Infection of Ixodes ricinus by Borrelia burgdorferi sensu lato in peri-urban forests of France

Abstract

Lyme borreliosis is the most common tick-borne disease in the northern hemisphere. In Europe, it is transmitted by Ixodes ticks that carry bacteria belonging to the Borrelia burgdorferi sensu lato complex. The objective of this work was to explore eco-epidemiological factors of Lyme borreliosis in peri-urban forests of France (Sénart, Notre-Dame and Rambouillet). We investigated whether the introduction of Tamias sibiricus in Sénart could alter the density of infected ticks. Moreover, the density and tick infection were investigated according to the tree species found in various patches of Sénart forest. For this purpose, ticks were sampled during 3 years. In the Sénart forest, the density of nymph and adult ticks showed no significant difference between 2008, 2009 and 2011. The nymph density varied significantly as a function of the month of collection. Regarding the nymphs, a higher rate of infection and infected density were found in 2009. Plots with chipmunks (C) presented a lower density of both nymphs and adult ticks than plots without chipmunks (NC) did. A higher rate of infection of nymphs with Borrelia was seen in C plots. The prevalence of the various species of Borrelia was also found to vary between C and NC plots with the year of the collect. The presence of chestnut trees positively influenced the density of both nymphs and adults. The infected nymph density showed a significant difference depending on the peri-urban forest studied, Sénart being higher than Rambouillet. The prevalence of Borrelia species also differed between the various forests studied. Concerning the putative role that Tamias sibiricus may play in the transmission of Borrelia, our results suggest that its presence is correlated with a higher rate of infection of questing ticks by Borrelia genospecies and if its population increases, it could play a significant role in the risk of transmission of Lyme borreliosis.

The scale affects our view on the identification and distribution of microbial communities in ticks

“…Contrasting results were observed [12] in three geographically distinct areas of eastern Romania where the estimated prevalence of eight Borrelia species was very similar between adults and nymphs. Similar results have been already confirmed for I. ricinus [61] over a three-year survey in a peri-urban forest in the south of Paris, France. Strnad et al [49] reported that the overall prevalence of B. burgdorferi (s.l.)…”

Tick-borne pathogen detection in midgut and salivary glands of adult Ixodes ricinus

“…Several Borrelia burgdorferi ( s.l. ) genospecies ( B. lusitaniae , B. spielmanii and B. garinii ) were detected in ticks which was not surprising as they have already been identified in many European countries and particularly in the Senart Forest [7]. Interestingly, these species were only detected in questing females.…”

A three-years assessment of Ixodes ricinus-borne pathogens in a French peri-urban forest

“…In addition to these general patterns, some unexpected data were observed, the most striking being no peak activity in spring 2017 (April and May) with tick densities very similar to those recorded in March. Abiotic factors such as temperature, relative humidity and rainfall, or fluctuating host numbers in the sampling area are known to influence questing tick abundance and activity patterns [29–34] and could explain these unusual observations. It is important to note that 2017 was distinguished by an abnormally wet March, with total rainfall much higher than that recorded in previous years in the same area (71.3, compared to 11.2, 33.6 and 61.7 mm rain/month in 2014, 2015 and 2016, respectively).…”

“…Continued detection is consistent with the year-round presence of reservoir hosts in the sampling area (wood mice, bank voles, Siberian chipmunks, roe deer, common blackbird, European robin, song thrush, etc.) [34, 44, 45]. The continued presence of reservoir hosts could facilitate the circulation of dominant species, and maintain, even at low rates, less prevalent pathogen species that may not be detected by a single sampling.…”