Three weeks after a river rafting trip, three family members experienced symptoms of coughing, fever, and chest pain. During the rafting trip, the family had consumed crayfish that they caught along the river banks. An examination of the patients' sputum revealed helminth eggs, and serum samples were positive for antibodies to Paragonimus. All of the family members recovered following treatment with praziquantel. In the Paragonimus life cycle,
A) both humans and crayfish are intermediate hosts.
B) the source of the infection was the river water.
C) the crayfish are the definitive host and humans are the intermediate host.
D) both humans and crayfish are definitive hosts.
E) humans are the definitive host and crayfish are the intermediate host.

Question

Quizplus · Accepted Answer

In the Paragonimus life cycle, humans are the definitive host and crayfish are the intermediate host. The infection is caused by consuming undercooked or raw crayfish that contain infective larvae. The helminth eggs found in the patients' sputum are a result of the worms migrating from the lungs to the throat, where they are coughed up and swallowed. The positive serum samples indicate that the patients had developed antibodies to the Paragonimus worm. Treatment with praziquantel is effective against the adult worms in humans. The river water itself is not the source of infection, but rather the crayfish that live in the river and become infected with the Paragonimus larvae.

Three Weeks After a River Rafting Trip, Three Family Members