Climate and environmental changes affect the occurrence of diseases transmitted between animals and humans

How are human and animal diseases in general affected by the climate becoming "wilder, wetter and warmer"? 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 changes are the easiest to detect and are probably most pronounced near the 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.

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 tick-borne (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. Jore 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 bites.

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.

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.

More information: 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"

add to favorites email to friend print save as pdf

Related Stories

Ticks challenge climate theory

Jun 08, 2007

As key players in the spread of disease ticks aren’t exactly man’s best friend but, according to Oxford University scientists, they may offer a vital clue that climate change is not to blame for an upsurge in many human ...

Migratory birds can spread haemorrhagic fever

Oct 23, 2012

A type of haemorrhagic fever that is prevalent in Africa, Asia, and the Balkans has begun to spread to new areas in southern Europe. Now Swedish researchers have shown that migratory birds carrying ticks are the possible ...

Ticks are on the march in Britain

Mar 23, 2011

The prevalence of ticks attaching to dogs in Great Britain has been mapped by scientists as part of a national tick survey. The findings reveal that the number of dogs infested with the blood-sucking parasites ...

Surprising study results: More cattle means less Lyme disease

Apr 16, 2012

(Phys.org) -- The abundance of cattle is the primary influence on the prevalence of two tick-borne pathogens, according to a paper in the April Applied and Environmental Microbiology. One of these, Anaplasma phagocytophilum, causes ...

Recommended for you

Florida university opens TB lab in Haiti

16 minutes ago

The University of Florida on Wednesday opened a state-of-the-art lab in Haiti to train researchers to better understand and fight tuberculosis.

Impact of whooping cough vaccination revealed

3 hours ago

The most comprehensive study to date of the family of bacteria that causes whooping cough points to more effective vaccine strategies and reveals surprising findings about the bacteria's origin and evolution. The new results ...

Saudi announces 11 new MERS infections

7 hours ago

Saudi Arabia on Wednesday announced 11 new cases of MERS, including a 13-year-old child, as its acting health minister vowed to keep the public better informed on the coronavirus.

User comments