Infectious diseases caused by Enteroviruses. Poliomyelitis. Flashcards
what’re the CHARACTERISTICS OF ENTEROVIRUS ?
replicate within and are TRANSMITTED BY THE FECAL- ORAL ROUTE - BUT DOES NOT NECESSARILY NEED TO CAUSE GI SYMPTOM
The virions are
resistant to stomach acid, proteases, and bile
Most enteroviruses are
cytolytic
replicating rapidly and causing direct damage to the
target cell.
The ENTEROVIRUSES ARE EXCLUSIVELY HUMAN PATHOGENS AND especially newborns are at risk because they are not vaccinated yet
what is the PATHOGENESIS OF ENTEROVIRUS ?
however the virus s still shed from the upper resp and GI with feces
Viral replication takes place several times at
different locations in the body:
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1st viral replication:
initiated in the mucosa and lymphoid tissue of
the tonsils and pharynx,
(Some enteroviruse
s can also affect the lungs-
> thus transmission
from oral to oral )
from there the virus travels downwards and later infects M
cells and lymphocytes of the Peyer patches and enterocytes in the intestinal mucosa.
they usually do not cause
gastroenteritis
they leave the GI tract and enter into the blood stream
Primary viremia = virus enters the blood
spreads to receptor-bearing target tissues = reticuloendothelial cells of the lymph nodes, spleen, and liver
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initiate a second phase of viral replication, resulting in a secondary viremia and
symptoms.
the GENUS ENTEROVIRUS CAN BE SUBDIVIDED / CLASSIFIED into categories such as
poliovirus
non poliovirus - - coxsackieviruses a and B echovirus - enteric ,
human orphan virus
EPIDEMIOLOGY OF POLIOVIRUS ?
vaccination
only 3 endemic countries in the would still has poliomyelitis - nigeria , afghanistan and pakistan
what is the AVERAGE INCUBATION PERIOD OF THE GENUS ENTEROVIRUS ?
3-10 days
PATHOGENESIS OF PARALYTIC POLIOMYELITIS ?
the virus has spread from the blood to the anterior horn of the spinal cord and motor cortex of the brain - the virus here replicates inside the neurones and destroys these neurones
large pyramidal cells of gyrus precentralis - the nuclei of the brainstem - subcortical nuclei of the cerebellum
principally affects motor
and autonomic
neurons (not sensory)
what is the INCUBATION PERIOD FOR POLIOVIRUS
5-35 days
average - 7-12 days
TRANSMISSION OF POLIOVIRUS ?
fecal oral
or
airborne
what are the THREE SEROTYPES OF HUMAN POLIOVIRUS TYPES
only 3 serotypes list
85% of the cases of paralytic polio is caused by type 1.
what are all the OUTCOMES THAT POLIO CAN DO FOR UNVACCINATED PEOPLE /?
1) asymptomatic - viral infection and replication is only limited to the oropharynx and gut - 90 percent of polio virus infection is asymptomatic
2) abortive poliomyelitis - minor
Fever, headache, malaise, sore throat, and
vomiting
usually passes after 5-6 days
3) Nonparalytic poliomyelitis or aseptic meningitis
virus progresses into the central nervous
system and the meninges, causing back pain and muscle spasms
in addition to the
symptoms of the minor illness
fever
headache
vomitting
during the 2nd temperature wave - neck stiffness , kerning and brodzinski sign and triad sign
4) Paralytic polio, the major illness, occurs in 0.1% to 2.0
there are different paralytic forms according to localisation
spinal vs bulbar vs cantal vs mixed eg bulbospinal
Occurs 2–3 days following the meningitic form after a brief symptom-free interval
then fever
Severe back, neck, and muscle pain
2) Asymmetric flaccid paralysis worsens over hours to days
Most commonly affects the leg muscles
Paralysis is usually more severe in proximal muscles than in distal muscles.
Ascending paralysis with diaphragmatic involvement → respiratory failure
Bulbar form with brain stem involvement (rare): damage to the cerebral or autonomic nerve centers (cranial nerves and respiratory center) → central respiratory paralysis
Diminished deep tendon reflexes
Muscle atrophy
Hypotonia
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recovery stage - lasting 2-5 years
first months reflexes are restored
muscle tone improved
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reconvalescent stage - inadequate treatmnet and rehab leads to disabilities and limb deformities
what are the CLINICAL CHARACTERISTICS OF DIFFERENT FORMS OF POLIOVIRUS ?
Bulbar form:
respiratory center involvement. Patients have high fever, vomiting,
severe intoxication
Cranial nerve malfunctions occur.
-
Spinobulbar form:
Paralyses starts from the lower limbs; for a short time, work way up to respiratory muscles. The worst forms are :
emerging
ascending or descending paralysis Landry type, which often end fatal.
-
Pontine form: manifested by paresis /paralysis/ of n. facialis, most often unilaterally.
what is the DIAGNOSIS OF POLIOVIRUS ?
paralytic stage is based on the clinical manifestations
EMG studies that detect delicate muscle damage
for poliomyelitis :
PCR amplification of poliovirus RNA from CSF.
seroconversion detection with a 4-fold increase in the antibody titer confirms the diagnosis
Poliovirus RNA can also be isolated from stool or oropharynx (throat swab).
CSF will show:
High protein levels
Pleocytosis with either neutrophils (early infection) or lymphocytes (late infection)
Normal glucose levels
what is the DD OF POLIO?
meningeal forms - viral serous meningitis cosackie virus a and b , echo , influenza
paralytic forms - polio like caused by other enterovirus - cosackeivirus a, b , ECHO - esp ev-17
POLYradiculoneuritis
Gullian barre syndrome - typically symmetrical - also no CSF pleocytosis
spinal muscular atrophy
if you get VACCINATED WITH POLIOVIRUS DOES IT MEAN YOU WILL NOT BE INFECTED ?
vaccinated people are HEALTHY CARRIERS - they get the atypical / non paralytic abortive form
= which is most likely only a fever
In case of incomplete immunization, paralytic events may occur but they are more
favorable
what is the TREATMENT FOR POLIO?
rest
pain relief
mechanical ventilation i needed
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in the acute phase - preventing the heamtogenous virus dissemination - hyperimmunogenic immunoglobulin
pathogenic treatmnet - anti cholinesterase - NIVALIN
resp = mechnaical ventilation or tracheostomy
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children should be isolated for 40 days and then active rehab and balneotherapy with stimulation therapy - this active rehab lasts months to years
