CENTRALCENTRALNERVOUSNERVOUSSYSTEMSYSTEM

PARASITESPARASITES

CNS CNS CESTOIDEACESTOIDEA Order:Order: CyclophyllideaCyclophyllidea

ECHINOCOCCUSECHINOCOCCUSGRANULOSUSGRANULOSUS

Echinococcus granulosus infection has a world-Echinococcus granulosus infection has a world-wide distribution with a higher prevalence in wide distribution with a higher prevalence in South-America (Argentina, Uruguay), Europe South-America (Argentina, Uruguay), Europe (mediterranean bassin), Northern Africa, Middle (mediterranean bassin), Northern Africa, Middle East, South-Central and East Asia.East, South-Central and East Asia.

Echinococcus granulosus: Echinococcus granulosus: hydatidosis is caused by hydatidosis is caused by the larval stage of the larval stage of E.granulosus.E.granulosus. After ingestion of eggs the onchospheres After ingestion of eggs the onchospheres penetrate the intestinal mucosapenetrate the intestinal mucosa and reach host and reach host organs (mainly liver and lung) where they encyst organs (mainly liver and lung) where they encyst within a week reaching 1 cm in diameter in about 5 within a week reaching 1 cm in diameter in about 5 months.months.

Echinococcus granulosus: Echinococcus granulosus: the cysts (2 to 30 cm) the cysts (2 to 30 cm) are constituted by an externalare constituted by an external acellular cuticule acellular cuticule and an inner cellular "germinal" layer (10-25 µ) and an inner cellular "germinal" layer (10-25 µ) that producesthat produces the brood capsules containing 6-12 the brood capsules containing 6-12 protoscolices or single protoscolices. (Germinal protoscolices or single protoscolices. (Germinal layer with a protoscolex).layer with a protoscolex).

Echinococcus granulosus: the larvae (scolices) Echinococcus granulosus: the larvae (scolices) develop from the germinal layer. develop from the germinal layer. The protoscolices are at first evaginated and The protoscolices are at first evaginated and measure 120-220 by 70-120 µ.measure 120-220 by 70-120 µ.

Echinococcus granulosus: the mature rotoscolices Echinococcus granulosus: the mature rotoscolices have 4 suckers and a rostellumhave 4 suckers and a rostellum with hooklets and with hooklets and can be observed in the hydatid fluid.can be observed in the hydatid fluid.

Echinococcus granulosus: detail of the rostellum.Echinococcus granulosus: detail of the rostellum.

Echinococcus granulosus: Echinococcus granulosus: the protoscolices then the protoscolices then become invaginated andbecome invaginated and measure 90-140 by 70-120 measure 90-140 by 70-120 µm.They can transform into daughter cysts. µm.They can transform into daughter cysts. These cysts can proliferate both internally and These cysts can proliferate both internally and externally giving exogenous cysts.Spontaneous or externally giving exogenous cysts.Spontaneous or surgical rupture of the cyst can originate a surgical rupture of the cyst can originate a secondary hydatidosis.secondary hydatidosis.

Echinococcus granulosus: Echinococcus granulosus: the liver is the most the liver is the most common site of development of cysts (50-75%). common site of development of cysts (50-75%). Lesions can be detected by CT scan or Lesions can be detected by CT scan or echography;a septate structure is a characteristic echography;a septate structure is a characteristic of active cysts. of active cysts. Treatment is based on surgical and/or medical Treatment is based on surgical and/or medical therapy (albendazole)therapy (albendazole)

Echinococcus granulosus: Echinococcus granulosus: definitive diagnosis is definitive diagnosis is obtained by meansobtained by means of serologic tests (EIA, IHA, of serologic tests (EIA, IHA, CIEP/Western Blot);the last two are confirmatory CIEP/Western Blot);the last two are confirmatory teststests and are useful for the follow-up of treated and are useful for the follow-up of treated patients.patients.--Detail of liver lesion, CT-scan with septa. Detail of liver lesion, CT-scan with septa. --Western blot analysis: both Ag5 (55 and 65 Kd) Western blot analysis: both Ag5 (55 and 65 Kd) and AgB (8, 16, 24 Kd) bands are present.and AgB (8, 16, 24 Kd) bands are present.

Echinococcus granulosus: Echinococcus granulosus: pulmonary infection is pulmonary infection is observed in about 20-30% of patients. observed in about 20-30% of patients. RoentRoentggenografic examination shows round mass enografic examination shows round mass lesionslesions and CT scan demonstrates the fluid and CT scan demonstrates the fluid content of the lesion. content of the lesion. Serology has a lower sensitivity in extrahepatic Serology has a lower sensitivity in extrahepatic hydatidosis.hydatidosis.

Echinococcus granulosus: Echinococcus granulosus: any other organ can be any other organ can be affected:nervous system, heart, bones, spleen affected:nervous system, heart, bones, spleen eyes, muscles are the most common sites. eyes, muscles are the most common sites. Multiple involvement is frequent.Symptoms and Multiple involvement is frequent.Symptoms and signs depend on the size,the site and the signs depend on the size,the site and the pressure of the cyst on host structures.pressure of the cyst on host structures.--CT scan of a spleen cyst.CT scan of a spleen cyst.--MRI scans of a muscular cyst.MRI scans of a muscular cyst.

Echinococcus granulosus: Echinococcus granulosus: medullary hydatidosis medullary hydatidosis is a severe form of the infection.In this case the is a severe form of the infection.In this case the mechanical pressure of host tissues caused mechanical pressure of host tissues caused paraplegia.The surgical treatment allowed paraplegia.The surgical treatment allowed resolution of symptoms.The infection relapsed resolution of symptoms.The infection relapsed and responded partially to medical treatment.and responded partially to medical treatment.

Echinococcus granulosus: Echinococcus granulosus: MRI imaging can MRI imaging can demonstrate the relationshipdemonstrate the relationship between the cyst between the cyst and the medulla on the longitudinal axis. and the medulla on the longitudinal axis. The serology is often negative in infections in The serology is often negative in infections in sites other than liver or lung.(Medullary sites other than liver or lung.(Medullary hydatidosis) hydatidosis)

TAENIA SOLIUM TAENIA SOLIUM

Taenia solium:Taenia solium: life cycle. life cycle. Cysticercosis exists world-wide but is prevalent in Cysticercosis exists world-wide but is prevalent in Mexico, Africa, South-Est Asia and South-America.Mexico, Africa, South-Est Asia and South-America.

T.solium: cysticercus cellulosae with invaginated scolexT.solium: cysticercus cellulosae with invaginated scolex

T.solium: cysticercus cellulosae with evaginated scolexT.solium: cysticercus cellulosae with evaginated scolex

Cysticercosis: nervous cysticercosis is the most Cysticercosis: nervous cysticercosis is the most severe manifestation of the disease. severe manifestation of the disease. MRI showing an occipital lesion. Diagnosis of MRI showing an occipital lesion. Diagnosis of cysticercosis, cysticercosis, suspected on a clinical-radiological basis, is suspected on a clinical-radiological basis, is confirmed by serology.confirmed by serology.

Cysticercosis:Cysticercosis: the onchospheres migrate to the the onchospheres migrate to the tissues and develop to cysticerci. tissues and develop to cysticerci. The cysticercus dies and becomes calcified. The cysticercus dies and becomes calcified. Calcified cysticerci in muscle. Calcified cysticerci in muscle. Localization in muscles depends on the Localization in muscles depends on the geographical origin geographical origin (unfrequent in american patients).(unfrequent in american patients).      

TAENIA MULTICEPSTAENIA MULTICEPS(COENUROSIS)(COENUROSIS)

Taenia multiceps:Taenia multiceps: dogs are the definitive host: dogs are the definitive host: sheep, other mammals and,rarely, man are sheep, other mammals and,rarely, man are infected by eating embryonated eggs. infected by eating embryonated eggs. World-wide distribution. The larvae penetrate World-wide distribution. The larvae penetrate via oral route and developvia oral route and develop to the coenurus stage to the coenurus stage in host's tissues.(Brain lesion). in host's tissues.(Brain lesion).

Taenia multiceps:Taenia multiceps: the lesion can be the lesion can be differentiated from the cysticercus larvadifferentiated from the cysticercus larva for the for the presence in the same cyst of hundreds of presence in the same cyst of hundreds of protoscolices. protoscolices. Section of a protoscolex in brain cyst. Section of a protoscolex in brain cyst.

PHASMIDEAPHASMIDEAOrder:Order: StrongylidaStrongylida

ANGIOSTRONGYLUSANGIOSTRONGYLUSCANTONENSIS CANTONENSIS

Angiostrongylus cantonensis:Angiostrongylus cantonensis: the rat lung worm is a the rat lung worm is a nematodenematode producing human eosinophilic producing human eosinophilic meningoencephalitis.Human infections have been meningoencephalitis.Human infections have been described in Asia (Philippines, Indonesia, Malaisia, described in Asia (Philippines, Indonesia, Malaisia, Thailand, Viet-Nam, Taiwan, Hong-Kong, Japan), Thailand, Viet-Nam, Taiwan, Hong-Kong, Japan), Oceania [Pacific Island (Tahiti, New Caledonia), Oceania [Pacific Island (Tahiti, New Caledonia), Papua Nuova Guinea, Australia],Cuba, Puerto Rico, Papua Nuova Guinea, Australia],Cuba, Puerto Rico, Hawaii;in the USA the parasite has been found in Hawaii;in the USA the parasite has been found in rats and molluscs and one human case has been rats and molluscs and one human case has been reported from New Orleans;in Africa (Madagascar) reported from New Orleans;in Africa (Madagascar) A.cantonensisA.cantonensis has been found in rats. has been found in rats. Section of Section of A.cantonensisA.cantonensis young adults within young adults within pulmonary blood vessel. pulmonary blood vessel. The sections show the reproductive tubes (RT), The sections show the reproductive tubes (RT), lateral chords (LR) and the intestine (I) of the lateral chords (LR) and the intestine (I) of the worms.(Hematoxylin and Eosin, H&E)worms.(Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: adult worms(male: 20-22 mm by adult worms(male: 20-22 mm by 320-420 µm, female: 22-34 mm by 340-560 µm) 320-420 µm, female: 22-34 mm by 340-560 µm) live in the blood vessels of the lungs of rats where live in the blood vessels of the lungs of rats where they lay eggs.Eggs lodge in the terminal branches they lay eggs.Eggs lodge in the terminal branches of the pulmonary arteriesof the pulmonary arteries where they hatch where they hatch liberating first-stage larvae which migrateliberating first-stage larvae which migrate to the to the intestine via the alveolar space, the trachea, the intestine via the alveolar space, the trachea, the pharynxpharynx and the esophagus; larvae are then and the esophagus; larvae are then eliminated with faeces. eliminated with faeces. First stage larvae infect the intermediate hosts, First stage larvae infect the intermediate hosts, molluscs (snails and slugs),where they develop to molluscs (snails and slugs),where they develop to the infective third-stage larvae.Rats become the infective third-stage larvae.Rats become infected by eating infected snails or slugs. The infected by eating infected snails or slugs. The ingested larvae migrate from rat's intestine to the ingested larvae migrate from rat's intestine to the CNS where they develop to adults through two CNS where they develop to adults through two stages of development in 2-3 weeks.Adults then stages of development in 2-3 weeks.Adults then migrate to the subarachnoid space, enter the migrate to the subarachnoid space, enter the venous systemvenous system and gain the pulmonary arteries and gain the pulmonary arteries where they become mature.Larvae can be detected where they become mature.Larvae can be detected in rat's faeces 40-60 days after infection.in rat's faeces 40-60 days after infection.

A.cantonensis:A.cantonensis: several species of terrestrial several species of terrestrial snailssnails ((Achatina fulicaAchatina fulica, the Giant African snail), , the Giant African snail), acquatic snails (acquatic snails (PilaPila spp., spp., Viviparus javanicaViviparus javanica), ), or slugs (or slugs (Veronicella alteVeronicella alte and and V.siamensisV.siamensis) may ) may act as intermediate hostsact as intermediate hosts for the development of for the development of the larvae to third stage.The existance of the larvae to third stage.The existance of paratenic hosts has been demonstrated: paratenic hosts has been demonstrated: in freshwater prawns, land crabs and frogs in freshwater prawns, land crabs and frogs which feed on snails or slugs,larvae remain which feed on snails or slugs,larvae remain infective for a certain period of time and may infective for a certain period of time and may infect rats, infect rats, or humans, when eating the paratenic host. or humans, when eating the paratenic host. Achatina fulicaAchatina fulica (the Giant African snail) (the Giant African snail)

A.cantonensis: A.cantonensis: humans become infected by eating humans become infected by eating rawraw or undercooked snails, slugs, contaminated or undercooked snails, slugs, contaminated vegetables or transport hosts;in man larvae vegetables or transport hosts;in man larvae migrate to the CNS, where the development migrate to the CNS, where the development generally stops, generally stops, and cause eosinophilic meningoencephalitis. and cause eosinophilic meningoencephalitis. Section of Section of A.cantonensisA.cantonensis in the subarachnoid space in the subarachnoid space with inflammation and hemorrhage. with inflammation and hemorrhage. (Hematoxylin and Eosin, H&E)(Hematoxylin and Eosin, H&E)

A.cantonensis:A.cantonensis: the pathogenesis depends on the pathogenesis depends on direct damage causeddirect damage caused by the motile larvae and by the motile larvae and young adults (7-13 mm in lenght by 100-260 µm), young adults (7-13 mm in lenght by 100-260 µm),

and on the host's inflammatory granulomatous and on the host's inflammatory granulomatous reaction. reaction. Section of Section of A.cantonensisA.cantonensis in the subarachnoid in the subarachnoid space with inflammation and hemorrhage. space with inflammation and hemorrhage. (Hematoxylin and Eosin, H&E)(Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: histologic examination shows histologic examination shows sectionssections of the worms surrounded by of the worms surrounded by inflammatory cells(histiocytes, neutrophils and inflammatory cells(histiocytes, neutrophils and eosinophils), vascular congestion, subduraleosinophils), vascular congestion, subdural and and subarachnoid hemorrhage, focal necrosis and subarachnoid hemorrhage, focal necrosis and hemorrhage in the brain. hemorrhage in the brain. Section of young adult of Section of young adult of A.cantonensisA.cantonensis in the in the brain withoutbrain without any inflammatory response: any inflammatory response: I: intestine, LCI: intestine, LC:: lateral chords. lateral chords. (Hematoxylin and Eosin, H&E) (Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: the incubation period ranges from 1 the incubation period ranges from 1 to 5 weeks (average 2 weeks). to 5 weeks (average 2 weeks). Symptoms consist of headache (mainly occipital and Symptoms consist of headache (mainly occipital and temporal),stiff neck, nausea, vomiting, mild fever, temporal),stiff neck, nausea, vomiting, mild fever, rash, pruritus,abdominal pain, constitutional rash, pruritus,abdominal pain, constitutional symptoms. symptoms. Section of young adult of Section of young adult of A.cantonensisA.cantonensis in the in the brain, higher magnification:the intestine (I) and the brain, higher magnification:the intestine (I) and the lateral chords (LC) are well identifiable. lateral chords (LC) are well identifiable. (Hematoxylin and Eosin, H&E) (Hematoxylin and Eosin, H&E)

A.cantonensis:A.cantonensis: meningeal signs, cranial nerves meningeal signs, cranial nerves palsies (III, IV, VI, VII),paresthesias, pain and palsies (III, IV, VI, VII),paresthesias, pain and weakness are the commonest signs.Death is weakness are the commonest signs.Death is uncommon. uncommon. An ocular form with the presence of young adults An ocular form with the presence of young adults of of A.cantonensisA.cantonensis in the anterior chamber of the eye in the anterior chamber of the eye has been described with visual loss,pain, has been described with visual loss,pain, blepharospasm, iridocyclitis and increased ocular blepharospasm, iridocyclitis and increased ocular tension. tension. Section of young adult of Section of young adult of A.cantonensisA.cantonensis in the in the brain, higher magnification:the prominent lateral brain, higher magnification:the prominent lateral chords (LC) and the cuticle (C) (5 µm) are well chords (LC) and the cuticle (C) (5 µm) are well identifiable. identifiable. (Hematoxylin and Eosin, H&E)(Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: pulmonary involvement is pulmonary involvement is uncommon but rarelyuncommon but rarely some worms may migrate to some worms may migrate to the lungs causing severe pneumoniathe lungs causing severe pneumonia with massive with massive inflammation, exudation andinflammation, exudation and hemorrhage. hemorrhage. Section of lung during pulmonary involvement by Section of lung during pulmonary involvement by A.cantonensisA.cantonensis. . (Hematoxylin and Eosin, H&E) (Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: several adults, male and female several adults, male and female may lie within the same pulmonary vessel. may lie within the same pulmonary vessel. Sections of adults of Sections of adults of A.cantonensisA.cantonensis within within pulmonary vessel: pulmonary vessel: RT: reproductive tubes; MC: muscular cells; I: RT: reproductive tubes; MC: muscular cells; I: intestine. intestine. (Hematoxylin and Eosin, H&E)(Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: no treatment is recognized as no treatment is recognized as effective;moreover anthelminthics are not effective;moreover anthelminthics are not recommended. recommended. Section of adult female within pulmonary vessel: Section of adult female within pulmonary vessel: RT: reproductive tubes; MC: muscular cells; I: RT: reproductive tubes; MC: muscular cells; I: intestine; LC: lateral chord. intestine; LC: lateral chord. (Hematoxylin and Eosin, H&E) (Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: laboratory diagnosis is based on laboratory diagnosis is based on the observationthe observation of an eosinophilic CSF of an eosinophilic CSF pleocytosis (500-5.000 cells/mm3, with 20-90% of pleocytosis (500-5.000 cells/mm3, with 20-90% of eosinophils),with elevated CSF proteins and eosinophils),with elevated CSF proteins and normal or slightly decreased CSF glucose. normal or slightly decreased CSF glucose. Section of adult female within pulmonary vessel: Section of adult female within pulmonary vessel: RT: reproductive tubes; MC: muscular cells; I: RT: reproductive tubes; MC: muscular cells; I: intestine; LC: lateral chord. intestine; LC: lateral chord. (Hematoxylin and Eosin, H&E)(Hematoxylin and Eosin, H&E)

A.cantonensis: A.cantonensis: Charcot-Leyden crystals may be Charcot-Leyden crystals may be observedobserved in the CSF. Blood leukocytosis with in the CSF. Blood leukocytosis with eosinophilia (>10%) is common. eosinophilia (>10%) is common. The diagnosis may be confirmed by serological The diagnosis may be confirmed by serological testing (IF or EIA). testing (IF or EIA). Charcot-Leyden crystal. Bright field Charcot-Leyden crystal. Bright field examination of wet mount preparation.examination of wet mount preparation.

SPOROZOEASPOROZOEAOrder:Order: EucoccidiidaEucoccidiida

TOXOPLASMA GONDIITOXOPLASMA GONDII

T. gondii:T. gondii: T.gondiiT.gondii encephalitis (TE) is the most encephalitis (TE) is the most common cerebralcommon cerebral opportunistic infection in opportunistic infection in patients with AIDS. patients with AIDS. The typical lesion is an ipodense focal area with The typical lesion is an ipodense focal area with ring contrast-enhancement and edema. ring contrast-enhancement and edema. (CT scan of a toxoplasmic encephalitis).(CT scan of a toxoplasmic encephalitis).

T. gondii:T. gondii: tissue cysts, 100-300 µm, may contain tissue cysts, 100-300 µm, may contain up to 3.000 bradyzoites.The wall of mature up to 3.000 bradyzoites.The wall of mature pseudocysts is believed to represent a pseudocysts is believed to represent a combination of host and parasitic components. combination of host and parasitic components.

T. gondii:T. gondii: diagnosis of TE is usually presumptive, diagnosis of TE is usually presumptive, based on clinical and radiologic findings and on the based on clinical and radiologic findings and on the response to treatment; cerebral biopsy sometimes response to treatment; cerebral biopsy sometimes allows identification of pseudocysts in tissue allows identification of pseudocysts in tissue sections. (H&E stain).sections. (H&E stain).

T. gondii:T. gondii: toxoplasmic pseudocyst within an toxoplasmic pseudocyst within an inflammatory tissue reaction. (H&E stain).inflammatory tissue reaction. (H&E stain).

T. gondii: the pseudocysts of T.gondii can be T. gondii: the pseudocysts of T.gondii can be observed in tissue sections with monoclonal observed in tissue sections with monoclonal antibodies. antibodies.

T. gondii: T. gondii: direct detection of direct detection of T.gondii T.gondii in clinical in clinical specimens is rare;parasites can be isolated from specimens is rare;parasites can be isolated from blood, CSF, amniotic fluid,tissue biopsies on cell lines blood, CSF, amniotic fluid,tissue biopsies on cell lines (THP-1 or MRC-5). (THP-1 or MRC-5). In clinical specimens the presence of parasites can In clinical specimens the presence of parasites can alsoalso be demonstrated by PCR analysis. be demonstrated by PCR analysis.

T. gondii:T. gondii: intracellular trophozoites of intracellular trophozoites of T.gondiiT.gondii in in a cell culture. a cell culture. The trophozoites proliferate within the vacuole The trophozoites proliferate within the vacuole developing a pseudocyst. developing a pseudocyst. (Trophozoites in a THP-1 cell, Giemsa stain).(Trophozoites in a THP-1 cell, Giemsa stain).

T. gondii:T. gondii: in cell cultures in cell cultures T.gondiiT.gondii proliferates to proliferates to form a pseudocyst of 8-20 parasites. form a pseudocyst of 8-20 parasites. (Trophozoites in a THP-1 cell, Giemsa stain).(Trophozoites in a THP-1 cell, Giemsa stain).

T. gondii:T. gondii: lysis of a THP-1 cell with release of lysis of a THP-1 cell with release of tachizoites in culture. tachizoites in culture. (Trophozoites in a THP-1 cell, Giemsa stain). (Trophozoites in a THP-1 cell, Giemsa stain).

T. gondii:T. gondii: microscopical features of tachizoites of microscopical features of tachizoites of Toxoplasma gondiiToxoplasma gondii and peritoneal macrophages and peritoneal macrophages of mouse in peritoneal exudate. (SEM)of mouse in peritoneal exudate. (SEM)

T. gondii:T. gondii: microscopical features of tachizoites of microscopical features of tachizoites of Toxoplasma gondiiToxoplasma gondii and peritoneal macrophages of and peritoneal macrophages of mouse in peritoneal exudate. (SEM)mouse in peritoneal exudate. (SEM)

T. gondii:T. gondii: the anterior pole of an endozoid in the anterior pole of an endozoid in tangential projection.Several subpellicular tangential projection.Several subpellicular fibrils and their insertion onfibrils and their insertion on the anterior polar the anterior polar ring are visible.ring are visible.

T. gondii:T. gondii: transmision electron microscopic picture.  transmision electron microscopic picture. Longitudinal section of an endozoid.Longitudinal section of an endozoid.

T. gondii:T. gondii: cross-section through an endozoid  cross-section through an endozoid in an advanced stage of endodiogeny. in an advanced stage of endodiogeny. The daugther cells appear to be surrounded. The daugther cells appear to be surrounded. In each of these news cells there are two round In each of these news cells there are two round bodiesbodies that lengthen forming the first that lengthen forming the first rhoptries.rhoptries.

ZOOMASTIGOPHOREA ZOOMASTIGOPHOREA Order:Order: KinetoplastidaKinetoplastida

TRYPANOSOMA TRYPANOSOMA BRUCEI RHODESIENSE /BRUCEI RHODESIENSE /

T.B. GAMBIENSE T.B. GAMBIENSE

Sleeping sickness occurs in Africa between the Sleeping sickness occurs in Africa between the 15° North and the 20° South. 15° North and the 20° South. The T.b.rhodesiense form is found in East and The T.b.rhodesiense form is found in East and Central-East Africa whereas theCentral-East Africa whereas the T.b.gambiense T.b.gambiense infection occurs in Central and West Africa.infection occurs in Central and West Africa.

The African The African trypanosomiasis trypanosomiasis is transmitted is transmitted by several by several species of tse-species of tse-tse flies tse flies ((GlossinaGlossina spp.). spp.).

Larva and Larva and pupae of pupae of Glossina Glossina morsitans morsitans 

Adult Glossina Adult Glossina tachinoides in tachinoides in West Africa West Africa

T. b. gambiense and rhodesiense:T. b. gambiense and rhodesiense: two forms of two forms of trypomastigotetrypomastigote can be seen in peripheral blood: can be seen in peripheral blood: one is long slender, 30 µm in lengtone is long slender, 30 µm in lengthh,and is ,and is capable of multiplying in the host, the other is capable of multiplying in the host, the other is stumpy, not dividing,18 µm in lengtstumpy, not dividing,18 µm in lengthh..

Trypanosoma brucei gambiense andTrypanosoma brucei gambiense and rhodesiense:rhodesiense: trypanosomes appeartrypanosomes appear in the peripheral blood 5 to in the peripheral blood 5 to 21 days after the infecting bite.21 days after the infecting bite.

Trypanosoma brucei gambiense and Trypanosoma brucei gambiense and rhodesiense: rhodesiense: the terminal stage of the infection the terminal stage of the infection ("sleeping sickness") is the result of a chronic ("sleeping sickness") is the result of a chronic meningoencephalomyelitis. (H&E stain).meningoencephalomyelitis. (H&E stain).

Trypanosoma brucei gambiense and Trypanosoma brucei gambiense and rhodesiense:rhodesiense: the typical pathological lesion the typical pathological lesion of of trypanosomiasis is a perivascular round-cell trypanosomiasis is a perivascular round-cell infiltration (perivascular cuffing)infiltration (perivascular cuffing) due to glial due to glial cells, lymphocytes and plasmocytes (Mott cells). cells, lymphocytes and plasmocytes (Mott cells). (H&E stain). (H&E stain).

LOBOSEA LOBOSEA Order:Order: AmoebidaAmoebida

ACANTHAMOEBA SP.ACANTHAMOEBA SP.

AcanthamoebaAcanthamoeba spp.: free living amoebae of the spp.: free living amoebae of the AcanthamoebaAcanthamoeba genus genus cause two clinical syndrome:cause two clinical syndrome:1) Granulomatous amoebic encephalitis (GAE)1) Granulomatous amoebic encephalitis (GAE)2) Subacute and chronic amoebic keratitis2) Subacute and chronic amoebic keratitisA disseminated form of GAE is described in A disseminated form of GAE is described in individuals with the Acquiredindividuals with the Acquired Immunodeficiency Immunodeficiency Syndrome (AIDS)Syndrome (AIDS)Several species of Several species of AcanthamoebaAcanthamoeba have been have been identified:identified:A.castellani, A.culberstoni, A.polyphaga, A.castellani, A.culberstoni, A.polyphaga, A.zhysodes, A.hatchetti,A.astronyxis,A.palestinensis.A.zhysodes, A.hatchetti,A.astronyxis,A.palestinensis.(Trophozoites, trichrome stain).(Trophozoites, trichrome stain).

AcanthamoebaAcanthamoeba spp.: clinical manifestations include spp.: clinical manifestations include chronicchronic granulomatous encephalitis and keratitis granulomatous encephalitis and keratitis (in particular in individuals who wear contact lens); (in particular in individuals who wear contact lens); some case of disseminatedsome case of disseminated cutaneous infection cutaneous infection have been reported in AIDS patients.have been reported in AIDS patients.

AcanthamoebaAcanthamoeba spp.: the trophozoite is irregular, spp.: the trophozoite is irregular, 15-45 µm,having micropseudopodia called 15-45 µm,having micropseudopodia called acanthopodia;in trichrome stain the cytoplasm of acanthopodia;in trichrome stain the cytoplasm of trophozoites appears greenish pink,the central trophozoites appears greenish pink,the central located kariosome pink or red.(Trichrome stain).located kariosome pink or red.(Trichrome stain).

Acanthamoeba spp.: the cysts are spherical, Acanthamoeba spp.: the cysts are spherical, 15-20 µm in diameter,having a thick double 15-20 µm in diameter,having a thick double wall. The outer wall may be spherical or wall. The outer wall may be spherical or wrinkled, wrinkled, the inner wall appear stellate or polyhedral. the inner wall appear stellate or polyhedral. (Acanthamoeba trophozoites and a cyst, (Acanthamoeba trophozoites and a cyst, trichrome stain).trichrome stain).

Acanthamoeba Acanthamoeba spp.: both forms have a single spp.: both forms have a single nucleus with a largenucleus with a large centrally located nucleolus. centrally located nucleolus. With trichrome stain, the cysts stain red.Species With trichrome stain, the cysts stain red.Species identification is based on morphology of cysts identification is based on morphology of cysts (stellate, polyhedral). (stellate, polyhedral). 

Acanthamoeba spp.: trophozoite as seen under Acanthamoeba spp.: trophozoite as seen under phase contrast microscope.Its big nucleolus, both phase contrast microscope.Its big nucleolus, both lobopodia and acanthopodia and various vacuoles lobopodia and acanthopodia and various vacuoles can be seen clearly. can be seen clearly.

Acanthamoeba spp.: trophozoites as seen Acanthamoeba spp.: trophozoites as seen under phase contrast microscope. under phase contrast microscope.

Acanthamoeba spp.: cysts stained with Acanthamoeba spp.: cysts stained with Heidenhain’s iron alum-haematoxylin method.Heidenhain’s iron alum-haematoxylin method.

NAEGLERIA FOWLERINAEGLERIA FOWLERI

Naegleria fowleri Naegleria fowleri is the agent of a severe purulent is the agent of a severe purulent meningoencephalitis: the "Primary amoebic meningoencephalitis: the "Primary amoebic meningoencephalitis". meningoencephalitis". N.fowleriN.fowleri are free living are free living amoebas that live in warm fresh water all over the amoebas that live in warm fresh water all over the world. world. The lyfe cycle consist of three stages: the The lyfe cycle consist of three stages: the amoeboid growing form that lives in the mud and amoeboid growing form that lives in the mud and at the bottom of the ponds; the rapidly motile at the bottom of the ponds; the rapidly motile biflagellate trophozoite who lives in surface layers biflagellate trophozoite who lives in surface layers of water (the infective form); the dormant cyst. of water (the infective form); the dormant cyst. Primary amoebic meningoencephalitis occurs in Primary amoebic meningoencephalitis occurs in individuals who have been exposed to freshwater individuals who have been exposed to freshwater lakes or ponds usually during swimming; the lakes or ponds usually during swimming; the incubation period is about 3 to 7 days (but it may incubation period is about 3 to 7 days (but it may last up to 2 weeks). Invasion of the CNS occurs last up to 2 weeks). Invasion of the CNS occurs after nasal inhalation of contaminated water after nasal inhalation of contaminated water containig the biflagellate trophozoites; containig the biflagellate trophozoites; trophozoites (in the amoeboid form once arrived in trophozoites (in the amoeboid form once arrived in the nasal cavity) penetrate the epithelium and the nasal cavity) penetrate the epithelium and enter the CNS through the olphactory nerve enter the CNS through the olphactory nerve branches in the cribriform plate and cause a branches in the cribriform plate and cause a purulent meningoencephalitis. purulent meningoencephalitis. Trophozoites are 10-to 30 m m in diameter and Trophozoites are 10-to 30 m m in diameter and have a clear nucleus with a prominent dense have a clear nucleus with a prominent dense central nucleolus; the cytoplasm contains central nucleolus; the cytoplasm contains mytochondria and the rough endoplasmic mytochondria and the rough endoplasmic reticulum; usually ingested red blood cells, reticulum; usually ingested red blood cells, leukocytes and bacteria are visible.leukocytes and bacteria are visible.  Cysts are 9 m m in diameter; they are spherical Cysts are 9 m m in diameter; they are spherical with a central nucleus. with a central nucleus. 

N. gruberi: N. gruberi: trophozoite as seen under phase trophozoite as seen under phase contrast microscope. contrast microscope. Its big nucIts big nuclleeoolus, four lobopod type lus, four lobopod type pseudopodia pseudopodia and the contractile vacuole can be clearly seen.and the contractile vacuole can be clearly seen.

NaegleriaNaegleria spp spp..: trophozoite stained with : trophozoite stained with Greenstein’s five dye stainGreenstein’s five dye stain and observed under and observed under dark field microscope.dark field microscope.