Hans Olav Hygen

Prevalence of tick borne encephalitis virus in tick nymphs in relation to climatic factors on the southern coast of Norway

BackgroundTick-borne encephalitis (TBE) is among the most important vector borne diseases of humans in Europe and is currently identified as a major health problem in many countries. TBE endemic zones have expanded over the past two decades, as well as the number of reported cases within endemic areas. Multiple factors are ascribed for the increased incidence of TBE, including climatic change. The number of TBE cases has also increased in Norway over the past decade, and the human cases cluster along the southern coast of Norway. In Norway the distribution and prevalence of TBE virus (TBEV) in tick populations is largely unknown. The objectives of this study were to estimate the TBEV prevalence in Ixodes ricinus from seven locations and to assess the relationship between the TBEV prevalence and site-specific climatic variables.MethodsA total of 5630 questing nymphs were collected and analyzed in pools of ten. All pools were screened with an in-house real-time RT-PCR, and the positive pools were pyrosequenced. Two methods, minimum infection rate (MIR) and a frequentist method (EPP) for pooled prevalence estimations were calculated and compared. Climatic data were descriptively compared to the corresponding EPP of each location in order to explain variations in TBEV prevalence.ResultsThe seven foci of TBEV had an estimated overall prevalence (EPP) in pools of nymphs combined, of 0.53% with 95% CI (0.35–0.75), with point prevalence ranging between 0.11%–1.22%. The sites with the highest point prevalences were within the municipalities which had the highest numbers of registered TBE cases. The results indicate that the location with highest point prevalence had the highest relative mean humidity and lowest mean saturation deficit and vice versa for the lowest EPP.ConclusionOur study confirms the existence of TBEV endemic foci in Norway. These results are of importance to increase the awareness of TBEV infections in Norway and could be used for public information and recommendations of TBE vaccination. EPP is the method of choice for pooled prevalence calculations, since it provides estimated prevalences with confidence intervals. Our findings emphasise the possible importance of microclimatic conditions regarding the TBEV prevalence in ticks.

An approach to impact assessments of buildings in a changing climate

Future climate change caused by global warming could have dramatic consequences for the built environment. An approach is presented to understand and assess these impacts on the Norwegian building stock in a changing climate. The approach is tested using calculations for the decay potential in timber structures (possessing wood cladding, timber frames or both). First, building data and climate data are compiled in a Geographic Information System (GIS). Second, the computer model calculates the number of buildings that could be affected by a particular climate parameter for historical climate data (1961–1990) and a future climate scenario (2071–2100). The results show that today approximately 615 000 buildings are situated in areas with a high potential risk of rot-decay. In 2100 this number could increase to roughly 2.4 million. The large current amount of wooden buildings and a high number of building defects indicates that future new and refurbished buildings need to be built more robustly to meet the future impacts of climate change. Other climate parameters, e.g. sea level rise, changes in permafrost, the risk of frost decay, temperature change and changes in the amount of wet winter precipitation – are under investigation for their effect on the Norwegian building stock. Les changements climatiques futurs causés par le réchauffement planétaire pourraient avoir des conséquences dramatiques sur l’environnement bâti. Il est présenté une approche visant à comprendre et évaluer ces impacts sur le parc bâti norvégien sous un climat en évolution. Cette approche est testée en utilisant des calculs relatifs aux possibilités de pourrissement des structures en bois de construction (possédant des bardages en bois, des ossatures bois, voire les deux). Dans un premier temps, les données relatives aux bâtiments et les données relatives aux climats sont compilées dans un Système d’Information Géographique (SIG). Dans un second temps, le modèle informatique calcule le nombre de bâtiments qui pourraient être affectés par un paramètre climatique particulier dans le cadre des données climatiques historiques (1961–1990) et d’un scénario climatique futur (2071–2100). Les résultats montrent qu’aujourd’hui environ 615 000 bâtiments se situent dans des régions présentant un risque potentiel élevé de pourrissement. En 2100, ce nombre pourrait s’accroître jusqu’à atteindre environ 2,4 millions. La grande quantité actuelle de bâtiments en bois et un nombre élevé de défauts de construction indiquent qu’il faudrait que les futurs bâtiments neufs et rénovés soient construits de manière plus solide afin de répondre aux impacts futurs du changement climatique. D’autres paramètres climatiques – tels que par exemple l’élévation du niveau de la mer, les modifications du permafrost, le risque de pourrissement par le gel, les changements de température et les changements dans la quantité de précipitations des hivers humides – sont étudiés sous l’angle de leur effet sur le parc bâti norvégien. Mots clés: mesures d’adaptation, parc bâti, changement climatique, études d’impact, bâtiments solides, risque de pourrissement, bâtiments en bois, Norvège

HAIR-LOSS EPIZOOTIC IN MOOSE (ALCES ALCES) ASSOCIATED WITH MASSIVE DEER KED (LIPOPTENA CERVI) INFESTATION

Deer keds (Lipoptena cervi) are blood-sucking flies in the family Hippoboscidae; moose (Alces alces) are their main host in Scandinavia. There are no detailed reports of the negative impacts of deer keds on moose. In 2006 and 2007, hunters in southeastern Norway and midwestern Sweden found several moose cadavers with severe alopecia; numerous moose had extensive hair loss. Between February 2006 and June 2007, materials from 23 moose were submitted for laboratory examination and large numbers of deer keds were found in the coat of most animals. The body condition of the moose varied but was poor in animals with severe alopecia. The findings of enormous numbers of deer keds in the coat of the majority of the affected animals and a consistent histologic image (acute to chronic, multifocal to coalescing, eosinophilic to lymphocytic dermatitis), concurrent with the absence of any other lesions, trace element deficiencies, or dermal infections which are known to cause alopecia, suggest that the hair-loss epizootic was linked to massive infestations with deer keds. The emergence of this hair-loss syndrome implies that the dynamics between parasite and host have been disrupted by a currently unknown environmental or ecological factor. A high moose density, combined with extraordinarily mild weather June 2006–June 2007 and a particularly long period with the absence of night-frost in autumn of 2006, may have been ideal for deer ked development, survival, and optimal host acquisition.