NEUROPARASITIC INFECTIONS

8/10/2019 NEUROPARASITIC INFECTIONS

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NEUROPARASITIC

INFECTIONSbasis, diagnosis and limitatio

Dr.T.V.Rao MD


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How Parasites Enter Blood BBarrier

Some intracellular andextracellular parasites cantraverse the BBB during thecourse of infection and causeneurological disturbances and/ordamage which are at times fatal.

The means by which parasitescross the BBB and how theimmune system controls theparasites within the brain arestill unclear.


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Methods to Diagnose Infecti

Methods for the diagnosis ofinfectious diseases havestagnated in the last 2030years.Few major advancesin clinical diagnostic testing

have been made since theintroduction of PCR,although new technologiesare being investigated.


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Are we Practising Older Meth

Many tests that form thebackbone of themodern microbiology

laboratory are based on

very old and labour-intensive technologiessuch as microscopy formalaria or many parsites


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Parasitic Infections Migrating froDeveloping Nations to Developed Na

Parasitic infections of theCNS, previously restrictedmainly to people living indeveloping countries, arebecoming increasinglymore prevalentthroughout the world.With the advent ofincreasing global travel,


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Immune suppression changesAdoptability of Infections

Potentimmunosuppression,and HIV infection,parasitic infectionswill likely becomeeven morecommonplace.


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Overall familiarity is ImportantEvaluate the Matters

Basic familiarity withcommon pathogens canmake diagnosis moreexpeditious and efficient.For the clinicianconfronted with a patientwith suspected parasiticinfection, additionalassistance with

diagnostic evaluation


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Beginning of Career to Learn and Prof parasitology at Mansa General ho

Zambia


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Is it easy to Diagnose ParasitInfections of Nervous system

Parasitic infection of thenervous system canproduce a variety ofsymptoms and signs.Because symptoms ofinfection are often mildor nonspecific, diagnosiscan be difficult.


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Be familiar with Epidemioland Radiology

Familiarity with baepidemiologicalcharacteristics andistinguishingradiographic find

increase the likelof detection and ptreatment of parasinfection of the nersystem.


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We are still using the Microscas a Traditional tool in Diagno

The primary tests currently used todiagnose many parasitic diseases havchanged little since the developmentmicroscope in the 15th century by Anvan Leeuwenhoek. Furthermore, mosthe current tests cannot distinguishbetween past, , latent, acute, and

reactivated infections. Di ti M th d i


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Diagnostic Methods inParasitology are Complex

If we wish sensitivity and specifi The methods currently in use

range from rather simple, easilymanaged and routinetechniques to the extremelycomplex cutting edgetechnologies of modernmolecular biology and high-

throughput miniaturisedmethods usually done as part ofthesis and research work andrarely for diagnostic work


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Newer Serological Assa

Firstly, a number of newerserology-based assays that arehighly specific and sensitivehave emerged, such as theFalcon assay screening testELISA (FAST-ELISA) , Dot-ELISArapid antigen detectionsystem (RDTS), and luciferaseimmunoprecipitation system(LIPS).


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Emerging Molecular metho

Secondly, molecular-basedapproaches such as loop-mediated isothermalamplification (LAMP) , real-time polymerase chainreaction and Luminex have

shown a high potential foruse in parasite diagnosiswith increased specificityand sensitivity.


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Parasites Infections of the CentNervous System

Toxoplasma gondii associated with congendefects and AIDS

African trypanosomes African sleeping sic

Plasmodium falciparum cerebral malaria

Endamoeba histolytic rare invasion of the

Free-living amebae rare cases


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MALARIA


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Malaria Continues to be aEmergency in many countri

Malaria should beconsidered a potentialmedical emergency andshould be treatedaccordingly. Delay in

diagnosis and treatment is aleading cause of death inmalaria patients in ManyCountries


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Peripheral Blood Smear a Great

Clinicians seeing a mapatient may forget to cmalaria among the potdiagnoses and not ordeneeded diagnostic testLaboratories may lack

experience with malarto detect parasites wheexamining blood smeathe microscope


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Making a Smear is Most Important PMicroscopy


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Microscopic Diagnosi

Malaria parasites can beidentified by examining underthe microscope a drop of thepatient's blood, spread out as a"blood smear" on a microscopeslide. Prior to examination, the

specimen is stained(most often with the Giemsastain) to give the parasites adistinctive appearance. Thistechnique remains the goldstandard for laboratoryconfirmation of malaria.


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Appearance of P.vivax and P. falc


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Malaria Diagnosis is a Emerge


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Clinical examination a collaborapoint

Cerebral malaria, withabnormal behaviour,impairment ofconsciousness,

seizures, coma, orother neurologicabnormalities


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Antigen Detection Various test kits are avai

detect antigens derived malaria parasites. Suchimmunologic("immunochromatograpmost often use a dipstickcassette format, and proresults in 2-15 minutes. T"Rapid Diagnostic Tests" offer a useful alternativemicroscopy in situationsreliable microscopic diagnot available.

HRP2 l l di t lik lih d f b l


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HRP2 levels predict likelihood of cerebral maAfrican children

. While only about 1% of Plasmodium falciparum infectioprogress to cerebral malaria, mortality occurs in 1020%affected patients. plasma concentrations of the Plasmodprotein HRP2 (histidine rich protein 2) can predict the oddeveloping cerebral malaria in Malawian children. Their

show that mean plasma HRP2 concentrations were signhigher in the children who developed cerebral malaria tones with uncomplicated malaria.


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QBC SYSTEM CANNOTDIFFERENTIATE Species


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No Single Test is Perfe

Current evidence indicates that no single meththe diagnosis of malaria is perfect nor can any them be a stand-alone accurate and effectivediagnostic criterion . Accurate and effective madiagnosis should thus involve a rational approa

each patient with suspected malaria employingsymptoms/signs-based and laboratory-based mdiagnostic methods.


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Emerging methods at even SmaClinks

The prioritizing of any of themalaria diagnostic methods, atall times, should be influencedby various factors includingmalaria endemicity, transmissionpattern, the urgency of the

diagnosis, the experience of thehealth worker, effectiveness ofthe health care system, andavailable budget resources.


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Rapid Diagnostic Test

RDTs do not require laboratory equipment andbased on the same principle and detect malariantigen in blood flowing along a membranecontaining specific anti- malaria antibodies . Mthe available RDTs are P. falciparum protein spe

(either histidine rich protein II -HRP-II or lactasdehydrogenase-LDH) while some RDTs detect Pfalciparum and other Plasmodium proteins sucaldolase or pan-malaria pLDH.

R id di ti t t


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Rapid diagnostic tests provuseful

Several studies havereported theperformance of RDTs tobe excellent. Inarguably,RDTs are enhancing the

benefits of parasite-based diagnosis ofmalaria though notwithout problems or

limitations


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Molecular Malaria laboratory diagnostic Molecular malaria techniques

such as PCR on blood or, more

recently, even on saliva samplesdevised in Zambia by(Mharakurwa et al), the loop-mediated isothermalamplification (LAMP),microarray, mass spectrometry

(MS), and flow cytometry (FCM)assay techniques are all newdevelopments mainly utilized inresearch settings than duringroutine patient care.


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Serology Serology detects antibodies

against malaria parasites,using either indirectimmunofluorescence (IFA)or enzyme-linked

immunosorbent assay(ELISA). Serology does notdetect current infection butrather measures pastexposure.


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Rapid Tests

RDTs currently avain the market are a few and includbrands such as OA L , P a r a c h e

C T, p a r a - s i g parascreen, and SBioline.

A t f t


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Artefacts


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Free Living AmoebicInfections

PARASITIC MENINGITIS


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Free Living Amoeba Naegleria fowleri and

Acanthamoeba spp., arecommonly found in lakes,swimming pools, tap water, andheating and air conditioning units.While only one species ofNaegleria, N. fowleri, is known toinfect humans An additional agent

of human disease, Balamuthiamandrillaris, is a related free-livingamoeba that is morphologicallysimilar to Acanthamoeba in tissuesections in light microscopy.


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Diagnostic Findings In Naegleria infections, the

diagnosis can be made bymicroscopic examination ofcerebrospinal fluid (CSF). A wetmount may detect motiletrophozoites, and a Giemsa-stainedsmear will show trophozoites withtypical morphology. Confocal

microscopy or cultivation of thecausal organism, and itsidentification by directimmunofluorescent antibody, mayalso prove useful.

Naegleria fowleri/Primary Amoe


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Naegleria fowleri/Primary AmoeMeningo encephalitis

Early symptoms include severe,

throbbing headache, fever, nausea,and vomiting.Most patients have ahistory of swimming or bathing instagnant water.

Meningismus is common, andsome patients present with

seizures or coma. Differentiationbetween PAM and bacterialmeningitis can be difficult but iscrucial given the rapid progressionof N. fowlerii infection.


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Wet mounts are benefic

Organisms are not visualizedwith Grams stain because

amoebas are killed duringthe fixation process.

CSF wet mount should be

performed to look fortrophozoites. Giemsastaining of CSF may also beuseful. In the past,

A th b


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Acanthamoeba In Acanthamoeba infections,

the diagnosis can be madefrom microscopicexamination of stainedsmears of biopsy specimens(brain tissue, skin, cornea)or of corneal scrapings,which may detecttrophozoites and cysts

Acanthamoeba histolytica and Balam


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Acanthamoeba histolytica and Balammandrillaris/Granulomatous Amoe

CNS infection by A.histolytica is uncommonin immunocompetenthosts. In contrast to A.histolytica, B.

mandrillaris causesinfectioninimmunocompetent andimmunosuppressed hosts

with equal frequency

Corneal scrapings


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Corneal scrapings

Definitive diagnosiscan be obtained bydemonstration oftrophozoites or cysts

of A. histolytica onstained smears ofbiopsy specimens orcorneal scrapings


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Immunofluorescence stud

Direct IFA tests can

useful. Differentiatiobetween B. mandrilA. histolytica infectirequiresimmunofluorescencstudies. Examinatiocontact lenses fromwith keratitis can rehistolytica

1Trophozoite of N. fowleri in CSF, stained with haeand eosin


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and eosin2Trophozoite of N. fowleri in CSF, stained with haeand eosin

1Cyst of Acanthamoeba sp. from brain tissue, stainedhaematoxylin and eosin


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y2Trophozoites of Acanthamoeba sp. in a corneal scra

stained with H&E.

R l Ti PCR


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Real-Time PCR

A real-time PCR was

developed at CDC foridentification ofAcanthamoeba spp.,Naegleria fowleri, andBalamuthia mandrillaris inclinical samples.1 This assayuses distinct primers andTaqMan probes for thesimultaneous identificationof these three parasites


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Toxoplasmosis

Cerebral toxoplasmosis : CentreDi C t l (CDC) it i


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Disease Control (CDC) criteria diagnosis

Recent onset of focal neurologicalabnormality consistent with intracranidisease or reduced consciousness

Evidence from brain imaging of a lesio

or MRI)Positive serum antibody to T. gondii oresponse to treatment

Di i f t l


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Diagnosis of toxoplasmos

Diagnosis of toxoplasmosis is rarely made throdetection or recovery of organisms, but relies hon serological procedures. Parasites can be detin biopsied specimens, buffy coat cells, or cerespinal fluid. These materials can also be used t

inoculated mice or tissue culture cells. Howevedetecting tachyzoites from these materials is dTherefore, serologic tests are recommended fodiagnosis

I M d T l


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IgM and Toxoplasmos

Acute infections are

characterized by high IgMtitres and/or a significantincrease in total antibodytitre in a sample taken twoweeks later. The serologymay also correlate with theacute stage symptoms insome individuals.

Di ti t t f T l


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Diagnostic tests for Toxoplas

Sabin-Feldman dye test (DT)

Enzyme immunoassay for T. gondii specific(EIA)

Immunsorbent agglutination assay (ISAGA

Enzyme immunoassay for IgG avidity Isolation and culture of parasite

Direct detection by microscopy and PCR

Persons ith oc lar disea


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Persons with ocular disea Eye disease (most

frequently retinochoroiditis)from Toxoplasma infectioncan result from congenitalinfection or infection afterbirth by any of the modes oftransmission discussed onthe epidemiology and riskfactors page.

Persons with compromise


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pimmune systems

Persons withcompromised immunesystems mayexperience severe

symptoms if they areinfected withToxoplasma whileimmune suppressed.

Serology


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SerologyIn the second situation, a second specshould be drawn and both specimenssubmitted together to a reference lab employs a different IgM testing system

confirmation. Prior to initiation of patmanagement for acute toxoplasmosis,IgG/IgM positives should be submittedreference lab for IgG avidity testing.

Diagnosis


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Diagnosis The diagnosis of toxopla

typically made by seroloA test that measuresimmunoglobulin G (IgG) determine if a person hainfected. If it is necessaryestimate the time of infewhich is of particular im

for pregnant women, a tmeasures immunoglobuis also used along with osuch as an avidity test.

Diagnosis by staining meth


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Diagnosis by staining meth

Diagnosis can be made by

direct observation of theparasite in stained tissuesections, cerebrospinal fluid(CSF), or other biopsymaterial. These techniques

are used less frequentlybecause of the difficulty ofobtaining these specimens.


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:

Cysticercosis

Cysticercosis


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Cysticercosis This infection is caused by pork

tapeworm larvae (see TapewormInfection). It is the most commonparasitic infection in the WesternHemisphere. After people eat foodcontaminated with cysticercuseggs, secretions in the stomach

cause the eggs to hatch into larvae.The larvae enter the bloodstreamand are distributed to all parts ofthe body, including the brain

MRI AND CT SCNNING CONTINUES T


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MAIN IN STAY IN DIAGNOSIS

Magnetic resonan

imaging (MRI) orcomputed tomog(CT) can often shocysts. But blood te

a spinal tap (lumbpuncture) to obtasample of cerebrofluid are often neeconfirm the diagn

PRIMARY EXAMINATION


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PRIMARY EXAMINATION

Infection with adult T. solium

worms can usually bediagnosed by microscopicexamination of stool samplesand identification of eggsand/or proglottids. However, T.

solium eggs are present in 50% of stool samples frompatients with cysticercosis.

CDC standarsises the Immuno


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Testing The CDC's immuno

assay (using a serumspecimen) is highly and more sensitive tother enzymeimmunoassays (partwhen > 2 CNS lesionpresent; sensitivity when only a single cpresent).

Immunoblot assay


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Immunoblot assay

CDC's immunoblot assay with

purified Taenia solium antigenshas been acknowledged by theWorld Health Organization andthe Pan American HealthOrganization as theimmunodiagnostic test of choice

for confirming a clinical andradiologic presumptive diagnosisof neurocysticercosis.

We mainly Dependent o


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We mainly Dependent o

There are two available

serologic tests to detectcysticercosis, theenzyme-linkedimmunoelectrotransfer

blot or EITB, andcommercial enzyme-linked immunoassays.

Antigen Detection


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Antigen Detection

Tests that detect circulat

cysticercal antigens in seCSF have been developeprove to be most useful response to therapy in insubarachnoid and ventriof neurocysticercosis. Anlevels drop quickly in cur

patients, so serum antigmonitoring is useful for atreatment and determinclinical cases.

Antigen Detection Methods li i i


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sensitivity

Antigen detectiontesting is not assensitive as antibodydetection and shouldnot be used todiagnoseneurocysticercosis

Molecular Detection


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Molecular Detection

PCR tests have been

developed to detect T.solium DNA in CSF butthese are not widelyused for clinicallaboratory diagnosis ofneurocysticercosis.

Schistosomiasis (Bilhar


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Schistosomiasis (Bilhar EPIDEMIOLOGYSchistosomiasis

occurs in up to 300 million peopleworldwide each year and is causedby five species of blood flukes(digenetic trematodes):Schistosoma mansoni,S.haematobium, S. japonicum, S.intercalculatum, and S. mekongi.62

CNS involvement has beenreportedwith three of the five species: S.mansoni, S. haematobium, S.

japonicum

Neurological involveme


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Neurological involveme Neurological involvement usually

appears weeks ormonths afterinitial infection when eggs migratethrough the vascular system to thebrain orspinal cord; symptoms mayresult from mass effect of the eggitself or from granulomaformationaround the egg. Because the

parasite likely enters the CNS viaBatsons plexus,the spinal cord andposterior fossa are the mostcommon sites of involvement

DIAGNOSIS


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DIAGNOSIS

Definitive diagnosis of

schistosomiasis is obtaidentification ofan eggtissue. Detection of scheggs in stool or urine cthe diagnosisofschistosomiasis.14 Sto

examination is more seS. mansoni and S. japoexamination of urine isS. hematobium.


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Echinococcus

(Hydatid Disease)

Echinococcus (Hydatid DiseCESTODES


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CESTODES Hydatid infection often remains

undetected until cystenlargement producessymptoms. The cyst can causemore severe symptoms if itruptures or becomes super-infected. Central nervous system

(CNS) involvement complicates 2and 5% of infections with E.granulosis and E. multilocularis,respectively.1,3

DIAGNOSIS


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DIAGNOSIS Diagnosis of E. granulosus infection

can be confirmed by serum indirecthemagglutination (IHA), indirectfluorescent antibody (IFA), orenzyme-linked immunosorbentassay (ELISA), with assay sensitivityrates ranging from 50 to 60% inpatients with pulmonary cysts to98% in patients with hepatic cysts.9

Serum assays to detect E.multilocularis are more sensitivethan assays for E. granulosis and arenot cross-reactive

NEUROIMAGING


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NEUROIMAGING

ontrast-enhanced computerized

tomography (CT) of the brain isusually sufficient for evaluation,but magnetic resonance imaging(MRI) is warranted if surgicalintervention is planned. CTdemonstrates cysts of various

sizes, sometimes in grapelikeclusters.13 Chronic disease maydevelop a granulomatousappearance

Serum indirecthemagglutination (IHA)


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hemagglutination (IHA) Diagnosis of E.granulosus infection

can be confirmed by serum indirecthemagglutination (IHA),indirectfluorescent antibody (IFA),or enzyme-linked immunosorbentassay (ELISA), with assaysensitivityrates ranging from 50 to 60% inpatients with pulmonary cysts to

98% in patientswith hepatic cysts.9Serum assays to detect E.multilocularis are more sensitivethan assaysfor E. granulosis and arenot cross-reactive.


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CDC Helps in Diagnosof Parasitic Infections

I wish many use this Fac


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y

The modern generation

of Microbiologists canuse digital imagingtechnology of parasiticinfections with Web site

developed andmaintained by CDC'sDivision of ParasiticDiseases and Malaria(DPDM)

CDC Helps with Tele diagnosiPaasitic Infection


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Paasitic Infection DPDx is a unique on

educational resourcincludes visual depiparasite lifecycles, areference library of images of parasites,

guidance on properlaboratory techniqudiagnostic parasitoloit is much more thansite.

1Encysted larvae of Trichinella sp. in muscle 2 Babesia and Falciparum


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2 Babesia and Falciparum

Diagnostic Assistance funct


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A Diagnostic Assistancefunction, in whichlaboratory and other healthprofessionals can askquestions and/or senddigital images of specimens

for expedited review andconsultation with DPDxstaff. This assistance is freeof charge.

Why we Stand Today InDiagnosis


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Diagnosis In spite of many Advances in Medical prof

the Parasitology suffers much lacunae indiagnosis for optimal treatment, great reabeing lack of human dedication in the maconcerned, and lack of evaluation of skills

matters of diagnostic talents in postgraduexaminations, and above all non-availabiliadvancing technologies

The reat uestion huntmany of us, If we are true


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your Job

Are we reallydiagnosing the

Parasitic Infections

Say


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y

OR NO

What Can be Done?


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Speciality of Parasitology

hangs between thedomains of Microbiologyand Pathologists. Howeverit needs more inputs and

coordination of Vetenarysciences and ZoologyProfessionals.


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NEUROPARASITIC INFECTIONS