Search

Fundamento: Recientemente se han registrado brotes de parotiditis en España y en otros países desarrollados. Los motivos barajados son la baja cobertura vacunal de las poblaciones afectadas y/o la baja efectividad de las cepas vacunales empleadas. Este trabajo describe un brote de parotiditis ocurrido en Bizkaia y valora la efectividad de las cepas vacunales y la utilidad de las pruebas diagnósticas actualmente empleadas. Métodos: Se etiquetaron como casos aquéllos con clínica compatible y vínculo epidemiológico en el periodo de estudio (febrero-mayo-2006). Se recogieron muestras de sangre para estudio de IgM e IgG y de saliva para detección de RNA y genotipo. Se averiguó el estado vacunal y la cepa empleada mediante los registros del reparto vacunal. Se realizó un análisis univariante de los datos y se obtuvieron riesgos relativos según las cepas vacunales empleadas. Resultados: Se detectaron 63 casos; 52 eran alumnos del mismo colegio. El 50% tenía entre 9 y 13 años. El 88,5% de los casos del colegio estaba correctamente vacunado. La sensibilidad de la IgM fue del 9% y la de la PCR del 37%. El riesgo relativo de los alumnos vacunados con una primera dosis de cepa Rubini frente a los vacunados con cepa Jeryl-Lynn fue de 3,8 (IC95% 2,27-6,49). Conclusiones: La elevada cobertura vacunal no impide el desarrollo de brotes en lugares con un alto grado de exposición. La IgM se muestra poco sensible para el diagnóstico de parotiditis. Parece necesario replantearse las estrategias vacunales y los métodos diagnósticos actuales.

The Laboratory is a fundamental component on the surveillance of measles and rubella. Cases need to be properly confirmed to ensure an accurate estimation of the incidence. Strains should be genetically characterized to know the transmission pattern of these viruses and frequently, outbreaks and transmission chains can be totally discriminated only after that. Finally, the susceptibility of the population is estimated on the basis of sero-prevalence surveys. Detection of specific IgM response is the base of the laboratory diagnosis of these diseases. It should be completed with genomic detection by RT-PCR to reach an optimal efficiency, especially when sampling is performed early in the course of the disease. Genotyping is performed by genomic sequencing according to reference protocols of the WHO. Laboratory surveillance of measles and rubella in Spain is organized as a net of regional laboratories with different capabilities. The National Center of Microbiology as National Reference Laboratory (NRL), supports regional laboratories ensuring the availability of all required techniques in the whole country and watching for the quality of the results. The NRL is currently working in the implementation of new molecular techniques based on the analysis of genomic hypervariable regions for the strain characterization at sub-genotypic levels and use them in the surveillance.

Outbreaks of parotiditis have recently been recorded in Spain and in other developed countries. The possible reasons currently under consideration are the low degree of immunization coverage among the populations involved and/or the low degree of effectiveness of the vaccine strains employed. This study describes one outbreak of parotiditis having occurred in Bizkaia and assesses, the effectiveness of the vaccine strains and the usefulness of the diagnostic tests currently used.Those cases having compatible clinical symptoms and an epidemiological link within the period under study (February-May 2006) were labeled as cases. Blood samples were taken to study IgM and IgG and saliva for genotype and RNA detection. The immunization status and the strain used were found through the vaccine distribution records. A univariate analysis was conducted on the data and relative risks calculated according to the vaccine strains used.A total of 63 cases were detected, 52 being students from one school. Fifty percent were 9-13 years of age. A total of 88.5% of the cases detected at the school had been properly immunized. The IgM sensitivity was 9%, PCR sensitivity being 37%. The relative risk of those students immunized with an initial dose of Rubini strain as compared to those immunized with Jeryl-Lynn strain was 3.8 (95% CI:2.27-6.49).The high degree of immunization coverage does not prevent outbreaks from occurring in places having a high degree of exposure. The IgM reveals itself to be sensitive to a very small degree for the diagnosis of parotiditis. It seems necessary that the current immunization strategies and diagnostic methods be reconsidered.