Parasitology VIVA Question and Answer

1) What is a parasite?

• The organism that depends on the host (other organisms) for all of its lifecycle or for some parts of its lifecycle is known as a parasite.

2) What is the host?

• The host is any organism or animal that harbors the parasite.
• There it provides nourishment and shelter.

3) What is the difference between definitive, intermediate, and reservoir host?

•  Definitive host:  Sexual reproduction of parasites takes place. In its most highly developed form of a parasite occurs.  Examples: Mosquito is the definitive host of the malarial parasite. Humans are the definitive host for Taenia saginata. 
•  Intermediate host: Asexual form of parasite takes place. It is essential for the completion of the lifecycle of the parasite. Examples: Cattle are the intermediate host for Taenia saginata. Tsetse fly for Trypanosome.
• Reservoir host:  Host which harbors the parasites and serves as an important source of infection to other susceptible hosts. The infected person or animal may act as a reservoir ( source of parasitic infection ) for transmission. Examples: Dog is the reservoir host for cystic echinococcosis. Antelope is the reservoir host of African Trypanosomiasis.

4) What is the difference between ectoparasite and endoparasite?

• Ectoparasite: Lives on the outer surface or in the superficial tissue of the host. Example: Lice.
• Endoparasite: Lives within (inside) the host. Example: Roundworm.

5) Define

• Temporary parasite: visits host for a short period of time.
• Permanent parasite: leads a parasitic life throughout the whole period of its life.
• Facultative parasite : lives a parasitic life when opportunity arises.
• Obligatory parasite: which cannot exist without a parasitic life.
• Occasional or Accidental parasite: attacks on the unusual host.
• Wandering or Aberrant parasite: happens to reach a place where it cannot live.

6) How does reproduction occur in protozoa ?

• Asexual multiplication: a) By binary fission      b) By multiple fission or schizogony
• Sexual multiplication:   a) By conjugation         b) By syngamy or sporogony

7) Classify the pathogenic protozoa on the basis of the organ of locomotion.

• Rhizopoda: move with the help of pseudopodia.
• Mastigophora: have elongated, thread-like filaments, flagella (Trypanosoma ).
• Sporozoa: exhibit no movement. Example: the malarial parasite.
• Ciliata: move with the help of cilia. Example: Balantidium coli.

8) What do you mean by pseudopodia?

• In order to engulf food material, protozoa have false feet like structure which is called pseudopodia.
• It looks like feet and helps in movement.

9) What is the difference between flagella and cilia?

• Flagella are hair-like long filaments whereas cilia are short processes.

10) Define

• Trophozoite: It is the invasive form of parasite and motile stage.
• Cyst: it is the infective stage of the parasite and resistant stage.
• Encystment: The process in which trophozoite of protozoa encloses itself in a resistant wall to form a cyst.
• Excystation: The process of coming out from a cyst.

Read Also: VIVA Alert: Basic Microbiology with mnemonics

12) Common names and Scientific names

• Roundworm: Ascaris lumbricoides
• Pinworm: Enterobius vermicularis
• Whipworm: Trichuris trichiura
• Hookworm: Ancyclostoma duodenale
• Beef Tapeworm: Taenia saginata
• Pork Tapeworm: Taenia solium 

13) Give examples of important parasites in humans, that complete the lifecycle in a single  (1)  host i.e. Simple life cycle.

• Entamoeba histolytica
• Giardia lamblia
• Ascaris lumbricoides
• Enterobius vermicularis
• Trichuris trichiura
• Strongyloides stercoralis
• Ancylostoma duodenale

Mnemonics: STRONG CAR and TRI CYcLe  ENTER GIAnt HISTOry in 1 (single) time.

14) Give the examples of parasites that complete the lifecycle in 2 hosts ( 1 definitive and 1 intermediate) i.e. complex lifecycle.

• Plasmodium species
• Leishmania donovani
• Wuchereria bancrofti
• Taenia solium
• Taenia saginata

Mnemonics: LEISHaa WitCH BANned TaSa SO gave PLASMA (2 times).

15) Name the species of Leishmania which causes disease in the human being?

• Leishmania donovani causes Kala-azar
• Leishmania tropica causes oriental sore
• Leishmania braziliensis causes mucocutaneous leishmaniasis.

16) What are the two differences between Taenia solium and Taenia saginata?

• Taenia solium: Intermediate host is Pig, and the larva is Cysticercus cellulosae.
• Taenia saginata: Intermediate host is Cattle, and the larva is Cysticercus bovis.

17) What is the larval form of Echinococcus granulosus called?

• Hydatid cyst

18 )What is the terminology used for an embryo having 3 pairs of hooklets?

• Hexacanth embryo

19) How will you recognize the eggs of Hookworm?

• Its egg is surrounded by a thin transparent hyaline shell membrane and contains 7-8 blastomeres.

20) In the lab, how will you identify Whipworm ( Trichuris trichiura ). Any unique property?

• Its egg is barrel-shaped with a colorless protruding mucus plug at each end.

21) What is karyosome? What is its use?

• The minute mass in the center of the nucleus is called the karyosome. It is useful in distinguishing between genera and species.

22) Which protozoa thrive on bacterial flora?

• Intestinal protozoa.

23 ) What is the major route of infection of Entamoeba histolytica?

• Ingestion of mature quadrinucleated cysts (4 nuclei ) containing food and water.

24) How many species of Entamoeba are present?

• Six
• Entamoeba histolytica is pathogenic to humans.

25) How can you differentiate Entamoeba histolytica from E. coli?

• By the position of karyosome in the nucleus.
• E. histolytica has a central karyosome.
• E. coli has an eccentric karyosome.

26) How can you differentiate E. histolytica from E. dispar?

• By ingested RBC.
• The tropozoite of E. histolytica contains ingested RBCs whereas E. dispar doesnot contain it.
• The cysts of E. dispar and E. histolytica cannot be differentiated under a microscope.

References and Sources

1. Chatterjee KD (2009), Parasitology, 13th edition, CBS publishers, and distributors Pvt. Ltd.
2. Panjarathinam R (2007), Textbook of Medical Parasitology, 2nd edition, Orient Longman Private Limited.
3. Mandal PK (2016), A Textbook of Microbiology for Nursing, 2nd edition, Vidyarthi Pustak Bhandar.
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