Temporal and spatial variation in<i>Anaplasma phagocytophilum</i>infection in Swedish moose (<i>Alces alces</i>)

Malmsten, Jonas; Widén, Dolores Gavier; Rydevik, Gustaf; Yon, Lisa; Hutchings, Michael R.; Thulin, Carl‐Gustaf; Söderquist, L.; Aspán, Anna; Stuen, Snorre; Dalin, Anne-Marie

doi:10.1017/s0950268813002094

Cited by 21 publications

(18 citation statements)

References 42 publications

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“…However, more studies are needed to confirm this. Most of the moose in this study, 173 animals, had been previously screened for infection with tick-borne Anaplasma phagocytophilum [ 29 ]. All had markers of Anaplasma , and signs of ongoing infections peaked in the age 0–2 years [ 29 ], which was the similar age class for ongoing HEV infections.…”

Section: Discussionmentioning

confidence: 99%

“…Most of the moose in this study, 173 animals, had been previously screened for infection with tick-borne Anaplasma phagocytophilum [ 29 ]. All had markers of Anaplasma , and signs of ongoing infections peaked in the age 0–2 years [ 29 ], which was the similar age class for ongoing HEV infections. Anaplasma , is known to have immunosuppressive properties [ 43 ] and may increase the susceptibility of moose to HEV infection and prolong the infection time period, as has been seen in immunosuppressed humans [ 2 ].…”

Section: Discussionmentioning

confidence: 99%

“…Samples from 231 moose were used for detection of HEV RNA and anti-HEV antibodies. Out of these, 57 serum and 51 fecal samples from 57 moose were sent in by hunters, while serum samples previously collected from 173 moose as part of a study on Anaplasma infections were also provided with the assistance of hunters [ 29 ]. An additional moose liver sample positive for HEV [ 28 ] was also included in this study.…”

Section: Methodsmentioning

confidence: 99%

“…Most samples were collected during September to November 2012 and 2013. For most animals, pathological examinations were performed in the field by a trained wildlife pathologist who, after being contacted by hunters, travelled to the recently harvested moose carcass to collect adequate samples for the parallel Anaplasma study [ 29 ]. The carcass and its internal organs were thus macroscopically inspected for lesions.…”

Section: Methodsmentioning

confidence: 99%

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High Prevalence of Hepatitis E Virus in Swedish Moose – A Phylogenetic Characterization and Comparison of the Virus from Different Regions

et al. 2015

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BackgroundHepatitis E virus (HEV) infects a range of species, including humans, pigs, wild boars and deer. Zoonotic transmission may contribute to the high HEV seroprevalence in the human population of many countries. A novel divergent HEV from moose (Alces alces) in Sweden was recently identified by partial genome sequencing. Since only one strain was found, its classification within the HEV family, prevalence in moose and zoonotic potential was unclear. We therefore investigated samples from 231 moose in seven Swedish counties for HEV, and sequenced a near complete moose HEV genome. Phylogenetic analysis to classify this virus within the family Hepeviridae and to explore potential host specific determinants was performed.Methods and FindingsThe HEV prevalence of moose was determined by PCR (marker for active infection) and serological assays (marker of past infection) of sera and 51 fecal samples from 231 Swedish moose. Markers of active and past infection were found in 67 (29%) animals, while 34 (15%) were positive for HEV RNA, 43 (19%) were seropositive for anti-HEV antibodies, and 10 (4%) had both markers. The number of young individuals positive for HEV RNA was larger than for older individuals, and the number of anti-HEV antibody positive individuals increased with age. The high throughput sequenced moose HEV genome was 35-60% identical to existing HEVs. Partial ORF1 sequences from 13 moose strains showed high similarity among them, forming a distinct monophyletic clade with a common ancestor to HEV genotype 1-6 group, which includes members known for zoonotic transmission.ConclusionsThis study demonstrates a high frequency of HEV in moose in Sweden, with markers of current and past infection demonstrated in 30% of the animals. Moose is thus an important animal reservoir of HEV. The phylogenetic relationship demonstrated that the moose HEV belonged to the genotype 1-6 group, which includes strains that also infect humans, and therefore may signify a potential for zoonotic transmission of this HEV.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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High Prevalence of Hepatitis E Virus in Swedish Moose – A Phylogenetic Characterization and Comparison of the Virus from Different Regions

et al. 2015

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“…Unlike the simultaneous exposure to multiple strains under conditions of coinfection, the sequential exposure of the vector to multiple strains frequently prevents establishment of the second strain, a phenomenon termed superinfection exclusion (16)(17)(18), and only the primary strain is transmitted. As a consequence, superinfection exclusion has the potential to greatly limit genetic diversity in the host population, which is difficult to reconcile with the observed high degree of genetic diversity maintained among many vector-borne pathogens (6,(19)(20)(21)(22)(23).…”

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confidence: 99%

Superinfection Exclusion of the Ruminant Pathogen Anaplasma marginale in Its Tick Vector Is Dependent on the Time between Exposures to the Strains

Noh

Dark

Reif

et al. 2016

Appl Environ Microbiol

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The remarkable genetic diversity of vector-borne pathogens allows for the establishment of superinfection in the mammalian host. To have a long-term impact on population strain structure, the introduced strains must also be transmitted by a vector population that has been exposed to the existing primary strain. The sequential exposure of the vector to multiple strains frequently prevents establishment of the second strain, a phenomenon termed superinfection exclusion. As a consequence, superinfection exclusion may greatly limit genetic diversity in the host population, which is difficult to reconcile with the high degree of genetic diversity maintained among vector-borne pathogens. Using Anaplasma marginale, a tick-borne bacterial pathogen of ruminants, we hypothesized that superinfection exclusion is temporally dependent and that longer intervals between strain exposures allow successful acquisition and transmission of a superinfecting strain. To test this hypothesis, we sequentially exposed Dermacentor andersoni ticks to two readily tick-transmissible strains of A. marginale. The tick feedings were either immediately sequential or 28 days apart. Ticks were allowed to transmission feed and were individually assessed to determine if they were infected with one or both strains. The second strain was excluded from the tick when the exposure interval was brief but not when it was prolonged. Midguts and salivary glands of individual ticks were superinfected and transmission of both strains occurred only when the exposure interval was prolonged. These findings indicate that superinfection exclusion is temporally dependent, which helps to account for the differences in pathogen strain structure in tropical compared to temperate regions. IMPORTANCEMany vector-borne pathogens have marked genetic diversity, which influences pathogen traits such as transmissibility and virulence. The most successful strains are those that are preferentially transmitted by the vector. However, the factors that determine successful transmission of a particular strain are unknown. In the case of intracellular, bacterial, tick-borne pathogens, one potential factor is superinfection exclusion, in which colonization of ticks by the first strain of a pathogen it encounters prevents the transmission of a second strain. Using A. marginale, the most prevalent tick-borne pathogen of cattle worldwide, and its natural tick vector, we determined that superinfection exclusion occurs when the time between exposures to two strains is brief but not when it is prolonged. These findings suggest that superinfection exclusion may influence strain transmission in temperate regions, where tick activity is limited by season, but not in tropical regions, where ticks are active for long periods.

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Habitat–performance relationships of a large mammal on a predator‐free island dominated by humans

Allen

Dorey

Malmsten

et al. 2016

Ecology and Evolution

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The demographic consequences of changes in habitat use driven by human modification of landscape, and/or changes in climate, are important for any species. We investigated habitat–performance relationships in a declining island population of a large mammal, the moose (Alces alces), in an environment that is predator‐free but dominated by humans. We used a combination of demographic data, knowledge of habitat selection, and multiannual movement data of female moose (n = 17) to understand how space use patterns affect fecundity and calf survival. The calving rate was 0.64 and was similar to calving rates reported in other populations. Calf survival was 0.22 (annually) and 0.32 (postsummer), which are particularly low compared to other populations where postsummer survival is typically above 0.7. Home ranges were mainly composed of arable land (>40%), and selection for arable land was higher in winter than in summer, which contrasts with previous studies. Females that spent more time in broadleaf forest in the summer prior to the rut had higher fecundity rates, while more time spent in arable land resulted in lower fecundity rates. Females that spent more time in thicket/scrubland habitats during winter had lower calf survival, while females that had higher use of mixed forests tended to have higher calf survival. The dominance, and subsequent use, of suboptimal foraging habitats may lead to poor body condition of females at parturition, which may lower calf body weights and affect the mother's ability to lactate. In addition, our results indicated that the growing season has advanced significantly in recent decades, which may be causing a mismatch between parturition and optimal resource availability. These effects may exacerbate the female's ability to meet the energetic demands of lactation. Therefore, the observed low calf survival appears to be caused by a combination of factors related to current land use and may also be due to changing vegetation phenology. These results have important implications for the management of species in human‐dominated landscapes in the face of climate change, and for an increased understanding of how species may adapt to future land use and climate change.

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Temporal and spatial variation inAnaplasma phagocytophiluminfection in Swedish moose (Alces alces)

Cited by 21 publications

References 42 publications

High Prevalence of Hepatitis E Virus in Swedish Moose – A Phylogenetic Characterization and Comparison of the Virus from Different Regions

High Prevalence of Hepatitis E Virus in Swedish Moose – A Phylogenetic Characterization and Comparison of the Virus from Different Regions

Superinfection Exclusion of the Ruminant Pathogen Anaplasma marginale in Its Tick Vector Is Dependent on the Time between Exposures to the Strains

Habitat–performance relationships of a large mammal on a predator‐free island dominated by humans

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