INTRODUCTION TO PARASITOLOGY (PANIKERS)

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ANTONIE VAN LEEUWENHOEK OF HOLLAND

The pioneer Dutch microscopist in 1681, first introduced single lens microscope and observed Giardia in his own stools.

LOUIS PASTUER

in 1870, first published scientific study on a protozoa (disease leading to its control and prevention during investigation of an epidemic silk worm disease in South Europe.

PATRICK MANSON

A seminal discovery was made in 1878 by ____________ about the role of mosquitoes in filariasis. This was the first evidence of vector transmission.

Laveran in Algeria

Afterwards, _________ _________ discovered the malarial parasite (1880), and Ronald Ross in Secunderabad and Calcuna in India, showed its transmission by mosquitoes (1897). A large nwnber of vector-borne disease have since then been identified.

PARASITES

are living organisms, which depend on a living host for their nourishment and survival. They multiply or undergo development in the host.

PROTOZOA

UNICELLULAR ORGANISMS

HELMINTHS

MULTICELLULAR ORGANISMS

ECTOPARASITE

inhabit only the body surface of the host without penetrating the tissue. Lice, ticks and mites are examples of this.

INFESTATION

The term __________ is often employed for parasitization with ectoparasites.

ENDOPARASITE

A parasite, which lives within the body of the host and is said to cause an infection is called an ____________

ENDOPARASITES

Most of the protozoan and helminthic parasites causing human disease are ______________.

FREE-LIVING PARASITE

It refers to nonparasitic stages of active existence, which live independent of the host, e.g. cystic stage of Naegleria fowleri.

OBLIGATE PARASITES

The parasite, which cannot exist without a host, e.g. Toxoplasma gondii and Plasmodium.

FACULTATIVE PARASITES

Organism which may either live as parasitic form or as free-living form, e.g. Naegleria fowleri.

ACCIDENTAL PARASITES

Parasites, which infect an unusual host are known as accidental parasites. Echinococcus granulosus infects man accidentally, giving rise to hydatid cysts.

ABBERANT PARASITES

Parasites, which infect a host where they cannot develop further are known as __________ or wandering parasites, e.g. Toxocara canis (dog roundworm) infecting humans.

HOST

is defined as an organism, which harbors the parasite and provides nourishment and shelter to latter and is relatively larger than the parasite.

DEFINITIVE HOST

The host, in which the adult parasite lives and undergoes sexual reproduction is called the ____________ host, e.g. mosquito acts as definitive host in malaria

INTERMEDIATE HOST

The host, in which the larval stage of the parasite lives or asexual multiplication takes place is called the ____________ host.

PARATENIC HOST

A host, in which larval stage of the parasite remains viable without further development is referred as a ____________ host. Such host transmits the infection to another host, e.g. fish for plerocercoid larva of D. latum.

RESERVOIR HOST

In an endemic area, a parasitic infection is continuously kept up by the presence of a host, which harbors the parasite and acts as an important source of infection to other susceptible hosts, e.g. dog is the _____________ host of hydatid disease.

ACCIDENTAL HOST

The host, in which the parasite is not usually found, e.g. man is an ______________ host for cystic echinococcosis.

RUDOLF VIRCHOW

zoonosis was introduced by _______ _______ in 1880 to include the diseases shared in nature by man and animals.

World Health Organization (WHO)

Who defined zoonosis later in 1959

ZOONOSIS

those diseases and infections, which are naturally transmitted between vertebrate animals and man.

SYMBIOSIS

Both host and parasite are dependent upon each other. None of them suffers any harm from the association

COMMENSALISM

Only the parasite derives benefit from the association without causing any injury to the host.

PARASITISM

The parasite derives benefits and the host is always harmed due to the association. The parasite cannot have an independent life

DIRECT LIFE CYCLE

When a parasite requires only single host to complete its development, it is called as ____________________, e.g. Entamoeba histolytica requires only a human host to complete its life cycle

INDIRECT LIFE CYCLE

When a parasite requires two or more species of host to complete its development, the life cycle is called as _________________, e.g. malarial parasite requires both human host and mosquito to complete its life cycle

VECTORS

an agent, usually an arthropod that transmits an infection from man to man or from other animals to man, e.g. female Anopheles is the vector of malarial parasite

BIOLOGICAL VECTOR

refers to a vector, which not only assists in the transfer of parasites but the parasites undergo development or multiplication in their body as well. They are also called as true vectors. Example of true vectors are:

MOSQUITO

MALARIA, FILARIASIS

SANDFLIES

KALA-AZAR

TSETSE FLIES

SLEEPING SICKNESS

REDUVIID BUGS

CHAGAS DISEASE

TICKS

BABESIOSIS

MECHANICAL VECTOR

a vector, which assists in the transfer of parasitic form between hosts but is not essential in the life cycle of the parasite. Example of mechanical vectors is: Housefly: Amebiasis

CARRIER

A person who is infected with parasite without any clinical or subclinical disease is known as _______. He can transmit parasite to others.

ORAL TRANSMISSION

The most common method of transmission is through oral route by contaminated food, water, soiled fingers, or fomites. Many intestinal parasites enter the body in this manner; the infective stages being cysts, embryonated eggs, or larval forms. Infection with E. histolytica and other intestinal protozoa occurs when the infective cysts are swallowed.

SKIN TRANSMISSION

Entry through skin is another important mode of transmission. Hookworm infection is acquired, when the larvae enter the skin of persons walking barefooted on contaminated soil. Schistosomiasis is acquired when the cercarial larvae in water penetrate the skin.

VECTOR TRANSMISSION

Many parasitic diseases are transmitted by insect bite, e.g. malaria is transmitted by bite of female Anopheles mosquito, filariasis is transmitted by bite of Culex mosquito. A vector could be a biological vector or a mechanical vector.

DIRECT TRANSMISSION

Parasitic infection may be transmitted by person-to-person contact in some cases, e.g. by kissing in the case of gingival amebae and by sexual intercourse in trichomoniasis.

VERTICAL TRANSMISSION

Mother to fetus transmission may take place in malaria and toxoplasmosis.

IATROGENIC TRANSMISSION

It is seen in case of transfusion malaria and toxoplasmosis after organ transplantation.

LYTIC NECROSIS

(PATHOGENIC MECHANISMS)

Enzymes produced by some parasite can cause _____________. E. histolylica lyses intestinal cells and produces amebic ulcers.

TRAUMA

(PATHOGENIC MECHANISMS)

Attachment of hookworms on jejunal mucosa leads to traumatic damage of villi and bleeding at the site of attachment.

ALLERGIC MANIFESTATIONS

(PATHOGENIC MECHANISMS)

Clinical illness may be caused by host immune response to parasitic infection, e.g. eosinophilic pneumonia in Ascaris infection and anaphylactic shock in rupture of hydatid cyst.

PHYSICAL OBSTRUCTION

(PATHOGENIC MECHANISMS)

Masses of roundworm cause intestinal obstruction. Plasmodium falciparum malaria may produce blockage of brain capillaries in cerebral malaria

INFLAMMATORY REACTION

(PATHOGENIC MECHANISMS)

Clinical illness may be caused by inflammatory changes and consequent fibrosis, e.g. lymphadenitis in filariasis and urinary bladder granuloma in Schistosoma haematobium infection.

NEOPLASIA

(PATHOGENIC MECHANISMS)

A few parasitic infection have been shown to lead to malignancy. The liver fluke, Clonorchis may induce bile duct carcinoma, and S. haematobium may cause urinary bladder cancer.

SPACE OCCUPYING LESSIONS

(PATHOGENIC MECHANISMS)

Some parasites produce cystic lesion that may compress the surrounding tissue or organ, e.g. hydatid cyst

A

Definitive host is one

a. In which sexual multiplication takes place and harbors adult form
b. In which asexual multiplication takes place and harbors adult form
c. In which sexual multiplication takes place and harbors larval form
d. In which asexual multiplication takes place and harbors adult form

PREMUNITION

Once the parasitic infection is completely eliminated, the host becomes again susceptible to reinfection. This type of immunity to reinfection is dependent on the continued presence of residual parasite population and is known as ___________

D

Autoinfection is seen in all except

a. Hymenolepis nano
b. Enterabius vermicularis
c. Taenia solium
d. Ascaris lumbricoides

C

Antigenic variation is exhibited by

a. Entamoeba
b. Schistosoma
c. Trypanosoma
d. Leishmania

C

Which parasite enters, the body by piercing the skin

a. Trichuris trichiura
b. Ascaris
c. Necator americanus
d. Plasmodium

B

Which parasitic infection leads to malignancy

a. Babesiosis
b. Clonorchis sinensis
c. Trypanosoma cruzi
d. Schistosoma haematobium

D

Xenodiagnosis is useful in

a. Wuchereria bancrofti
b. Trypanosoma cruzi
c. Trichinella spiralis
d. All of the above

C

The following are zoonotic disease except

a. Leishmaniasis
b. Balantidiasis
c. Scabies
d. Taeniasis

A

Two hosts are required in

a. Taenia solium
b. Entamoeba histolytica
c. Trichuris trichiura
d. Giardia

D

Which of the following parasite passes its life cycle through three hosts

a. Fasciola hepatica
b. Fasciola buski
c. Schistosoma haematobium
d. Clonorchis sinensis

B

Man is the intermediate host for

a. Strongyloides stercoralis
b. Plasmodium vivax
c. Entamoeba histolytica
d. Enterobius vermicularis

ZOONOSES

Diseases which can be transmitted to humans from animals, e.g. malaria, leishmaniasis, trypanosomiasis and echinococcosis.

LEEUWENHOEK

in 1681, He first observed the parasite Giardia in stools

LAVERAN

in 1880, he discovered malarial parasite and

RONALD ROSS

in 1897 He showed the transmission of malaria by mosquitoes

KINGDOM ANIMALIA

PROTOZOA BELONGS TO KINGDOM PROTISTA WHILE HELMINTHS BELONG TO ____________ ____________.

DEFINITIVE HOST

The host in which the adult stage lives or the sexual mode of reproduction takes place

INTERMEDIATE HOST

The host in which the larval stage of the parasite lives or the asexual multiplication takes place.