Large outbreak of tularaemia, central Sweden, July to September 2019.

On 31 of July 2019, the Public Health Agency of Sweden was alerted about an increasing number of tularaemia cases in Gävleborg, a county in central Sweden. The number of cases increased thereafter peaking at about 150 reports of illnesses every week. As at 6 October, a total of 979 cases (734 laboratory-confirmed) have been reported, mainly from counties in central Sweden. The outbreak is now considered over (as at 14 October).

Different Hatching Rates of Floodwater Mosquitoes Aedes sticticus, Aedes rossicus and Aedes cinereus from Different Flooded Environments.

In the lower Dalälven region, floodwater mosquitoes cause recurring problems. The main nuisance species is Aedes (Ochlerotatus) sticticus, but large numbers of Aedes (Aedes) rossicus and Aedes (Aedes) cinereus also hatch during flooding events. To increase understanding of which environments in the area give rise to mosquito nuisance, soil samples were taken from 20 locations from four environmental categories: grazed meadows, mowed meadows, unkept open grassland areas and forest areas. In each location 20 soil samples were taken, 10 from random locations and 10 from moisture retaining structures, such as tussocks, shrubs, piles of leaves, logs, and roots. The soil samples were soaked with tap water in the lab, and mosquito larvae were collected and allowed to develop to adult mosquitoes for species identification. Fewer larvae hatched from mowed areas and more larvae hatched from moisture retaining structure samples than random samples. The results showed that Aedes cinereus mostly hatch from grazed and unkept areas and hatched as much from random samples as from structures, whereas Aedes sticticus and Aedes rossicus hatched from open unkept and forest areas and hatch significantly more from structure samples. When the moisture retaining structures in open unkept areas where Aedes sticticus hatched were identified it was clear that they hatched predominantly from willow shrubs that offered shade. The results suggest that Ae. sticticus and Ae. cinereus favor different flooded environments for oviposition.

The Human Biting Culex pipiens Bioform molestus Detected in Several Areas in Southern Sweden.

Background: The mosquito species Culex pipiens is a known vector of several pathogens and occurs in two distinct bioforms, pipiens and molestus. The bioform molestus thrives in urban environments where there are below-ground habitats; it can mate in confined spaces and feed on mammals as well as birds. In contrast, the bioform pipiens is found above ground, is thought to require more space for mating, and mainly feeds on birds. The pipiens bioform is present in large parts of Sweden but the molestus bioform has previously only been found in major cities. Materials and Methods: People experiencing mosquito nuisance in southern Sweden submitted mosquito samples as part of a citizen science project, and these samples were analyzed to determine the geographical distribution of the molestus bioform of Cx. pipiens. Mosquito specimens were identified to the species level by DNA barcoding of the cytochrome C oxidase subunit I (COI) gene, and the bioforms were determined through the CQ11 microsatellite marker. Results:Culex pipiens f molestus was observed to be spread across large parts of Gothenburg as well as in the suburbs. This bioform was found both in urban and rural areas at several sites across southern Sweden. In one site, hybrids between the two bioforms were found. Conclusions: The detection of Cx. pipiens f molestus in several rural areas was surprising, indicating that it may be more widely spread than urban areas alone, where it has been previously reported.