Serological signature of tick-borne pathogens in Scandinavian brown bears over two decades

Abstract

BackgroundAnthropogenic disturbances are changing the geographic distribution of ticks and tick-borne diseases. Over the last few decades, the tick Ixodes ricinus has expanded its range and abundance considerably in northern Europe. Concurrently, the incidence of tick-borne diseases, such as Lyme borreliosis and tick-borne encephalitis, has increased in the human populations of the Scandinavian countries.MethodsWildlife populations can serve as sentinels for changes in the distribution of tick-borne diseases. We used serum samples from a long-term study on the Scandinavian brown bear, Ursus arctos, and standard immunological methods to test whether exposure to Borrelia burgdorferi sensu lato, the causative agent of Lyme borreliosis, and tick-borne encephalitis virus (TBEV) had increased over time. Bears had been sampled over a period of 18 years (1995–2012) from a southern area, where Ixodes ricinus ticks are present, and a northern area where ticks are uncommon or absent.ResultsBears had high levels of IgG antibodies against B. burgdorferi sensu lato but not TBEV. Bears at the southern area had higher values of anti-Borrelia IgG antibodies than bears at the northern area. Over the duration of the study, the value of anti-Borrelia IgG antibodies increased in the southern area but not the northern area. Anti-Borrelia IgG antibodies increased with the age of the bear but declined in the oldest age classes.ConclusionsOur study is consistent with the view that ticks and tick-borne pathogens are expanding their abundance and prevalence in Scandinavia. Long-term serological monitoring of large mammals can provide insight into how anthropogenic disturbances are changing the distribution of ticks and tick-borne diseases.

Infection with Borrelia afzelii and manipulation of the egg surface microbiota have no effect on the fitness of immature Ixodes ricinus ticks

“…Some reviews have suggested that B. burgdorferi sl can adaptively manipulate its Ixodes tick vector to enhance its own transmission, and hence the R 0 of Lyme borreliosis 11 , 28 . Ixodes ticks infected with B. burgdorferi sl differ from their uninfected counterparts in several phenotypes including questing behaviour, survival, body weight, and energy reserves 29 – 35 . However, most of these studies are correlational in nature, and there is a lack of controlled infection experiments investigating the effects of B. burgdorferi sl on the fitness of their tick vectors.…”

Goats as sentinel hosts for the detection of tick-borne encephalitis risk areas in the Canton of Valais, Switzerland

“…One such method is the detection of TBEV-specific antibodies in sentinel vertebrate hosts. Various wild and domestic vertebrates such as rodents [ 13 , 34 , 35 ], roe deer [ 36 ], goats [ 37 , 38 ], sheep [ 39 ], dogs [ 40 , 41 ], and even brown bears [ 42 ] have been used as sentinels in endemic areas. A disadvantage of this method is that detection of antibodies does not provide any information on the time and place of infection.…”

Zoonoses and potential zoonoses of bears

“…Prevalence of B. burgdorferi DNA in 321 black bears from Humboldt County, California was 26%. A serosurvey of 569 brown bears showed high antibody prevalence in brown bears from southern Scandinavia, whereas prevalence was lower in bears from Northern Scandinavia (Paillard et al, ).…”

“…Additional antibodies to viral pathogens, like West Nile virus and related encephalitis viruses, have been detected in black bears in the United States and in brown bears in Europe, but bears are unlikely to play a significant role in those disease transmission cycles (Bronson et al, ; Farajollahi et al, ; Madić et al, ). Tick‐borne encephalitis virus was not detected in a serosurvey of brown bears from Scandinavia (Paillard et al, ).…”