Clinical Testing and Diagnosis for Paragonimiasis

Considerations

The clinical picture of chronic paragonimiasis resembles chronic bronchitis or tuberculosis. Patients may cough up coffee-colored or blood-tinged sputum, often accompanied by chest pain and/or shortness of breath. The sputum may be peppered consisting of clumps of eggs produced by the adult fluke living in the lung.

Peripheral eosinophilia is common and can be intense, especially during the early larval migration stages. Many patients have a spectrum of abnormalities on chest radiographs: lobar infiltrates, coin lesions, cavities, calcified nodules, hilar enlargement, pleural thickening and effusions. Ring-shaped opacities of contiguous cavities giving the characteristic appearance of a bunch of grapes are highly suggestive of pulmonary paragonimiasis. Central nervous system disease may provide similar "grapebunch" findings, characteristically seen in the temporal and occipital lobes on computed tomography of the brain. CNS involvement occurs in up to 25% of hospitalized patients and may be associated with Paragonimus-induced meningitis. CNS symptoms may include headaches, seizures, and visual disturbances. Paragonimus flukes may also invade the liver, spleen, intestinal wall, peritoneum, and abdominal lymph nodes.

Ectopic lesions from aberrant migration of flukes can involve any organ, including abdominal viscera, the heart, and the mediastinum. The infection can also affect the liver, spleen, abdomen, and skin. The most clinically recognizable ectopic lesions arise from cerebral paragonimiasis, which, in highly endemic countries, more commonly affects children. These children present with eosinophilic meningoencephalitis, seizures, or signs of space-occupying lesions. Many patients with central nervous system disease also have pulmonary infections. P. skrjabini often produces skin nodules, subcutaneous abscesses, or a type of creeping eruption known as "trematode larva migrans."

Testing for Paragonimus

Sputum examined microscopically may reveal Paragonimus eggs released by the flukes in the lungs. Keep in mind that the acid-fast stain that is used for TB testing of sputum destroys eggs. The eggs may also be found by multiple stool exams on different days as a result of coughed-up eggs that are swallowed. The microscopic eggs are yellowish brown, 80 – 120 µm long by 45 – 70 µm wide, thick-shelled, and with an obvious operculum. Serologic tests can be especially useful for early infections (prior to maturation of flukes) or for ectopic infections where eggs are not passed in stool.