DNA Viruses Virology Short Essay Question And Answers

DNA Viruses Important Notes

1. Herpesvirus Subfamilies:

• Alpha herpes virus
  • Herpes simplex 1
  • Herpes simplex 2
  • Varicella zoster
• Beta herpes virus
  • Cytomegalovirus
• Gamma herpes virus
  • Epstein Burr virus
  • Human herpes type 8

2. Infections caused by Epstein Barr virus

• Infectious mononucleosis
• Burkitt’s lymphoma
• Nasopharyngeal carcinoma

DNA Viruses Short Essays

Question 1. Herpes virus
Answer:

The Herpes virus belongs to the Herpes viridian family

Subfamilies:

Herpes virus Morphology:

• Size: 100-200 nm in diameter
• It contains:
  • Icosahedral caused containing 162 capsomers
  • Double-stranded DNA genome
    • It is surrounded by a lipid envelope containing peplomers
    • The tegument is present between capsid and envelope

Read And Learn More: Microbiology Question and Answers

Herpes virus Laboratory Diagnosis:

• It includes
  • Collection of specimen
  • Smear preparation
  • Staining of specimen
  • Observation
    • It shows Tzanck cells, Multinucleated giant cells, Cowdry type A intranuclear inclusion bodies
  • Tissue culture
  • Polymerase Chain Reaction

Question 2. Herpes simplex virus?
Answer:

• It is a DNA virus
• It belongs to the herpesviridae family.
• Man is the only natural host.
• Herpes simplex virus are two types as follows.
  • Herpes simplex type 1 – is usually associated with oral and ocular lesions.
  • Herpes simplex type 2 – is usually associated with genital infections.
    • Lesions caused by herpes simplex depend on the site of infection, age and immune status of the individual are as follows:
  • Cutaneous infections: These include:
    • Fever
    • Blisters on the cheeks, chins around the mouth, (or) on the forehand
    • Napkin rash on the buttocks of children, – Herpetic widow in medical professionals.
  • Eczema herpeticum:
    • The generalized herpetic eruption is seen in children suffering from eczema.
  • Mucosal lesions:
    • Acute gingivostomatitis
    • Recurrent herpes labialis.
  • Ophthalmic lesions:
    • Keratoconjunctivitis
    • Follicular conjunctivitis.
  • Visceral lesions:
  • Nervous system:
    • HSV meningitis,
    • Sacral autonomic dysfunction.
  • Genital lesions:
    • Infection of the cervix, vagina, or vulva (females)
  • Congenital lesions:
    • Subclinical or localised infection of skin mouth or eyes.
    • Besides primary infections, herpes viruses may present as latent infection, reactivation and re- crude scene.

Herpes simplex virus Laboratory Diagnosis:

Question 3. Cytomegalovirus?
Answer:

• Cytomegalovirus is included in herpeviridae family.
• It is a Human Herpes Virus 5 (HHV-5)
• The virus is shed in urine, saliva, semen, cervical secretions, tears and breast milk.

Cytomegalovirus Pathogenesis:

• Cytomegalo virus infections are almost always inapperent leading to prolonged latency with occasional re-activation.
  • Congenital infections:
    • Cytomegalovirus can be transmitted transplacentally from a mother with latent infection to the foetus.
    • Infections are asymptomatic at birth (or) it may lead to cytomegalic inclusion disease which is often fatal.
    • Cytomegal inclusion disease is characterised by:
      • Hepatosplenomegaly.
      • Jaundice
      • Thrombocytopenic purpura
      • Haemolytic anaemia
      • Microcephaly.
  • Post Natal Infections:
    • Are usually asymptomatic
    • Clinical disease in adults resembles infectious mononucleosis.
    • It can cause dissemeinated infection in immune-compromised individuals like AIDS patients.

Cytomegalovirus Laboratory diagnosis:

• Specimens can be obtained from saliva, urine, breast milk, semen etc.
• The smear shows enlarged cytomegalic cells with large intra-nuclear owl’s eye appearance
• Inclusions can be demonstrated in the centrifuged de-posits from urine (or) saliva.
• The virus can be grown in human fibroblast culture detected by ELISA test.

Cytomegalovirus Treatment:

Ganciclovir is the drug of choice.

Question 4. Adenovirus
Answer:

• Adenovirus belongs to the Adenoviridae family
• They replicate in the nucleus of infected cell

Adenovirus Classification:

• Adenovirus are grouped into
  • Aviadenovirus- Possess avian adenovirus
  • Mastadenovirus- Possess mammalian adenovirus

Adenovirus Morphology:

• Size- 70-75 nm in diameter
• It is non-enveloped
• Contains
  • Icosahedral capsid
  • Double-stranded DNA

Adenovirus Pathogenesis:

• Adenovirus causes infections of the respiratory tract, eye, GIT and urinary tract
• The mode of the spread of infections include
  • Conjunctiva
  • Nasal mucosa
  • Faeco-oral spread
• The incubation period is 5-7 days

Adenovirus Laboratory Diagnosis:

DNA Viruses Short Question And Answers

Question 1. Smallpox
Answer:

• The causative organism of smallpox is the variola virus
• It was exclusively human infection with no animal reservoir
• It used to occur in two distinct varieties

1. Florid

• It is a highly fatal disease
• Seen in Asia

2. Alastrim

• It is a mild non-fatal disease
• Seen in Latin America
• Variola major caused smallpox
• Now it has been eradicated
• Due to which the vaccination of it is now stopped
• It was last detected in Somalia, in October 1977.
• On May 8, 1980, WHO announced the global eradication of small pox

Question 2. Name the disease caused by DNA viruses.
Answer:

Question 3. Herpes Zoster
Answer:

• It is caused by the Varicella Zoster virus
• It is a disease of old age
• It occurs in persons who had chickenpox several years earlier

Herpes Zoster Pathogenesis:

• The virus remains latent in the sensory ganglia
• Due to a decrease in immunity, this virus gets reactivated
• It is triggered by some precipitating stimulus
• It results in the inflammation of the nerve

Herpes Zoster Clinical Features:

• Skin lesions
• Neuritic pain- It is severe and persists for weeks or months
• Unilateral Vesicles
• Oral manifestations include:
  • Unilateral involvement of skin areas supplied by ophthalmic, mandibular or Maxillary nerves
  • Painful vesicles are present on the buccal mucosa, tongue, pharynx and larynx
  • Vesicles rupture leaving areas of erosion

Question 4. Antiviral agents
Answer:

Antiviral agents are agents that selectively attack one of the stages of viral replication without harming the host cells.

Examples:

Question 5. Epstein- Barr virus or EB virus
Answer:

• Epstein-Barr virus is named after its discoverers Epstein, Barr and Achong in 1964.
• Infection with the EB virus leads to
  • Latency
  • Periodic reactivation
  • Lifelong persistence
  • Infects B lymphocytes
• Diseases caused by it are
  • Infectious mononucleosis
  • EBV associated malignancies

• • • Burkin’s lymphoma
    • Lymphoma in immuno-deficient persons
    • Nasopharyngeal carcinoma