2. MORPHOLOGY
Size : Medium sized , 70-75 nm in diameter .
Shape : Spherical
Nucleic acid : Double stranded DNA ,
Envelope : Present .
Symmetry : Icosahedral
3. STRUCTURE :
The capsid is composed of 252 capsomers arranged as an icosahedron
with 20 triangular facets and 12 vertices . Of the 252 capsomers, 240
have six neighbours and are called hexons, while the 12 capsomers at
the vertices have five neighbours and are called pentons. Each penton
unit consists of a penton base anchored in the capsid and a projection or
fibre consisting of a rod-like portion with a knob attached at the distal
end. Thus, the virion has the appearance of a space vehicle
4. RESISTANCE
The viruses are heat liable and can be destroyed in minutes at 56°C
Adenoviruses are relatively stable, remaining viable ( stable ) for
about a week at 37°C.
They are resistant to ether and bile salts.
5. CULTIVATION :
Human adenoviruses grow only in tissue cultures of human origin,
such as human embryonic kidney, HeLa or HEp-2.
Cytopathic changes may take several days to develop and consist
of cell rounding and aggregation into grape-like clusters.
Intranuclear inclusions may be seen in stained preparations.
6. MODE OF TRASMISSION :
Adenovirus are transmitted by direct contact , faeco – oral route
and sometimes through water.
The infection may occur through conjunctiva or nasal mucosa . In
children , it may occur through faeco – oral route
7. INCUBATION PERIOD 6 – 7 DAYS
PATHOGENICITY
The viruses multiply in the conjunctiva or pharynx or small
intestine and then spread to the lymph nodes .
More than one type of virus may produce the same clinical
syndrome and one type of virus may cause clinically different
diseases
Some types leads to persistent asymptomatic infection in the tonsils ,
adenoids , intestine
8. Adenoviruses cause infections of the respiratory tract, eye, bladder and
intestine.
The following syndromes have been recognised:
Pharyngitis and tonsillitis, presenting as febrile common cold. Types 1-
7 are commonly responsible.
Pneumonia: Adenovirus types 3 and 7 are associated with pneumonia
Acute respiratory diseases (ARD): Due to Serotypes 4, 7 and 21
Pharyngoconjunctival fever: This syndrome of febrile pharyngitis and
conjunctivitis usually associated with serotypes 3, 7 and 14
9. Epidemic keratoconjunctivitis (EKC): This is a serious condition,
usually caused by type 8 and less often by types 1 9 and 37 .
Acute follicular conjunctivitis: This is a nonpurulent inflammation of
the conjunctiva with enlargement of the submucous lymphoid follicles
and of the pre-auricular lymph nodes. Types 3, 4 and 11 are commonly
responsible
Acute hemorrhagic cystitis due to serotype 11 and 21 .
Infantile gastroenteritis due to serotype 40 and 41 .
10. LABORATORY DIAGNOSIS
Adenovirus infection can be diagnosed in the laboratory by antigen
detection , polymerase chain reaction , virus isolation and serology .
SPECIMENS – Throat swab , conjunctival swab , anal swab , urine ,
genital secretions , bronchial lavage , transtracheal aspirate ,
nasopharyngeal aspirate , autopsy ,biopsy materials .
MICROSCOPY – Demonstration of viral particles in faecal specimens by
electron microscope
11. IMMUNOFLUORESCENCE – Demonstration of viral antigens
in the cells from respiratory tract , eye , urine , autopsy or biopsy
material and infected cell cultures by immunofluorescence using
monoclonal antibodies .
ISOLATION – Isolation of virus in tissue culture and
identification by the cytopathic effects .
SEROLOGY – For serological diagnosis rise in titre of antibodies
should be demonstrated in paired sera
