluke (flat worm). More than 30 species of trematodes (flukes) of the genus Paragonimus have been reported which can infect animals and humans; the most important is Paragonimus westermani, which occurs primarily in Asia. Although rare, human paragonimiasis from Paragonimus kellicotti has been acquired in the United States.
Transmission occurs through consumption of raw, salted, pickled, or partially cooked freshwater crabs or crayfish (crawfish) containing infectious larvae (metacercariae). The larvae are released when the crab or crayfish is digested and they migrate within the body, most often ending up in the lungs. Infection can also be acquired by ingestion of raw meat from other infected vertebrae hosts that contain young flukes (e.g., wild boars). Transmission has also been implicated from contaminated utensils, such as knives or cutting boards. Infection is not transmitted directly from person to person.
Initial signs and symptoms may be diarrhea and abdominal pain followed several days later by fever, chest pain, and fatigue. The symptoms may also include a dry cough, which later becomes productive with rusty-colored or blood-tinged sputum on exertion, and pleuritic chest pain. Extrapulmonary disease is not uncommon, with flukes found in such sites as the CNS, subcutaneous tissues, intestinal wall, peritoneal cavity, liver, lymph nodes and genitourinary tract. Infection usually lasts for years, and the infected person may be asymptomatic. The symptoms of paragonimiasis can be similar to those of tuberculosis, clinically and on chest X-rays.
- Routine hand washing with soap and warm water.
- Never eat raw freshwater crabs or crayfish. Cook crabs and crayfish to at least 145°F (~63°C).
- Travelers should be advised to avoid traditional meals containing undercooked freshwater crustaceans.
School Exclusion Policy
Children with confirmed paragonimiasis should be kept out of school or childcare until they are diarrhea and fever-free. Rules for exclusion of sick children from school and childcare are outlined in the Texas Administrative Code, specifically Rule 97.7 for schools and Rule 746.3603 for childcare.
Recent Texas Trends
Paragonimiasis became a notifiable condition in Texas in 2016. There have been no cases reported in Texas from 2016 through 2020.