poliomyelitis
@ Identification:
*A viral infection, polio virus(genus: Enterovirus) types 1,2,3 . all types can cause paralysis.
*Type 1 often isolated from paralytic cases, type 3 less so, & type 2 least . *commonly,Type 1 most frequently causes epidemics. Most vaccine associated cases are due to type 2 or 3.
*One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.
*Poliomyelitis most often recognized by acute onset of flaccid paralysis, polio virus occur in the GI tract spread to the regional nodes, & in minority of cases to the nervous system.
*Symptoms include :
fever, malaise, headache, nausea & vomiting. If the disease progresses to major illness, severe muscle pain & stiffness of the neck & back with flaccid paralysis may occur.
*Flaccid paralysis occur in less than 1% of polio virus infection, greater than 90% of infections are either in apparent or a non-specific fever, Aseptic meningitis occurs in about 1% of cases.
*The paralysis of poliomyelitis
is asymptomatic with fever present at onset.
The maximum extent of paralysis is reached within 3-4 days, the site of paralysis depends on location of nerve cell destruction in spinal cord or brain stem.
The legs are affected more often than the arms. Paralysis of the muscles of respiration &/or swallowing is life threatening .
*Any paralysis present after
60 days is likely to be permanent.
*Polio remains primarly a disease of infants & young childrens, 70-80 % of cases are less than 3 year of age & 80-90 % of cases are less than 5 years of age.
*WHO has set the end of the year 2000 as the target for world wide eradication but it still have little longer to accomplish.
@Occurrence:World wide, it occur sporadically or epidemic the greatest risk of polio occurs in India & to lesser extent in west & central Africa. with increase in cases during the late summer & autumn in temperate countries & in hot , rainy seasons in tropical countries.
@Reservoir: Humans, the virus dose not survive long in environment outside the human body. There is no long term carriers state.
@Mode of tranismission:
1- person to person by feco-oral route & pharangeal spread .
2- milk, food-staffs, & other material contaminated with feces have been incremented as vehicles (rare).
@ Incubation period: 7-14 days for paralytic patients.
@Period of communicability:
As long as the virus is excreted. Poloi virus is demonstrable in throat secretion as early as 36 hr & in feces 72 hr after exposure to infection in both clinical & unapparent cases. Virus typically persist in the throat about 1 week & in the feces for 3-6 weeks or longer.
Cases are most infectious during the first few days before & after onset of the symptoms.
@Susceptibility & Resistance:
Susceptibility to infection is universal but paralysis occur in 1%. The rate of paralysis among infected, non-immune adult is higher than that among non –immunized infants & young children.
The specific immunity is life long duration follows both clinically & unapparent infection . seconds attacks are rare & results from infection with a polio virus of a different type. Infant born to immune mothers have transient passive immunity .
IM injection, trauma or surgery during incubation period or prodromal illness may provoke paralysis in the affected extremity.
@Methods of control:
A- preventive measures:
1- educate the public on the advantages of immunization in early childhood.
2- polio vaccines: there are two types of polio vaccine:
* trivalent oral polio vaccine & *inactivated or killed polio vaccine.
Trivalent oral polio vaccine:
Consist of life attenuated polio viruses & is a safe & effective vaccine. OPV stimulates natural infection by inducing both circulating antiboby & intestinal resistence. As aresult , children immunize with OPV are unlikely to spread wild polio virus to other children. When administered during a mass campaign, OPV can interrubed wiled polio virus tranismissin in the community. These compaign are ideally conducted during the cool, dry sessons to achieve maximam effect.