[Genotyping results, laboratory diagnosis, and epidemiology of the mumps virus circulating in the Czech Republic in 2012]

Abstract

Goal: To extend the present routine serological diagnosis of mumps with the methods of direct detection of the pathogen and subsequent genotyping of the isolated viruses in an attempt to obtain more detailed data on recent mumps viruses circulating in the Czech Republic. Sub-goals were to point out the particularities of the laboratory examination in the population with a high vaccine coverage and to evaluate the current epidemiological situation.

Material and methods: Altogether 47 buccal swabs from patients with suspected mumps were included in the study. Clinical specimens collected at the onset of clinical symptoms were obtained from five administrative regions of the Czech Republic from February 2012 to December 2012. Vero cell cultures were used for virus isolation and isolates were identified using real-time quantitative polymerase chain reaction (RT-qPCR). Genotyping was performed by the WHO Regional Reference Laboratory for Measles, Mumps, and Rubella (RRL MMR), Robert Koch Institute, Berlin. The EPIDAT system was used as a source of epidemiological data.

Results: From 47 buccal swabs, 20 mumps viruses were isolated on Vero cells and in seven other specimens, the presence of viral RNA without positive isolation was only detected by RT-qPCR. Nineteen isolates were referred for genotyping. The phylogenetic analysis of the SH gene classified them into genotype G, as four variants. In both 2011 and 2012, most cases occurred in vaccinated patients (80%), with 15-19-year-olds being the most affected age group. The leading complication was orchitis, followed by meningitis. More complications were reported in non-vaccinated individuals.

Conclusions: The increased incidence of mumps cases in the Czech Republic in 2012 was due primarily to genotype G, the leading cause of mumps in most European countries since 2005. The presence of genotype G was first reported in the Czech Republic in 2006. In the context of the unfavourable epidemiological trend, molecular epidemiological studies including genotyping of recent mumps virus strains appear to be necessary. A detailed monitoring could be helpful in elucidating the pattern of virus circulation and in designing strategies to control emerging outbreaks. The vaccination efficacy in relation to the causative genotype and possible role of waning immunity in mumps outbreaks are the issues that need to be addressed.