Chapter 56 Paragonimiasis Lung Fluke Kimberly Hayden Biol 423 SP 2010 General Characteristics Class: Trematodes Red/Brown short, leaf-like worm Bilateral symmetry Operculated eggs -golden brown Discovery (2010) Morphology Two suckers: oral and ventral
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Red/Brown short, leaf-like worm
Two suckers: oral and ventral
aid in attachment and
above testes and on the
right side of body
Paragonimiasis has infected 22 million people globally.
Discovered by Kerbert 1878 in the lungs of Bengal tigers from India, which had later died in a zoo.
Far East: Japan, China, Taiwan, Indonesia, Manchuria, New Guinea, Philippines, and other areas of Southeast Asia
Recent spread to :
Eastern U.S. and Canada:
-rarely results in
High prevalence in the Far East due to cultural eating habits and proximity to infected crabs/crayfish.
Food preparation such as drunken crab or crab soaked in soybean-sauce will not kill Paragonimiasis.
Spread by contamination by crab juice to other work areas.
Paragonimiasis was widespread across S. Korea by the late 1960’s.
Industrialization in the 1970’s and 1980’s caused runoff polluting many streams.
Pollution killed many crab and crayfish almost to extinction.
Subsequently, rates of those infected by Paragonimiasis dramatically decreased to 1/100th of previous numbers.
TODAY: A priority on health education and surveillance to control infection rates.
The Imaging of Tropical Diseases
-found in stool or sputum
-golden eggs are coughed up along with blood
-eggs must find their way to a freshwater source
-upon finding fresh water the eggs will hatch and turn into ciliated larvae: miracidia
2. Primary host: SnailApprox. 3-5 months
-miracidia infect the snail
-asexual reproduction inside snail results in thousand of larvae: cercariae
-cercariae leave the snail and swim around until they find the secondary host
3. Secondary Host: Freshwater crab/crayfish
Approx. 6-8 weeks
-cercariae infect crab and undergo a second transformation
-transformation into the infective stage: metacercariae
-infected crab ingested by human
4. Human infection
- once ingested the metacercariae burrow themselves through the gut and eventually up into the lungs*
- in the lungs they will reach maturity in 5-6 weeks
- flukes encapsulate themselves and lay eggs
-capsules burst into the bronchioles to be coughed up
*migration to other sites possible, most commonly the brain
Migration stage:nonspecific symptoms
-diarrhea -abdominal & chest pain
-allergic rxn - fever & chills
Once Established in Lungs:elicit eosinophilic inflammatory rxn
-one or more parasites become encapsulated in 1-2cm lesions
-secondary infections occur after capsules burst : may clinically appear as chronic bronchitis
-cough -night sweats
-haemoptyisis -general malaise
-pleurisy -persistent rales
-clubbed fingers -pneumothorax
*Ectopic infection in the brain will exhibit neurological symptoms: paralysis, epilepsy, homonymous hemianopsia, optic atrophy, papilledema
(brain infections occur most commonly in children)
10-20% of radiograph findings will be normal
Most show infiltrates that eventually lead to calcification and look clinically similar to TB on x-rays
Many cases of P. westermani are diagnosed after TB treatment has failed, therefore a careful differential diagnosis is key in determining Paragonimiasis infections.
75% of infected individuals will have eggs detectible in their sputum after the first 3 months have passed so retesting of sputum is necessary
Complement Fixation (CF) Test: standard test; sensitive and good indicator of cure
Enzyme Immunoassay Tests: antibodies
-can be used but cannot distinguish between past and current infection
Immunoblot (IB) assay: antibodies
Used by CDC but may not be able to detect for other species of Paragonimiasis besides P. westermani
Bithionol:phenol drug class
- uncouples phosphorylation
- NOT available in the United States
Praziquantel:causes severe spasms and paralysis of the worms muscles- worms destroyed in intestines or excreted in feces
Dosage: 25mg/kg 3 times a day-3 days
>90% effective in case studies
PREVENTION: adequate cooking of shellfish before consuming.
Baumann (2001) http://www.stanford.edu/class/humbio103/ParaSites2001/paragonimiasis/Paragonimiasis_Home.html HealthToKnow (2008) http://www.health2know.com/mini-lobsters/
Discovery (2010) http://animal.discovery.com/invertebrates/monsters-inside-me/lung-fluke-paragonimus-westermani/
Rohde (2010) http://knol.google.com/k/flukes-trematodes-the-biology-morphology-and-medical-economic-importance-of#
The Imaging of Tropical Diseases http://www.isradiology.org/tropical_deseases/tmcr/chapter22/epidemiology.htm
Thompson (2004) http://www.flmnh.ufl.edu/malacology/fl-snail/snails1.htm