Quantifying the Northward Spread of Ticks (Ixodida) as Climate Warms in Northern Russia

Abstract

Climate change is affecting human health worldwide. In particular, changes to local and global climate parameters influence vector and water-borne diseases like malaria, dengue fever, and tick-borne encephalitis. The Republic of Sakha in northern Russia is no exception. Long-term trends of increasing annual temperatures and thawing permafrost have corresponded with the northward range expansion of tick-species in the Republic. Indigenous communities living in these remote areas may be severely affected by human and livestock diseases introduced by disease vectors like ticks. To better understand the risk of vector-borne diseases in Sakha, we aimed to describe the increase and spatial spread of tick-bite cases in the Republic. Between 2000 and 2018, the frequency of tick bite cases increased 40-fold. At the start of the period, only isolated cases were reported in southern districts, but by 2018, tick bites had been reported in 21 districts in the Republic. This trend coincides with a noticeable increase in the average annual temperature in the region since the 2000s by an average of 1 °C. Maps illustrate the northward spread of tick-bite cases. A negative binomial regression model was used to correlate the increase in cases with a number of climate parameters. Tick bite case frequency per district was significantly explained by average annual temperature, average temperature in the coldest month of the year, the observation year, as well as Selyaninov’s hydrothermal coefficient. These findings contribute to the growing literature that describe the relationship between tick abundance and spread in Northern Latitudes and changes in temperatures and moisture. Future studies might use these and similar results to map and identify areas at risk of infestation by ticks, as climates continue to change in Sakha.

The impact of climatic factors on tick-related hospital visits and borreliosis incidence rates in European Russia

“…Recent studies report increases in Ixodes tick activity and tick-borne diseases in the northern areas previously not inhabited by ticks. These trends have been reported for Sweden [ 13 ], Norway [ 14 , 15 ], Iceland [ 16 ], USA [ 17 ], Canada [ 18 ] and Russia [ 19 – 21 ]. In Sweden, climate change and the associated rise in temperature and the increased population of deer are most likely driving the recorded range expansion of tick-borne diseases [ 13 ].…”

“…A similar growing trend was also observed in the Komi Republic, for both the mean annual air temperature and encephalitis incidence rates for a period of forty two years [ 20 ]. A recent study focusing on the Sakha Republic in Eastern Siberia reported a significant correlation between the tick bite rates with the mean annual air temperature, average temperature in the coldest month of the year and hydrothermal coefficient [ 21 ]. However, other studies criticize the approach solely based on the climatic variables and emphasize the importance of other factors driving ecosystem changes such as urbanization, change in land use and forest fires [ 1 ].…”

Linking climate and infectious disease trends in the Northern/Arctic Region

“…At whole-region scale, the incidences of TBE are negatively correlated with all (hydro-)climate variables, while those of borreliosis are positively correlated with all climate variables. This is despite the fact that these diseases share the same vector, Ixodidae ticks, for which increased annual temperature is reported to increase incidences of tick bites 21 and the geographic range of ticks, due to the expanded geographic range of associated vegetation communities and mammals caused by a prolonged vegetation period 22 . Some researchers have also argued that the reporting of tick bites has increased due to increased public awareness 23 and more time spent outdoors 24 , along with the changes in climate, tick bites, and tick range.…”

Assessing the Influence of Climate Change and Environmental Factors on the Top Tick-Borne Diseases in the United States: A Systematic Review

“…Secondly, by focusing entirely on the US, we eliminated evidence collected from other countries and regions with a high prevalence of TBDs, for instance, many parts of Europe and Russia [ 106 , 107 ]. The relationship between TBDs and climate or land use changes has been widely studied in these areas, while we did not find a similar quantity of evidence published for the US.…”