Infections caused by ECHO Viruses
Special features of ECHO viruses
Echoviruses (abbreviation of enteric cytopathogenic human orphan viruses) are grouped together as they infect human enteric tract and can be recovered from humans by inoculation into certain cell lines. More than 30 serotypes are known, but not all of them affect humans.
Echoviruses display typical traits of enteroviruses. Several echovirus strains possess hemagglutinin.
Pathogenesis, clinical findings and immunity
Echoviruses can cause different alimentary infections (e.g. gastroenteritis), aseptic meningitis, encephalitis, acute respiratory viral infections, generalized viral disease of newborns and other viral disorders usually with non-specific findings.
Parechoviruses of serotype 1 cause literally the same disorders like group ECHO viruses.
Pathogenesis is similar to other enteroviral diseases.
Echoviruses must be regarded as causative agents in outbreaks of aseptic meningitis and in summer seasonal epidemics of viral disorders with fever and rash, especially in young children.
Nowadays echoviruses are the major cause of aseptic meningitis in children. With the potential elimination of poliomyelitis in developed countries, the pathology of CNS associated with echoviruses is prevalent.
Immunity maintained by neutralizing antibodies is long-term and type-specific. Laboratory diagnosis
It is difficult to diagnose an echoviral infection on clinical grounds.
Isolation of virus is possible from throat swabs, stools, rectal swabs, and, in case of aseptic meningitis, from cerebrospinal fluid.
For clinical specimen testing various rapid methods are employed. Immunofluorescence assay of throat swab and ELISA are used for primary virus detection.
Viral cultivation is available in cell cultures (e.g. primary monkey kidney cells). If a viral agent is isolated, it is tested against the wide number of antisera against enteroviruses. Determination of viral type present is made by immunofluorescence or neutralization tests. Infection with two or more enteroviruses may occur simultaneously.
As some echoviruses carry hemagglutinin, hemagglutination inhibition test is suitable in these cases for viral identification.
For rapid identification of various enteroviral strains reverse transcription PCR (RT-PCR) is widely used.
Serological diagnosis is impractical because of the many different viral types.
Principles of infection treatment and prophylaxis
Administration of immune globulin for infants with suspected enterovirus infections is of limited value. There are no antiviral drugs or vaccines available for the treatment or prevention of any echoviral disease.