Extra-pulmonary infection is due to migration of the young worms away from the normal route to the lungs. In such case, any other part of the body can be infected. Cutaneous paragonimiasis is common in children and is generally indicated by skin nodules that move from one place to another. Cerebral paragonimias is most severe extra-pulmonary symptoms that affect the brain and leads to seizure, headache, visual disturbance, and motor and sensory disturbances.The acute phase (invasion and migration) may be marked by diarrhea, abdominal pain, fever, cough, urticaria, hepatosplenomegaly, pulmonary abnormalities, and eosinophilia. During the chronic phase, pulmonary manifestations include cough, expectoration of discolored sputum containing clumps of eggs, hemoptysis, and chest radiographic abnormalities. Extrapulmonary locations of the adult worms result in more severe manifestations, especially when the brain is involved. Diagnosis is based on microscopic demonstration of eggs in stool or sputum, but these are not present until 2 to 3 months after infection. (Eggs are also occasionally encountered in effusion fluid or biopsy material.) Concentration techniques may be necessary in patients with light infections. Biopsy may allow diagnostic confirmation and species identification when an adult or developing fluke is recovered.Diagnosis is done by microscopic examination of sputum and stool samples, and presence of the eggs is a confirmation. However, eggs are not always to be found. In such case, serological tests based on antibody detection using ELISA is a better method. A more arduous method like immunoblotting is also used.
Paragonimiasis is a food-borne parasitic disease caused by several species of lung flukes belonging to genus Paragonimus. Infection is acquired by eating crustaceans such as crabs and crayfishes which host the infective forms called metacercariae, or by eating raw or undercooked meat of mammals harboring the metacercariae from crustaceans.More than 40 species of Paragonimus have been identified; 10 of these are known to cause disease in humans. The most common cause of human paragonimiasis is P. westermani, the oriental lung fluke.About 22 million people are estimated to be affected yearly worldwide. It is particularly common in East Asia. Paragonimiasis is easily mistaken for other diseases with which it shares clinical symptoms, such as tuberculosis and lung cancer. Life cycle
Not all Paragonimus species infect humans. However, all of them target mammals as their final (definitive) hosts. In mammalian lung tissue, the adult flukes live as encapsulated pairs. As hermaphrodites, they produce and fertilise their own eggs that are released through the respiratory tract. The eggs are excreted to the environment either through the sputum or swallowed and passed out along the faeces.In the external environment, the eggs remain unembryonated until ideal conditions of temperature and humidity are encountered. Then, they embryonate and develop into ciliated larvae called miracidia. As the egg shells disintegrate, the motile miracidia hatch and swim to seek the first intermediate host, a snail, and penetrate its soft tissues.