Mathematical modelling of the impact of climatic conditions in France on Rhipicephalus sanguineus tick activity and density since 1960

Abstract

Abstract. Rhipicephalus sanguineus, the brown dog tick, has a worldwide distribution in areas with a relatively warm climate, including mild winters. This tick plays an important role as vector for various animal and human pathogens, including bacteria and protozoa. Based on precise daily meteorological data from the past 40 years, combined with mathematical modelling designed to predict tick activity, two modelling approaches were developed. The first examined the evolution of the number of weeks with favourable biological conditions for ticks in four French cities located at various latitudes of the country: Nîmes in the south, Paris in the north, Lyon in the east and Nantes in the west. The second analysed the extension of the geographical surface area in km 2 where the biological conditions favour tick activity for at least 12 weeks per year. Both analyses revealed clear evidence of increased temperatures coupled with an augmented tick activity index in three of the four cities. However, the change was not significant in Nîmes, where the climate is Mediterranean and the tick is already endemic. For Paris, Lyon and Nantes, the activity index values have increased significantly, i.e. by 4.4%, 4.0% and 3.4%, respectively. The distribution of the activity index values is evolving strongly with significantly fewer values below 50% since the 1960s and a clear decrease of values between 20% and 50% during the latest decade. Between 1960 and 2000, the theoretical extension of the surface area where the climatic index is suitable for R. sanguineus has increased by 66%. Even though several other important factors, such as changes in biotopes or human activity, are not included in this study, the resulting patterns and trends are noticeable. Our models constitute the first demonstration of the impact of climate change on the activity and distribution of ticks and confirm the observed northward migration trend for this Mediterranean domestic tick.

Trends in Clinical Diagnoses of Rocky Mountain Spotted Fever among American Indians, 2001–2008

“…sanguineus , thus leading to more human attacks. 37,38 These findings have raised the concern that changing climates could result in more emerging pathogens transmitted by the Rh. sanguineus in the future.…”

The diversity and prevalence of hard ticks attacking human hosts in Eastern Siberia (Russian Federation) with first description of invasion of non-endemic tick species

“…Several reports are beginning to confirm this for such tick species as I. ricinus, Boophylus annulatus, Dermacentor marginatus, Hyalomma marginatum, Hyalomma excavatum, Rhipicephalus bursa and R. turanicus (reviewed in EstradaPeña 2008). Mathematical analysis of climate conditions and R. sanguineus distribution in Europe over the last 40 years also indicated that since the 1960s the European ecosystems have evolved towards more suitable biological conditions for maintaining or increasing R. sanguineus populations (Beugnet et al 2011). Thus, the detection of R. sanguineus and A. americanum attacks on human host in Eastern Siberia may be the first sign of changes at climate conditions that results in increased survival rates of non-endemic ticks.…”

Epidemiology of Ehrlichiosis and Anaplasmosis among American Indians in the United States, 2000–2007

“…1,29,30,45 Some of the rate increase, particularly over the long term, is also possibly caused by changing ecology or climate, which results in varied vector and reservoir ranges and outdoor activities gaining popularity and residential growth expanding into rural geographic areas, thus increasing the interaction between humans and ticks. [46][47][48] Possible explanations for the higher incidence of ehrlichiosis and anaplasmosis among AIs in particular might be social or anthropogenic factors such as living in more rural areas and engaging in recreational, social, or community activities that more frequently expose them to ticks, thus putting them at higher risk of infection with tick-borne rickettsial diseases. 26 The epidemiology of ehrlichiosis and anaplasmosis infection among AIs also differs compared with other race groups.…”