RNA Viruses Virology Short Essay Question And Answers

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
Immunoprophylaxis for Poliomyelitis

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:

  • 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.

RNA Viruses RNA virues and Diseases caused by them

Question 2. Mention two important live viral vaccines.

Live viral vaccines are

RNA Viruses Viral vaccines

Question 3. Koplik’s spots?

  • 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?

  • 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

RNA Viruses Vaccines

Question 6. Mumps vaccine?

  • 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

  • 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
Immunization of rabies

  • 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

  • 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

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]

  • 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.

  • 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

Oncogenic herpes viruses cause various malignant diseases.

RNA Viruses Oncogenic herpes viruses

Question 14. Name oncogenic viruses

The various Oncogenic viruses are as follows:

RNA Viruses Various Oncogenic viruses

Question 15. Oncogenic RNA viruses

  • 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.

  • 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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