poliomyelitis

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Poliomyelitis : 

Poliomyelitis By: Reema I. Dabbas 6th year medical student Mutah university Jordan 2010-2011

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Poliomyelitis, often called polio or infantile paralysis, is an infectious disease caused by a virus. This virus is a member of the enterovirus subgroup of the Picornaviridae family and has three serotypes: PV1, PV2 and PV3. Immunity to one serotype of the virus does not provide significant protection against the other serotypes.

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Transmission is by faecal–oral Multiplies in the oropharynx and the small intestine. The virus invades the local lymphoid tissue in the GIT The virus continues to be excreted in the stools for several weeks after infection

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In a minority of cases, then enters the bloodstream “causing viremia” and spreads to the central nervous system. The virus may also spread to the central nervous system along the peripheral nerves. The incubation period for polio infection is usually between 7 and 14 days but may range from 2 to 35 days. By 3–5 days after exposure, the virus can be isolated in the blood, throat and faeces.

Epidemiology : 

Epidemiology As a result of vaccination, there has been a dramatic reduction in the incidence of poliomyelitis globally. However, the disease still remains endemic in four countries – Nigeria, India, Pakistan and Afghanistan. Other countries also have cases of wild-type poliomyelitis from time to time, due to importation

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The World Health Organization (WHO) aimed to eradicate poliomyelitis by the year 2005. Although this was not successful, WHO is still hopeful that polio eradication will be achieved by 2010 or soon after, primarily through ‘national polio days’ where all children in a certain region are given oral polio vaccine (OPV)

Clinical Picture : 

Clinical Picture Clinical manifestations of poliomyelitis can vary and they are categorised according to severity. A large majority (up to 95%) of polio infections are inapparent or asymptomatic. However, even those infected who don’t show any symptoms shed the virus in their stools and, therefore, are able to transmit the virus to others. In polio endemic areas, persons with inapparent infections, particularly children, act as the main reservoir of polio infection.

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Rarely “in less than 1% of polio infections”, the virus invades and damages or completely destroys the motor neurons of anterior horn cells of the spinal cord and brain stem. This form, known as paralytic polio, is the most severe and typical manifestation of poliomyelitis. Depending on the extent of central nervous system damage, paralytic polio is classified into: Spinal “80% of all paralytic polio cases” It is characterised by asymmetrical paralysis, commonly of the legs. Bulbar. Weakness of muscles innervated by cranial nerves Bulbospinal.

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About a tenth of patients who develop paralytic polio can die without appropriate respiratory support when their respiratory muscles are paralysed. Most patients, even with paralytic polio, recover completely and, in most others, muscle function returns to some degree. However, paralysis or weakness that persists 12 months after the onset is usually permanent.

Signs & Symptoms : 

Signs & Symptoms In mild cases, the following nonspecific signs and symptoms are observed and usually resolve within a few days: Fever Headache Nausea Vomiting Abdominal pain Oropharyngeal hyperemia Abortive polio

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Nonparalytic poliomyelitis is characterized by the symptoms described above in addition to the following: Nuchal rigidity More severe headache Back and lower extremity pain Meningitis with lymphocytic pleocytosis (usually) Paralytic poliomyelitis occurs in fewer than 5% of affected patients and is characterized by the following: Compromise of the motor neurons may be localized or widespread. More frequently, asymmetric loss of muscle function is observed with involvement of major muscle groups. Muscle atrophy is generally observed several weeks after the beginning of symptoms. Recovery may be complete, partial, or absent

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Persons with residual impairment following paralytic poliomyelitis can develop a condition called post polio syndrome (PPS), after a period of prolonged stability (usually 30–40 years). It is characterised by: Exacerbation of existing muscle weakness. The development of weakness/paralysis in previously unaffected muscles. PPS is believed to be caused by degeneration, with age, of over sized motor units created during the recovery process of initial paralytic polio. It is rarely life threatening but has a slow, step-wise, unpredictable course. PPS is not an infectious process and persons who develop PPS do not shed poliovirus.

DDx : 

DDx Guillain-Barre Syndrome Botulism Rabies Enteroviral Infections Tetanus Myotonic dystrophy Aseptic meningitis

Work-up : 

Work-up Obtain specimens from the cerebrospinal fluid (CSF), stool, and throat for viral cultures in patients with suspected poliomyelitis infection. Obtain acute and convalescent serum for antibody concentrations against the 3 polioviruses. A 4-fold increase in the immunoglobulin G (IgG) antibody titers or a positive anti-immunoglobulin M (IgM) titer during the acute stage is diagnostic.

treatment : 

treatment Medical Care No antivirals are effective against polioviruses. The treatment of poliomyelitis is mainly supportive. Analgesia is indicated in cases of myalgias or headache. Mechanical ventilation is often needed in patients with bulbar paralysis. Tracheostomy care is often needed in patients who require long-term ventilatory support. Physical therapy is indicated in cases of paralytic disease. In paralytic disease, provide frequent mobilization to avoid development of chronic decubitus ulcerations. Active and passive motion exercises are indicated during the convalescent stage. Fecal impaction is frequent in cases of paralytic disease and can be treated with laxatives as soon as it develops.

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Surgical Care Total hip arthroplasty is a surgical therapeutic options for patients with paralytic sequelae of poliomyelitis who develop of hip dysplasia and degenerative disease.

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Consultations Physical therapist and rehabilitation therapist Pulmonologist Neurologist Immunologist Infectious diseases specialist Diet Because patients with poliomyelitis are prone to develop constipation, a diet rich in fiber is usually indicated.

Prevention : 

Prevention

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Two types of vaccines used in the prevention of poliomyelitis: inactivated poliovirus vaccine “IPV” administered parenterally oral attenuated poliovirus vaccine “OPV”.

Inactivated poliovirus vaccine : 

Inactivated poliovirus vaccine IPV was the first polio vaccine available on the market, and its widespread administration began in the 1950s. An enhanced inactivated poliovirus vaccine (eIPV) formulation is now available. Nonenhanced early formulations had the disadvantages of not being as immunogenic as OPV, not being able to induce mucosal immunity, and having to be administered parenterally, which increased costs and decreased compliance. One of the major advantages of IPV is that it contains an inactivated virus; for that reason, IPV is not associated with the development of vaccine-associated poliomyelitis and can be given to immunocompromised patients.

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Although they do not induce mucosal immunity, new eIPV formulations have been proven to be as immunogenic as OPV. For that reason, countries in which no cases of wild-type disease have been reported during the last several years (eg, the United States) have now adopted eIPV immunization schedules. This new prophylactic approach has the advantage of eliminating vaccine-associated cases. This vaccine is administered when individuals are aged 2 months, 4 months, and 6-12 months and before school entry, which is usually at age 4 years.

Oral attenuated poliovirus vaccine : 

Oral attenuated poliovirus vaccine Trivalent OPV has been used since the early 1960s. Immunization with this formulation was responsible for the significant decrease in the prevalence of disease throughout the world. This formulation has the advantages of inducing mucosal immunity, providing appropriate herd immunity, and increasing vaccine uptake because of oral administration. Additionally, it is cost-effective, especially in countries in the developing world.

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The major disadvantage of trivalent OPV is its association with vaccine-associated paralytic poliomyelitis (VAPP). Although the virus contained in this formulation is attenuated, it may occasionally become neurotropic and be able to produce disease similar to wild-type virus. Trivalent OPV is being administered in developing countries when individuals are aged 2 months, 4 months, and 6 months and with a booster at age 4 years. VAPP occurs most frequently after the first dose of OPV but may also occur after administration of the second or third doses.

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A new high-potency monovalent oral poliovirus type 1 vaccine (mOPV1) was introduced in India in April 2005. This vaccine is targeted to eliminate some of the last poliovirus reservoirs. This product constitutes part of an international effort to eradicate wild poliovirus. Studies have revealed that mOPV1 is 3 times more effective against type 1 poliomyelitis than trivalent OPV. In addition, it has been demonstrated to be particularly efficacious in areas in which the efficacy of trivalent OPV may be compromised by the high prevalence of diarrhea and other infectious processes.

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Administration of OPV is contraindicated in children who are immunocompromised and in children whose caretakers are immunocompromised. A risk for development of poliomyelitis is present in those individuals who receive this vaccine and are immunocompromised

Who should be vaccinated : 

Who should be vaccinated Children Children are recommended a primary course of 3 doses of an IPV-containing vaccine at 2, 4 and 6 months of age and a booster dose at 4 years of age. The recommended interval between 2 doses is 2 months, but, for catch-up, the minimum interval can be 1 month

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Adults The schedule for unvaccinated adults is 3 doses administered at intervals of 1–2 months. Booster doses A booster dose is not required for fully vaccinated children or adults unless they are at increased risk of infection, such as Travelling to areas or countries where poliomyelitis is epidemic or endemic. Healthcare workers, including laboratory workers, in possible contact with poliomyelitis cases. For those exposed to a continuing risk of infection, booster doses are desirable every 10 years.

Vaccine efficacy/effectiveness : 

Vaccine efficacy/effectiveness IPV is highly effective in producing immunity to polio virus and protection from paralytic poliomyelitis. After 2 doses of the vaccine, over 90% of recipients develop protective antibodies to all three types of the polio virus. After 3 doses, at least 99% of the recipients will have protection against the disease. Protection against paralytic disease correlates with the presence of antibodies against the polio virus. IPV appears to produce less local gastrointestinal immunity than does OPV, so it is possible that persons who receive IPV are more readily infected with wild-type polio virus than OPV recipients.

Vaccine safety : 

Vaccine safety Inactivated poliomyelitis vaccines can be safely administered to either persons with impaired immunity or to persons living with someone with impaired immunity. IPV vaccines may cause erythema, pain, and induration at the injection site. Other symptoms reported following administration of IPV vaccines in young babies include fever, crying and decreased appetite.

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