Solveig Jore’s doctoral research shows that the tick Ixodes ricinus has spread over larger geographical areas in Norway and that climate and environmental changes, access to host animals and demography affect tick distribution in Norway. Furthermore, local climatic conditions can have a decisive influence on the ability of the tick to spread dangerous viruses. The climate can also play a role in the spread of gastrointestinal infections.

The effects of climate changes are the easiest to detect and are probably most pronounced near the geographical distribution limits of the infection or for the vector which carries the infection. Norway represents the northern distribution limit in Europe for the tick Ixodes ricinus and is therefore well suited as a location for investigating how climate changes affect the distribution of this tick.

The tick is spreading both further north and into higher altitudes
By correlating different sources of data on tick distribution, we find that occurrences of the commonest species of tick in Norway (I. ricinus) have been reported considerably further north and higher up in mountainous regions than was formerly the case.

The distribution pattern of I. ricinus has changed substantially over the last 50 years and we can now expect to find this tick as far north as Harstad, which is 400 km further north than previous records. The tick has also been detected at altitudes as high as 700-800 metres above sea level. This means that there is an increased risk of humans and animals becoming infected and falling ill in new areas of the country.

The occurrence of the viral disease tick-borne encephalitis (TBE) has been documented in several parts of Norway for the first time. Research shows that the occurrence of the TBEV virus responsible for TBE in infected areas is at an equivalent level to that shown in other European studies.

Photo: Norwegian Institute of Public HealthJore examined the relationship between the distribution of the virus in the tick and microclimatic conditions at seven different collection points along the southern coast of Norway. Her findings suggest that the degree of humidity in the air can have a decisive effect on how this virus can survive/reproduce in the tick and then be transmitted to humans via tick bites.

Climate, overgrowth, availability of host animals and demographics affect the prevalence of ticks
Jore discovered a strong connection between a higher prevalence of ticks and changes in certain climatic factors, overgrown vegetation, an increase in the number of deer and the number of farms with ruminants.

The analyses carried out in this study underline the importance of taking into account seasonal fluctuations in climatic variables and not just average changes. Since the current changes in the climate are expected to increase the fluctuations in certain variables (i.e. changes in extreme values), Jore’s doctoral research emphasises how important it is to focus on this aspect when evaluating the effects of climate changes and when modelling for the distribution of the disease.

One cause of gastrointestinal disease is probably linked to environmental and climate changes
Campylobacteriosis is the most common bacterial cause of gastrointestinal disease in humans in Norway and Europe, and chicken is believed to be a main source of infection in humans.

The occurrence of this disease in humans and chickens was studied in six European countries and in all the countries, there were clear seasonal and correlated variations in both types of the disease, with the highest incidence occurring in the summer. These variations may be due to the changes in temperature themselves, or to factors influenced by temperature changes in the summer season.

Solveig Jore’s PhD research was carried out at the Norwegian National Veterinary Institute. Key collaborative partners were researchers at the National Food Institute and the State Serum Institute in Denmark, the Finnish Food Safety Authority and the National Public Health Institute in Finland, the National Veterinary Institute and the Swedish Institute for Infectious Disease Control in Sweden, the Central Veterinary Institute and the National Institute for Public Health in the Netherlands, the Norwegian Institute of Public Health, the Norwegian National Veterinary Institute, the Norwegian School of Veterinary Science and the Norwegian Meteorological Institute in Oslo, the Georges Lemaite Centre for Earth and Climate Research in Belgium, the Northern Research Institute (NORUT) in Tromsø, the Centre for Ecological and Evolutionary Synthesis at the University of Oslo and the University of Liverpool.

Solveig Jore (Photo: Mari Press)BVSc Solveig Jore defended her doctoral research at the Norwegian School of Veterinary Science on 4th April 2013 with a thesis entitled: «The impact of climatic factors upon Zoonotic diseases – an epidemiological investigation»

Biography:
Solveig Jore lives in Asker but grew up in the municipality of Evje and Hornnes in the county of Aust-Agder in Southern Norway.  She qualified as a veterinary surgeon from the University of Bristol in 1994 and has worked at the Norwegian National Veterinary Institute since 2006, following several years’ experience in animal health and welfare, food safety, preparedness and clinical practice.

Contact information:
Solveig Jore
Tel.: +47 404 77 272
Email: solveig.jore@vetinst.no

Magnhild Jenssen, Information Officer at NVH
Tel.: +47 77 66 54 01
Mobile: +47 957 94 830
Email: magnhild.jenssen@nvh.no