#EcoTick: Land use, climate and tick-borne diseases in dynamic multi-host ecosystems: estimated risk and experienced fear

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2016

End date

12/31/2019

Budget

796,302 EUR

Fundings

Abstract

The overall aim for the project is to understand how changes in land use and climate have affected the increased incidences of tick-borne diseases in recent decades. Lyme borreliosis is the most known tick-borne disease in Norway. Ticks also spread the pathogens causing tick-borne fever in sheep and babesiosis in cattle. WP1. We have shown that the incidence of Lyme disease increases with denser populations of deer, but that the increase in the number of deer is not large enough alone to explain the increase that has been in incidence of Lyme disease in Norway (Nature Comm. 2016). This means that the management of deer can influence the incidence of Lyme disease to some degree if there is a will to do so, but that a reduction in the number of deer is not necessarily sufficient to mitigate and prevent increases in disease cases. We used a comparative approach to distinguish between general and more specific disease drivers (Scientific Reports 2017). All diseases have a common denominator in the tick vector, but the pathogens have different species of animals as reservoirs. We found an increased incidence of all tick-borne diseases since 1995 onwards, but for all the diseases it was a peak and then stabilization or decrease in disease incidence. We found that all the diseases had a certain correlation with climate and all showed positive co-variation with high populations of deer. There was limited correlation in space between the diseases. There was correlation of anaplasmosis and babesiosis in cattle, but not between anaplasmosis in sheep and cattle that would be expected if the presence of reservoir hosts and the pathogen was limiting for disease ("reservoir-host" hypothesis). That there was only correlation between the two cattle diseases indicates that the use of land and how livestock is exposed while grazing is limiting disease (the "exposure" hypothesis). We have published an analysis (PRSB 2019) on the link between bird populations, climate and incidence of Lyme borreliosis. There are 19 different genospecies of Borrelia with different chemical properties through adaptations to living in different host animals. Due to this, the genospecies also give different disease symptoms in humans. Birdborne-Borrelia is associated with acute symptoms and is the most common cause of infection in the nervous system, so-called neuroborreliosis. We investigated the relationship between the proportion of neuroborreliosis in patients with the proportion of bird-Borrelia in ticks in the ecosystem. By far, the most common variant in Norway is the small-mammalborne Borrelia, which accounts for 70-80% of infected ticks, while bird-Borrelia has been detected in around 20%. In comparison, there was 69% of neuroborreliosis among all severe cases of Lyme borreliosis, more than 3 times as high as expected from the proportion of bird-Borrelia in infected ticks. In WP2, we focus on understanding the natural dynamics of the tick-borne pathogens in the ecosystem. We have identified key host animals for both ticks and pathogens using a combination of standard field techniques and new molecular methods. In the period 2009-2015 we have collected ticks and mammals to be analyzed in order to understand the variation in infection. We have in 2016-18 similarly flagged for ticks and we have captured rodents and shrews in our two study areas. We have published a paper on how red deer habitat use affects local distribution of ticks (Parasites & Vectors 2016). In another paper (Parasites & Vectors 2018), we report very low prevalence of A. phagocytophilum in Akershus/Østfold compared to in Sogn & Fjordane. We have published two papers (Scientific Reports 2019, Oecologia 2019) on the ecology of Borrelia. One analyzes the prevalence of Borrelia between two areas in different mammal species at different times of the year, and over the years. In another paper we establish which of 16 different mammalian species are host animals for the different genotypes of Borrelia. We have published a paper (Parasites and Vectors 2019a) on the importance of moose, red deer and roe deer for the various ecotypes of A. phagocytophilum. It is suggested that red deer spreads ecotype I and roe deer spreads ecotype II. In a large material, we confirm these findings. In addition, we show for the first time that moose can spread both variants. This is of great management significance, since only ecotype I is thought to cause livestock fever in sheep. Our data was also used in a comparative study on genetics of phagocytophilum across Eurasia (Parasites and Vectors 2019b). In Norway, the utilization of outlying areas is an important element of economic activity associated with animal husbandry. In WP3 we seek knowledge of how fear of ticks affect recreation and grazing in outlying areas. We have conducted a questionnaire to members of the association for sheep and cattle farmers. A manuscript reporting results is submitted.