Vetle Malmer Stigum

• Lindsø, Lars; Anders, Jason Lee; Viljugrein, Hildegunn; Herland, Anders; Stigum, Vetle Malmer & Easterday, William Ryan [Vis alle 7 forfattere av denne artikkelen] (2023). Individual heterogeneity in ixodid tick infestation and prevalence of Borrelia burgdorferi sensu lato in a northern community of small mammalian hosts. Oecologia. ISSN 0029-8549. 203(3), s. 421–433. doi: 10.1007/s00442-023-05476-w. Fulltekst i vitenarkiv Vis sammendrag

  Abstract 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.

• Muinck, Eric de; Trosvik, Pål; Nguyen, Nga; Fashing, Peter J.; Stigum, Vetle Malmer & Robinson, Nina [Vis alle 9 forfattere av denne artikkelen] (2023). Reduced abundance of Faecalibacterium prausnitzii in the gut microbiota of children diagnosed with cancer, a pilot study. Frontiers in Mircobiomes. ISSN 2813-4338. 2. doi: 10.3389/frmbi.2023.1151889. Fulltekst i vitenarkiv Vis sammendrag

  Background There is an increasing awareness of the importance of the gut microbiome in disease progression and the maintenance of human health. However, links between the microbiome and cancer onset remain relatively unexplored. This is especially the case for childhood cancers, which although rare, are the predominant cause of death among children in Western countries. Methods Fecal samples were collected from patients, before the onset of treatment, by the Norwegian Childhood Cancer Biobank in Oslo and from children attending kindergartens in Oslo, Norway. Using 16S rRNA gene amplicon sequencing, we compared the gut microbiome compositions of the children diagnosed with cancer with children attending kindergarten. Results We observed significant differences in the relative abundances of several taxa, including a striking depletion of Faecalibacterium prausnitzii , an important taxa linked to gut health maintenance. Conclusions Our observations provide evidence that the gut microbiome may play an important role in physiological changes associated with the onset of childhood cancer. However, further studies should be designed in order to validate our findings. Furthermore, these results suggest that variations in the microbial community could potentially be used as an early indicator of childhood cancer.

• Tamirat, Temesgen; Stigum, Vetle Malmer & Robertson, Lucy (2022). Surveillance of berries sold on the Norwegian market for parasite contamination using molecular methods. Food Microbiology. ISSN 0740-0020. 104. doi: 10.1016/j.fm.2022.103980. Fulltekst i vitenarkiv
• Temesgen, Tamirat Tefera; Robertson, Lucy; Stigum, Vetle Malmer & Tysnes, Kristoffer (2021). Removal of Parasite Transmission Stages from Berries Using Washing Procedures Suitable for Consumers. Foods. 10(2). doi: 10.3390/foods10020481. Fulltekst i vitenarkiv Vis sammendrag

  Due to the delicate nature of berries and the reduced shelf-life once washed, producers usually do not wash berries. Therefore, consumers are expected to wash the berries prior to consumption, and this might be a more effective way of infection prevention. However, the efficacy of consumer berry-washing procedures in removing the parasite contaminants from the berries surface has not been investigated. The aim of the present study was, therefore, to compare the efficacy of three different washing techniques in removing parasite contaminants. Three alternatives to washing berries before consumption were compared on berries artificially contaminated with oo/cysts of Cyclospora cayetanensis, Cryptosporidium parvum, and Giardia duodenalis. The results show that simple washing of berries under the cold tap for 1 min could remove on average at least 80% of the parasites, except for C. cayetanensis, which seems to be stickier than both G. duodenalis and C. parvum. The percent removal was slightly lower for raspberries as compared to blueberries. Although the differences are expected, a relevant result of the study is that washing contaminated berries prior to consumption by the consumer removes a considerable proportion of parasites and thereby lowers the risk of ingesting parasites’ transmission stages.

• Stigum, Vetle Malmer; Jaarsma, Ryanne I.; Sprong, Hein; Rolandsen, Christer Moe & Mysterud, Atle (2019). Infection prevalence and ecotypes of Anaplasma phagocytophilum in moose Alces alces, red deer Cervus elaphus, roe deer Capreolus capreolus and Ixodes ricinus ticks from Norway. Parasites & Vectors. 12, s. 1–8. doi: 10.1186/s13071-018-3256-z. Fulltekst i vitenarkiv Vis sammendrag

  Background The geographical expansion of the tick Ixodes ricinus in northern Europe is a serious concern for animal and human health. The pathogen Anaplasma phagocytophilum is transmitted by ticks and causes emergences of tick-borne fever (anaplasmosis) in livestock. The transmission dynamics of the different ecotypes of A. phagocytophilum in the ecosystems is only partly determined. Red deer and roe deer contribute to circulation of different ecotypes of A. phagocytophilum in continental Europe, while the role of moose for circulation of different ecotypes is not fully established but an important issue in northern Europe. Methods We determined infection prevalence and ecotypes of A. phagocytophilum in moose (n = 111), red deer (n = 141), roe deer (n = 28) and questing ticks (n = 9241) in Norway. Results As previously described, red deer was exclusively linked to circulation of ecotype I, while roe deer was exclusively linked to circulation of ecotype II. Surprisingly, we found 58% ecotype I (n = 19) and 42% of ecotype II (n = 14) in moose. Both ecotypes were found in questing ticks in areas with multiple cervid species present, while only ecotype I was found in ticks in a region with only red deer present. Hence, the geographical distribution of ecotypes in ticks followed the distribution of cervid species present in a given region and their link to ecotype I and II. Conclusions Moose probably function as reservoirs for both ecotype I and II, indicating that the ecotypes of A. phagocytophilum are not entirely host-specific and have overlapping niches. The disease hazard depends also on both host abundance and the number of immature ticks fed by each host. Our study provides novel insights in the northern distribution and expansion of tick-borne fever.

• Mysterud, Atle; Stigum, Vetle Malmer; Jaarsma, Ryanne I. & Sprong, Hein (2019). Genospecies of Borrelia burgdorferi sensu lato detected in 16 mammal species and questing ticks from northern Europe. Scientific Reports. 9, s. 1–8. doi: 10.1038/s41598-019-41686-0. Fulltekst i vitenarkiv Vis sammendrag

  Lyme borreliosis is the most common vector-borne zoonosis in the northern hemisphere, and the pathogens causing Lyme borreliosis have distinct, incompletely described transmission cycles involving multiple host groups. The mammal community in Fennoscandia differs from continental Europe, and we have limited data on potential competent and incompetent hosts of the different genospecies of Borrelia burgdorferi sensu lato (sl) at the northern distribution ranges where Lyme borreliosis is emerging. We used qPCR to determine presence of B. burgdorferi sl in tissue samples (ear) from 16 mammalian species and questing ticks from Norway, and we sequenced the 5S–23 S rDNA intergenic spacer region to determine genospecies from 1449 qPCR-positive isolates obtaining 423 sequences. All infections coming from small rodents and shrews were linked to the genospecies B. afzelii, while B. burgdorferi sensu stricto (ss) was only found in red squirrels (Sciurus vulgaris). Red squirrels were also infected with B. afzelii and B. garinii. There was no evidence of B. burgdorferi sl infection in moose (Alces alces), red deer (Cervus elaphus) or roe deer (Capreolus capreolus), confirming the role of cervids as incompetent hosts. In infected questing ticks in the two western counties, B. afzelii (67% and 75%) dominated over B. garinii (27% and 21%) and with only a few recorded B. burgdorferi ss and B. valaisiana. B. burgdorferi ss were more common in adult ticks than in nymphs, consistent with a reservoir in squirrels. Our study identifies potential competent hosts for the different genospecies, which is key to understand transmission cycles at high latitudes of Europe.

• Mysterud, Atle; Stigum, Vetle Malmer; Linløkken, Harald Kolstad; Herland, Anders & Viljugrein, Hildegunn (2019). How general are generalist parasites? The small mammal part of the Lyme disease transmission cycle in two ecosystems in northern Europe. Oecologia. ISSN 0029-8549. 190(1), s. 115–126. doi: 10.1007/s00442-019-04411-2. Fulltekst i vitenarkiv Vis sammendrag

  The pathogens causing Lyme disease are all vectored by generalist tick species found on a wide range of vertebrates, but spatial and annual variation in host use has rarely been quantified. We here compare the load of Ixodes ricinus (the vector) on small mammals and investigate the infection prevalence of Borrelia burgdorferi s.l. (the pathogen) involved in the enzootic transmission cycle of Lyme disease in two contrasting ecosystems in Norway from 2014 to 2016. The most common larval tick host in the eastern region was the bank vole, while the common shrew dominated in the western region of Norway. However, the wood mouse and the bank vole had consistently higher larval tick loads than the common shrew in both ecosystems. Hence, the evidence indicated that species are differently suitable as hosts, regardless of their abundances. The pathogen infection prevalence was similar among small mammal species, but markedly higher in the region with larger small mammal populations and higher tick loads, while the seasonal and annual variation was less marked. Our study indicated that the generalist I. ricinus shows consistent patterns of load on species of small vertebrate hosts, while B. burgdorferi s.l. (B. afzelii) was a true generalist. The similar roles of host species across regions suggest that disease dynamics can be predicted from host community composition, but predicting the role of host community composition for disease dynamics requires a detailed understanding of the different species population limitations under global change.

• Mysterud, Atle; Stigum, Vetle Malmer; Seland, Ingrid Vikingsdal; Herland, Anders; Easterday, William Ryan & Jore, Solveig [Vis alle 8 forfattere av denne artikkelen] (2018). Tick abundance, pathogen prevalence, and disease incidence in two contrasting regions at the northern distribution range of Europe. Parasites & Vectors. 11(309). doi: 10.1186/s13071-018-2890-9. Fulltekst i vitenarkiv Vis sammendrag

  Background Emergence of tick-borne diseases is impacting humans and livestock across the Northern Hemisphere. There are, however, large regional variations in number of cases of tick-borne diseases. Some areas have surprisingly few cases of disease compared to other regions. The aim here is to provide a first step towards a better understanding of such contrasting regional patterns of disease emergences at the northern distribution range of Ixodes ricinus in Europe. Methods We compare disease incidence, vector abundance and pathogen prevalence in eastern and western Norway differing in the number of tick-borne disease cases. First, we analysed the incidence of Lyme borreliosis in humans, tick-borne fever (anaplasmosis) in sheep and anaplasmosis and babesiosis in cattle to verify if incidence differed. Secondly, we analysed extensive field data on questing tick density, pathogen prevalence, as well as the broad spatial pattern of human and livestock distribution as it may relate to tick exposure. Results The incidences of all diseases were lower in eastern, compared to western, Norway, but this was most marked for the livestock diseases. While the prevalence of Borrelia burgdorferi (sensu lato) in ticks was similar in the two regions, the prevalence of Anaplasma phagocytophilum was markedly lower in eastern, compared to western, Norway. We found overall a lower abundance of questing nymphs in the east. In the east, there were cases of babesiosis in cattle where anaplasmosis was absent, suggesting absence of the pathogen rather than differences in exposure to ticks as part of the explanation for the much lower incidence of anaplasmosis in eastern Norway. Conclusions Many factors contribute to different disease incidence across ecosystems. We found that regional variation in tick-borne disease incidence may be partly linked to vector abundance and pathogen prevalence, but differently for human and livestock diseases. Further studies are needed to determine if there is also regional variation in specific genospecies and strain frequencies differing in pathogenicity.

• Mysterud, Atle; Easterday, William Ryan; Stigum, Vetle Malmer; Aas, Anders Bjørnsgard; Meisingset, Erling L. & Viljugrein, Hildegunn (2016). Contrasting emergence of Lyme disease across ecosystems. Nature Communications. 7. doi: 10.1038/ncomms11882. Fulltekst i vitenarkiv Vis sammendrag

  Global environmental changes are causing Lyme disease to emerge in Europe. The life cycle of Ixodes ricinus, the tick vector of Lyme disease, involves an ontogenetic niche shift, from the larval and nymphal stages utilizing a wide range of hosts, picking up the pathogens causing Lyme disease from small vertebrates, to the adult stage depending on larger (non-transmission) hosts, typically deer. Because of this complexity the role of different host species for emergence of Lyme disease remains controversial. Here, by analysing long-term data on incidence in humans over a broad geographical scale in Norway, we show that both high spatial and temporal deer population density increase Lyme disease incidence. However, the trajectories of deer population sizes play an overall limited role for the recent emergence of the disease. Our study suggests that managing deer populations will have some effect on disease incidence, but that Lyme disease may nevertheless increase as multiple drivers are involved.

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• Easterday, William Ryan; Muinck, Eric de & Stigum, Vetle Malmer (2021). the not so straight-forward way of generating long reads on the PacBio. Fulltekst i vitenarkiv

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