Laboratory Diagnostics of Paragonimus westermani and Treatment

Paragonimus westermani MLTGEEKS

Paragonimus is a lung fluke (flatworm) that infects the lungs of humans after eating an infected raw or undercooked crab or crayfish. Less frequent, but more serious cases of paragonimiasis occur when the parasite travels to the central nervous system.Although rare, paragonimiasis has been acquired in the United States, with multiple cases reported from the Midwest and an extensively distributed in the Far East, and focally in West African countries such as Zaire, Nigeria, Cameroon and also in South America.

Habitat of lung fluke

  • The adult flatworm lives In the lung of human while
  • The eggs are found in the sputum of man
  • Metacercariae are found in freshwater crabs and crayfish

Morphology of Paragonimus westermani worm

Adult Worm

  • It has a size of  7.5mm-12mm by 4-6mm (1 by 0.7cm)  and is reddish-brown in color
  • The worm resembles one half of a pea with integument covered with toothed spines which are similar to the other adult trematodes.
Adult paragonimus westermani worm
Adult paragonimus westermani worm


  • The average egg of Paragonimus westermani ranges from 78 to 120 µm by 45 to 60 µm in size.
  • The oval egg consists of an undeveloped miracidium which are  protected by a thin smooth shell.
  • It  has a flat opercular rim (shoulders) surrounds the prominent operculum and a terminal shell thickening  located on the end opposite the operculum.
  • In terms of operculum,Paragonimus eggs should not be confused to Diphyllobothrium latum egg though they are similar in morphology, Paragonimus westermani lack opercular shoulders and are more rounded in shape
  • Diphyllobothrium latum eggs also has an abopercular knob which is not found in in Paragonimus westermani therefore
  • Size is also helpful in distinguishing the two eggs in stool specimens.
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paragonimus westermani Operculated Egg

paragonimus westermani Operculated Egg

Life Cycle of Paragonimus westermani

Paragonimus westermani is transmitted in undercooked crayfish or crabs. On ingestion of these freshwater products, the immature flukes  which often occurs in pairs are released into the body.

They then migrate through the intestinal wall, through the peritoneal cavity, into the diaphragm, and finally into lung tissue where their encystation occurs.

Migration of immature flukes to other areas of the body, such as the brain or liver, has been known to take place

Life cycle of paragonimus westermani
Life cycle of paragonimus westermani

Clinical Symptoms of Paragonimus westermani

Paragonimus westermani causes a diseases known as Paragonimiasis

Paragonimiasis  also known as Pulmonary Distomiasis as the common name oriental lung fluke suggests.Patients infected with Paragonimus typically experience the following symptoms associated with pulmonary discomfort

  • Cough
  • Fever
  • chest pain
  • increased production of blood-tinged sputum.
  • chronic bronchitis
  • Eosinophilia and also the production of fibrous tissue.

Symptoms paragonimiasis often mimic those seen in persons infected with tuberculosis. Those patients who develop infections in areas other than the lung also experience symptoms corresponding to the affected organ or tissue and one of these area is the brain causing cerebral paragonimiasis.This is the migration of immature Paragonimus westermani to the brain  which may result in the development of a serious neurologic condition like

  • Seizures
  • visual difficulties
  • decreased precision of motor skills.

Laboratory Diagnosis of paragonimus westermani

  • Diagnosis of these lungs fluke  is accomplished by the recovery of eggs in sputum specimens mixed with blood (Haemoptysis).
  • The eggs are commonly found in sample containing blood like blood in sputum lung cancer
  • Occasionally, the eggs may be seen in stool (stool o&p) samples when sputum is swallowed.
  • Serologic tests like immunoblot,Eliza  which measure the serum levels of anti-Paragonimus antibody have been developed for this diagnosis
Also read  Loa Loa Filariasis Laboratory diagnosis and treatment

fluke worm treatment or fluke treatment

  • The drug or medication of choice is Praziquantel for the treatment of Paragonimus.
  • Bithionol is also an acceptable alternative drug for paragonimiasis
praziquantel tablet
praziquantel tablet

Prevention and Control

The primary prevention and control measures for the eradication of these lung flukes Paragonimus include

  • Avoiding human ingestion of undercooked crayfish and crabs
  • Practising proper disposal of human waste products.
  • Avoid using faeces as fertilizer mostly in tropical and underdeveloped countries
  • Main good sanitation

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About the Author: Arthur Westmann

DEFFE ARTHUR (AMOEBAMANN) is the founder and author of MLTGEEKS and MLTEXPO.He’s from Cameroon and is currently a Final year State Medical Laboratory Technician (MLT MA). Beyond lab works, he’s a passionate internet user with a keen interest in web design and blogging. Furthermore He likes traveling, hanging around with friends and social networking to do in his spare time.

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