You are in: eMedicine Specialties > Pediatrics: General Medicine > Parasitology ParagonimiasisArticle Last Updated: Mar 30, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Seth D Rosenbaum, MD, Fellow, Department of Medicine, Division of Infectious Diseases, Cooper University Hospital Seth D Rosenbaum is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, and Infectious Diseases Society of America Coauthor(s): Annette C Reboli, MD, Professor of Medicine, University of Medicine and Dentistry of New Jersey; Head, Division of Infectious Diseases, Department of Medicine, Cooper University Hospital and University Medical Center Editors: Robert W Tolan Jr, MD, Chief of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Leslie L Barton, MD, Professor, Program Director, Department of Pediatrics, University of Arizona School of Medicine; Robert W Tolan Jr, MD, Chief of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine; Russell W Steele, MD, Professor and Vice Chairman, Department of Pediatrics, Head, Division of Infectious Diseases, Louisiana State University Health Sciences Center Author and Editor Disclosure Synonyms and related keywords: Paragonimus, Paragonimus westermani, P westermani, Oriental lung fluke, parasitic infection, trematodes, paragonimiasis, inflammation of the lung INTRODUCTIONSection 2 of 11
  BackgroundTrematodes of the Paragonimus genus cause paragonimiasis, a parasitic disease that strikes carnivores, causing a subacute to chronic inflammatory disease of the lung. Of the 10 or more Paragonimus species that are human pathogens, only 8 cause significant infections in humans. The most common is the Oriental lung fluke, Paragonimus westermani. The adult trematode is reddish-brown and ovoid. Adults have 2 muscular suckers, an oral sucker situated anteriorly and a ventral sucker at mid-body on the ventral surface. The eggs, golden brown and asymmetrically ovoid, have a thick shell with an operculum. PathophysiologyThe life cycle of these flukes involves 2 intermediate hosts plus humans. Its complex life cycle involves 7 distinct phases: egg, miracidium, sporocyst, redia, cercaria, metacercaria, and adult. Adult flukes live in human lungs and deposit eggs into the bronchi. Eggs are expelled either by coughing or by being swallowed and passed in human feces. Eggs then develop in water for 2-3 weeks and ultimately release miracidia, which invade the first intermediate host, ie, a specific species of fresh water snail. These miracidia develop through sporocyst and rediae stages into cercariae. The cercariae emerge and invade the second intermediate host, ie, a crustacean such as crabs or crayfish, in which they become metacercariae. 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. Lung flukes may live 20 years or more. In Japan, transmission has also occurred following human ingestion of raw pork from wild pigs that contained the juvenile stages of Paragonimus species. FrequencyUnited StatesGenerally, small numbers of cases have occurred in immigrants from endemic areas; however, the first case of paragonimiasis was reported in the United States in 1986 in a nonimmigrant adult. It is an important infection to consider in Southeast Asians who have settled in various areas of the United States. InternationalParagonimus species are found in Asia, Africa, and Latin America. An estimated 20 million people are infected worldwide. Prevalence of infection in endemic areas ranges from 0.1-23.75%. Mortality/MorbidityDeath may occur during the acute phase of infection. For those who survive the acute phase, spontaneous recovery usually occurs within 1-2 months, but symptoms may recur intermittently over several years. Complications of untreated heavy infection include interstitial pneumonia, bronchitis, and bronchiectasis. Secondary complications may include bronchopneumonia, lung abscess, pleural effusion, or empyema. Untreated cerebral paragonimiasis has a mortality rate of approximately 5%. RaceParagonimiasis is most common in Asians, Africans, and Hispanics. SexPrevalence of infection is higher among females. An increase in infection in men, most notably those who are middle aged, because of their traditional culinary habits, has been observed in Japan. AgePrevalence reportedly increases with age to a peak prevalence in older adolescents and young adults; prevalence then declines progressively with age. By the sixth decade of life, prevalence is less than 25% of its peak in young adulthood. CLINICALSection 3 of 11
HistoryAbout 20% of patients with paragonimiasis are asymptomatic. Abdominal pain, diarrhea, and urticaria occur during the acute phase, which corresponds to the period of invasion and migration of immature flukes. These initial symptoms are followed a few days later by fever, cough, dyspnea, chest pain, malaise, and sweats. The acute phase usually persists several weeks. During the chronic phase, manifestations may be pulmonary or extrapulmonary. Chronic pulmonary symptoms consist of dry cough followed by a cough productive of tenacious and rusty or golden sputum. Pulmonary symptoms begin approximately 6 months after infection and are often mistaken for symptoms of tuberculosis (TB). Eosinophilia and lack of fever suggest the true diagnosis. Patients frequently report vague chest discomfort, dyspnea on exertion, or wheezing. Life-threatening hemoptysis may occur in some cases. Extrapulmonary paragonimiasis can be divided into cerebral, abdominal, subcutaneous, and miscellaneous forms of the disease.
PhysicalPhysical findings usually are not impressive in pulmonary paragonimiasis.
CausesAmong the factors that facilitate the life cycle of the flukes and subsequent transmission of infection to humans are (1) large numbers of reservoir and intermediate hosts, (2) behaviors such as spitting, and (3) culinary habits. In Asia, raw and undercooked crab or crayfish are popular foods. In Korea and Japan, raw crayfish are used to treat measles, diarrhea, and skin conditions. Some tribes in Africa eat raw crustaceans to cure infertility. Peruvians eat raw crab with vegetables and lemon juice. Paragonimiasis may also be acquired by consuming raw meat from a paratenic host that contains young flukes (eg, wild boar as "shashimi"). Infection may also be transmitted via contaminated kitchen utensils (eg, cutting boards, knives) or from cloths used to squeeze and strain juices from crabs for the preparation of soup. DIFFERENTIALSSection 4 of 11
Acute Respiratory Distress Syndrome Amebic Meningoencephalitis Ancylostoma Infection Ascariasis Aspergillosis Asthma Atelectasis, Pulmonary Bronchiectasis Bronchiolitis Bronchitis, Acute and Chronic Coccidioidomycosis Cutaneous Larva Migrans Cysticercosis Dracunculiasis Fascioliasis Gnathostomiasis Histoplasmosis Loffler Syndrome Meningitis, Aseptic Meningitis, Bacterial Naegleria Neurocysticercosis Nocardiosis Pleural Effusion Pneumonia Strongyloidiasis Taenia Infection Tuberculosis Whipworm
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| Drug Name | Praziquantel (Biltricide) |
|---|---|
| Description | Increases cell membrane permeability in susceptible worms, resulting in loss of intracellular calcium, massive contractions, and paralysis of musculature. Produces vacuolization and disintegration of schistosome tegument, followed by attachment of phagocytes to parasite and death. Tab should be swallowed whole with some liquid during meals. Keeping tab in mouth may reveal bitter taste, which can produce nausea or vomiting. |
| Adult Dose | 25 mg/kg PO tid for 2 d |
| Pediatric Dose | Administer as in adults |
| Contraindications | Documented hypersensitivity; ocular cysticercosis |
| Interactions | Hydantoins may reduce serum praziquantel concentrations, possibly leading to treatment failures |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Destruction of parasite within eyes can cause irreparable lesions (do not treat ocular cysticercosis with praziquantel); caution while driving or performing other tasks requiring alertness on day of and day following treatment; minimal increases in liver enzymes reported; when schistosomiasis or fluke infection associated with cerebral cysticercosis occurs, hospitalize patient for duration of treatment; use during pregnancy only if clearly indicated; do not breastfeed during or 72 h after treatment; seizures and coma have been observed because of an inflammatory reaction that accompanies worm death (add corticosteroids when treating cerebral paragonimiasis to reduce this reaction); frequent adverse effects include abdominal pain, diarrhea, malaise, dizziness, and headache; other adverse effects include fever, nausea, rash, and pruritus |
| Media file 1: This micrograph depicts an egg from the trematode parasite Paragonimus westermani.Eggs range in size from 68µm-118µm x 39µm-67µm. They are yellow-brown, ovoidal or elongated, with a thick shell, and often asymmetrical with one end slightly flattened. At the large end, the operculum, i.e., lid or covering is visible.(Photo courtesy of Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases, Atlanta, GA, [http://www.dpd.cdc.gov/dpdx/HTML/Paragonimiasis.htm]) | |
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| Media file 2: This is an illustration of the life cycle of Paragonimus westermani, one of the causal agents of paragonimiasis.(Photo courtesy of Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division of Parasitic Diseases, Atlanta, GA, [http://www.dpd.cdc.gov/dpdx/HTML/Paragonimiasis.htm]) | |
 | View Full Size Image | Media type: Image |
Article Last Updated: Mar 30, 2006
