Central nervous system parasites (74)Document Transcript
CENTRAL NERVOUS SYSTEMPARASITES
CNS CESTOIDEAOrder: Cyclophyllidea
Echinococcus granulosus infection has a world-wide distribution with a higher prevalence inSouth-America (Argentina, Uruguay), Europe(mediterranean bassin), Northern Africa, MiddleEast, South-Central and East Asia.
Echinococcus granulosus: hydatidosis is caused bythe larval stage of E.granulosus.After ingestion of eggs the onchospheres penetratethe intestinal mucosa and reach host organs(mainly liver and lung) where they encyst within aweek reaching 1 cm in diameter in about 5 months.
Echinococcus granulosus: the cysts (2 to 30 cm)are constituted by an external acellular cuticuleand an inner cellular "germinal" layer (10-25 µ)that produces the brood capsules containing 6-12protoscolices or single protoscolices. (Germinallayer with a protoscolex).
Echinococcus granulosus: the larvae (scolices)develop from the germinal layer.The protoscolices are at first evaginated andmeasure 120-220 by 70-120 µ.
Echinococcus granulosus: the mature rotoscoliceshave 4 suckers and a rostellum with hooklets andcan be observed in the hydatid fluid.
Echinococcus granulosus: detail of the rostellum.
Echinococcus granulosus: the protoscolices thenbecome invaginated and measure 90-140 by 70-120µm.They can transform into daughter cysts.These cysts can proliferate both internally andexternally giving exogenous cysts.Spontaneous orsurgical rupture of the cyst can originate asecondary hydatidosis.
Echinococcus granulosus: the liver is the mostcommon site of development of cysts (50-75%).Lesions can be detected by CT scan orechography;a septate structure is a characteristicof active cysts.Treatment is based on surgical and/or medicaltherapy (albendazole)
Echinococcus granulosus: definitive diagnosis isobtained by means of serologic tests (EIA, IHA,CIEP/Western Blot);the last two are confirmatorytests and are useful for the follow-up of treatedpatients.-Detail of liver lesion, CT-scan with septa.-Western blot analysis: both Ag5 (55 and 65 Kd)and AgB (8, 16, 24 Kd) bands are present.
Echinococcus granulosus: pulmonary infection isobserved in about 20-30% of patients.Roentgenografic examination shows round masslesions and CT scan demonstrates the fluidcontent of the lesion.Serology has a lower sensitivity in extrahepatichydatidosis.
Echinococcus granulosus: any other organ can beaffected:nervous system, heart, bones, spleeneyes, muscles are the most common sites.Multiple involvement is frequent.Symptoms andsigns depend on the size,the site and the pressureof the cyst on host structures.-CT scan of a spleen cyst.-MRI scans of a muscular cyst.
Echinococcus granulosus: medullary hydatidosisis a severe form of the infection.In this case themechanical pressure of host tissues causedparaplegia.The surgical treatment allowedresolution of symptoms.The infection relapsedand responded partially to medical treatment.
Echinococcus granulosus: MRI imaging candemonstrate the relationship between the cystand the medulla on the longitudinal axis.The serology is often negative in infections in sitesother than liver or lung.(Medullary hydatidosis)
TAENIA SOLIUMTaenia solium: life cycle.Cysticercosis exists world-wide but is prevalent inMexico, Africa, South-Est Asia and South-America.
T.solium: cysticercus cellulosae with invaginated scolexT.solium: cysticercus cellulosae with evaginated scolex
Cysticercosis: nervous cysticercosis is the mostsevere manifestation of the disease.MRI showing an occipital lesion. Diagnosis ofcysticercosis,suspected on a clinical-radiological basis, isconfirmed by serology.
Cysticercosis: the onchospheres migrate to thetissues and develop to cysticerci.The cysticercus dies and becomes calcified. Calcifiedcysticerci in muscle.Localization in muscles depends on the geographicalorigin(unfrequent in american patients).
TAENIA MULTICEPS (COENUROSIS)
Taenia multiceps: dogs are the definitive host:sheep, other mammals and,rarely, man areinfected by eating embryonated eggs.World-wide distribution. The larvae penetrate viaoral route and develop to the coenurus stage inhosts tissues.(Brain lesion).
Taenia multiceps: the lesion can be differentiatedfrom the cysticercus larva for the presence in thesame cyst of hundreds of protoscolices.Section of a protoscolex in brain cyst.
ANGIOSTRONGYLUS CANTONENSISAngiostrongylus cantonensis: the rat lung worm is anematode producing human eosinophilicmeningoencephalitis.Human infections have beendescribed in Asia (Philippines, Indonesia, Malaisia,Thailand, Viet-Nam, Taiwan, Hong-Kong, Japan),Oceania [Pacific Island (Tahiti, New Caledonia),Papua Nuova Guinea, Australia],Cuba, Puerto Rico,Hawaii;in the USA the parasite has been found inrats and molluscs and one human case has beenreported from New Orleans;in Africa (Madagascar)A.cantonensis has been found in rats.Section of A.cantonensis young adults withinpulmonary blood vessel.The sections show the reproductive tubes (RT),lateral chords (LR) and the intestine (I) of theworms.(Hematoxylin and Eosin, H&E)
A.cantonensis: adult worms(male: 20-22 mm by320-420 µm, female: 22-34 mm by 340-560 µm)live in the blood vessels of the lungs of rats wherethey lay eggs.Eggs lodge in the terminal branchesof the pulmonary arteries where they hatchliberating first-stage larvae which migrate to theintestine via the alveolar space, the trachea, thepharynx and the esophagus; larvae are theneliminated with faeces.First stage larvae infect the intermediate hosts,molluscs (snails and slugs),where they develop tothe infective third-stage larvae.Rats becomeinfected by eating infected snails or slugs. Theingested larvae migrate from rats intestine to theCNS where they develop to adults through twostages of development in 2-3 weeks.Adults thenmigrate to the subarachnoid space, enter thevenous system and gain the pulmonary arterieswhere they become mature.Larvae can be detectedin rats faeces 40-60 days after infection.
A.cantonensis: several species of terrestrialsnails (Achatina fulica, the Giant African snail),acquatic snails (Pila spp., Viviparus javanica),or slugs (Veronicella alte and V.siamensis) mayact as intermediate hosts for the development ofthe larvae to third stage.The existance ofparatenic hosts has been demonstrated:in freshwater prawns, land crabs and frogswhich feed on snails or slugs,larvae remaininfective for a certain period of time and mayinfect rats,or humans, when eating the paratenic host.Achatina fulica (the Giant African snail)
A.cantonensis: humans become infected by eatingraw or undercooked snails, slugs, contaminatedvegetables or transport hosts;in man larvae migrateto the CNS, where the development generally stops,and cause eosinophilic meningoencephalitis.Section of A.cantonensis in the subarachnoid spacewith inflammation and hemorrhage.(Hematoxylin and Eosin, H&E)
A.cantonensis: the pathogenesis depends ondirect damage caused by the motile larvae andyoung adults (7-13 mm in lenght by 100-260 µm),and on the hosts inflammatory granulomatousreaction.Section of A.cantonensis in the subarachnoidspace with inflammation and hemorrhage.(Hematoxylin and Eosin, H&E)
A.cantonensis: histologic examination showssections of the worms surrounded by inflammatorycells(histiocytes, neutrophils and eosinophils),vascular congestion, subdural and subarachnoidhemorrhage, focal necrosis and hemorrhage in thebrain.Section of young adult of A.cantonensis in thebrain without any inflammatory response:I: intestine, LC: lateral chords.(Hematoxylin and Eosin, H&E)
A.cantonensis: the incubation period ranges from 1to 5 weeks (average 2 weeks).Symptoms consist of headache (mainly occipital andtemporal),stiff neck, nausea, vomiting, mild fever,rash, pruritus,abdominal pain, constitutionalsymptoms.Section of young adult of A.cantonensis in the brain,higher magnification:the intestine (I) and the lateralchords (LC) are well identifiable.(Hematoxylin and Eosin, H&E)
A.cantonensis: meningeal signs, cranial nervespalsies (III, IV, VI, VII),paresthesias, pain andweakness are the commonest signs.Death isuncommon.An ocular form with the presence of young adults ofA.cantonensis in the anterior chamber of the eyehas been described with visual loss,pain,blepharospasm, iridocyclitis and increased oculartension.Section of young adult of A.cantonensis in thebrain, higher magnification:the prominent lateralchords (LC) and the cuticle (C) (5 µm) are wellidentifiable.(Hematoxylin and Eosin, H&E)
A.cantonensis: pulmonary involvement isuncommon but rarely some worms may migrate tothe lungs causing severe pneumonia with massiveinflammation, exudation and hemorrhage.Section of lung during pulmonary involvement byA.cantonensis.(Hematoxylin and Eosin, H&E)
A.cantonensis: several adults, male and femalemay lie within the same pulmonary vessel.Sections of adults of A.cantonensis withinpulmonary vessel:RT: reproductive tubes; MC: muscular cells; I:intestine.(Hematoxylin and Eosin, H&E)
A.cantonensis: no treatment is recognized aseffective;moreover anthelminthics are notrecommended.Section of adult female within pulmonary vessel:RT: reproductive tubes; MC: muscular cells; I:intestine; LC: lateral chord.(Hematoxylin and Eosin, H&E)
A.cantonensis: laboratory diagnosis is based onthe observation of an eosinophilic CSF pleocytosis(500-5.000 cells/mm3, with 20-90% ofeosinophils),with elevated CSF proteins andnormal or slightly decreased CSF glucose.Section of adult female within pulmonary vessel:RT: reproductive tubes; MC: muscular cells; I:intestine; LC: lateral chord.(Hematoxylin and Eosin, H&E)
A.cantonensis: Charcot-Leyden crystals may beobserved in the CSF. Blood leukocytosis witheosinophilia (>10%) is common.The diagnosis may be confirmed by serologicaltesting (IF or EIA).Charcot-Leyden crystal. Bright field examinationof wet mount preparation.
T. gondii: T.gondii encephalitis (TE) is the mostcommon cerebral opportunistic infection inpatients with AIDS.The typical lesion is an ipodense focal area withring contrast-enhancement and edema.(CT scan of a toxoplasmic encephalitis).
T. gondii: tissue cysts, 100-300 µm, may containup to 3.000 bradyzoites.The wall of maturepseudocysts is believed to represent acombination of host and parasitic components.
T. gondii: diagnosis of TE is usually presumptive,based on clinical and radiologic findings and on theresponse to treatment; cerebral biopsy sometimesallows identification of pseudocysts in tissuesections. (H&E stain).
T. gondii: toxoplasmic pseudocyst within aninflammatory tissue reaction. (H&E stain).
T. gondii: the pseudocysts of T.gondii can beobserved in tissue sections with monoclonalantibodies.
T. gondii: direct detection of T.gondii in clinicalspecimens is rare;parasites can be isolated fromblood, CSF, amniotic fluid,tissue biopsies on cell lines(THP-1 or MRC-5).In clinical specimens the presence of parasites canalso be demonstrated by PCR analysis.
T. gondii: intracellular trophozoites of T.gondii in acell culture.The trophozoites proliferate within the vacuoledeveloping a pseudocyst.(Trophozoites in a THP-1 cell, Giemsa stain).
T. gondii: in cell cultures T.gondii proliferates toform a pseudocyst of 8-20 parasites.(Trophozoites in a THP-1 cell, Giemsa stain).
T. gondii: lysis of a THP-1 cell with release oftachizoites in culture.(Trophozoites in a THP-1 cell, Giemsa stain).
T. gondii: microscopical features of tachizoites ofToxoplasma gondii and peritoneal macrophagesof mouse in peritoneal exudate. (SEM)
T. gondii: microscopical features of tachizoites ofToxoplasma gondii and peritoneal macrophages ofmouse in peritoneal exudate. (SEM)
T. gondii: the anterior pole of an endozoid intangential projection.Several subpellicularfibrils and their insertion on the anterior polarring are visible.
T. gondii: transmision electron microscopic picture.Longitudinal section of an endozoid.
T. gondii: cross-section through an endozoidin an advanced stage of endodiogeny.The daugther cells appear to be surrounded.In each of these news cells there are two roundbodies that lengthen forming the first rhoptries.
TRYPANOSOMABRUCEI RHODESIENSE / T.B. GAMBIENSE
Sleeping sickness occurs in Africa between the15° North and the 20° South.The T.b.rhodesiense form is found in East andCentral-East Africa whereas the T.b.gambienseinfection occurs in Central and West Africa.
The Africantrypanosomiasisis transmittedby severalspecies of tse-tse flies(Glossina spp.). Larva and pupae of Glossina morsitans Adult Glossina tachinoides in West Africa
T. b. gambiense and rhodesiense: two forms oftrypomastigote can be seen in peripheral blood:one is long slender, 30 µm in length,and iscapable of multiplying in the host, the other isstumpy, not dividing,18 µm in length.
Trypanosoma brucei gambiense and rhodesiense:trypanosomes appear in the peripheral blood 5 to21 days after the infecting bite.
Trypanosoma brucei gambiense and rhodesiense:the terminal stage of the infection ("sleepingsickness") is the result of a chronicmeningoencephalomyelitis. (H&E stain).
Trypanosoma brucei gambiense andrhodesiense: the typical pathological lesion oftrypanosomiasis is a perivascular round-cellinfiltration (perivascular cuffing) due to glialcells, lymphocytes and plasmocytes (Mott cells).(H&E stain).
ACANTHAMOEBA SP.Acanthamoeba spp.: free living amoebae of theAcanthamoeba genus cause two clinical syndrome:1) Granulomatous amoebic encephalitis (GAE)2) Subacute and chronic amoebic keratitisA disseminated form of GAE is described inindividuals with the Acquired ImmunodeficiencySyndrome (AIDS)Several species of Acanthamoeba have beenidentified:A.castellani, A.culberstoni, A.polyphaga,A.zhysodes, A.hatchetti,A.astronyxis,A.palestinensis.(Trophozoites, trichrome stain).
Acanthamoeba spp.: clinical manifestations includechronic granulomatous encephalitis and keratitis(in particular in individuals who wear contact lens);some case of disseminated cutaneous infectionhave been reported in AIDS patients.
Acanthamoeba spp.: the trophozoite is irregular,15-45 µm,having micropseudopodia calledacanthopodia;in trichrome stain the cytoplasm oftrophozoites appears greenish pink,the centrallocated kariosome pink or red.(Trichrome stain).
Acanthamoeba spp.: the cysts are spherical,15-20 µm in diameter,having a thick doublewall. The outer wall may be spherical orwrinkled,the inner wall appear stellate or polyhedral.(Acanthamoeba trophozoites and a cyst,trichrome stain).
Acanthamoeba spp.: both forms have a singlenucleus with a large centrally located nucleolus.With trichrome stain, the cysts stain red.Speciesidentification is based on morphology of cysts(stellate, polyhedral).
Acanthamoeba spp.: trophozoite as seen underphase contrast microscope.Its big nucleolus, bothlobopodia and acanthopodia and various vacuolescan be seen clearly.
Acanthamoeba spp.: trophozoites as seenunder phase contrast microscope.
Acanthamoeba spp.: cysts stained withHeidenhain’s iron alum-haematoxylin method.
NAEGLERIA FOWLERINaegleria fowleri is the agent of a severe purulentmeningoencephalitis: the "Primary amoebicmeningoencephalitis". N.fowleri are free livingamoebas that live in warm fresh water all over theworld.The lyfe cycle consist of three stages: theamoeboid growing form that lives in the mud andat the bottom of the ponds; the rapidly motilebiflagellate trophozoite who lives in surface layersof water (the infective form); the dormant cyst.Primary amoebic meningoencephalitis occurs inindividuals who have been exposed to freshwaterlakes or ponds usually during swimming; theincubation period is about 3 to 7 days (but it maylast up to 2 weeks). Invasion of the CNS occursafter nasal inhalation of contaminated watercontainig the biflagellate trophozoites;trophozoites (in the amoeboid form once arrived inthe nasal cavity) penetrate the epithelium andenter the CNS through the olphactory nervebranches in the cribriform plate and cause apurulent meningoencephalitis.Trophozoites are 10-to 30 m m in diameter andhave a clear nucleus with a prominent densecentral nucleolus; the cytoplasm containsmytochondria and the rough endoplasmicreticulum; usually ingested red blood cells,leukocytes and bacteria are visible.Cysts are 9 m m in diameter; they are sphericalwith a central nucleus.
N. gruberi: trophozoite as seen under phasecontrast microscope.Its big nucleolus, four lobopod type pseudopodiaand the contractile vacuole can be clearly seen.
Naegleria spp.: trophozoite stained withGreenstein’s five dye stain and observed underdark field microscope.