Protozoans Virology Short And Long Essay Question And Answers

Protozoans Important Notes

1. Entamoeba histolytica

• Occurs in three forms
  • Trophozoites
  • Pre cystic stage
  • Cyst
    • It passes its life cycle only in man
    • Diseases caused by it
      • Intestinal amoebiasis
      • Extra intestinal amoebiasis
        • Other Entamoeba are
          • Entamoeba coli
          • Entamoeba gingivalis

2. Species of Plasmodium

• Pvivax
• P falciparum
• P malariae
• P ovale

3. Stages of the life cycle of Plasmodium

• Pre erythrocytic schizogony
• Erythrocytic schizogony
• Gametogony
• Exo erythrocytic schizogony

4. Malarial pigment

• Yellowish brown – P. vivax
• Dark brown – P.falciparum, P.malariae
• Dark yellowish brown- P.ovale

5. Malaria

• Clinical features
  • Febrile paroxysm
  • Anaemia
  • Splenomegaly
• Complications
  • Pernicious malaria
  • Black water fever

Read And Learn More: Microbiology Question and Answers

6. Cestodes

• Taenia saginata
• Taenia solium

7. Nematodes

• Ascaris lumbricoides or round worm
• Hookworm
  • Ankylostoma duodenale
  • Wuchereria bancrofti

Protozoans Long Essays

Question 1. Describe the morphology, pathogenesis, and life cycle of Entamoeba histolytica. Write about laboratory diagnosis of intestinal amoebiasis.
Answer:

Entamoeba histolytica causes intestinal amoebiasis and hepatic amoebiasis

Entamoeba histolytica Morphology:

The parasite exists in 3 forms

Entamoeba histolytica Life Cycle:

• E. histolytica passes its life cycle in only one host, the man.
• The mature quadranucleate cysts are infective forms.
• These cysts enter in to men through ingestion of water and food containing it
• These reach the caecum or lower part of the ileum called excystation
• Each mature cyst liberates tetranuclear amoeba
• Forms eight meta cystic Trophozoites by binary fission
• It gets lodged in the submucous tissue of the large intestine
• E.histolytica secretes a proteolytic enzyme
• Causes destruction and necrosis of tissues
• Results in the formation of flask-shaped ulcers
• Next, these Trophozoites are
  • Excreted along with blood and mucous in feces
  • Results in amoebic dys­entery
  • Enter into deeper layers
  • Enter into the portal vein
  • Reaches liver
  • Forms amoebic hepatitis and amoebic liver abscess
• Effect of the parasite on the host decreases
• This increases host tolerance and healing starts
• Encystation occurs which is the transformation of Trophozoites into cysts and cysts.

Entamoeba histolytica Pathogenesis:

E. Histolytica can cause two types of pathological lesions as follows

1. Primary (or) Intestinal Amoebiasis:

• This condition is called as amoebic dysentery.
• This ulcer maybe generalized (or) may be localized to the ileocaecal (or) sigmoidorectal region.
• Occasionally ulcers may involve deeper tissues and may cause perforation (or) peritonitis.
• Erosion of blood vessels may lead to hemorrhage.
• The superficial lesions generally heal without scar¬ring.
• Deep ulcers form scars leading to strictures, partial obstruction, and thickening of the gut wall

2. Extra-intestinal amoebiasis [or) secondary (or) metastatic lesions.

• Amoebic liver abscess:

Laboratory Diagnosis of Intestinal Amoebiasis:

1. Stool examination:

• The stool is collected directly into a wide-mouthed con¬tainer and examined without delay.
  • Macroscopic Examination
    • The stool is an offensive odor
    • Dark brown and semifluid
    • Acid in reaction
    • Mixed with blood and mucous
  • Microscopic Examination
    • The cellular exudates is scanty, and consist of nuclear masses of a few pus cells, macrophages, and epithelial cells
    • RBCs are seen in clumps
    • Charcot- Leyden crystals are also seen

2. Blood Examination

• In early cases, it is always negative
• The antibody can be detected in later stages of invasive intestinal amoebiasis
• The test used is ELISA haemagglutination assay (HIA).

3. DNA Probes:

• DNA probes have been used to detect E. histolytica in stool specimens.

Question 2. Describe the life cycle of malarial parasites in man. Give a brief description of pathological lesions produced in man.
Answer:

Malaria is a disease caused by four plasmodium species which are as follows:

• P. vivax
• P. Falciparum
• P. Malaria
• P. Ovale.

Malarial Life Cycle:

The malarial parasites pass their life cycle in two. hosts.

1. Man intermediate host [a sexual development]
2. Female anopheles mosquito – definitive host [sexual development].

Human cycle or schizogony or a sexual cycle:

• The sporozoite is the infective form of a malarial parasite.
• Man gets infected by the bite of the infected female Anopheles mosquito
• This mosquito contains sporozoites in the salivary gland which enter directly into the blood circulation of man
• By this human cycle starts which comprises of following stages.

1. Pre-erythrocytic schizogony

• It is a developmental phase of sporozoites inside the liver cells
• The shape of sporozoites- Round
• Size-Varies
• They undergo nuclear division to develop schizont
• Each schizont contains 20,000-50,000 merozoites
• Duration of this stage
  • P. vivax           – 8 days
  • P. falciparum  – 6 days .
  • P. malariae     – 13-16 days
  • P. ovale          –  9 days
• After this period, the liver cells rupture
• As a result, merozoites are released into the bloodstream

2. Erythrocytic schizogony:

• Release of merozoites into the blood
• Penetration of it into RBCs
• Rupture of RBCs which leaves behind a residue of hemoglobin pigment called hemozoin
• Release of merozoites
• These attack new RBCs
• Thus the cycle continues

3. Gametogony:

• Some merozoites develop sexual forms known as microgametocytes and macro gametocytes

4. Exo-erythrocytic schizogony:

• Some sporozoites enter liver cells but don’t multi-ply
• Enter in the resting phase and are known as Hypno- zoite
• These hypnozoites get reactivated
• Forms schizonts
• Releases merozoites called phanerozoic
• Attack RBCs
• Causes relapse of malaria

Malaria Clinical Features:

• Intermittent fever which is named as malaria is caused by plasmodium
• It consists of

1. Febrile paroxysm

• It comprises of three stages

2. Anaemia

• Microcytic or normocytic hypochromic anemia develops

3. Spenomegaly.

• The spleen becomes enlarged and palpable
• Black water fever, and pernicious malaria are the most commonly seen complications in falciparum malaria.

Protozoans Short Essays

Question 1. Laboratory diagnosis of extraintestinal amoe¬biasis
Answer:

Diagnostic methods for extraintestinal amoebiasis are as follows

Question 2. Leishmania donovani
Answer:

It causes visceral leishmaniasis or kala-azar

Leishmania donovani Morphology:

It occurs in two forms:

Leishmania donovani Life Cycle:

• The parasite has two stages in its life cycle
  • Amastigote form
  • Promastigote form
• Initially, multiplication of amastigote form occurs in the reticuloendothelial cells in the host
• Enlargement of host cells occurs
• These cells rupture to release parasites into circulation
• Blood-sucking insect obtains it by sucking
• Development of Promastigote form from Amastigote form

Leishmania donovani Clinical Features:

• Pyrexia
• Splenomegaly
• Hepatomegaly
• Lymphadenopathy
• Anaemia

Question 3. The life cycle of plasmodium in mosquito
Answer:

• The sexual development of plasmodium occurs in mosquito
• It starts in the human host by the formation of Gametocytes
• The cycle includes the following steps
• Bite of female anopheles from the patient
• Mature sexual forms develop in the mosquito
• In the midgut
• 1 microgametocytes- develops 4-8 microgametes
• 1 macrogametocyte- Develops 1 macrogamete
• Fertilization of macrogamete occurs
• Formation of zygote
• Lengthening and maturation of zygote to form ookinete
• Formation of oocyst from ookinete
• Maturation of oocyst
• Increase in size and number of sporozoites
• Rupture of oocyst to release sporozoites in the body of the mosquito
• Distribution of sporozoites into various organs and tissues especially in salivary glands

Question 4. Laboratory diagnosis of malaria
Answer:

The demonstration of the parasite in the blood is the most important method for the diagnosis of malaria.

1. Microscopic examination of blood film:

• Thick and thin smears of blood are prepared on the same slide (or) two different slides.
• Blood is collected prior to antimalarial therapy

2. Fluorescent microscopy:

• A blood smear is prepared on a slide and is stained with acridine orange
• The slide is observed under a fluorescent microscope.
• The nuclear DNA of the malarial parasite is stained green and cytoplasmic RNA is stained red.

3. Blood counts:

• Blood shows moderate leukopenia and monocytosis.

4. Serological tests:

• Serological tests used are
  • ELISA
  • Indirect haemagglutination assay
  • Indirect immunofluorescence test.

5. DNA probes:

• These are sensitive and specific diagnostic methods for the diagnosis of malaria
• It can detect even a low parasitemia i.e., <10 parasites/dl

6. Polymerase chain reaction (PCR):

• It can also be used.

7. Rapid diagnostic tests:

• These are based on the detection of antigens using immune chromatographic methods.
• In these tests, a dipstick containing monoclonal antibodies is directed against the parasitic antigens.
• This test takes about 15 minutes.
• Several commercial kits are available.
• Kits available detect histidine-rich protein (HRP – II) of P. falciparum.
• The test is commercially available as the parasite ‘F’ test.

Question 5. Complications of plasmodium falciparum infection?
Answer:

Complications of P.Falciparum are:

1. Pernicious malaria
2. Black water fever.

1. Pernicious malaria:

• It is life-threatening condition

Pernicious malaria Cause:

• It is due to heavy parasitization.

Pernicious Malaria Clinical Features:

• It is grouped into the following:

2. Blackwater fever:

Occurs in persons who are previously infected and had inadequate doses of quinine

Black water fever Clinical Features:

• Intravascular hemolysis,
• Fever,
• Haemoglobinuria
• Vomiting and prostration with the passage of dark red (or) blackish urine hence called backwater fever.

Black water fever Mechanism:

• An autoimmune mechanism may be involved in hemolysis
• Parasitized erythrocytes during previous infection act as antigen
• Antibodies are formed against it
• Due to this antigen-antibody reaction, massive destruction of erythrocytes occurs
• There is excessive deposition of haemosiderin pigment in the liver, spleen, and kidneys.
• Sequel of black water fever include
  • Circulatory failure
  • Renal failure,
  • Liver failure,
  • Anaemia.

Protozoans Short Question And Answers

Question 1. Draw morphological forms of Entamoeba His¬tolytica
Answer:

Question 2. Amoebic dysentery
Answer:

• Amoebic dysentery is also known as intestinal amoebiasis
• It is a condition in which the infection is confined to the intestine and is characterized by the passage of blood and mucus in the stool

Amoebic dysentery Types:

1. Acute amoebic dysentery

• Multiple ulcers occur
• These ulcers are deep and extensive
• Its complications are
  • Pericaecal and pericolic abscess
  • Amoebic appendicitis
  • Perforation
  • Generalized peritonitis
  • Gangrene of guts
  • Fistula

2. Chronic amoebic dyssentery

• A single latent ulcer is present in the caecum while multiple small superficial ulcers are scattered throughout the large intestine
• Stricture formation occurs
• Amoeboma in the caecum and large intestine develops

Question 3. E.gingivalis / Morphology of E.gingivalis
Answer:

E.gingivalis Morphology:

• It is a small amoeba measuring 10 – 20 (m in diameter and is actively motile by multiple pseudopodia.
• It has the only trophozoite stage and there is no cystic phase.
• It contains
  • The cytoplasm which is divided into clear ectoplasm and granular endoplasm.
  • Cytoplasmic inclusions consisting of bacteria leucocytes but never RBCs
  • Nucleus is spherical
  • Central karyosome.
  • Nuclear membrane lined with closely packed chromatin granules.

E.gingivalis Pathogenesis:

• E.gingivalis is a parasite of human mouth.
• It occurs as a commensal in gingival tissue around the teeth particularly in the unhealthy tissues such as in pyorrhoea alveolaris.
• It is also found in the crypts and histologic sections of diseased tonsils.
• It is transmitted by close contact like kissing.
• Laboratory diagnosis depends on the demonstration of tro¬phozoites of E. Gingivalis in the material removed from the gingival margin of the gum (or) from the denture.

Question 4. Erythrocytic schizogony
Answer:

• It is the second stage of the human cycle of the malaria parasite
• During this phase, the parasite resides inside RBC and passes through stages of Trophozoites, schizonts, and merozoites.
• Following changes occur during this phase
• Release of merozoites into the blood

Question 6. Plasmodium falciparum
Answer:

Plasmodium falciparum is one of the malarial parasites

Stages of Human Cycle in P. Falciparum:

• P. falciparum is the most pathogenic among the plasmodium species infecting man
• No relapse occurs in P.falciparum infection
• It invades erythrocytes of all ages
• The incubation period of it is 10-14 days

Complications:

• Pernicious malaria
• Black water fever

Question. Black water fever
Answer:

Occurs in persons who are previously infected and had inadequate doses of quinine

Black water fever Clinical Features:

• Intravascular hemolysis,
• Fever,
• Haemoglobinuria
• Vomiting and prostration with the passage of dark red (or) blackish urine hence called backwater fever.

Question 9. Kala-azar
Answer:

Leishmania denovani produces the disease Salazar (or) visceral leishmaniasis.

Kala-azar Clinical Features:

• Pyrexia,
• Splenomegaly,
• Hepatomegaly,
• Lymphadenopathy and
• Anaemia.

Kala-azar Laboratory Diagnosis:

1. Direct evidence:

2. Indirect evidence:

3. Rapid immune chromatographic strip test:

• It detects antibodies against the K39 antigen of L. donovani
• It indicates active kala-azar

Question 10. Benign tertian malaria
Answer:

• Benign tertian malaria is caused by Plasmodium vivax
• Initially, there may be continuous or remittent fever
• In later stages, typical intermittent periodic fever develops
• Initially, two broods of parasites undergo schizogony on alternate days but then one brood drops out.

Question 11. Mention the parasites found in peripheral blood smear.
Answer: