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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
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