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.
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