ADENOVIRUSES

							ADENOVIRUSES

 Human Adenoviruses
           DNA VIRUSES
                 All are DS except Parvoviridae
         All replicate in the nucleus except Poxviridae

               Icosahedral                            Complex
                                                     1- Poxviridae

   Naked                              Enveloped
non-enveloped                      ether-sensitive
ether-resistant
1- Parvoviridae                   1- Herpesviridae
2- Papillomaviridae               2- Hepadnaviridae
3- Polyomaviridae

4-   Adenoviridae
     Human Adenoviruses
• Adenoviruses were first isolated in 1935 from
  human adenoid tissues.

• Since then, at least 49 distinct antigenic types
  have been isolated from humans and many other
  types from animals.

• All human serotypes are included in a single
  genus within the family Adenoviridae.
            Morphology

   –   ds-DNA viruses,
   –   media sized in diameter,
   –   icosahedral
   –   Nonenveloped

Antigenic structure
• All human Adenoviruses share a common group-specific
  antigen.

• Type specific antigens are important in serotyping.
           Classification
Adenoviruses are divided into six groups (A to F) based on:

– physical,
– chemical
– biological properties

Antigenic structure divides adenoviruses into:
- 49 serotypes:

- About 1/3 of the 49 known human serotypes are responsible
for most cases of Adenovirus disease.
        Pathogenesis:


• Adenoviruses spread by:
  – direct contact,
  – respiratory droplets
  – feco-oral route.
              Pathogenesis:

• Adenoviruses infect and replicate in the epithelial
  cells of the:
   –   pharynx,
   –   conjunctiva,
   –   urinary bladder
   –   small intestine.


  They usually do not spread beyond the regional
  lymph nodes EXCEPT IN THE IMMUNE
  COMPROMIZED HOST.
      Pathogenesis:

• The virus has a tendency to become
  latent in lymphoid tissue,

• The virus can be reactivated by
  immunosuppression.
     Clinical Syndromes:


• Adenoviruses cause primary infection in:
  – children
  – less commonly adults.


• Several distinct clinical syndromes are
  associated with Adenovirus infection.
CLINICAL SYNDROMES
A. Respiratory diseases:

B. Eye infections:

C. Gastrointestinal disease

D. Other diseases:

E. Adenoviral infections of the immune
  compromised host
A. Respiratory diseases:
•    The most important etiological association of
    adenoviruses is with the respiratory diseases.

• They are responsible for 5% of acute
  respiratory diseases in:
    – young children
    – and much less in adults.
A. Respiratory diseases:
  Four different syndromes of respiratory infection have
  been linked to Adenoviruses.

• Acute febrile pharyngitis:
   – most commonly seen in infants and young children,
   – symptoms include cough, stuffy nose, fever and sore throat.

• Pharyngo conjunctival fever:
   – symptoms are similar to those of acute febrile pharyngitis but
     conjunctivitis is also present.
   – It tends to occur in outbreaks such as at children's summer
     camps (swimming pool conjunctivitis).
A. Respiratory diseases:
• Acute respiratory disease:
  – is characterized by pharyngitis, fever, cough
    and malaise.
  – It occurs in an epidemic form among young
    recruits under conditions of fatigue and
    overcrowding

• Pneumonia: a complication of acute
  respiratory disease in both children and
  adults.
              NOTE
       Outbreaks & epidemic
       adenovirus infections
• Pharyngo conjunctival fever:
   – outbreaks
   – in children's summer camps (swimming pool
     conjunctivitis).


• Acute respiratory disease:
   – occurs in an epidemic form
   – among young recruits


• Epidemic keratoconjunctivitis:
          B. Eye infections:
• Mild conjunctivitis:
  – can occur as a part of respiratory pharyngeal syndromes.
  – Complete recovery with no lasting sequelae is the
    common outcome.
  – Can occur sporadically or in outbreaks.


• Epidemic keratoconjunctivitis:
     • a highly contagious and a more serious disease occurring
       mainly in adults.
     • Corneal involvement may be followed by
       various degrees of visual disability.
             C. Gastrointestinal
                  disease:
1.    No disease association
     1.   Many Adenoviruses replicate in intestinal cells and are
          present in the stools without being associated with
          GIT disease.


2. Infantile gastroenteritis
     1. Two serotypes (40, 41) have been etiologically
        associated with infantile gastroenteritis.
NOTE
1. The enteric Adenoviruses are very difficult
   to cultivate.
2. Lab diagnosis depend on direct detection
       D. Other diseases:

• Acute haemorrhagic cystitis:
  – types 11, 21 may cause acute haemorrhagic
    cystitis in children especially boys.
 E. Adenoviral infections of
the immune compromised host

• The most common clinical manifestations are:
     • pneumonia,

     • hepatitis

     • gastroenteritis.
   Laboratory Diagnosis
• Direct detection:

• Isolation

• Serology
    Laboratory Diagnosis
Direct detection:
• Virus particle by EM can be detected by direct
   examination of fecal extracts

• Detection of adenoviral antigens by ELISA.
              Enteric Adenoviruses

• Detection of adenoviral NA by Polymerase chain
  reaction: can be used for diagnosis of Adenovirus infections
  in tissue samples or body fluids.
Laboratory
 Diagnosis
Isolation
• Isolation depending on the
  clinical disease, the virus may
  be recovered from throat, or
  conjunctival swabs or and
  urine.
• Isolation is much more
  difficult from the stool or
  rectal swabs
  Laboratory Diagnosis
Serology
• Haemagglutination inhibition
&
• Neutralization tests can be used to
  detect specific antibodies following
  Adenovirus infection.
   Prevention and control
• Careful hand washing is the easiest way to prevent
  infection.

• Disinfection of Environmental surfaces with
  hypochlorites.

• The risk of water borne outbreaks of conjunctivitis can
  be minimized by chlorination of swimming pools.

• Epidemic keratoconjunctivitis can be controlled by strict
  asepsis during eye examination.