Paragonimus westermani

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Paragonimus westermani

Text of Paragonimus westermani


2. HISTORY Most discoveries made between 1874-1918 Discovered in Brazil in 1850 by Diesing First described in Bengal tigers housed in zoos inHamburg and Amsterdam in 1877 Coenraad Kerbert named the parasite after themanager of the zoo G.F WestermanDR.T.V.RAO MD2 3. CONTINUED Sidney Ringer discovered the parasite in a human in aPortuguese man during an autopsy in 1879 Rudolf Luekart found that the parasite found in the tiger is thesame as the parasite that caused hemoptysis in Formosa andJapan 1916-1922 Japanese workers discovered the life cycle in thesnail Nine cases of paragonimiasis have been encountered inLaotian Hmong immigrants from Camp Ban Vinai in Thailand 12 Human infestations were described later in Asia DR.T.V.RAO MD 3 4. GEOGRAPHIC DISTRIBUTION P. westermani infections occur in limited areaswhere local people eat improperly cookedcrustaceans. P. westermani occurs in the Far Eastspecifically in the countries of Korea, Japan,China, Taiwan, far-east Russia, Malaysia, India,the Philippines, and Indonesia. Other species of Paragonimus are encounteredin Asia, the Americas, and Africa.DR.T.V.RAO MD4 5. INTRODUCTION Agent: Paragonimus westermani also known as theoriental lung fluke. Disease: Paragonimiasis More than 30 species of trematodes (flukes) of thegenus Paragonimus have been reported to infectanimals and humans. Among them, more than 10species are reported to infect humans, the mostcommon is P. westermani.DR.T.V.RAO MD5 6. TRANSMISSION Eating raw, undercooked orpickled crustaceans such ascrab or crayfish Spitting, a habit in asiancountries Cultures that eat rawcrustaceans Drunken Crab in China Raw Crab or Crayfish andalcohol in The Philippines Gye Muchim in Korea Sushi crab, ama ebi and odoriin JapanDR.T.V.RAO MD 6 7. LIFE CYCLE1. Infective stage: Metacercariae2. Infective mode: eating raw fresh water crabs and crayfish with metacercariae3. Infective route: by mouth4. Site of inhabitation: lungs5. 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 etc7. Life span: 5-6 years DR.T.V.RAO MD7 8. DR.T.V.RAO MD 8 9. DR.T.V.RAO MD 9 10. MORPHOLOGY The living adult worms are a pinkish-brown colour andbean shaped (7 to 15 mm in length to 8 mm in width,and 3 to 5 mm in thickness). It contains a characteristicovary in the middle of the worm. The golden brown colored immature eggs areapproximately 45-60 m by 80-100 m. The metacercariae in the second intermediate host arespherical in shape measuring 220-450 m.DR.T.V.RAO MD 10 11. HOW THE EGGS APPEAR The oval ova havean operculum andare 80-110 by 48-80m. It is goldenyellow in color. Theshell is uneven inthickness. Thecontent is an ovumand more than 10DR.T.V.RAO MDyolk cells.11 12. MORPHOLOGY OF EGGSThe egg form leaves the definitive The adult fluke is found inhost and hatches in the miracidium its mammalian host.that penestrates the snail. DR.T.V.RAO MD 12 13. METACERCARIAE AND CERCARIAThe metacercaria is the form The cercaria is the form thatingested by humans.penetrates the crab.DR.T.V.RAO MD13 14. INTERMEDIATE HOSTS The eggs are passed in sputum or feces. The eggs flow downstream and have a small chance of survival but this isoffset by the fact that the eggs are produced in large numbers. The miracidium hatches and penetrates its first intermediate host a snail inthe family of Thieridae. In the snail, the miracidium forms a sporocyst that produces rediae, which inturn develop many cercariae. The cercariae are spined with knoblike tails and minute oral stylets. It iscapable of creeping over rocks in inchworm fashion. It enters its second intermediate host of a crab or crayfish. There are at least11 different species it infects. Also, there is some evidence that the crabscan be infected by eating snails. Once in the crab, they encyst in the muscles and viscera. DR.T.V.RAO MD14 15. DEFINITIVE HOST The last stage of the parasites developmentis fulfilled when a mammalian host ingestsan infected crab. Specifically humans, pigs, dogs, and avariety of feline species. Infections of P. westermani can persist inhumans for up to 20 years!DR.T.V.RAO MD15 16. PATHOPHYSIOLOGY When humans ingest raw infected crustaceans, larval flukesdevelop in the small intestine, penetrate the intestinal wall intothe peritoneal cavity 30 minutes to 48 hours after excysting.They then migrate into the abdominal wall or liver, where theyundergo further development. Approximately 1 week later, adultflukes reenter from the abdominal cavity and penetrate thediaphragm to reach the pleural space and lungs. Flukes mature,a fibrous cyst wall develops around them, and then eggdeposition starts 5-6 weeks after infection. The symptoms of the early stages of this disease appear to befew with some people beingDR.T.V.RAO MD16 17. 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 byinfection of the heart. Cerebral cases result in cerebral cysticercosis (condition in which fluid-filled cysts surrounding theworm are present). DR.T.V.RAO MD 17 18. DIAGNOSIS1. Sputum examination: (1) Alkali digestive method (10%NaOH), (2) Direct sputum smear2. Stool examination: (1) Alkali digestion , (2) Watersedimentation method, (3) Direct fecal smear3. Biopsy for Subcutaneous type4. CT for brain type5. Immunological tests for reference. 19. DIAGNOSIS The adult worms can be discovered during surgery orbiopsy. However, it is usually through microscopic examinationof the characteristic eggs present in sputum, aspiredpleural fluid, feces, and matter of ulcers caused by theparasite. The eggs may not be present in these sources until 2 to3 months after infection. X-ray examination of a pulmonary infection may bemistaken for tuberculosis, pneumonia, spirochatosis,etcDR.T.V.RAO MD19 20. DIAGNOSIS Cerebral involvement requires differentiation from tumors,cysticercosis, cysts, encephalitis, and others. Since egg detection rates are low, it would be useful to utilizeserological techniques to detect Paragonimus antibodies. ELISA serological tests are highly sensitive at >92% detection. Intradermal skin tests performed with an extract of adultParagonimus is sensitive and has few false positives. Theresults of the skin test may remain positive for up to 20 yearsafter 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.DR.T.V.RAO MD 20 21. TREATMENT Praziquantel-Oral, causes severespasms and paralysis of the wormsmuscles 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 DR.T.V.RAO MD21 22. TREATMENT Extrapulmonary lesions may need to besurgically excised. Intraventricular shunts may also be needed tomanage hydrocephalus. Therapy may also be required for seizurescaused by an inflammatory reaction to dyingworms in the brain.DR.T.V.RAO MD 22 23. COMPLICATIONS Pulmonary complications include pneumonia,bronchitis, bronchiectasis (bronchial dilation),lung abscess, pleural effusion, and empyema(pus in the plural cavity). Cerebral complications include seizures andcoma. Skin complications include migratory allergicskin lesions.DR.T.V.RAO MD23 24. 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 DR.T.V.RAO MD24 25. EPIDEMIOLOGY It is estimated that 20 million are infected withParagonimus westermani It is endemic in China, Korea, Japan, the Philippines, andTaiwan Japan, Korea, Formosa, China, Manchuria, the PhilippineIslands and India Infection is also found in parts of tropical West Africa,from the Congo and Nigeria, especially from SouthernCameron Rare in the US but it is found in Missouri DR.T.V.RAO MD25 26. Programme Created by Dr.T.V.Rao MDfor Medical and Paramedical Students in the Developing World Email doctortvrao@gmail.comDR.T.V.RAO MD 26