RNA Viruses Virology Short Essay Question And Answers

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RNA Viruses Important Notes

1. Inclusion bodies

RNA Viruses Inclusion Bodies

2. Infections caused by human papillomavirus

  • Verruca Vulgaris
  • Focal epithelial hyperplasia
  • Condyloma acuminatum

Read And Learn More: Microbiology Question and Answers

3. Types of rabies vaccine

  • Semple vaccine
  • BPL (Beta propriolactone) vaccine
  • Infant brain vaccine

RNA Viruses Short Essays

Question 1. Polio Vaccine
(or)
Immunoprophylaxis for Poliomyelitis
Answer:

The two types of polio vaccines are as follows

1. Salk’s Polio Vaccine:

  • It was developed by Salk in 1953.
  • It is formalin in-activated preparation of the three types of the polio virus grown in monkey kidney tissue cultures.
  • Viral pools of adequate titre are filtered to remove the cell debris and clumps and inactivated with formalin at 37°C for 12-15 days.

Router of Administration:

The vaccine is given by deep subcutaneous (or) in- tra muscular injection.

Salk’s Polio Vaccine Doses:

Three doses are given 4-6 weeks apart followed by a booster dose should be given six months later.

  • The first dose should be given after the age of six months so that antibody response is not impaired by the residual maternal antibodies.
  • Immunity can be sustained by booster doses every 3-5 years thereafter.

Salk’s Polio Vaccine Mechanism:

  • This vaccine produces long-lasting immunity to all three poliovirus types.
  • Induces serum antibodies

2. Sabin’s Vaccine:

  • It was developed by Sabin in 1962
  • It contains live attenuated strains of poliovirus types, 1, 2, and 3 grown either in monkey kidney cells (or) human diploid cell cultures.

Sabin’s Vaccine Route of Administration:

  • It is administered orally so known as the oral polio vaccine (OPV).

Sabin’s Vaccine Mechanisms:

  • It stimulates both local secretory IgA antibodies in the intestine as well as humoral antibodies (IgM and IgG).
  • When the virus is excreted in the faeces, it may spread to close contacts
  • Thus it protects the individual and the community

Sabin’s Vaccine Doses:

  • Three doses are given
  • All doses are generally given along with DPT.
  • In addition to it, the following doses are given

RNA Viruses Sabin's vaccine Doses

Question 2. Mumps:
Answer:

  • Mumps is an acute viral infectious disease character¬ised by unilateral (or) bilateral nonsuppurative enlargement of the salivary glands usually the parotid gland.
  • Submandibular and sublingual glands are occasionally involved.
  • Usually, children are affected. May also occur in adults.
  • Also known as epidemic parotitis

Mumps Causative organism:

  • Organisms involved in paramyxovirus.

Mumps Route of infection:

  • Infection is acquired by inhalation (or) direct contact or through the conjunctiva.
  • The incubation period is 12 – 18 days.

Mumps Clinical Features:

  • Unilateral (or) bilateral swelling of parotid glands.
  • Fever, malaise
  • Local pain and tender
  • The involvement of extra parotid sites can cause more serious problems as follows.
    • CNS involvement may lead to
    • Meningitis,
    • Meningoencephalitis
    • Orchitis

Mumps Complications:

  • Orchitis
  • Oophoritis
  • Arthritis
  • Nephritis
  • Pancreatitis
  • Thyroiditis and myocarditis.

Mumps Laboratory Diagnosis:

  • Isolation of viruses from CSF, saline (or) urine.
  • Serological tests with paired serum samples are tested for the rise in the titer of antibodies by complement fixation test ELISA, haemagglutination tests.
  • Serum amylase levels are elevated in both parotitis and acute pancreatitis.
  • Mumps Treatment: Treatment is conservative maintaining hydration.
  • Prevention is by means of the MMR vaccine.

RNA Viruses Short Question And Answers

Question 1. Name 3 RNA viruses and diseases caused by them.
Answer:

RNA Viruses RNA virues and Diseases caused by them

Question 2. Mention two important live viral vaccines.
Answer:

Live viral vaccines are

RNA Viruses Viral vaccines

Question 3. Koplik’s spots?
Answer:

  • Koplik’s spots are named after Henry Koplik who first described it in 1896
  • Koplik’s spots are seen in measles (or) rubella
  • Immune reaction to the virus in endothelial cells of dermal capillaries plays a role in the development of spots.

Koplik’s Spots Appearance:

  • These are small irregularly shaped flecks
  • They appear as bluish-white flecks surrounded by a bright red margin.
  • The spots disappear after the onset of the rash.
  • Orally they are most commonly observed on the buccal mucosa opposite to the lower molars
  • With the decline of acute symptoms, widespread mac papular rash over the neck
  • It then spreads to the rest of the body
  • The rash fades in about a week
  • The patient recovers by 10-14 days

Question 4. Inclusion bodies?
Answer:

  • Inclusion bodies are distinctive structures frequently formed in the nucleus (or) cytoplasm in cells infected with certain viruses.
  • These are 3 types based on location
    • Intranuclear
    • Intra cytoplasmic
    • Both.
  • They are also known as cellular inclusions.
  • Examples are:
    • Intra-cytoplasmic and intra-nuclear
      • Negri bodies – rabies
    • Intra-cytoplasmic
      • Henderson – Peterson bodies – molluscum conta- gypsum
    • Intra – nuclear
      • Cow dry type A – Herpes, yellow fever
      • Cow dry type B – Adenovirus, poliomyelitis.

Question 5. Name four vaccines
Answer:

RNA Viruses Vaccines

Question 6. Mumps vaccine?
Answer:

  • An effective live attenuated vaccine [Jeryl Lynn strain of mumps virus] grown in chick embryo fibroblast cul¬ture is against mumps.
  • The vaccine is given as single subcutaneous infections either alone (or) in combination with the MMR vaccine.
  • The vaccine is not protective to individuals already exposed to the virus and whose are in the incubation stage of the disease.
  • The MMR vaccine provides effective protection for a period of 10 years.

Mumps vaccine Contra-indications:

  • Pregnancy
  • Immunodeficiency
  • Hypersensitivity neomycin or egg protein.

Question 7. Arboviruses
Answer:

  • Arboviruses are RNA viruses that are transmitted by blood-sucking arthropods from one vertebrate host to another
  • Mosquitoes, ticks and sandflies are the principal vectors
    • They are named according to the
      • Disease caused by them- example. Yellow fever
      • Place of isolation- for example Kyasanur forest disease
      • The local name of the disease- for example Chickengunya
    • They are classified according to their physical and chemical features into five families
      • Togaviridae
      • Flaviviridae
      • Bunyaviridae
      • Rheoviridae
      • Rhabdoviridae

Arboviruses Disease Caused by Them:

  • Encephalitis
  • Haemorrhagic fever

Arboviruses Diagnosis:

The diagnosis is made by virus isolation and serologi¬cal tests

Question 8. Rabies vaccine
(or)
Immunization of rabies
Answer:

  • Rabies vaccines are two types
  1. Neural
  2. Non-neural

1. Neural Vaccines:

  • Semple vaccine:
    • The most widely used vaccine
    • Developed by Semple at Central Research Insti¬tute, Kasauli.
    • It is a 5% suspension of infected sheep brain and inactivated by 5% phenol at 37°C leaving no re¬sidual live virus.
  • Beta Propiolactone (BPL) Vacine:
    • Modified semple vaccine
    • Instead of phenol, BPL is used as inactivating agent.
  • Infant brain vaccine:
    • Used widely in South America
    • Reduce neurological complications.
  • Vaccination Schedules:
    • Nowadays not used.
    • In the past, they were given subcutaneously on the anterior abdominal wall.
    • 7 – 14 injections depend on the degree of risk.

2. Non-Neural Vaccines:

  • Duck Egg Vaccine:
    • BPL is used as an inactivating agent
    • It has poor immunogenicity so not used now.
  • Tissue culture vaccines: Following cell culture vaccines are available in India.
    • Human diploid cell strain vaccine [HDCS]
      • The HDCS vaccine is prepared by growing rabies virus on human diploid cells and is in¬activated with BPL.
      • This vaccine is highly antigenic and free of side effects
    • Purified chick embryo cell vaccine [PCEC]
      • PCEC is now widely used.
      • It is cheaper
      • It contains BPL inactivated flurry LEP strain
    • Purified Vero cell vaccine [PVC]
      • This vaccine is under study

Question 9. Kyasanur forest disease
Answer:

  • It is a tick-borne haemorrhagic fever that occurs in Agar and Sorab, Shikarpur talukas of Shimoga district in Karnataka state
  • It is locally known as monkey fever as it infects mon¬keys also
  • But infection in monkeys is fatal

Kyasanur forest disease Causative Organism:

  • It is caused by the Russian Spring-Summer Encephalitis ( RSSE) Complex
  • Forest birds, and small mammals are the reservoir hosts
  • Principal vector is Haemaphysalis spinigera

Kyasanur forest disease Clinical Features:

  • Sudden onset with fever, headache, conjunctivitis, myalgia and severe prostration
  • Some may develop haemorrhages in the skin, mucosa and viscera

Question 10. Japanese Encephalitis
Answer:

Japanese Encephalitis Causative Organism:

  • Japanese encephalitis virus causes Japanese B encepha¬litis.
  • The virus in one of the mosquito-borne groups of a valve viruses.
  • Culex tritaeniorhyncus – Principal vector
  • Herons – Reservoir hosts.
  • Pigs – Amplifier hosts.

Japanese Encephalitis Clinical Features:

  • The disease typically has an abrupt onset with fever, headache and vomiting.
  • The fever is high and continuous.
  • The majority of infections are asymptomatic.
  • After 1-6 days signs of encephalitis set in with nuchal rigidity, convulsions, altered sensorium and coma.
  • The majority of infections are asymptomatic.
  • After 1-6 days signs of encephalitis set in with nuchal rigidity, convulsions, altered sensorium and coma.

Japanese Encephalitis Laboratory Diagnosis:

  • There is neutrophil leucocytosis in the peripheral blood
  • Pleocytosis with normal (or) raised sugar and slightly raised protein in the CSF.

Japanese Encephalitis Immunisation:

  • A formalin-inactivated mouse brain vaccine produced by using Nakayama strain has been successfully used for human immunization in Japan and even in India also.
  • 2 doses at 2 weeks interval followed by a booster 6 – 12 months later constitutes a full course.
  • Subsequent booster doses are recommended every 3 – 4 years as the immunity produced by the vaccine is short-lived.

Question 11. Human papillomaviruses [HPV]
Answer:

  • Human papilloma viruses belong to papovaviruses.
  • These are small, non-enveloped. Icosahedral oncogenic DNA viruses.
  • It can cause cutaneous warts, genital warts, recurrent respiratory papillomatosis, and oral papillomatosis.
  • These infections are transmitted by indirect (or) direct contact including sexual contact.
  • An association between HPV infection (HPV types 16 and 18) and cancer of the uterine cervix.

Question 12. Viruses causing diarrhoea.
Answer:

  • Diarrhoea is defined as an increase in the frequency, fluidity or volume of bowel movements relative to the usual habits of an individual.
  • Viruses causing diarrhoea include.
    • Rotavirus
    • Norwalk virus
    • Adenovirus
    • Astrovirus
    • Coronavirus
    • Calicivirus

Question 13. Oncogenic herpes viruses
Answer:

Oncogenic herpes viruses cause various malignant diseases.

RNA Viruses Oncogenic herpes viruses

Question 14. Name oncogenic viruses
Answer:

The various Oncogenic viruses are as follows:

RNA Viruses Various Oncogenic viruses

Question 15. Oncogenic RNA viruses
Answer:

  • Oncogenic RNA viruses belong to Retroviruses, which are enveloped, spherical viruses
  • They developed by budding through the host cell membrane
  • It contains enzyme RNA-dependent DNA polymerase or reverse transcriptase within the virion
  • It is classified into three subfamilies as follows
    • Oncovirinae
    • Spumavirinae
    • Lentivirinae
  • These viruses induce tumours by
    • Introducing into the cellular genome or by
    • Inducing or altering the expression of a pre-existing cellular gene.

Question 16. MMR.
Answer:

  • It is a live viral vaccine
  • It is used for Mumps, Measles and Rubella
  • It provides effective protection for a period of 10 years
  • It is recommended for all infants at the age of 15 months followed by a booster at the age of 4-6 years.

Side effects of MMR vaccine:

  • Sore arm
  • Fever
  • Mild rash
  • Temporary pain and stiffness in joints

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