DR.T.V.RAO MD 1

PARAGONIMUS WESTERMANIDR.T.V.RAO MD

DR.T.V.RAO MD 2

HISTORY• Most discoveries

made between

1874-1918

• Discovered in Brazil

in 1850 by Diesing

• First described in Bengal tigers housed in zoos in Hamburg and Amsterdam in 1877

• Coenraad Kerbert named the parasite after the manager of the zoo G.F Westerman

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CONTINUED• Sidney Ringer discovered the parasite in a human in a

Portuguese man during an autopsy in 1879• Rudolf Luekart found that the parasite found in the tiger is the

same as the parasite that caused hemoptysis in Formosa and Japan

• 1916-1922 Japanese workers discovered the life cycle in the snail

• Nine cases of paragonimiasis have been encountered in Laotian Hmong immigrants from Camp Ban Vinai in Thailand

• 12 Human infestations were described later in Asia

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GEOGRAPHIC DISTRIBUTION • P. westermani infections occur in limited areas

where local people eat improperly cooked crustaceans.

• P. westermani occurs in the Far East specifically in the countries of Korea, Japan, China, Taiwan, far-east Russia, Malaysia, India, the Philippines, and Indonesia.

• Other species of Paragonimus are encountered in Asia, the Americas, and Africa.

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INTRODUCTION • Agent: Paragonimus westermani also known as the

oriental lung fluke.

• Disease: Paragonimiasis

• More than 30 species of trematodes (flukes) of the genus Paragonimus have been reported to infect animals and humans. Among them, more than 10 species are reported to infect humans, the most common is P. westermani.

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• Eating raw, undercooked or pickled crustaceans such as crab or crayfish

• Spitting, a habit in asian countries

• Cultures that eat raw crustaceans• Drunken Crab in China

• Raw Crab or Crayfish and alcohol in The Philippines

• Gye Muchim in Korea

• Sushi crab, ama ebi and odori in Japan

TRANSMISSION

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LIFE CYCLE 1. Infective stage: Metacercariae

2. Infective mode: eating raw fresh water crabs and crayfish with metacercariae

3. Infective route: by mouth

4. Site of inhabitation: lungs

5. Intermediate hosts: 1st int. host is melania snail. 2nd int. hosts are crab and crayfish.

6. Reservoir hosts: carnivores such as tiger, lion, wolf, fox, dog, leopard, cat and etc

7. Life span: 5-6 years

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MORPHOLOGY• The living adult worms are a pinkish-brown colour and

bean shaped (7 to 15 mm in length to 8 mm in width, and 3 to 5 mm in thickness). It contains a characteristic ovary in the middle of the worm.

• The golden brown colored immature eggs are approximately 45-60 μm by 80-100 μm.

• The metacercariae in the second intermediate host are spherical in shape measuring 220-450 μm.

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• The oval ova have an operculum and are 80-110 by 48-80 µm. It is golden yellow in color. The shell is uneven in thickness. The content is an ovum and more than 10 yolk cells.

HOW THE EGGS APPEAR

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MORPHOLOGY OF EGGS

The egg form leaves the definitive host and hatches in the miracidium that penestrates the snail.

The adult fluke is found in its mammalian host.

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METACERCARIAE AND CERCARIA

The metacercaria is the form ingested by humans.

The cercaria is the form that penetrates the crab.

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INTERMEDIATE HOSTS• The eggs are passed in sputum or feces.

• The eggs flow downstream and have a small chance of survival but this is offset by the fact that the eggs are produced in large numbers.

• The miracidium hatches and penetrates its first intermediate host a snail in the family of Thieridae.

• In the snail, the miracidium forms a sporocyst that produces rediae, which in turn develop many cercariae.

• The cercariae are spined with knoblike tails and minute oral stylets. It is capable of creeping over rocks in inchworm fashion.

• It enters its second intermediate host of a crab or crayfish. There are at least 11 different species it infects. Also, there is some evidence that the crabs can be infected by eating snails.

• Once in the crab, they encyst in the muscles and viscera.

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DEFINITIVE HOST• The last stage of the parasites development

is fulfilled when a mammalian host ingests an infected crab.

• Specifically humans, pigs, dogs, and a variety of feline species.

• Infections of P. westermani can persist in humans for up to 20 years!

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PATHOPHYSIOLOGY• When humans ingest raw infected crustaceans, larval flukes

develop in the small intestine, penetrate the intestinal wall into the peritoneal cavity 30 minutes to 48 hours after excysting. They then migrate into the abdominal wall or liver, where they undergo further development. Approximately 1 week later, adult flukes reenter from the abdominal cavity and penetrate the diaphragm to reach the pleural space and lungs. Flukes mature, a fibrous cyst wall develops around them, and then egg deposition starts 5-6 weeks after infection.

• The symptoms of the early stages of this disease appear to be few with some people being

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PATHOPHYSIOLOGYOnce the parasite is in the lung or another organ, the

worm stimulates an inflammatory response that eventually coats tissue.

If worms enter the CSF of the spinal cord, it can result in partial or total paralysis.

There have also been fatal cases of Paragonimiasis by infection of the heart.

Cerebral cases result in cerebral cysticercosis (condition in which fluid-filled cysts surrounding the

worm are present).

DIAGNOSIS 1. Sputum examination: (1) Alkali digestive method

(10%NaOH), (2) Direct sputum smear

2. Stool examination: (1) Alkali digestion , (2) Water

sedimentation method, (3) Direct fecal smear

3.  Biopsy for Subcutaneous type

4.  CT for brain type

5.  Immunological tests for reference.

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DIAGNOSIS• The adult worms can be discovered during surgery or

biopsy.

• However, it is usually through microscopic examination of the characteristic eggs present in sputum, aspired pleural fluid, feces, and matter of ulcers caused by the parasite.

• The eggs may not be present in these sources until 2 to 3 months after infection.

• X-ray examination of a pulmonary infection may be mistaken for tuberculosis, pneumonia, spirochatosis, etc

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DIAGNOSIS• Cerebral involvement requires differentiation from tumors,

cysticercosis, cysts, encephalitis, and others.

• Since egg detection rates are low, it would be useful to utilize serological techniques to detect Paragonimus antibodies.

• ELISA serological tests are highly sensitive at >92% detection.

• Intradermal skin tests performed with an extract of adult Paragonimus is sensitive and has few false positives. The results of the skin test may remain positive for up to 20 years after the infection has been cured.

• An assay that detects worm antigens with monoclonal antibodies is also available and can be used in conjunction with the intradermal skin test.

TREATMENT• Praziquantel-Oral, causes severe

spasms and paralysis of the worms' muscles• Not for pregnant women

• Stomach pains, dizziness, fever, nausea, vomiting, headache

• Better tolerated than Bithionel

• Bithionol• Diarrhea, use is limited due to side effects

• Triclabendazole• Can cure cases other drugs failed

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TREATMENT• Extrapulmonary lesions may need to be

surgically excised.

• Intraventricular shunts may also be needed to manage hydrocephalus.

• Therapy may also be required for seizures caused by an inflammatory reaction to dying worms in the brain.

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COMPLICATIONS• Pulmonary complications include pneumonia,

bronchitis, bronchiectasis (bronchial dilation), lung abscess, pleural effusion, and empyema (pus in the plural cavity).

• Cerebral complications include seizures and coma.

• Skin complications include migratory allergic skin lesions.

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PREVENTION• Fully cook shellfish

• Heat water to 55oC for 5 minutes

• Freeze Fish

• -20 C for 7 days

• -35 C for 15 hours

• Make spitting illegal

• Use Moluskicide to control snail population

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EPIDEMIOLOGY • It is estimated that 20 million are infected with

Paragonimus westermani• It is endemic in China, Korea, Japan, the Philippines, and

Taiwan• Japan, Korea, Formosa, China, Manchuria, the Philippine

Islands and India• Infection is also found in parts of tropical West Africa,

from the Congo and Nigeria, especially from Southern Cameron

• Rare in the US but it is found in Missouri

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• Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in

the Developing World

• Email• doctortvrao@gmail.com