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Parasitology. FA 3108. Maria Immaculata Iwo School of Pharmacy ITB. INTRODUCTION. Parasitic diseases continue to be a major public health problem all over the world with associated high degree of mortality, morbidity, and man-day loss.

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FA 3108

Maria Immaculata Iwo

School of Pharmacy


  • Parasitic diseases continue to be a major public health problem all over the world with associated high degree of mortality, morbidity, and man-day loss.
  • WHO statistics put parasites as leading cause of death after HIV/AIDs and tuberculosis
  • One out of ten living persons suffer from one or more of seven major tropical diseases, of which five are parasitic in nature.
  • Out of 60 million deaths in world, more than 25% are accounted to parasites.
  • Parasites affect over half the world’s population and are a major cause of mortality in the developing country.
With increasing
    • population,
    • urbanization,
    • industrialization,
    • poor socio-economic conditions and
    • poor sanitation facilities in developing countries,
    • deforestation,
    • unplanned reforestation and climatic changes,

 some diseases which were previously unrecognized, are emerging.

  • Ethnic eating habits,
  • poverty,
  • tourism to exotic areas and
  • environmental degradation
  •  have led to
  • emergence
  • of food-borne
  • parasitic infections
Five parasitic infections
    • Malaria
    • Trypanosomiasis
    • Leishmaniasis,
    • Schistosomiasis
    • Filariasis
  • A number of parasites are now world-wide in their distribution

Presenting the greatest

challenges in the

developing country

Many infections once thought to be harmless, are now known to be life-threatening in immunocompromised individuals and those suffering from acquired immunodeficiency syndrome (AIDS).

These include:

    • Toxoplasma gondii
    • Cryptosporidium parvum
    • Isospora belli
    • Microsporidia

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Currently no vaccineagainst any parasitic infection, in human, is available
  • Parasite also have capacity to develop drug resistance
  • Vectors transmitting certain parasitic infections have developed insecticide resistance

Therefore, parasitic infections

present enormous challenges

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This lecture will cover
    • Essential details of general parasitology
    • Description of various protozoa and helminths
      • Geographical distribution
      • Habitat
      • Morphology
      • Life cycle
      • Pathogenicity, (and Immunity)
      • Epidemiology
      • Laboratory diagnosis,
      • Treatment and prevention
    • Description of various virus

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1. Arora, D. R. and B. Arora, 2007, Medical Parasitology, 2nd ed., CBS Publ. & Distributor, New Dehli

2. Markell, E. K., M. Voge, and D. T. John, 1992, Medical Parasitology, 7th ed., WB Saunders Co., Philadelphia

3. Peters, W. & H. M. Gilles, A Colour Atlas of Tropical Medicine & Parasitology, 3rd. ed., Wolfe Medical Publ. Ltd, Netherlands

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blood and Tissue


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Reverse transcription





Nuclear localization




RNA export



Genomic RNA





Replication of HIV

Lyfe cycle of DNA virus

1. Attachment


8.Budding from

nucleus and

release of virus


(pinocytosis. etc)

7. Assembly of virus

particles in nucleus

3.Uncoating and

Transfer of DNA

to nucleus

Inhibition of viral

DNA polymerase:



6. Late translation of

viral mRNA into

structural proteins

4.Early transcription

and translation of

viral mRNA

5. Synthesis of viral DNA

and late transcription

of viral mRNA

the objective of this lecture
The objective of this lecture

Known the characteristic of parasitic infection is benefit for…

 morphologic specific, important for diagnoses

life cycle complex, need or need not other host, more then one host,

 for completely elimination of the parasite

Location treatment strategic

E. histolytica: intestine (GIT), lung, liver, brain, etc

A. lumbricoides : GIT, lung, reproductive organ, brain,

Trypanomiasis  two biological stadium:

- haemolymphatic & meningoencephalitic

the objective of this lecture1
The objective of this lecture

Clinical symptoms

- similar to organ system clinical symptom?

- with or without clinical symptom

- can be acute or chronic infections

harmful effect of parasitic infection

- pharmacologic and or immunologic effects

cause by a burden of parasite inside our body,

its existence (colic of Ascariasis, encephalitis of N. fowlery)

its stadia morphologic (eggs of Shistosome spp., sucker of worm),

toxin secreted, toxic metabolite,

dead parasite (Filarial worm  Mazotti reaction, T. solium blindness),

granulomma (E. histolytica);

Lymphoma, abortion (Toxoplasmosis)

treatment not only used antiparasitic drugs but also agent to cure clinical manifestations

 Treatment : not only used antiparasitic drugs, but also agent to cure clinical manifestations.

 Sanitation and hygienicity

Leuchorrhea  T. vaginalis


 eating habits back to nature: eating raw vegetables, undercooked meat, fish, rabbit,

insect time to suck the blood

Children  health education

 Health condition (Immunity)

 “healthy - clean” food

Better prevent than cure

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General parasitology

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Parasitology is the area of biology concerned with the phenomenon of dependence of one living organism on another.

A parasite is an organism that is entirely dependent on another organism, referred to as its host, for all or part of its life cycle and metabolic requirements.

It is of two types:

• Microparasite

• Macroparasite

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It is small, unicellular and multiplies within its vertebrate host, often inside cells.

Viruses, bacteria and protozoa are microparasites.

  • Macroparasite

It is large, multicellular and has no direct reproduction within its vertebrate host.

This category includes helminths.

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On the basis of their location, parasites may also be divided into two types:

• Ectoparasites

• Endoparasites

  • Ectoparasites

Organisms which live on the surface of the skin or temporarily invade the superficial tissues of the host (e.g. lice).

The infection by these parasites is known an infestation.

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 Organisms that live within the body of the host

All protozoan and helminthic parasites of man are endoparasites.

The invasion by endoparasites is known as infection.

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On the basis of host, parasites are subdivided into the following types:

Obligate parasites:

Organisms that cannot exist without a host

(e g. Taxoplasma gondii)

 Facultative parasites:

Organisms that under favourable circumstances may live either a parasitic or free-living existence (e.g. Naegleria fowleri, Acanthamoeba spp. and Balamuthia mandrillaris).

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On the basis of host, parasites are subdivided into the following types:

Obligate parasites:

Organisms that cannot exist without a host

(e g. Taxoplasma gondii)

 Facultative parasites:

Organisms that under favourable circumstances may live either a parasitic or free-living existence

(e.g. Naegleria fowleri, Acanthamoeba spp.)

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Accidental parasites:

Organisms that attack an unusual host

(e.g. Echinococcus granulosus in man).

Aberrant parasites:

Organisms that attack a host where they cannot live or develop further

(e.g. Toxocara canis in man).


The term free-living describes the non-parasitic stages of existence which are lived independently of a host.

e.g. hookworms have active free-living stages in the soil.

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  • is defined as an organism which harbours the parasite and provides the nourishment and shelter to the latter.

Definitive host

This is the host in which sexual reproduction of the parasite takes place or in which the most highly developed form of a parasite occurs.

When the most mature form is not obvious, the definitive host is the mammalian host.

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intermediate host

The host which alternates with the definitive host and in which the larval or asexual stages of a parasite are found.

Some parasites require two intermediate hosts for completion of their life cycle

Paratenic host

A host in which larval stage of a parasite survives but does not develop further. It is often not a necessary part of the life cycle.

Reservoir host

A host which harbours the parasite and serves as an important source of infection to other susceptible hosts.

Epidemiologically, reservoir host are important in the control of parasitic diseases

  • This term is used to describe an animal infection that is naturally transmissible to humams either directly or indirectly via a vector.

Examples of parasitic diseases that are zoonosis include:

- Leishmaniasis,

- South American trypanosomiasis,

- rhodesiense trypanosomiasis.

- japonicum schistosomiasis,

- trichinosis, fascioliasis,

- hydatid disease, and cryptosporidiosis

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  • A vector is an agent, usually an insect, that transmits an infection from one human host to another.
  • The term mechanical vector is used to describe a vector which assists in the transfer of parasitic forms between hosts but is not essential in the life cycle of the parasite

e.g. a housefly that transfers amoebic cysts from infected food that is eatenby humans.

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host parastte relationships
  • Symbiosis

An association in which both host and parasite are so dependent upon each other that one can not live without the help of the other.

  • Commensalism

An association in which only parasite derives benefit without causing any injury to the host.

  • Parasitism

Parasitism is a relationship in which a parasite benefits and the host provides the benefit. The host gets nothing in return and always suffers from some injury.

The degree of dependence of a parasite on its host varies

sources of infection

Parasitic infections originate from following sources:

1. Contaminated soil and water;

Soil polluted with human excreta acts as a source

of infection with

- Ascaris lumbricoides,

- Trichuris trichiura,

- Ancylostoma duodenale,

- Necator americanus and

- Strongyloides stercoralis

Before acquiring infectivity for man, eggs of these parasites undergo certain development in the soil.

 These are known as soil transmitted helminths

sources of infection1
  • Water polluted

with human excreta may contain viable cystsof

    • Entamoeba histolytica,
    • Giardia lamblia,
    • Balantidium coli,

eggs of

- Taenia solium,

- Hymenolepis nana,

and the infective cercarial stageof

- Schistosoma haematobium,

- S. mansoni

- S. japonicurn.

sources of infection2

2. Freshwater fishes

constitute the source of Diphylobothrium latum and Clonorchis sinensis.

3. Crab and crayfishes

are the sources of Paragonimus westermani.

4. Raw or undercooked pork

is the source of Trichinella spiralis, T. solium, Fasciola hepatica, T. saginata, and S. suihominis.

5. Raw or undercooked beef

is the source of T. saginata, Toxoplasma gondii, and S. hominis.

sources of infection3

6. Watercress

is the source of Fasciola hepatica.

7. Blood-sucking insects

transmit Plasmodium spp., Wuchereria bancrofti,

Brugia malayi, Onchocerca volvulus, T. brucei, T. cruzi,

Leishmania spp. and Babesia spp.

8. Housefly (mechanical carrier)

is the source of E. histolytica.

9. Dog

is the source of Echinococcus granulosus and

Toxocara canis (visceral larva migrans).

sources of infection4

10. Cat

is the source of T. gondii,

11. Man

is the source of E. histolytica, Enterobius vermicularis,

and H. nana.

12. Autoinfection

may occur with E. vermicularis and S. stercoralis,

leading to hyperinfection,

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portal of entry into the body

1. Mouth

The commonest portal of entry of parasites is oral, through contaminated food, water, soiled fingers or fomites.

  • This mode of transmission is referred to as faecal-oral route.
  • e.g.
    • E. histolytica, G lamblia, B. coli.
    • E. vermicularis, T. trichiura, A. lumbricoides,
    • T. spiralis, T. solium, T. saginata,
    • D. latum, F. hepatica, C. sinensis
    • Fasciolopsis buski, P. westermani

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portal of entry into the body1

2. Skin

  • Infection with A. duodenale, N. americanus and S. stercolaris is acquired when filariform larvae of these nematodes penetrate the unbroken skin of an individual walking over faecally contaminated soil.
  • Schistosomiasis caused by S. haematabium, S. mansoniand S. japonicumis acquired when the cercarial larvae, in water, penetrate the skin.
  • A large number of parasites e.g, Plasmodium spp., W. bancrofti, B. malayi, O. volvulus, T. brucei, T. cruzi, Leishmania spp. and Babesia spp. are introduced percutaneoursly when blood-sucking arthropods puncture the skin lo feed.
portal of entry into the body2

3. Sexual contact

Trichomonas vaginalisis transmitted by sexual contact, E. histolyticaand G. lamblia may also be transmitted by anal-oral sexual practices among male homosexual

4. Kissing

E. gingivalisis transmitted from person-to-person by kissing or from contaminated drinking utensils.

5. Congenital

Infection with T. gondii and Plasmotiium spp. may be

transmitted from mother to foetus transplacentally

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portal of entry into the body3

6. Inhalation

Airborne eggs of E. vermicularis may be inhaled into posterior pharynx leading to infection.

7. latrogenic infection

- Malaria parasites  transmitted by transfusion of blood from the donor with malaria containing asexual forms of erythrocytic schizogony  This is known as trophozoite-induced malaria or transfusion malaria.

- Malaria parasites may also be transmitted by the use of contaminated syringes and needles  This may occur in drug addicts.

life cycle of human parasites
  • On the basis of their life cycles human parasites can he divided into three major groups:



Entamoeba histolytica

G. lamblia

Chilomastix mesnili

T. vaginalis

B. coli


E. vermicularis

T. trichiura

Ascaris lumbricoides

A. duodenale

N. americanus

H. nana

two intermediate hosts

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  • A parasite may live in or on the tissues of its host

- without causing evident harm.

- However, in majority of cases the parasite has the

capacity to produce damage.

  • With the advent of AIDS, there is an increase in the incidence of newer parasitic infections caused by Cryptosporidium parvum, Isospora belli, and other hitherto unheard of parasites.
    • These parasites also cause infections in patients who are immunocompromised

e.g, patients receiving cytotoxic drugs or organ transplant.

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damage may be produced by the parasites
Damage may be produced by the parasites

1. Traumatic damage

Relatively slight physical damage is produced by entry of

- filariform larvae of S. stercoralis, A. duodenale and N. americanus and

- cercarial larvae of the Schistosoma spp. into the skin.

 Migration of several helminthic larvae through the lung produces traumatic damage of pulmonary capillaries leading to extravasation of blood into the lung.

 Similar damage in cerebral, retinal or renal capillaries may lead to serious injury.

 Eggs of S haematobium and S. mansoni cause extensive damage with haemorrhage as they escape from vesicle and mesenteric venules, respectively, into the lumen of the urinary bladder and the intestinal canal

 Attachment of hookworms(A. duodenale and N. americanus to the intestinal wall results in traumatic damage of the villi and oozing of blood at the site of attachment

 Large worms, such as A. lumbricoides and T. saginata may produce intestinal obstruction.

 Ascaris, in addition, may occlude lumen of the appendix or common bile duct, may cause perforation of the intestinal wall, or may penetrate into the parenchyma of the liver and the lungs.

2. Lytic necrosis

E. histolytica secretes lytic enzyme which lyses tissues for its nutritional needs and helps it to penetrate into the tissue of the colon and extraintestinal viscera.

 Obligate intracellular parasites e.g. Plasmodium spp., Leishmania spp., Trypanosoma cruzi and T. gondii cause necrosis of parasitized host cells during their growth and multiplication

3. Inflammatory reaction
  • Most of the parasites provoke cellular proliferation and infiltration at the site of their location.
  • In many instances the host reaction walls off the parasite by fibrous encapsulation.
  • In metazoan and in some protozoan parasitoses, there is a moderate-to-notable eosinophilia.
  • Iron-deficiency, pernicious and haemolytic anaemia develop in patients with hookworm disease, diphyllobothriasis and malaria, particularly blackwater fever, respectively.
  • E. histolyticamay produce inflammation of the large intestine leading to the formation of amoebic granuloma or amoeboma.
  • Parasitization of fixed macrophages in the spleen, bone marrow, and lymph nodes by L. donovani causes proliferation of reticuloendothelial cells.
4. Competition for specific nutrients

Diphyliohothrium latum competes with the host for vitamin B12 leading to parasite-induced pernicious anaemia.

5. Allergic manifestations

the normal secretions and excretions of the growing larvae of some helminthes and the products liberated from dead parasites may give rise to various allergic manifestations


• Schistosomes cause cercarial dermatitis and eosinophilia

• D. medinensis and T. spiralis infections

cause urticaria and eosinophillia,

• rupture of hydatid cyst may precipitate anaphylaxis.

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6. Neoplasia
  • Clonorchis sinensis and Opisthorchis viverrini have been associated with cholangiocarcinoma
  • S. haematobiumn with vesical carcinoma
  • E. histolytica with sigmoid granuloma / amoeboma.

7. Secondary Infection

  • Strongyloidiasis, trichinosis and ascariasis, the migrating larvae may carry bacteria and viruses from the intestine to the blood and tissues leading to secondary infection.
  • Leismaniasis Pasca Kala Azar
immunity in parasitic infections

Because of their biochemical and structural complexity, protozoa and helminths present a large number of antigens to their hosts.

  • Protozoa (micro parasites) are small and multiply within their vertebrate host, often inside the cells.
    • Thus posing an immediate threat unless contained by an appropriate immune response.
  • Helminths (macroparasites) are large and do not multiply within their vertebrate host.
    • Thus they do not present an immediate threat after initial infection.
      • Therefore, immune responses to protozoa and helminths are different from one another.
Immunological protection against parasite infections is much less efficient than it is against bacterial and virus infections. This is due t o the following factors:

1. As compared to bacteria and viruses, parasites are large and more complex structurally and antigenically so that immune system may not be able to mount immune response against the protective antigens.

2. Many protozoan parasites (e.g. Leishmania spp. and T. gondii) are intracellular.

This protects them from immunological attack.

3. Many parasites, both protozoa and helminths, live inside the intestines.

This location limits the efficiency of immunological attack and also facilities dispersal of the infective forms of the parasites.

4. T. brucei gambiense and T. b. rhodesiense exhibit antigenic variations within the host.

 When antibody response to one antigenic type reaches peak, antigenic variation of the parasite occurs by mutation.

The new antigenic type is unaffected by the antibodies against the parent strain.

 This enables the prolonged persistence of the parasite in the host.

5. Many nematodes have a cuticlewhich is antigenically inert and evokes little immune response.

6. L donovani causes extensive damage to the RES (reticuloendothelial system) thus leading to immunological tolerance.

7. Enterobius vermicularis does not breach the integrity of

gut wall, thus immune system is not stimulated.

8. In most of the parasitic infections, immunity lasts only till original infection remains active.

This is known as concomitant immunity (previously called premunition or infection-immunity).

A possible exception is cutaneous leishmaniasis in which the ulcer heals leaving behind good protection against reinfection.

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Constituting cell-mediated


The protective immune response to parasitic infections has four arms:

 Cytotoxic T (Tc) cells.

 Natural killer (NK) cells.

 Activated macrophages.

 Antibody (produced by B-cells)

The main classes of antibody produced are

  • IgM the first appear, mark the presence of acute infection
  • IgG  usually the most abundent type in parasitic infections
  • IgE  Helminths and ectoparasites also provoke high

titres of IgE antibodies

Constituting humoral


laboratory diagnosis
  • Laboratory diagnosis of parasitic infections can be carried out by

* Demonstration of parasite

* Immunodiagnosis

* Molecular biological methods

maria immaculata iwo, sf itb


two types:

Skin tests

 Serological tests.

maria immaculata iwo, sf itb

Skin tests

These tests are performed by intradermal injection of parasitic antigens and are read as under:

1. Immediate hyperensitivity reaction:

It reveals erythema and induration after 30 minutes of injection.

This reaction is seen in cases of hydatid disease, filariasis, schistosomiasis ascariasis, and strongyloidiasis

2. Delayed hypersensitivity reaction:

It reveals erythema and induration after 48 hours of injection.

This reaction is seen in cases of leishmaniasis, trypanosomiasis, toxoplasmosis and amoebiasis,

maria immaculata iwo, sf itb

Serological test

These tests detect antibodies or antigens in the patient serum and other clinical specimens

molecular biological methods
 Molecular biological methods

These include DNA probes and polymerase chain reaction (PCR).

1. DNA probes

 DNA probe is a radio labelled or chromogenically labelled piece of single- stranded DNA complementary to a segment of parasitic genome and unique to a particular parasitic strain, species and genus.

 Specific probe is added to the clinical specimen.

 If the specimen contains the parasitic DNA, probe will hybridize with it which can be detected.

 DNA probes are available for the detection of the infection with P. falciparum, W. Bancrofti,

T. b. gambiense, T. b. rhodesiense, T. cruzi


2. Polymerase chain reaction (POP)
  • PCR is a DNA amplification system that allows molecular biologist to produce microgram quantities of DNA from picogram amounts of sorting material.
  • It has been employed to detect faecal antigens for the diagnosis of intestinal amoebiasis, giardiasis and other intestinal parasitic infections.

maria immaculata iwo, sf itb

Community Participation

Method of


Parasitic diseases


- Chemotherapy

- Chemoprophylaxis

Health education

of population

at risk

Vector control

- Insecticides,

- molluscicides,

- Land development

- Drainage,

- Bush clearance

Reservoir host control

- Destruction of animal hosts

- Drug treatment of human