Viral gastrointestinal infections

Viral gastrointestinal infections(polio & echoviruses)Submitted to Madam Saba FarooqSubmitted by: Shumailah NayabRoll # AP402818

Gastrointestinal infections

Infections caused by microorganisms in gastrointestinal tract by the organisms which are not resident flora of individualThese infections may be Confined to GI tractOr initiated in the gut before spreading to other parts of

the body

Terms used in GI tract infections

Gastroenteritis: inflammation of the stomach and intestines rotaviruses, noroviruses

Diarrhoea: a condition in which faeces are discharged from the bowels frequently and in a liquid form rotaviruses, caliciviruses, adenoviruses, parvoviruses

Dysentery: inflammatory disorder of GI tract (large intestine) associated with pus and blood in faeces

Enterocolitis: inflammation involving the mucosa of intestines enteroviruses, rotaviruses, Norwalk virus, adenoviruses

Enteroviruses

 genus of the family picornaviridae (70 serotypes) ss RNA,+ sense, naked virus with icosahedral symmetry  stable to acid pH and resistant to lipid solvents since there is no

envelope capsid has 60 copies each of 4 proteins, VP1, VP2, VP3 and VP4 Enterovirus is divided into following groups Poliovirus Echovirus Coxsackievirus (a & b)

poliovirus

3 serotypes (distinct variations within a specie)

Humans are the only natural hosts for polioviruses

Infection occurs via the faecal–oral route and replication occurs in the alimentary tract

poliovirus infection is asymptomatic

Pathogenesis

replication occurs in the alimentary tract Virus is shed in the faeces of infected individuals presence of viremia (virus in the bloodstream) occurs

for short time period

Subclinical infection

 in apparent subclinical infection account for the vast majority of poliovirus infections

90 - 95% cases are subclinical infections

Abortive infection

4 - 8% cases are abortive infections virus spreads and replicates in other sites such

as brown fat, reticuloendothelial tissue, and muscles causes secondary viremia symptoms fever headache sore throat

Paralytic poliomyelitis (Major illness) occurs in less than 1% of poliovirus infections virus enters the CNS and replicates in motor neurons within the spinal

cord, brain stem, or motor cortex cause the selective destruction of motor neurons leading to temporary

or permanent paralysis muscle pain and spasms are observed in paralysis it leads to respiratory arrest and death (rare)

How a gastrointestinal infection cause neurological infection ????????

This mechanism is poorly understood, but 3 hypothesis have been suggested

primary viremia is required1-virions pass directly from the blood into the central nervous system by crossing the blood–brain barrier independent of CD1552- virions are transported from peripheral tissues that have been bathed in the viremic blood, for example muscle tissue, to the spinal cord through nerve pathways via retrograde axonal transport3- virus is imported into the CNS via infected monocytes or macrophages

Laboratory Diagnosis

Virus isolation:   Cerebrospinal fluid usually show the changes typical for that of viral

meningitis with lymphocytosis and a high protein level molecular assays  Specific sera neutralize the cytopathic effects, it can be identified

Serology: not widely used

Prevention

1. Inactivated Salk Vaccine:formalin inactivated intramuscular polio vaccine (IPV)  It contains an injected dose of three antigenic strains of killed polio virus

2. Live Attenuated Vaccine:live attenuated oral polio vaccine (OPV)induces long lasting immunityinduces IgA formation

Epidemiology

Polioviruses are disseminated globally densely populated developing countries, almost 100% of the

population have Abs to all 3 types of the virus before 5 years of age

Epidemics do not occur and paralytic disease is rare as the incidence of paralytic poliomyelitis increases with age, especially after 15 years of age

Pakistan is one of three countries in the world where poliomyelitis is still categorized as an endemic viral infection

ECHOvirus

enteric cytopathic human orphan (ECHO) virus  largest Enterovirus subgroup, 34 serotypes Cause opportunistic infections and diseases faecal-oral transmission its primary target is children and immuno

compromised people resistant to pH (3-10) and are ether and alcohol

pathogenesis

 replication begins in the pharynx or gut (M cells) after ingestion of contaminated material

virus spread to regional lymph nodes and cause subclinical transient viremia, spread to liver, spleen, bone marrow, and distant lymph nodes

Secondary sites of infection include the CNS, liver, spleen, bone marrow, heart, and lungs

Epidemiology

associated with both epidemic and endemic patterns of infection Infection rates vary with the season, geography, and the age and

socioeconomic status of the population  Echovirus 9 was the most commonly reported enterovirus from 1970-

2005 and accounted for 11.8% of reports with known serotypes Epidemics have been reported in Panama, Mexico, Switzerland, Cuba,

the United States, and Turkey. Asian-Pacific countries have reported major enteroviral epidemics with significant morbidity and mortality

Diseases caused by echovirus

Acute aseptic meningitis Encephalitis Rash Respiratory illness Herpangina Epidemic pleurodynia (Bornholm disease)-  disease of muscle Paralysis Myocardial/pericardial disease

Vesicular rashes

 lesions on the head, trunk, and extremities do not progress to pustules and scabs Petechial and purpuric rashes have been reported with echovirus 9 When these rashes have a haemorrhagic component (flow of blood ), the

illness can be confused with meningococcal disease, particularly when aseptic meningitis occurs

Laboratory Diagnosis

Virus Isolation from faecal samples  from the pharynx during the acute phase of the illness,

especially in cases with respiratory infections

 Serological Techniques  Neutralization tests are generally the best serological tests

available

 Direct detection of viral genomes  PCR assays are becoming increasingly used

Prevention

Vaccination is not available only effective measures for their control are

high standards of personal and community hygiene

References

 Acute Poliomyelitis at eMedicine Pediatric Poliomyelitis at eMedicine Charles Chan and Roberto Neisa. "Poliomyelitis". Brown University.  ped/629 at eMedicine Ryan KJ; Ray CG, ed. (2004). Sherris Medical Microbiology (4th ed.).

McGraw Hill. pp. 537–9. ISBN 0-8385-8529-9. Yin-Murphy M, Almond JW (1996). Baron S; et al., eds. Picornavirues. in:

Baron's Medical Microbiology (4th ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1.

The facts about enterovirus D68". http://www.childrensmn.org/. Children's Hospitals and Clinics of Minnesota.

Any question?????????

Thank you