Paragonimus westermani

Paragonimus westermani

Paragominus westermaniTaxonomyKingdom:AnimaliaPhylum:PlatyhelminthesClass:TrematodaOrder:PlagiorchiidaFamily:TroglotrematidaeGenus:ParagonimusSpecies:P. westermani

Geographic RangeThree main foci of Paragonimus spp.Asia and OceaniaWest and sub-Saharan AfricaSouth and Central AmericaHistoryFirst described from Bengal tigers that died in zoos in Europe in 1878. Later, it was found in humans. Named after Dutch zookeeper who kept the Bengal Tigers

HostsDefinitive: Humans, cats, dogs, weasels, rodents, pigs

IntermediateSnails, freshwater crayfish, crabsMorphology

Size, shape, and color resemble coffee bean when alive. AdultSkin is heavily covered with scalelike spinesOral and ventral suckers are about equal in size, with theventral sucker being placed slightly preequatorially. Morphology

Eggs

Yellow-brown, ovoid, with a long thick shell

Often are asymmetrical with one end flattenedMorphology

Cercaria

Often are indistinguishable betweenspecies

Large posterior sucker with spined exteriorLife cycle

Life cycle in intermediate hosts1st intermediate hostEggs hatch into Miracidium after approximately 16 daysMiracidium must find a snail to surviveOnce in the snail the mirocidium forms a sporocyst that produces RediaRedia become Cercariae, which is passed into the water

2nd intermediate host life cycle2nd intermediate hostCercariae penetrate into the tissues of crabs (usually the muscles or mucosa)The definitive host is infected when they eat the undercooked crab

Life cycle in definitive hostWorms form cysts in the duodenumUpon leaving the cyst the metacercariae leave the intestines and penetrates the diaphragm and pleuraOnce in the lungs they encapsulate and become adultsWorms mate in the pleural spacesMated pairs form cysts which can hatch in the lungsHowever most eggs are coughed up and oed by the host.They leave the host by the fecesParagonimus kellicotti Causes American paragonimiasis in feline and canine speciesLife cycle is essentially the same as P. westermaniEggs are passed in the fecesAnimals become infected after eating infected crawfishWorms form cysts in the lungsAnimals can tolerate low numbers of cystsWith large numbers of cysts animals can show respiratory signs, including coughing, dyspnea, bronchiectasis, and hemoptysisPulmonary cysts can be seen on lung radiographsA transtracheal wash is used to find cystsTreated with either Praziquantel or AlbendazolePathologyFew symptoms in the early stages of the infectionCauses local inflammation which causes the formation of granulation tissue around the cyst.Eggs form pseudotubercles in the lungsJuvenile worms can migrate to the heart, brain and spinal fluid. Cerebral cases are similar to cysticercosisWorms in the spinal fluid can cause paralysisPulmonary cases characterized by chronic cough and blood in the sputum SymptomsDry coughBloody or rust colored sputum Chest painPossibly paralysis (if it migrates to spinal chord)Epileptic symptoms (if it migrates to brain)DiagnosisExamination of sputum, aspirated pleural fluid, or feces for eggs (eggs not present till 2-3 months post infection)Seroimmunological diagnosis is helpful if infection is ectopic Need to differentiate from tuberculosis Treatment and ControlPraziquantelUntreated individuals can have infection for up to 20 years, but clinical symptoms diminish after 5-6 yearsAdequate cooking of crustaceans Paragonimus kellicotti Causes American paragonimiasis in feline and canine speciesLife cycle is essentially the same as P. westermaniEggs are passed in the fecesAnimals become infected after eating infected crawfishWorms form cysts in the lungsAnimals can tolerate low numbers of cystsWith large numbers of cysts animals can show respiratory signs, including coughing, dyspnea, bronchiectasis, and hemoptysisPulmonary cysts can be seen on lung radiographsA transtracheal wash is used to find cystsTreated with either Praziquantel or Albendazole

ReferencesCenter For Disease Control: Paragonimus westermani Gerald D. Schmidt and Larry S. Roberts Foundations of Parasitology by Larry S. Roberts and John Janovy, Jr.,8th editionMetropolitan State College of Denver Department of Medical Technology