medical parasitology

MEDICAL PARASITOLOGY

Laboratory diagnosis Of parasitic diseases

S.S Eghbali ApCp BPUMS 2008

By

DefinitionsDefinitions• Medical parasitologyMedical parasitology:: the study of the parasites of the study of the parasites of

man and their medical consequences.man and their medical consequences.• ParasiteParasite:: living organism requiring intimate living organism requiring intimate

prolonged contact with another living organism to prolonged contact with another living organism to meet some of its basic nutritional needs. meet some of its basic nutritional needs.

In a more restricted definition, it refers to organisms In a more restricted definition, it refers to organisms that are not viruses, bacteria, fungi, rickettsia, or that are not viruses, bacteria, fungi, rickettsia, or chlamydia and obviously include organisms of chlamydia and obviously include organisms of varying complexity from a unicellular protozoa to a varying complexity from a unicellular protozoa to a complex multicellular helminths.complex multicellular helminths.

• HostHost:: organism harboring a parasite. organism harboring a parasite.

• Definitive hostDefinitive host:: animal harboring the adult or animal harboring the adult or sexually mature stage of the parasite.sexually mature stage of the parasite.

• Intermediate hostIntermediate host:: animal in which development animal in which development occurs but in which adulthood is not reached.occurs but in which adulthood is not reached.

• Life cycleLife cycle: for survival and reproduction reasons : for survival and reproduction reasons many parasites evolve through a number of many parasites evolve through a number of morphologic stages and several environments or morphologic stages and several environments or different hosts. The sequence of morphologic and different hosts. The sequence of morphologic and environmental stages is referred to as the life cycle.environmental stages is referred to as the life cycle.

• Parasitic infection:Parasitic infection: invasion by endoparasites invasion by endoparasites (protozoa and helminths).(protozoa and helminths).

• Parasitic diseaseParasitic disease:: invasion and pathology produced by invasion and pathology produced by endoparasites.endoparasites.

• Parasitic infestationParasitic infestation:: external parasitism by ectoparasites external parasitism by ectoparasites (arthropods).(arthropods).

• CommensalismsCommensalisms:: the association of two different species or the association of two different species or organism in which one is benefited and the other is neither organism in which one is benefited and the other is neither benefited nor harmed. (e.g. non pathogenic intestinal benefited nor harmed. (e.g. non pathogenic intestinal protozoa)protozoa)

• Reservoir host:Reservoir host: an animal that harbors a species of parasite an animal that harbors a species of parasite that can be transmitted to and infect man.that can be transmitted to and infect man.

• Vector:Vector: an arthropod or other living carrier that an arthropod or other living carrier that transports a pathogenic organism from an infected transports a pathogenic organism from an infected to a non-infected host. to a non-infected host. CarrierCarrier: a host that harbors a : a host that harbors a parasite but exhibits no clinical signs or symptoms.parasite but exhibits no clinical signs or symptoms.

• ZoonosisZoonosis:: a disease involving a parasite for which a disease involving a parasite for which the normal host is an animal, and wherein man can the normal host is an animal, and wherein man can also be infected.also be infected.

• ProtozoaProtozoa:: a subkingdom consisting of unicellular a subkingdom consisting of unicellular eukaryotic (Greek-karyon=nut=nucleus) animals.eukaryotic (Greek-karyon=nut=nucleus) animals.

INFORMATION EMPHASIS

• Agent ID and general importance

• Epidemiology (transmission, distribution, etc)

• Agent damage capability

• Diagnostics

• Control

Epidemiology• Although parasitic infections occur globally,

the majority occur in tropical regions, where there is poverty, poor sanitation and personal hygiene

• Often entire communities may be infected with multiple, different organisms which remain untreated because treatment is neither accessible nor affordable

• Effective prevention and control requires "mass intervention strategies” and intense community education. Examples include:– General improved sanitation: pit latrines,

fresh water wells, piped water– Vector control: insecticide impregnated

bed nets, spraying of houses with residual insecticides, drainage, landfill

– Mass screening and drug administration programmes which may need to be repeated at regular intervals

The burden of some major parasitic infections

Parasite Diseases No. people infected Deaths/yr

Plasmodium malaria 273 million 1.12 million

Soil transmitted helminths:

• Roundworm (Ascaris)

• Whipworm (Trichuris)• • Hookworm (Ancylostoma and

Necator)

Pnemonitis, intestinal obstruction

Bloody diarrhoea, rectal prolapse

Coughing, wheezing, abdominal pain and anaemia

2 billion 200,000

Schistosoma Renal tract and intestinal disease 200 million 15,000

Filariae Lymphatic filariasis and elephantiasis 120 million Not fatal but 40 million disfigured or incapacitated

Trypanasoma cruzi Chagas disease (cardiovascular) 13 million 14,000

African trypanosomes African sleeping sickness 0.3 – 0.5 million 48,000

Leishamania Cutaneous, mucocutaneous and visceral leishmaniasis

12 million; 2 million new cases/yr

50,000

Parasitology - protozoology (protozoa),

helmintology(worms),

enthomology(insects)• Laboratory diagnosis: - life cycle of parasits,

material v laboratory diag.

• Protozoa – intestinal, genital, urinary, blood, tissue

• Worms - Helmints: Nematodes, Cestodes,Trematodes

• Ectoparasits: louse, ticks, flies – important as vectors

Life cycle of parasits -terminology

• Complex life cycle – key to diagnosis• Host – hosts• Definitive host – parasit finishes the growing cycle and is

becoming adult in it• Not typical host - parasit cannot develop in it • Transient host – larves are developing in it and not sexual

multiplication is performed• Helmints : egg - larvae - adult worm

Protozoa :trophozoite - motile cysts – non motile - sexual multiplication - zygota - asexual- schizonts, sporogons

Diagnosis• Problematic, not ususals outside endematic areas• Nonspecific clinical manifestation• eosinophilia in helmintoses – not constant sign• Importance of history – personal, travellers, social, economic, food,

therapy• Conditions for successful dg: - think on parasitosis- také a good sample – right sample, with good method at right time, send

it in appropriate conditions to the lab that is able to identify the parasite, good interpretation:

- Knowledge of life cycle is principal

Laboratory diagnosis• Usually based on morphology (microscopic) • Demonstration of the parasit in different stages of life cycle in

clinical material• Macroscopic examination of the sample (stool or tissue)• Microscopic examination – native smear, staining, concentration

method• Serology – detection of antibodies, detection of antigénes• Genetic probes - detection, identification• Cultivation• Animal model

Stool for parasitological examination• Macroscopy – blood, mucous, adult worms• Microscopy - native smear - iodine – motility, eggs

of helmints, cysts of protozoa, Rbc,Wbc• Concentration methods – separation of cysts of

protozoa and eggs of helmints from other material in the stool

• Staining - identification – smear of native stool + hematoxylin eosin, trichrome

Other material acc.to clinical manifestation

• Perianal - Enterobius vermicularis• Sigmoidoscopy - Entamoeba histolytica• Duodenal aspiration - Giardia lamblia• Biopsy of abscess of liver - Entameba histolytica• Sputum - Ascaris lumbricoides, Strongyloides, • Urine - Schistosoma Hematobium• Urogenital sample - Trichomonas • Blood - (malaria, trypanosomiasis, leishmaniosis, filariosis)

smear, thick drop - staining Giemsa, H&E, • Serum (Hydatid cyst)

Protozoa

• Amoeba - Entamoeba histolytica, Entamoeba coli, Naegleria fowleri, Acanthamoeba, Endolimax nana

• Flagelata - Giardia lamblia, Trichomonas vaginalis, Leishmania, Trypanosoma

• Ciliata - Balantidium coli• Coccidia a Sporosoa - Cryptosporidium,

Blastocystis, Microsporidia, Plasmodia, Babesia,, Toxoplasma

Nematodes -worms• Enterobius vermicularis, Ascaris lumbricoides, Toxocara

canis,cati, Trichuris trichiura, Ancylostoma duodenale, Strongyloides stercoralis, Trichinella spiralis, Wuchereria bancrofti, Dracunculus medinensis

• Nonsegmented body, adult worms living in the GIT-e, - diagnosisa: identification of eggs in the stool (morphology of eggs)

• Filariae – tin worms parasiting in eye, skin, tissue, transmitted by insects. Larval form- microfilariae penetrate to blood and are transmitted by suckling insect

Cestodes -• Head - scolex, segmented body• Hermafrodit, male and female organs are present in every

segment - dif.dg. They have not GIT, absorbtion of food. Complex life cycle with transient host (sometimes - human – larval stage of cysticerkósis, echinococcosis)

• Taenia solium, Taenia saginata, Diphylobotrium latum, Echinococcus granulosus, Hymenolepsis nana

Trematodes -• Usually hermafrodits (ex Schistosoma)

• Need transient host

• Fasciolopsis, Clonorchis, Paragonimus, Schistosoma

Enterobius vermicularis

• Definitive host - human

• transient - none

• dg. – perianal sample – microscopy of eggs

• fecal oral transmission - autoinfection

Enterobius vermicularis

Ascaris lumbricoides

• Definitive host: human

• Larva migrans: intestin, colon - muc.membrane - blood- lung - cough - mouth - colon

• dg. Egg in stool

• Infection via contaminated food

• Symptoms acc.to localisation of the larva

Ascaris lumbricoides

Toxocara canis, cati

• Definitive host dog, cat

• Transient host: rat

• Human incidental: human (larves)

• dg. serology

• transmission: hand food

Taenia saginata

• Definitive: human

• transient: cattle

• dg. Segments in stool

• Transmission cysticercus in beef

Taenia solium

• Definitive: pig

• transient: rat

• incidental: human in small intestin

• dg. Serology,body Rare

• Contaminated food

Echinococcus granulosus

• definitive: dog• transient:sheep• incidental: human• Diagnosis: serology,Direct methods• transmission: cyste in meat• infection: mechanic pressure from

expanded cyst, prolonged growing, rupture of the cyst and dissemination

Echinococcus granulosus

Entamoeba histolytica

• definitive: human

• Diagnosis:trophozoites in stool, serology

• dysenteria – diarhea with blood

Entamoeba histolytica

Naegleria fowleri, Acantamoeba,Balamuthia

• Free Living in water

• Human (via nose)

• Diagnosis:microscopy in CSF- identification of invasive strains

Diseases:Negleriafowleri:P.A.M Balamuthia:G.A.E,Acantamoeba:Keratitis

Toxoplasma gondii• Definitive: cat• transient: rat• incidental: human• Diagnosis: serology , IgA, IgG, IgM• transmission: food borne, hand, annimal• disease: - intrauterine primoinfection

- generalized lymphadenopathy, encystation in organs – abortion, eye……..

Trichomonas vaginalis

• Definitive: human

• transient: none

• dg. Cultivation - microscopy trophozoite - from vagina, urine

• Sexual transmission

• Therapy of both (all) partners

Giardia lamblia

• definitive: human – small intestin,dog, cat

• transient: non

• Diag:microscopy – cysts and trophozoits in stool, transient in duodenal secretion

• Transmission contaminated food

• malabsorption

Giardia lamblia

Trypanosoma gambiensis (spavá choroba)

• Definitive host: insect - fly tse tse

• transient: human, monkey

• dg.microscopy – thick drop

• Transmission bite

• Disease – sleeping disease, myalgia, arthralgia, lymphadenopathy, hyperactivity in acute phase, lethargy, meningoencephalitis, coma

Plasmodium-malariae, falciparum • Definitive host:Anopheles • Transient host: human, monkey• Diag:microscopy thick drop• Transmission insect bite• disease: malaria acc.to the rate of schizogonia- clinically as

fever attacks - tercianna, quartana,

CONTROL OF PARASITIC DISEASESCONTROL OF PARASITIC DISEASES

A CHALLENGE FOR OUR FUTURE

Studies on geographical distribution and epidemiology of zoonoses by using modern tools are crucial to establish the appropriate local control measures

Studies on geographical distribution and epidemiology of zoonoses by using modern tools are crucial to establish the appropriate local control measures

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COMPLEXITY OF PARASITIC DISEASES AND PROBLEMSCOMPLEXITY OF PARASITIC DISEASES AND PROBLEMS

Although the general knowledge on the disease epidemiology and transmission is usually available, the knowledge on local epidemiology and transmission characteristics is still lacking in many cases

Although the general knowledge on the disease epidemiology and transmission is usually available, the knowledge on local epidemiology and transmission characteristics is still lacking in many cases

The complexity of zoonotic infectious diseases offers, however, several problems which must be solved:

The complexity of zoonotic infectious diseases offers, however, several problems which must be solved:

Multisdisciplinary approaches and transprofessional team networks are needed for both research and training. Efforts will be needed to convince different ministries and health responsibles to co-work and related political-strategic difficulties must be solved

Multisdisciplinary approaches and transprofessional team networks are needed for both research and training. Efforts will be needed to convince different ministries and health responsibles to co-work and related political-strategic difficulties must be solved

Field work shall again be encouraged Field work shall again be encouraged

The need for “old-fashioned” disciplines as Medical Malacology and Entomology shall be emphasized

The need for “old-fashioned” disciplines as Medical Malacology and Entomology shall be emphasized

Funding agencies shall be convinced about the need for increasing efforts at animal level

Funding agencies shall be convinced about the need for increasing efforts at animal level

THE NEED TO AGAIN EMPHASIZE THE IMPORTANCE OF FIELD STUDIES


Experimental work has sense if it is for the understanding of what happens outside

Experimental work has sense if it is for the understanding of what happens outside

During years and years we have been developping numerous new, modern, sophisticated molecular tools for the diagnosis of many infectious diseases; once the new test obtained, a field trial has been usually performed to verify its usefulness; and afterwards, only a few or nobody is applying it in endemic areas

During years and years we have been developping numerous new, modern, sophisticated molecular tools for the diagnosis of many infectious diseases; once the new test obtained, a field trial has been usually performed to verify its usefulness; and afterwards, only a few or nobody is applying it in endemic areas

Too sophisticated to be applied in many developing countries Too sophisticated to be applied in many developing countries

Too expensive and consequently unaffordable Too expensive and consequently unaffordable

Too much similar tests for the same disease, so that health responsibles become lost

Too much similar tests for the same disease, so that health responsibles become lost



Divorce between traditional methods (as those for simple epidemiological surveys) and new technologies

Divorce between traditional methods (as those for simple epidemiological surveys) and new technologies

In many centres of developing countries, health responsibles think that traditional diagnostic methods are old fashioned and make efforts to incorporate modern methods which are usually more expensive, need sophisticated infrastructure and not appropriate for large epidemiological studies in endemic areas

In many centres of developing countries, health responsibles think that traditional diagnostic methods are old fashioned and make efforts to incorporate modern methods which are usually more expensive, need sophisticated infrastructure and not appropriate for large epidemiological studies in endemic areas

The consequence is that those modern techniques are only used in a few centres and applied to only a few patients, and that almost nobody is carrying out surveys in the endemic areas any more

The consequence is that those modern techniques are only used in a few centres and applied to only a few patients, and that almost nobody is carrying out surveys in the endemic areas any more



Consequences: Consequences:

Today, one of the greatest problems we have is that in many areas of the developing world we do not know which are the epidemiological situations

Today, one of the greatest problems we have is that in many areas of the developing world we do not know which are the epidemiological situations

So, for given diseases we dispose of more or less effective control methods and we cannot apply them

So, for given diseases we dispose of more or less effective control methods and we cannot apply them



Interestingly, when we go today again to the field and perform surveys, the results usually suggest that many diseases are emerging / re-emerging

Interestingly, when we go today again to the field and perform surveys, the results usually suggest that many diseases are emerging / re-emerging

Whether this is related to the higher performance of today diagnostic methods when compared to old ones or not, one conclusion is evident: all those diseases are still there and continue to be as prevalent as always !

Whether this is related to the higher performance of today diagnostic methods when compared to old ones or not, one conclusion is evident: all those diseases are still there and continue to be as prevalent as always !

Thus, evidence is suggesting small impact or sometimes even no impact at all of all our efforts against neglected infectious diseases in recent years; given diseases are really re-emerging and/or expanding !

Thus, evidence is suggesting small impact or sometimes even no impact at all of all our efforts against neglected infectious diseases in recent years; given diseases are really re-emerging and/or expanding !

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TRAINING, TECHNOLOGY TRANSFER, CAPACITY BUILDING TRAINING, TECHNOLOGY TRANSFER, CAPACITY BUILDING

Control of all kind of infectious diseases needs sustainability Control of all kind of infectious diseases needs sustainability

Sustainibility needs specifically trained scientists in endemic countries and areas

Sustainibility needs specifically trained scientists in endemic countries and areas

Consequently, we need to include training and technology transfer high in the agendas of research projects on zoonotic diseases

Consequently, we need to include training and technology transfer high in the agendas of research projects on zoonotic diseases

Problems appeared in recent years: Problems appeared in recent years:

There begins to be a lack of people in traditional but always necessary disciplines for the fight against vector-borne diseases, as Medical Entomology and Medical Malacology, or even coprological methodology, needed for patient diagnosis in many diseases, mainly in endemic areas of developing countries

There begins to be a lack of people in traditional but always necessary disciplines for the fight against vector-borne diseases, as Medical Entomology and Medical Malacology, or even coprological methodology, needed for patient diagnosis in many diseases, mainly in endemic areas of developing countries

Molecular tools may be very helpful in attracting young researchers to disciplines as Medical Entomology and Medical Malacology, as well as to diagnostic methodologies as coprology

Molecular tools may be very helpful in attracting young researchers to disciplines as Medical Entomology and Medical Malacology, as well as to diagnostic methodologies as coprology

CONTROL OF PARASITIC DISEASESCONTROL OF PARASITIC DISEASES

A CHALLENGE FOR OUR FUTURE

Thank you for your attention

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medical parasitology

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noninfected host

normal host

intermediate host

definitive host

living organism

species of parasite

pathogenic organism

living carrier