viral gastrointestinal infections, main focus of presentation is on pathogenesis of polio and echoviruses

1. Viral gastrointestinal infections
(polio & echoviruses)
Submitted to Madam Saba Farooq
Submitted by: Shumailah Nayab
Roll # AP402818

2. Gastrointestinal infections
Infections caused by microorganisms in gastrointestinal
tract by the organisms which are not resident flora of
individual
These infections may be
 Confined to GI tract
Or
 initiated in the gut before spreading to other parts of
the body

3. 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

4. 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)

6. 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

7. 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

11. Subclinical infection
 in apparent subclinical
infection account for the vast
majority of poliovirus infections
 90 - 95% cases are subclinical
infections

12. 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

13. 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)

14. How a gastrointestinal infection cause neurological
infection ????????
 This mechanism is poorly understood, but 3 hypothesis have been
suggested
primary viremia is required
1-virions pass directly from the blood into the central nervous system by
crossing the blood–brain barrier independent of CD155
2- 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 transport
3- virus is imported into the CNS via infected monocytes or macrophages

15. 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

16. 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 immunity
induces IgA formation

17. 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

18. 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

19. 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

20. 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

21. Diseases caused by echovirus
 Acute aseptic meningitis
 Encephalitis
 Rash
 Respiratory illness
 Herpangina
 Epidemic pleurodynia (Bornholm disease)- disease of muscle
 Paralysis
 Myocardial/pericardial disease

22. 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

23. 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

24. Prevention
 Vaccination is not available
 only effective measures for their control are
high standards of personal and community
hygiene

25. 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.

26. Any question?????????