Zoonotic and arthropod-borne diseases in the Nordic countries

In 2011, a nationwide outbreak of tularaemia occurred in Norway with 180 recorded cases. It was associated with the largest peak in lemming density seen in 40 years. Francisella tularensis was isolated from 18 patients. To study the geographical distribution of F. tularensis genotypes in Norway and correlate genotype with epidemiology and clinical presentation, we performed whole genome sequencing of patient isolates. All 18 genomes from the outbreak carried genetic signatures of F. tularensis subsp. holarctica and were assigned to genetic clades using canonical single nucleotide polymorphisms. Ten isolates were assigned to major genetic clade B.6 (subclade B.7), seven to clade B.12, and one to clade B.4. The B.6 subclade B.7 was most common in southern and central Norway, while clade B.12 was evenly distributed between the southern, central and northern parts of the country. There was no association between genotype and clinical presentation of tularaemia, time of year or specimen type. We found extensive sequence similarity with F. tularensis subsp. holarctica genomes from high-endemic tularaemia areas in Sweden. Finding nearly identical genomes across large geographical distances in Norway and Sweden imply a life cycle of the bacterium without replication between the outbreaks and raise new questions about long-range migration mechanisms.

From January to March 2011, 39 cases of tularaemia were diagnosed in three counties in central Norway: 21 cases of oropharyngeal type, 10 cases of glandular/ulceroglandular type, two of respiratory and two of typhoid type. Three cases were asymptomatic and clinical information was unavailable for one case. The mean age was 40.3 years (range 2-89 years). Thirty-four reported use of drinking water from private wells. An increased rodent (lemming) population and snow melting may have led to contamination of the wells with infected rodents or rodent excreta.

Five cases of trichinellosis with onset of symptoms in September 2009, were reported in France, and were probably linked to the consumption of meat from a grizzly bear in Cambridge Bay in Nunavut, Canada. Travellers should be aware of the risks of eating raw or rare meat products in arctic regions, particularly game meat such as bear or walrus meat.

Tularaemia cases are being detected increasingly in southern parts of Sweden. In 1999, in the county of Värmland in central Sweden (bordering Norway), the first outbreak of more than 20 cases was detected