RESUMO

La poliomielitis es una enfermedad viral, generalizada y aguda, que afecta al sistema nervioso central con severidad variable, y a veces se complica con parálisis. Si ocurre esto último, se trata de una parálisis fláccida, generalmente asimétrica, de diversos músculos estriados que a veces se acompaña de trastornos respiratorios y vasomotores. La poliomielitis solamente afecta al ser humano y al no haberse demostrado que en la naturaleza existen reservorios animales, se trata de una enfermedad que puede ser erradicada si se consigue inmunizar el número adecuado de sujetos como para interrumpir definitivamente la cadena de transmisión. Los subtítulos en que se divide el trabajo son: Historia, Agente, Patogenia, Diagnóstico, Inmunología, Epidemiología, Vacunas disponibles, Vacunas inactivadas, Vacuna atenuada, Reacciones diversas, Otros esquemas de inmunización, y Nuevas vacunas

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Highly sensitive case definitions were first introduced by national poliomyelitis eradication programmes to avoid missing true cases of the disease, though false-positive diagnostic errors could still occur owing to low specificity. Extensive data from all 1620 cases of acute, flaccid paralysis reported in Brazil during 1987-88 provided an opportunity to study the characteristics of confirmed poliomyelitis cases and epidemiologically to evaluate potential case definitions that maximized both sensitivity and specificity. Cases that had been confirmed by wild poliomyelitis virus isolation were compared with those that had been rejected (non-polio cases). To guarantee the consistency of clinical, epidemiological and laboratory investigations, only cases less than 10 years of age that had been investigated within 15 days of the onset and with complete laboratory specimens were included. No single practical case definition combining both high sensitivity and high specificity emerged from the study. However, the results showed that poliomyelitis endemic countries with limited resources should give priority to the investigation of cases in less than 5-year-olds, cases with prodromal fever, cases without involvement in all four limbs, cases without progression greater than 3 days after the onset, and cases occurring in areas where poliomyelitis had recently been confirmed. In countries without laboratory resources, cases of acute, flaccid paralysis with initial involvement in one or both lower limbs and residual neurological sequelae at 60 days should be confirmed. Countries that are close to eradication may selectively reject any cases lacking laboratory confirmation, despite adequate specimen collection, if they do not have initial involvement in one or both lower limbs and residual neurological sequelae at 60 days.

PIP: In Sao Paulo, Brazil, physicians followed 85 full term, healthy, breast fed infants born between March 1986-September 1988 monthly for 1 year to compare their immunologic response to immunization with trivalent oral poliovirus vaccine (TOPV). They either received doses 1 day after birth and at 2, 4, and 9 months (group A) or at 2, 4, and 6 months (group B). They analyzed blood samples from the mother at childbirth, from the umbilical cord, and from the infant at 2, 4, 6, 9, and 12 months to measure poliovirus neutralizing antibodies. All but 1 infant had passively transferred antibodies at birth. Group A had higher polio antibodies during the 1st few months, greater seropositivity, and a lower proportion of susceptible infants than group B. In fact, at the end of 12 months, only 3.7% of infants in group A were susceptible to all 3 poliovirus types compared to 25.9% in group B. Seroconversion rates were considerably higher in group A infants from the 3rd dose forward (96.3-100%) than for those in group B (74.1-100%). The response for polioviruses 1 and 2 were essentially the same in both groups at 12 months (96.3-100%). The immunological response to poliovirus type 3 in group A was superior to that of group B at the end of 1 year (96.3% vs. 74.1%), however. Yet group B infants received their 1st dose of the vaccine at 2 months with a higher level of poliovirus 3 type (500,000 TCID50/dose) than group A infants received at birth (300,000 TCID50/dose). Thus immunization of newborns with TOPV provided more protection against polio than a higher vaccine concentration administered to infants beginning at months. This finding is especially relevant since polio type 3 was responsible for the polio outbreak in 1986 in northern Brazil.

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Synthetic oligodeoxynucleotide probes, 21-23 nucleotides in length, were prepared which specifically hybridize to the genomes of the wild type 1 and 3 polioviruses currently endemic to the northeastern region of Brazil. The probes are complementary to sequences near the 5'-terminus of the VP1 gene that differ substantially among genetically distant polioviruses but are largely conserved among related isolates. The probes have been routinely used in the laboratory surveillance of poliomyelitis cases in Brazil, permitting direct, rapid identification of the indigenous wild polioviruses by dot-blot hybridization.

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Between April 1982 and June 1983 four children 3 to 24 months of age were referred for evaluation of neurologic abnormalities found to be compatible with vaccine-related poliovirus infection, which had not been suspected by referring physicians. Patients were epidemiologically unrelated residents of Indiana, and none had prior symptoms suggestive of immunodeficiency. All had received poliovirus vaccine orally (first dose in three, fourth dose in one) and a diphtheria-tetanus-pertussis injection in the left anterior thigh within 30 days of symptoms. A vaccine-like strain of poliovirus was isolated from each patient, and each had symptoms (left leg paralysis in three; developmental regression, spasticity, and progressive fatal cerebral atrophy in one) persisting for at least 6 months. Immune function was normal in two with poliovirus type 3 infection, and abnormal (hypogammaglobulinemia, combined immunodeficiency) in two with type 1 and type 2 infection, respectively. The incidence of observed vaccine-related poliovirus infection in Indiana recipients of orally administered poliovirus vaccine was 0.058 per 100,000 per year, significantly greater (P less than 0.001) than predicted.

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Paralytic poliomyelitis was observed in a child with a sex-linked defect in immunoglobulin synthesis. Evidence is presented that this was secondary to administration of oral, live poliovaccine. The demonstration of a familial sex-linked gammaglobulin deficiency and the failure to document a defect in cell-mediated immunity in this child extends the risk of vaccine associated poliomyelitis to virtually all forms of immunodeficiency. The critical host factors in the pathogenesis of poliovirus vaccine infection and in particular its unfavorable outcome appear to include either a deficiency in the humoral (B cell) system or in the cell-mediated (T cell) system.

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Epidemics of paralytic poliomyelitis has been reported with increasing frequency in the Caribbean area over the last decade. During the first weeks of a type 1 poliomyelitis epidemic in British Guiana in the winter of 1962-63, it was possible to study "wild" poliovirus infections in pre-school children, and to obtain information concerning the effectiveness of a country-wide control programme using trivalent oral poliovirus vaccine. Serological studies indicated that many Guianese children had had previous asymptomatic poliovirus infections by school age. However, there were more children with antibodies to types 2 and 3 than with antibodies to type 1. Following the first of two feedings of trivalent vaccine, there were significant increases in the percentage of children with poliovirus antibodies. Though begun only three weeks after the hospitalization of several paralysed children, a rectal-swab survey indicated that in some areas over one-third of the pre-school children were excreting "wild" poliovirus. In one area of the country, where only 2 percent of the children were excreting poliovirus type 1, vaccine feeding seemed most effective in containing the epidemic. These results support the suggestion that to be successful an epidemic control programme in a developing tropical country should be rapidly organized and completed (AU)

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