COMMUNICABLE DISEASESPoliomyelitis“Infantile Paralysis”Professor Qayser Sahib Al Habeeb Specialist inInternal and Community MedicineDepartment of Family and Community MedicineCollege of Medicine / University of Duhok
Poliomyelitis ( Infantile Paralysis) Enteroviral infection that causes damage and death of anterior horn cells. It remains a predominantly childhood illness with 80% - 90% of cases occurring in U5 children
Unlike developed countries, the disease is still a major problem in developing countries.
Prior to vaccination programs polio occurred worldwide. The Global Polio Eradication Initiative was launched in 1988. 1 in 200 infections leads to irreversible paralysis. Among those paralyzed, 5% to 10% die because of respiratory failure.
Clinical Spectrum of Polio Virus Infection:1- Inapparent infection (sero conversion) 90 – 95%2- Non paralytic , minor illness (aseptic meningitis) 4 – 8% 3- Paralytic ,major illness. (anterior horn cell death) < 1 %
Clinically:
The minor illness consists of few days of mild fever & headache.The major illness restarts after a week of wellbeing as recurrence of fever headache & meningism.
Weakness starts later in one muscle group and can progress to wide – spread asymmetric paresis. Respiratory failure may supervene if the intercostal muscles are paralyzed or the medullary motor nuclei are involved.
Maximum extent of paralysis is usually reached within 3 or 4 days. Progression of paralysis almost invariably halts when the patient becomes afebrile. After 60 days the degree of existing paralysis is likely to be permanent
I.P. : usually 7 – 14 days C.P. : few days before and up to 3 – 6 weeks after onset of symptomsMOT --- primarily, person to person principally through fecal – oral route. --- rarely, respiratory & vehicle spread have been incriminated( milk, food stuffs ………etc)
Infectious Agent: --- polio virus (enterovirus) type I, II & III. --- all can cause paralysis. The most virulent is type I (the most frequently causing epidemics) No type II has been detected anywhere in the world since 1999 In cold environment, it can live --- in water for 4 months --- in feces for 6 months
Vaccine virus: are 3 correspondingly attenuated vaccine viruses that can be distinguished from wild v. by RNA sequencing or PCR
‘Live’ oral polio vaccine (OPV) virus can be shed in the feces for 6 weeks and may lead to infection in unvaccinated contacts.
Reservoir : --- humans, mostly as “inapparent infection”. --- no carriers Susceptibility: --- universal. --- 2nd attack is rare, usually by a different virus
N.B : I.M injections, trauma, surgery & excessive muscular activity , all can provoke paralysis. Tonsillectomy the risk of bulbar involvement. Paralytic events are more common in non immune adults than in non immunized infants & children
Diagnosis:Clinical suspicion – any case of AFPConfirmation 1- isolation of the wild v. from stool. rarely from CSF or oro pharyngeal secretion 2- differentiation of wild and vaccine v. in special labs.
Differential diagnosis: 1. Guillian Barre Syndrome: most common cause of AFP, symmetrical, sensory changes, CSF ….etc. 2. Transverse myelitis, 3. Spinal cord trauma4. Myasthenia Gravis , Polymyositis5. Infectious and toxic neuropathies6. Insect (tick) bites ………….etc.
Prevention & Control: 1- Notification 2- Active case finding, especially among children, ensures early detection of related cases and facilitates control. 3- Isolation. ? home or ? Hospital Enteric precautions should be initiated in hospital settings. These are often of little benefit in household settings as susceptible contacts are likely to have been exposed prior to diagnosis.
4- Hygiene and safe disposal of feces. 5- Immunization. --- both IPV and OPV give mucosal and humoral protection, however , IPV produces considerably lower levels of intestinal immunity than OPV. --- both vaccines give protection against all three types of poliovirus.
6- Surveillance of Acute Flaccid Paralysis (AFP) This is conducted to: --- identify all remaining infected areas, --- monitor progress towards eradication and --- target supplementary immunization properly. The WHO recommends: --- the immediate reporting and investigation of every case of AFP in children ˂ 15 yr. and --- collection of 2 stool samples for analysis in a WHO accredited laboratory.
Actions on suspecting a case:1- Immediate notification to health authority.2- Dispatch 2 stool samples 24 – 48 hrs apart immediately after detection of the case and should be delivered to the lab. with a well maintained reversed cold chain. 3- Filling of the AFP investigation form and submitting it to the PHC. Two separate fecal specimens at least 24 hrs apart and within 14 days of onset give the best chance of diagnosis.
4- Re examine the patient with AFP after 60 days of onset of paralysis.5- Classify the case as either confirmed or discarded after consultation with the CDC center.6- Conduct local immunization campaign after consultation with the EPI manager of the MOH. “outbreak control for cases confirmed or suspected to be poliomyelitis to stop transmission”
The WHO has estimated the risk of vaccine-associated paralysis to be: --- ~ 1 case per million vaccinees--- ~ 1 case per 5 million doses of vaccine for a close contact of a vaccinee . IPV is preferred for: --- exposed non immunized adults and --- when OPV is contraindicated e.g. immuno compromised patients or individuals whose contacts are immuno compromised ٌ
The Global Eradication Strategy: 1- High routine immunization coverage with OPV (its use is central to eradication worldwide)
OPV is still recommended in developing countries because of: --- the higher risk of exposure to wild poliovirus --- the low cost of the vaccine --- the ease of its administration and --- its excellent capacity to provide population-level immunity
2- Supplementary immunization in the form of “National immunization days” “Pulse Polio Immunization”- ( PPI ) i.e. mass campaigns in which all children ˂ 5 are vaccinated twice 4-6 weeks apart regardless of vaccine history.
3- Effective surveillance for AFP. The wild poliovirus serving as an indicator for poliomyelitis.4- Door to door immunization(mopping up” campaigns ). are usually the last stage in polio eradication It involves door to door immunization in high risk districts, where wild polio virus is known or suspected to be still circulating.
Useful ancillary control measures in polio endemic countries include: 5- Aggressive outbreak responses. 6- Cross border vaccination activities.
Breastfeeding does not generally interfere with successful immunization of infants, despite IgA antibody secretion in breast milk.