Classify Viruses
, Discribe Morphology Antigenic property , Transnoission and lab diagnosis of
polio 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.
