Polio is an enteroviral infection that manifests in four differentforms: inaparenta infection, polio nonparalitica, abortive disease, and paralytic disease.
The poliovirus is an RNA virus that is transmitted by fecal-oral routeor through ingestion of contaminated water. Three serotypes cancause human infection. Incubation is 5-35 days. Initial viral particlesreplicate in the nasopharynx and alimentary tract and then invade the lymphoid tissues with secondary hematologic extension. Aftera period of viremia, the virus is neurotropic and causes destructionof the horn spinal motor neurons previously. Destruction of motor neurons leads to the development of flaccid paralysis with bulbaror spinal distribution.
Picornaviridiae virus belongs to the family. The virus is resistant to solvents and stable at low pH due to the viral envelope. There arethree distinct antigenic strains in which type I is found in 85% ofcases of paralytic disease. Infection with one type does notprovide protection against other types of immunity for the threetypes is life.
The virus enters the nervous system by crossing the blood-brainbarrier or by axonal transport from peripheral nerves. May causenervous system infection by affecting the precentral girusului,thalamus, hypothalamus, and motor nuclei formation cross-linked,and vestibular nuclei neurons in cerebelari and anterior andintermediate spinal columns. Cromatoliza suffer central neuronsand muscle paralysis or muscle atrophy occurs when less than10% of neurons that survive the nerve cords. Gliosis developswhen the inflammatory infiltrate resolved, but most of neurons that survive shows the total recovery.
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