Host in reserve: The role of common shrews (<i>Sorex araneus</i>) as a supplementary source of tick hosts in small mammal communities influenced by rodent population cycles

Pelsmaeker, Nicolas De; Korslund, Lars; Steifetten, Øyvind

doi:10.1002/ece3.8776

Cited by 7 publications

(6 citation statements)

References 83 publications

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“…Nevertheless, our results suggest that even a very low rodent density is sufficient to support the circulation of B. afzelii . Alternatively, B. afzelii might have been supported by other reservoir species, such as shrews or squirrels [ 15 , 50 – 54 ], although the abundance of these species was not estimated reliably in this study. Irrespective of the mechanism supporting pathogen persistence, our results suggest that the removal of rodents even on small islands may not limit the transmission cycle of B. afzelii as: (i) we were not able to detect any effect on NIP t+1 and (ii) B. afzelii was detected on all islands with ticks in May 2020 and rodents 2019.…”

Section: Discussionmentioning

confidence: 86%

Effects of rodent abundance on ticks and Borrelia: results from an experimental and observational study in an island system

Kiran,

Brila,

Mappes

et al. 2024

Parasites Vectors

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Background Lyme borreliosis is the most common tick-borne disease in Europe and is often caused by Borrelia afzelii, which is transmitted by Ixodes ricinus ticks. The prevalence and abundance of infected ticks fluctuate in time and space, influencing human infection risk. Rodents are reservoir hosts for B. afzelii and important feeding hosts for larval ticks. In the study reported here, we examined how variation in rodent abundance is associated with B. afzelii infection prevalence in ticks, the density of nymphs (DON) and the density of infected nymphs (DIN) in the following year. We further analysed the relationships between the abundance of infected rodents and nymphal infection prevalence (NIP) and DIN. Methods We conducted a study that combined experimental and observational approaches on 15 islands (10 small islands and 5 large islands) in Finland. On all of the islands, ticks and rodents were monitored and sampled during the summer of 2019, with the monitoring of tick abundance and sampling continuing into the spring of 2020. On five of the 10 small islands, captured rodents were removed from the island (“removal” islands), and on the other five small islands, captured rodents were released back to the trapping site after marking and sampling (“control” islands). On the five large islands, captured rodents were released back to the trapping site after marking and sampling. The presence of B. afzelii from nymph and rodent samples was examined. Results The results of the experimental study showed that neither treatment (removal), rodent abundance index nor abundance index of infected rodents in 2019 was associated with DON, NIP or DIN in 2020. Based on data from the observational study, the NIP in 2020 decreased with increasing rodent abundance index and abundance index of infected rodents in 2019. However, the DIN in 2020 was not associated with the rodent abundance index or the abundance index of infected rodents in 2019. In addition, in the observational study, DON in 2020 increased with increasing rodent abundance index. Conclusions Our results suggest that low rodent abundance during the tick activity period is not sufficient for reducing the disease hazard and, hence, rodent removal may not be a feasible control measure in natural ecosystems. Graphical abstract

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Section: Discussionmentioning

confidence: 86%

Effects of rodent abundance on ticks and Borrelia: results from an experimental and observational study in an island system

Kiran,

Brila,

Mappes

et al. 2024

Parasites Vectors

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“…As such, the problem is that in some cases, there is no reference point against which to compare recent data [ 71 ]. However, insectivores may be important as vectors of pathogens [ 72 , 73 , 74 ], including Yersinia enterocolitica recently identified in S. araneus from Great Britain [ 75 ]. Therefore, our study is of value, as we provide long-term primary data on insectivores in the country for comparison purposes [ 27 ], although knowledge of the pathogen situation is still limited [ 76 ].…”

Section: Discussionmentioning

confidence: 99%

Shrews Under-Represented in Fruit Farms and Homesteads

Balčiauskas

Stirkė

Garbaras

et al. 2023

Animals

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Shrews are a less studied group of small mammals than rodents. Between 2018 and 2022, we surveyed 23 sites in Lithuania, including natural and anthropogenic habitats, with the aim to assess the proportion of Soricidae in small mammal communities and their diet based on stable isotope analysis. The average representation of Soricidae was 3.1%, about half the long-term average in other habitats in the country. The highest proportions were in meadows and farmsteads, at 4.9% and 5.0% respectively. Shrews were not trapped on farms or in young orchards, and their relative abundance was very low in intensively managed orchards (0.006 individuals per 100 trap days). Neomys fodiens and N. anomalus were unexpectedly found in homesteads, including in outbuildings. Sorex araneus and S. minutus had similar diets. The trophic carbon/nitrogen discrimination factor between invertebrates and shrew hair was 2.74‰/3.98‰ for S. araneus, 1.90‰/3.78‰ for S. minutus in the orchards. The diet of N. fodiens and N. anomalus at the homesteads requires further investigation. We propose that the under-abundance of shrews may be due to contamination by plant protection products and a lack of invertebrates under intensive agricultural practices.

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“…Most studies of tick-borne pathogens in small mammals only concern rodents. Common shrews are important hosts for feeding instar stages of ixodid ticks (Mysterud et al 2015 ; De Pelsmaeker et al 2022 ), and they can maintain significant reservoirs for tick-borne pathogens in some ecosystems (Bown et al 2011 ; Mysterud et al 2019b ; Sormunen et al 2023 ). Shrews differ in life history strategy compared to rodents by being shorter lived and exerting much higher metabolic rates (Gliwicz and Taylor 2002 ).…”

Section: Discussionmentioning

confidence: 99%

“…Previous studies at the northern distribution range of I. ricinus have focussed on identifying key host species for the epidemiological cycle of Lyme disease including small mammals with potential reservoir competence for B. burgdorferi s.l. (Mysterud et al 2019b ; Sormunen et al 2023 ) and relative tick aggregation across species (Mysterud et al 2015 , 2019b ; De Pelsmaeker et al 2022 ). However, ticks may also aggregate on specific individuals within host populations resulting in differential patterns of infestation (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…At the northern distribution range, there is a limited understanding of aggregation patterns of I. ricinus in host communities with multiple small mammal species. This includes less studied host species like the common shrew Sorex araneus (Bown et al 2011 ; De Pelsmaeker et al 2022 ; Sormunen et al 2023 ), and whether patterns of tick aggregation affect the transmission dynamics of B. burgdorferi s.l. Shrews have lower levels of sexual body-size dimorphism compared to rodents, and this could allow for testing of mechanisms causing sex-biased parasitism.…”

Section: Introductionmentioning

confidence: 99%

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Individual heterogeneity in ixodid tick infestation and prevalence of Borrelia burgdorferi sensu lato in a northern community of small mammalian hosts

Lindsø,

Anders,

Viljugrein

et al. 2023

Oecologia

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Heterogeneous aggregation of parasites between individual hosts is common and regarded as an important factor in understanding transmission dynamics of vector-borne diseases. Lyme disease is vectored by generalist tick species, yet we have a limited understanding of how individual heterogeneities within small mammal host populations affect the aggregation of ticks and likelihood of infection. Male hosts often have higher parasite and infection levels than females, but whether this is linked to sexual body size dimorphism remains uncertain. Here, we analysed how host species, sex, and body mass influenced Ixodes ricinus tick infestations and the infection prevalence of Borrelia burgdorferi sensu lato (s.l.) in three species of small mammals involved in the enzootic transmission cycle of Lyme disease in Norway from 2018 to 2022. Larval and nymphal ticks were found on 98% and 34% of all individual hosts, respectively. In bank voles and wood mice, both larval and nymphal tick infestation and infection probability increased with body mass, and it increased more with mass for males than for females. Tick infestation in the common shrew increased with body mass and was higher in males, while pathogen infection was higher in females. Sex-biases in infestation did not correspond with level of sexual body mass dimorphism across species. This study contributes to our understanding of how individual heterogeneity among small mammalian hosts influences I. ricinus tick aggregation and prevalence of B. burgdorferi s.l. at northern latitudes.

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Host in reserve: The role of common shrews (Sorex araneus) as a supplementary source of tick hosts in small mammal communities influenced by rodent population cycles

Cited by 7 publications

References 83 publications

Effects of rodent abundance on ticks and Borrelia: results from an experimental and observational study in an island system

Effects of rodent abundance on ticks and Borrelia: results from an experimental and observational study in an island system

Shrews Under-Represented in Fruit Farms and Homesteads

Individual heterogeneity in ixodid tick infestation and prevalence of Borrelia burgdorferi sensu lato in a northern community of small mammalian hosts

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