Characterization of a Natural Focus of Puumala Hantavirus Infection in the Czech Republic

Article excerpt

SUMMARY

Hantaviruses are RNA viruses of the Bunyaviridae family, represented in the Czech Republic by three genospecies: Dobrava-Belgrade, Puumala and Tula. They persist in natural foci of infection. In 2004 to 2009, a local outbreak with 18 reported cases of nephropathia epidemica caused by Puumala hantavirus occurred in the Sumava mountains and foothills and was spacially associated with another outbreak in Lower Bavaria, Germany. In the Jelení locality in the Sumava mountains at 880 m above sea level, we identified a natural focus of infection suspected to be the source of hantavirus infection in forest workers. The focus was characterized geobotanically as a montane mixed forest with the predominance of beeches within the association Dentario enneaphylli-Fagetum, alliance Fagion, sub-alliance Eu-Fagenion, in a cold climate region with a podzolic soil. The biocenoses where hantaviruses are circulating typically show higher microclimate humidity. Their characteristization can be helpful in predicting where hantaviruses are likely to circulate.

Key words: hantavirus, Puumala, biocenosis, Myodes giareolus

INTRODUCTION

Hantaviruses are RNAviruses of the Bunyaviridae family. The virion contains negative single stranded RNA divided into three segments. Hantaviruses have been described relatively recently, in 1978 (1). From the ecological point of view, these viruses are so called roboviruses, i.e. viruses transmitted by rodents. In the nature, they are circulating among their hosts, independently from humans, in natural foci of non- vector-borne infection. Currently several dozens of distinct hantavirus genospecies have been known. Each hantavirus species has a specific rodent or insectivore host in which it causes persistent infection. Humans are infected accidentally by contaminated excreta from these hosts while entering the natural focus of infection or as a result of another contact with the causative agent. In Central Europe the following four hantavirus genospecies are circulating in the nature: Dobrava-Belgrade (DOB), among yellow-necked field mice (Apodemus ßavicollis), Puumala (PUU), among bank voles (Myodes giareoius}., Tula (TUL), among common voles (Microtus arvalis), and Saaremaa (SAA) among black-striped field mice (Apodemus agrarius}. In the Czech Republic the first three genospecies were established. Humans can be infected by any of these viruses, but the DOB infection is the most severe, while TUL is considered as non-pathogenic, although it has also been reported to cause infection in humans (2). A serosurvey in a sample of adults from the Czech Republic revealed the presence of anti-hantavirus antibodies in 1 .66 % of the screened subjects (3).

hi 2004, the first cases were reported in occupationally exposed forest workers in the Prachatice region. A small local outbreak was observed with 1 8 cases that differed in the severity of symptoms and five positives were detected by the screening (4). This outbreak was geographically associated with a similar one in Lower Bavaria, Germany.

We attempted to identify the natural focus where some patients might have acquired infection. Our decision was based on assumption that the PUU virus natural host is the bank vole that lives in woodland areas with deciduous trees. We decided to capture rodents in the suspected localities to analyze them in the laboratory. The locality where the PUUV antigen was detected in the lungs of bank voles was geobotanically characterized in detail.

MATERIAL AND METHODS

After identifying the localities suspected to be the source of infection, we captured the rodents. The suspected area was situated at the fringe of a Sumava commune called Jeleni, an administrative part of the village Nova Pec in the district Prachatice: GPS coordinates 48°49'34"N 13°52'16"E. The altitude was about 900 m above sea level.

The animals were captured by snap-trapping or live-trapping. They were euthanized when needed and dissected. …