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Classification of virus

 

                                               Classification of virus

On the basis of type of nucleic acids , viruses are classified into two group:-

v  Ribo virus or RNA virus→contains RNA.

v  DeoxyRibo virus or DNA virus →contains DNA.

ü  RNA virus

                 A) Picorana virus (20-30)

Eg→ a) Entero virus

       b) Rhino virus

       c) Rhro virus

       d) Hepato virus (HAV)

               B) Orthomyxo virus ( 80-120nm )

                   Eg:- a) Influenza virus

                C) Paramyxo virus (100-130nm)

                    Eg:- mumps, rubella viruses.

                 D) Arbo virus

                     Eg:- chickengunya , Denque , sendfly fever

                  E) Rhabdo virus (75-180nm)

                     Eg:- Lyssa virus (Rabies virus)

                  F) Reo virus

                  G) Corana virus

                  H) Hepatities – A virus

v  DNA virus

 a) pox virus → Infect vertibrates , birds and insects.

   Eg:- Small pox , cow pox , monkey pox.

                          b) Herpes virus (100- 200)

Eg:- Herpes simplex ( Infect only man) Varicella / chicken pox ( by varicella zoster )                                CVM .        

                          c) Adeno virus

                           d) Papovo virus

                           e) Parvo virus

                           f) Hepatitis – B virus

v  Polio virus

Morphology :- Spherical particle , 30 nm in size , icosahedral symmetry . It can be crystallised which can be seen in infected cell. It is RNA virus belong to family picrona virus.

Antigen:- Three distinct types:

   Type 1 or Brunhillda , Type 2 or Lansing , Type 3 or Leon. Type 1 is most virulent and couse most epidemics , Type 2 causes endemic infection & Type 3 causes epidemic occasionally.

        Transmission :- The virus enter in the body by ingestion or inhalation of contaminated food or drink . They muttifly in Lymphatic tissue of alimentary canal, from the tonsil to the peyer`s patches and enters the regional lymphatics . Then these viruses reaches blood , then spinal cord and then to CNS . In CNS they multiply in neurons and destroy them.

                                                                              The earliest change is the degeneration of Nissle bodies (chromatolysis) Necrotic cell lysis .  lesions are mostly in the anterior horn of spinal cord, causing flaccid paralysis but posterior horns and intermediate column may also be involved . In same cases it causes Encephalitis.

            Lab diagnosis :-

              1) Isolation of virus from threat swab in early stage , virus is grown in Robertson cooked meat media.

               2) Cultivation of virus in tissue culture , cytopathic effect is seen in 3 days . Virus is Identify by Neutralization test.

                3) Cultivation of virus from stool in late stage of disease on Robertson cooked meat media.

                4) Serological  diagnosis by Neutralization or complement fixation test.

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