Ecology of Borrelia burgdorferi sensu lato and epidemiology of borrelial infections in Cumbria

Hall, JL

Abstract

Borrelia burgdorferi sensu lato (s.l.) is the causative agent of the tick-borne zoonotic disease Lyme borreliosis (LB), of which around 2-3000 cases are reported annually in the UK. This project took a “One Health” approach to studying Borrelia burgdorferi s.l. in southern Cumbria exploring its medical and veterinary importance and quantifying the environmental hazard it presents in the region.
Under a “One Health” umbrella, this project comprised of three discrete studies: (1) a longitudinal study of tick population dynamics, and B. burgdorferi s.l. transmission dynamics in these ticks, was carried out between June 2013 and September 2017 in three separate but closely located woodlands, (2) the role of grey squirrels (Sciurus carolinensis) in the natural maintenance of B. burgdorferi s.l. was assessed, and (3) a veterinarian-based survey of ticks infesting companion animals was completed.
The most noteworthy findings in these studies were: (1) the phenologies of the three questing tick populations studied were similar, but there was consistent and significant variation in tick abundance between the three populations. Overall tick abundance rose during the study. B. burgdorferi s.l. circulated in all three tick populations, but at significantly different prevalences. The annual density of infected ticks varied significantly at all three sites but this variation was asynchronous. Four Borrelia genospecies were encountered in the study, but the relative contribution of each to the borrelial community varied markedly between populations and but stayed constant through time. (2) Grey squirrels were susceptible to B. burgdorferi s.l. (prevalence 19.74%) and infection with all four Borrelia genospecies was encountered. The prevalence of infections in ticks feeding on squirrels was almost 11.57% significantly higher than that in local questing tick populations (3.69%). (3) Three Ixodes species parasitized companion animals, with I. ricinus being the most common. Parasitism peaked in July. Infection rate in companion animal-associated I. ricinus ticks was 1.29%, was significantly lower than that observed in questing ticks.
This thesis provides an insight into tick phenology and what species of ticks bite companion animals in the area. Although the peak in tick bites on companion animals did not coincide with the peak in questing ticks from the longitudinal study this can be explained by behaviour and species of ticks. Regarding B. burgdorferi s.l. infections in questing ticks tend to fluctuate throughout the year with cases of temporary absence at some sites. Infection prevalence in ticks from companion animals was lower than that found in questing ticks and grey squirrels had a high prevalence of infection particularly B. afzelii and B. garinii. Both of which dominated sites during the longitudinal study. This holistic approach to disease ecology shows that B. burgdorferi should not only be discussed in regard to human disease but to explore the wider concept to gain a better insight into the spirochetes place in the world.

Citation

Hall, J. (in press). Ecology of Borrelia burgdorferi sensu lato and epidemiology of borrelial infections in Cumbria. (Thesis). University of Salford

• Thesis Type: Thesis
• Acceptance Date: Oct 30, 2018
• Deposit Date: Nov 28, 2018
• Publicly Available Date: Nov 28, 2018
• Additional Information: Funders : Graduate Teaching Studentship;Merial