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The genetic diversity of Borrelia afzelii is not maintained by the diversity of the rodent hosts
Coipan, Claudia E. ; Duijvendijk, L.A.G. van; Hofmeester, T.R. ; Takumi, Katsuhisa ; Sprong, H. - \ 2018
Borrelia burgdorferi - Ixodes ricinus larvae - rodents - IGS - ospC - dbpA
Background Small mammals are essential in the enzootic cycle of many tick-borne pathogens (TBP). To understand their contribution to the genetic diversity of Borrelia afzelii, the most prevalent TBP in questing Ixodes ricinus, we compared the genetic variants of B. afzelii at three distinct genetic loci. We chose two plasmid loci, dbpA and ospC, and a chromosomal one, IGS. Results While the larvae that fed on shrews (Sorex sp.) tested negative for B. afzelii, those fed on bank voles (Myodes glareolus) and wood mice (Apodemus sylvaticus) showed high infection prevalences of 0.13 and 0.27, respectively. Despite the high genetic diversity within B. afzelii, there was no difference between wood mice and bank voles in the number and types of B. afzelii haplotypes they transmit. Conclusions The genetic diversity in B. afzelii cannot be explained by separate enzootic cycles in wood mice and bank voles.
Data from: Cascading effects of predator activity on tick-borne disease risk
Hofmeester, T.R. ; Jansen, P.A. ; Wijnen, H.J. ; Coipan, E.C. ; Fonville, Manoj ; Prins, H.H.T. ; Sprong, Hein ; Wieren, S.E. van - \ 2017
Borrelia burgdorferi - predators - carnivores - rodents
Predators and competitors of vertebrates can in theory reduce the density of infected nymphs (DIN)—an often-used measure of tick-borne disease risk—by lowering the density of reservoir-competent hosts and/or the tick burden on reservoir-competent hosts. We investigated this possible indirect effect of predators by comparing data from 20 forest plots across the Netherlands that varied in predator abundance. In each plot, we measured the density of questing Ixodes ricinus nymphs (DON), DIN for three pathogens, rodent density, the tick burden on rodents and the activity of mammalian predators. We analysed whether rodent density and tick burden on rodents were correlated with predator activity, and how rodent density and tick burden predicted DON and DIN for the three pathogens. We found that larval burden on two rodent species decreased with activity of two predator species, while DON and DIN for all three pathogens increased with larval burden on rodents, as predicted. Path analyses supported an indirect negative correlation of activity of both predator species with DON and DIN. Our results suggest that predators can indeed lower the number of ticks feeding on reservoir-competent hosts, which implies that changes in predator abundance may have cascading effects on tick-borne disease risk.
The ecology of Lyme borreliosis risk : interactions between lxodes ricinus, rodents and Borrelia burgdorferi sensu lato
Duijvendijk, Gilian van - \ 2016
Wageningen University. Promotor(en): Willem Takken, co-promotor(en): H. Sprong. - Wageningen : Wageningen University - ISBN 9789462579408 - 186
rodents - ixodes ricinus - disease vectors - tickborne diseases - borrelia burgdorferi - borrelia miyamotoi - hosts - ecological risk assessment - risk analysis - knaagdieren - ixodes ricinus - vectoren, ziekten - ziekten overgebracht door teken - borrelia burgdorferi - borrelia miyamotoi - gastheren (dieren, mensen, planten) - ecologische risicoschatting - risicoanalyse
The sheep tick (Ixodes ricinus) is widespread throughout Europe and can transmit Borrelia burgdorferi sensu lato (s.l.), which can cause Lyme borreliosis and B. miyamotoi, the agent of Borrelia miyamotoi disease in humans. Borrelia afzelii is the most common genospecies of Borrelia burgdorferi s.l. in western Europe and it circulates between I. ricinus and rodents. The density of infected nymphs determines disease risk and is affected by complex multi-trophic interactions between factors that are not well understood. The aim of this thesis was, therefore, to gain insight into the multi-trophic interactions that affect the density of B. afzelii-infected and B. miyamotoi-infected I. ricinus nymphs.
Interactions between I. ricinus, rodents (wood mice and bank voles) and B. afzelii were reviewed to elucidate knowledge gaps concerning these interactions. The effect of rodent density on the density of infected nymphs and the factors that affect the contribution of a rodent to the density of infected nymphs were investigated in field experiments. The effects of a B. afzelii infection on larval tick burden of bank voles and nymphal body weight were investigated in the laboratory. The effects of CO2 and host odour on the host-seeking behaviour of I. ricinus were investigated in a Y-tube olfactometer. Finally, the ability of field-collected I. ricinus larvae to transmit B. afzelii and B. miyamotoi was analysed.
The review showed that rodent density, rodent infection rate, and larval tick burden are the major factors affecting the density of B. afzelii-infected nymphs one year later. The field experiments showed that rodent density can positively affect the density of B. burgdorferi s.l.- infected nymphs one year later. However, the effect of rodent density was small when the density of infected nymphs was limited by the density of questing larvae in the previous year. Rodent density had, however, no effect on the density of B. miyamotoi-infected nymphs. The field studies also showed that tick burdens are 2.4 times higher on wood mice than on bank voles and that body weight of emerged nymphs was 36% higher for ticks that fed on wood mice compared to ticks that fed on bank voles. Bank voles infected with B. afzelii acquired a larger larval tick burden, resulting in a 27% increase in nymphal infection prevalence. Furthermore, infected nymphs had a 10% greater the body weight. Ixodes ricinus nymphs are activated by but not attracted to CO2, whereas they are attracted to and not activated by host odour. Ixodes ricinus larvae transmitted both B. afzelii and B. miyamotoi to rodents and it was calculated that rodents have a chance of about 25-75% of acquiring B. afzelii from larvae relative to the chance of acquiring B. afzelii from nymphs. The main conclusions of this thesis are discussed and suggestions are made for future research.
Maintenance of Borrelia burgdorferi s.l. diversity in enzootic cycles
Swart-Coipan, Elena - \ 2016
Wageningen University. Promotor(en): Willem Takken; Herbert Prins, co-promotor(en): H. Sprong. - Wageningen : Wageningen University - ISBN 9789462579576 - 180
borrelia burgdorferi - life cycle - tickborne diseases - metastigmata - ixodes ricinus - disease vectors - rodents - mammals - genetic analysis - multilocus sequence typing - lyme disease - borrelia burgdorferi - levenscyclus - ziekten overgebracht door teken - metastigmata - ixodes ricinus - vectoren, ziekten - knaagdieren - zoogdieren - genetische analyse - multi-locus sequentie typering - lyme-ziekte
Lyme borreliosis is the most prevalent vector-borne disease in the temperate regions of the northern hemisphere. The bacteria that cause it are members of the Borrelia burgdorferi sensu lato complex, a group of spirochaetes which are transmitted by hard ticks of the Ixodes ricinus complex. In several European countries, including The Netherlands, the incidence of Lyme borreliosis has been on the rise for the last decades. The acarological risk of human infection with Borrelia burgdorferi s.l. has been defined as the density of infected questing nymphs. This definition assumes that the distribution of the various genospecies of Borrelia in Lyme borreliosis is reflected in their distribution in questing ticks; furthermore, it assumes that all Borrelia genospecies are considered equally hazardous for humans. In order to define effective intervention strategies for controlling the disease, more insight in the transmission dynamics of tick-borne pathogens, both between animals and ticks, but also from ticks to humans is needed. As part of a Dutch research programme – “Shooting the messenger” – this PhD thesis focussed on linking the transmission cycles of Lyme spirochaetes to the different clinical manifestations of Lyme borreliosis. To that end, I explored aspects of the ecology and molecular adaptations of B. burgdorferi s.l. at various scales, from complex to genospecies level.
The ecological adaptations of B. burgdorferi s.l. are underpinned by a complex genomic structure and gene expression, with large genetic variation among and within the genospecies. In Chapter 3, we prove that the 5S-23S rDNA intergenic spacer (IGS) is a suitable molecular marker for identification of B. burgdorferi s.l. to genospecies level, but also to characterize the genetic diversity at intragenospecies level and to detect genetic differentiation among the subpopulations of Borrelia. Consequently, we used this marker in combination with other genetic markers, in the studies addressing the genetic diversity of Borrelia in small mammals and humans.
The main transmission route of these bacteria is the interstadial one, from larvae to nymphs and from nymphs to adult ticks. Larvae of I. ricinus can become infected during a blood meal from an infected host and during a blood meal in the vicinity of an infected nymph feeding on a host, a process known as co-feeding. The infected engorged larvae then moult into infected nymphs, which can transmit the spirochaetes to new hosts. The same process is repeated in the next developmental stage – nymph to adult. Thus, the maintenance of the bacteria in enzootic cycles is dependent on various species of vertebrates and the ticks that feed on them. In order to identify the main vertebrate hosts responsible for the maintenance of B. burgdorferi in enzootic cycles, but also for feeding I. ricinus ticks, we conducted a meta-analysis on literature data (Chapter 2). Our quantification method suggests that only a few host species, which are amongst the most widespread species in the environment (rodents, thrushes and deer), feed the majority of I. ricinus individuals and that rodents infect the majority of I. ricinus larvae with B. burgdorferi s.l.. The increase in distribution and abundance of these species, could be one of the main causes for the increase in Lyme borreliosis incidence in Europe in recent decades.
While at genospecies level, there is host specificity, with B. afzelii associated with rodents and B. garinii with birds, we wanted to see if the same holds true at intragenospecies level, for the various genotypes of Borrelia. Chapter 4 focuses on the rodents, which were identified in the literature meta-analysis as being the main hosts for I. ricinus larvae as well as for Borrelia afzelii. We tested the multiple niche polymorphisms hypothesis, using IGS, dbpA and ospC as molecular markers for typing B. afzelii genotypes in fed larvae collected from rodents in various areas in The Netherlands. Despite the high genetic diversity within B. afzelii, there was no difference between wood mice and bank voles in the number and types of B. afzelii haplotypes they transmit. Additionally, we compared the quantitative role of bank voles and wood mice in B. afzelii and Neoehrlichia mikurensis maintenance, another emerging tick-borne pathogen in Europe. Neoehrlichia mikurensis prevalence was positively associated with B. afzelii. Mathematical models including tick burden and infection prevalence indicated that bank voles are better amplifiers of these two bacteria than wood mice. Our study suggests that wood mice and bank voles differ in their contribution to the dynamics of B. afzelii, and possibly other TBP, in questing ticks but not in their contribution to the genetic diversity of these microorganisms.
The density of the vertebrate hosts and the feeding preferences of the ticks should determine the prevalence of B. burgdorferi s.l. genospecies in questing ticks. We address this topic in Chapter 5, by testing 5,570 questing I. ricinus nymphs from 22 different areas in The Netherlands. We found an overall prevalence of 11.8% for B. burgdorferi s.l., with large and consistent variations among the various locations. As expected based on the results of Chapter 2, Borrelia afzelii was predominant (6.7 % of the questing ticks) among the B. burgdorferi s.l. genospecies. It was followed by B. garinii/B. bavariensis (1.5 %), B. valaisiana (1.2 %), and B. burgdorferi sensu stricto (0.2 %). We noticed that, over the usual range of questing ticks’ densities, the density of infected ticks is increasing with the overall density of questing ticks, and a downward trend might be observed only for questing tick densities of over 200/100 m2. This indicates that the density of questing nymphs is the main driver of the acarological risk of human exposure to B. burgdorferi s.l.
We also screened for the presence of other tick-borne pathogens that have previously been detected in questing ticks in The Netherlands: Rickettsia helvetica, Anaplasma phagocytophilum, Neoehrlichia mikurensis and several Babesia spp. (Chapter 5). To test whether these pathogens might share similar enzootic cycles we looked for patterns of coinfection and seasonal dynamics of infection in questing I. ricinus nymphs. One-third of the Borrelia-positive ticks were infected with at least one other pathogen. Coinfection of B. afzelii with N. mikurensis and with Babesia spp. occurred significantly more often than single infections, indicating the existence of mutual reservoir hosts. The diversity of tick-borne pathogens detected in I. ricinus in this study and the frequency of their coinfections with B. burgdorferi s.l. underline the need to consider them when evaluating the risks of infection and subsequently the risk of disease following a tick bite.
Chapter 6 addresses the pathogenicity of B. burgdorferi s.l. genospecies and genotypes for humans, using the eight multilocus sequence typing scheme housekeeping genes (MLST) and IGS as molecular markers. The frequency of the Borrelia spp. in humans is compared to the frequency in questing ticks to assess the infectivity of the various genospecies and genotypes. The fraction of STs that were isolated from human samples was significantly higher for the genospecies that are known to be maintained in enzootic cycles by mammals (B. afzelii, B. bavariensis, and spielmanii) than for genospecies that are maintained by birds (B. garinii and B. valaisiana) or lizards (B. lusitaniae). Just as in questing ticks, B. afzelii was the most prevalent Borrelia in in human Lyme borreliosis. Borrelia afzelii was associated with acrodermatitis chronica atrophicans, while B. garinii and B. bavariensis were associated with neuroborreliosis. Despite its high incidence in ticks and erythema migrans, in terms of disease burden (as measured by disability-adjusted life year), B. afzelii is of least concern for public health. Other Borrelia spirochaetes that are rarely found in questing I. ricinus ticks, such as B. bavariensis, seem to be responsible for most of the neuroborreliosis cases – a more severe clinical symptom of Lyme borreliosis. This implies that the prevalence of B. burgdorferi s.l. in questing ticks does not necessarily reflect the incidence of human Lyme borreliosis. We found six multilocus sequence types that were significantly associated with clinical manifestations in humans and five IGS haplotypes that were associated with the human Lyme borreliosis cases. While IGS could perform just as well as the housekeeping genes in the MLST scheme for predicting the infectivity of B. burgdorferi s.l., the advantage of MLST is that it can also capture the differential invasiveness of the various STs.
In this thesis, I have identified the most important vertebrate hosts for maintenance of B. burgdorferi s.l. in enzootic cycles. I have also shown that their density is reflected in the prevalence of B. burgdorferi s.l. in questing ticks. The comparative study of questing ticks and Lyme borreliosis indicated that some of the Borrelia genospecies have similar prevalences in the two sources. The findings in my thesis indicate, thus, that there is a link between the density of suitable hosts for ticks and Borrelia spp., the density of infected ticks and the distribution of the B. burgdorferi s.l. genospecies in Lyme borreliosis. There are exceptions, however, that cannot be explained by this simple thread line. Such a situation is the perceived association of B. bavariensis with rodents that is not reflected by its extremely low prevalence in questing ticks. Furthermore, this low prevalence cannot explain the overrepresentation of B. bavariensis in Lyme borreliosis. As result of the study of pathogenicity of the various Borrelia genospecies and genotypes, I suggest the separate hazard assignment for the Borrelia genospecies; this, in combination with the exposure (prevalence in questing ticks) would allow for individual genospecies/genotypes risk assessment. The findings in this thesis stress the importance of both ecological and clinical studies for addressing the public health issue of Lyme borreliosis.
Cage enrichment: rabbit does prefer straw or a compressed wooden block
Rommers, J.M. ; Bracke, M.B.M. ; Reuvekamp, B.F.J. ; Gunnink, H. ; Jong, I.C. de - \ 2014
World Rabbit Science 22 (2014). - ISSN 1257-5011 - p. 301 - 309.
zealand white-rabbits - environmental enrichment - behavior - objects - rodents - food
The effect of different food related materials on the behaviour of commercial meat rabbit does was investigated to provide them enrichment. Five different treatments were tested. Control (pens without additional enrichment, C) was compared with pens containing a pinewood stick (Pine), straw in a plastic bin (Straw), a compressed wooden block (Ply) or a combination of straw and a pinewood stick (Straw+Pine). The experiment was conducted on a commercial rabbit farm using 80 cages with multiparous lactating hybrid (Hycole) rabbit does. Behavioural observations were conducted in the first 4 wk of 2 successive lactations of 6 wk each, twice a week from 15:00 to 18:30 h. Once every week the consumption of gnawing materials and soiling of the cages was scored. More does were significantly occupied with Straw and Ply than with Pine (24±20, 11±9 and 4±3% of does, respectively) for a longer duration (4±4, 2±2, 0.1±0.2% of observed time, respectively). In does of Straw+Pine group, the pinewood was barely touched and straw was preferred. It can be concluded that straw (loose material) and wooden block are used by the animals as enrichment material to gnaw or chew on. The materials remain attractive for the 2 lactations which were measured. The pinewood stick as provided in this study was rarely used and it may be questioned whether it is sufficient as enrichment material or if it should be provided in another way than hanging on the roof of the cage. This study provides a first step towards a positive list of enrichment materials that can be used in commercial rabbit farming in The Netherlands.
Risico's van anticoagulantia rodenticides voor niet-doelsoorten en predatoren : een scan van beschikbare kennis in Europa en analyses in roofvogels uit Nederland
Brink, N.W. van den - \ 2014
Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2589) - 25
knaagdieren - roofvogels - ecotoxicologie - predatie - voedselwebben - rodents - predatory birds - ecotoxicology - predation - food webs
Knaagdierpopulaties kunnen zich lokaal ontwikkelen tot zeer hoge dichtheden en kunnen op deze manier een groot maatschappelijk probleem veroorzaken. Al eeuwen lang worden knaagdierplagen geassocieerd met de uitbraak van ziektes (waaronder de zwarte pest), maar ze kunnen ook economische schade toebrengen. Hierbij valt te denken aan het opeten en bederven van voedselvoorraden, transmissie van ziekteverwekkers tussen bijvoorbeeld boerderijen, terwijl tegenwoordig het knagen aan bedradingen e.d. ook een relevant probleem is. Het gedrag van deze dieren en het feit dat ze zeer snel in populatieomvang kunnen toenemen, maakt dat de bestrijding van knaagdieren continu aandacht behoeft. Er zijn verschillende methodes om knaagdieren te bestrijden.
Of mice and oaks : conditional outcomes in a seed-dispersal mutualism
Suselbeek, L. - \ 2014
Wageningen University. Promotor(en): Herbert Prins; Frans Bongers, co-promotor(en): Patrick Jansen; Sip van Wieren. - Wageningen : Wageningen University - ISBN 9789462571020 - 120
zaadverspreiding - verspreiding - mutualisme - knaagdieren - boomvruchten - sus scrofa - apodemus sylvaticus - ecologie - seed dispersal - dispersal - mutualism - rodents - tree fruits - sus scrofa - apodemus sylvaticus - ecology
PhD Thesis (defence scheduled for 10 October 2014, 4pm) – abstracts for library
Of Mice and Oaks: conditional outcomes in a seed-dispersal mutualism
Rodents like to wood mouse store acorns to overcome winter, but some of the stored acorns are never retrieved by the rodents. Those acorns that are not retrieved have a chance to germinate and establish into a new tree. Thus, the interaction between mice and oaks is potentially mutualistic. However, the interaction is only mutualistic when the acorns are placed in locations where germination is likely to take place. The aim of this study was to investigate whether and how the strategy of hoarding (i.e. storing the seeds) depended on the presence of wild boar (who are very fond of acorns too!), de abundance of acorns and the abundance of mice in the area. Wild boar did not seem to be very capable to detect the acorns that had been hidden in the soil by the rodents, and as a consequence they seem to have little effect on the hoarding strategy of rodents. The abundance of rodents and of acorns does affect the hoarding patterns of rodents. With more competition (i.e. more mice or fewer acorns), seeds are hidden more quickly and are being scattered more widely. The acorns benefit from this, as their chance to survive and successfully establish as a new tree increases with dispersal distance and seed spacing.
Muizen leggen een wintervoorraad aan van eikels, maar een deel van deze voorraad wordt vaak niet opgegeten door de muizen. De niet opgegeten eikels hebben een kans om zich te vestigen als nieuwe eik, en daarmee is de interactie tussen muizen en eiken in potentie een mutualisme. Echter, er is alleen sprake van een mutualisme als de eikels op goede kiemplaatsen terecht komen. Doel van deze studie was te onderzoeken of de verstopstrategie van muizen afhankelijk was de aanwezigheid van wilde zwijnen (die ook dol op eikels zijn!), van het aanbod aan eikels, en van het aantal muizen in het gebied. De wilde zwijnen lijken niet goed in staat te zijn om de door muizen in de grond verstopte eikels terug te vinden, en daardoor hebben zij weinig invloed op het hamstergedrag van de muizen. Het aantal eikels en muizen heeft wel invloed op de verstopstrategie. Hoe meer concurrentie (dus, meer muizen of juist minder eikels), hoe sneller en meer verspreid de zaden verstopt worden. De eikels profiteren daar van, want hoe beter ze verspreid worden des te groter hun overlevingskans.
Scatter hoarding and cache pilferage by superior competitors: an experiment with wild boar, Sus scrofa
Suselbeek, L. ; Adamczyk, V.M.A.P. ; Bongers, F. ; Nolet, B.A. ; Prins, H.H.T. ; Wieren, S.E. van; Jansen, P.A. - \ 2014
Animal Behaviour 96 (2014). - ISSN 0003-3472 - p. 107 - 115.
optimal-density model - dipodomys-merriami - kangaroo rats - environmental-conditions - acorn dispersal - red squirrel - wood mice - seed - behavior - rodents
Food-hoarding patterns range between larder hoarding (a few large caches) and scatter hoarding (many small caches), and are, in essence, the outcome of a hoard size–number trade-off in pilferage risk. Animals that scatter hoard are believed to do so, despite higher costs, to reduce loss of cached food to competitors against which they cannot defend their food reserves (henceforth: superior competitors). We tested the underlying assumption that the cost of having more caches under scatter hoarding, thus increasing the likelihood of cache encounter by superior competitors, is outweighed by the benefit of having small caches that are less likely to be detected upon encounter by superior competitors. We carried out a controlled experiment in which we distributed a fixed number of acorns over a fixed number of patches within a fixed area, varying cache size and cache depth, thus mimicking alternative hoarding patterns. We then recorded cache pilferage by a fixed number of wild boar, a well-known pilferer of acorn caches. The time wild boar needed to pilfer the first cache was shortest for scatter hoarding, but the time needed to pilfer all caches was slightly longer for scatter hoarding than for larder hoarding. Overall, however, the rate of pilferage did not differ between scatter hoarding and larder hoarding, and was not affected by cache depth. We conclude that the effects of alternative hoarding patterns on reducing cache pilferage by wild boar were smaller than expected, and that superior competitors may thus not be important drivers of scatter hoarding. Instead, other factors, such as conspecific pilferage or the risk of cross-contamination of food items in large caches, which can also cause catastrophic loss of food reserves, may be more important drivers of scatter hoarding.
Seed predation and defleshing in the agouti-dispersed palm Astrocaryum standleyanum
Jansen, P.A. ; Elschot, K. ; Verkerk, P.J. ; Wright, S.J. - \ 2010
Journal of Tropical Ecology 26 (2010)5. - ISSN 0266-4674 - p. 473 - 480.
bruchid beetle - forest - patterns - rodents - fruits - recruitment - germination - survival - poachers - peru
The agouti (Dasyprocta punctata) meticulously defleshes Astrocaryum standleyanum palm seeds before scatter hoarding. On Barro Colorado Island, Panama, we experimentally tested three hypotheses on how this behaviour could reduce seed predation to the mutual benefit of the tree and the rodent. The first and established hypothesis – that defleshing reduces seed predation by bruchid beetles by intercepting larvae – was rejected. Experiments in which manually defleshed seeds or entire fruits were incubated at different times showed that defleshing reduced bruchid infestation before fruit fall but not after fruit fall. The second hypothesis – that defleshing reduces cache pilferage by making seeds less conspicuous – was supported. An experiment in which intact fruits and manually defleshed seeds were placed in mimicked agouti caches and followed showed that seeds with flesh were pilfered at higher rates than defleshed seeds. The third hypothesis – that defleshing reduces post-dispersal infestation of cached seeds – was rejected. An experiment in which intact fruits and manually defleshed seeds were placed in mammal exclosures and later collected to assess infestation showed that burial reduced seed infestation but defleshing did not. Thus, seed defleshing reduced palm seed predation, but in a different way than previously believed. We also found that (1) bruchid beetles can be pre-dispersal rather than post-dispersal seed predators, (2) seed infestation by scolytid beetles may control bruchid larvae, and (3) scolytids rather than bruchids are the main invertebrate seed predators of this palm
Postdispersal seed predation and seed viability in forest soils: implications for the regeneration of tree species in Ethiopian church forests
Wassie Eshete, A. ; Bekele, T. ; Sterck, F.J. ; Teketay, D. ; Bongers, F. - \ 2010
African Journal of Ecology 48 (2010)2. - ISSN 0141-6707 - p. 461 - 471.
europaea ssp-cuspidata - tropical rain-forest - germination ecology - northern ethiopia - prunus-africana - fragments - distance - rodents - edge - microhabitat
Almost all dry Afromontane forests of Northern Ethiopia have been converted to agricultural, grazing or scrub lands except for small fragments left around churches ('Church forests'). Species regeneration in these forests is limited. We investigated (i) how intense postdispersal seed predation was in church forest, and if this seed predation varied with species and/or habitat, and (ii) for how long tree seeds maintained their viability while buried in forest soil. In the seed predation experiment, we monitored seeds of six tree species in four habitats for a period of 14 weeks (the peak seeding season). In the seed viability experiment, we assessed seed viability of five species in four habitats after being buried 6, 12, or 18 months. Ninety-two percent of the tree seeds were predated within 3.5 months. Predation was mainly dependent on species whereas habitat had a weaker effect. Seed viability decreased sharply with burial time in soil for all species except for Juniperus. To minimize seed availability limitation for regeneration of such species in the forest, the standing vegetation needs to be persistently managed and conserved for a continuous seed rain supply. Additional seed sowing, and seed and seedling protection (by e.g. animal exclosures) may increase successful regeneration of important species in these forests
Scatter hoarding by the Central American agouti: a test of optimal cache spacing theory
Gálvez, D. ; Kranstauber, B. ; Kays, R.W. ; Jansen, P.A. - \ 2009
Animal Behaviour 78 (2009)6. - ISSN 0003-3472 - p. 1327 - 1333.
density-dependent survival - barro-colorado island - dipodomys-merriami - pilferage - dispersal - squirrels - behavior - palm - forests - rodents
Optimal cache spacing theory predicts that scatter-hoarding animals store food at a density that balances the gains of reducing cache robbery against the costs of spacing out caches further. We tested the key prediction that cache robbery and cache spacing increase with the economic value of food: the ratio of food to consumer abundance. We quantified cache pilferage and cache spacing by the Central American agouti, Dasyprocta punctata, in the tropical forest of Barro Colorado Island, Panama, across 10 1 ha plots that encompassed a more than100-fold range in the availability of Astrocaryum palm seeds, the agouti's principal food. We found that caches were pilfered at higher rates in plots with lower seed availability, and that agoutis cached seeds further away and into lower densities where seed availability was lower. Food scarcity apparently increased the pressure of food competitors on caches, stimulating agoutis to put more effort into caching seeds to create lower cache densities, fully consistent with theory. We conclude that the optimal cache density depends not only on the nutritional value of food but also on the economic value, which may vary in space as well as time
Establishment limitation of holm oak (Quercus ilex subsp. Ballota (Desf.) Samp.) in a Mediterranean savanna - forest ecosystem
Smit, C. ; Díaz, M. ; Jansen, P.A. - \ 2009
Annals of Forest Science 66 (2009)5. - ISSN 1286-4560 - p. 511p1 - 511p7.
spatial-patterns - seed dispersal - food - regeneration - recruitment - rodents - shrubs - acorns - landscape - pilferage
¿Tree recruitment in Mediterranean savannas is generally hampered, in contrast with the original oak forests where these savannas are derived from. We asked whether this difference in recruitment success can be explained by differential post-dispersal survival. For one year we monitored experimentally cached holm oak acorns in a savanna ¿ forest ecosystem in Central Spain, and recorded cache pilferage, type of pilferer, boar rooting, seedling emergence, seedling survival and the cause of mortality. ¿Cache pilferage was significantly lower in savanna (8%) than in forest (21%). However, the higher cache survival was more than offset by lower seedling emergence and, particularly, by nine times higher seedling mortality in savanna, mainly due to desiccation. Wild boar rooting did not differ between experimental caches and controls without acorns, indicating that individual cached acorns do not trigger rooting activity. ¿Our results indicate that the difference in post-dispersal survival between savanna and forest is due to lower emergence and, primarily, higher seedling mortality in savanna, not to higher cache pilferage. Absence of safe sites such as shrubs, abundantly present in the forest, may well explain the lack of recruitment in the savanna. Management measures appear necessary for long-term persistence of Mediterranean savannas in general
Kleine zoogdieren in de nabijheid van veehouderijen: risico's voor voedselveiligheid?
Meerburg, B.G. ; Kijlstra, A. - \ 2009
Zoogdier 20 (2009)2. - ISSN 0925-1006 - p. 24 - 25.
knaagdieren - soricidae - veehouderij - zoönosen - voedselveiligheid - risicofactoren - rodents - livestock farming - zoonoses - food safety - risk factors
Overzicht van onderzoek dat is gedaan naar de overdracht van ziekteverwekkers door kleine zoogdieren, zoals: Rodentia, Soricidae. Na overdracht op landbouwhuisdieren kunnen deze uiteindelijk bij de mens tot gezondheidsproblemen leiden
Variations in Ixodes ricinus Density and Borrelia Infections Associated with Cattle Introduced into a Woodland in The Netherlands
Gassner, F. ; Verbaarschot, P.G.H. ; Smallegange, R.C. ; Spitzen, J. ; Wieren, S.E. van; Takken, W. - \ 2008
Applied and Environmental Microbiology 74 (2008)23. - ISSN 0099-2240 - p. 7138 - 7144.
burgdorferi sensu-lato - lyme borreliosis - ticks acari - ixodidae - transmission - infestation - prevalence - rodents - ehrlichia - afzelii
The effect of introduced large herbivores on the abundance of Ixodes ricinus ticks and their Borrelia infections was studied in a natural woodland in The Netherlands. Oak and pine plots, either ungrazed or grazed by cattle, were selected. Ticks were collected weekly by blanket dragging. Borrelia infections were determined by PCR and restriction fragment length polymorphism. Rodent densities were estimated using mark-release-recapture methods. On occasion, the cattle were inspected for tick infestations. Meteorological data were recorded for each habitat. Significantly more ticks were collected in the ungrazed woodland than in the grazed woodland. The ungrazed oak habitat had higher tick densities than the pine habitat, while in the grazed habitats, tick densities were similar. Borrelia infection rates ranged from zero in larvae to 26% in nymphs to 33% in adult ticks, and B. afzelii, B. burgdorferi sensu stricto, B. garinii, and B. valaisiana were the species involved. Coinfections were found in five ticks. There was no effect of the presence of cattle on Borrelia infections in the ticks. In the ungrazed area, Borrelia infections in nymphs were significantly higher in the oak habitat than in the pine habitat. More mice were captured in the ungrazed area, and these had a significantly higher tick burden than mice from the grazed area. Tick burden on cattle was low. The results suggest that grazing has a negative effect on small rodents as well as on ticks but not on Borrelia infections. Implications of these results for management of woodland reserves and risk of Lyme disease are discussed
Evidence for scatter-hoarding in a tropical peat swamp forest in Malaysia
Meer, P.J. van der; Kunne, P.L.B. ; Brunsting, A.M.H. ; Dibor, L. ; Jansen, P.A. - \ 2008
Journal of Tropical Forest Science 20 (2008)4. - ISSN 0128-1283 - p. 340 - 343.
mast-fruiting dipterocarpaceae - rain-forest - seed-dispersal - french-guiana - recruitment - predation - australia - rodents - tree
|Toxoplasma in de varkenshouderij: bestrijding van knaagdieren noodzakelijk
Meerburg, B.G. - \ 2008
Dierplagen informatie 3 (2008)11. - ISSN 1388-137X - p. 5 - 5.
varkenshouderij - varkens - toxoplasma - knaagdierenbestrijding - knaagdieren - pig farming - pigs - rodent control - rodents
Voorkomen en verspreiding van Rabbit Haemorrhagic Disease en Myxomatose in Nederlandse konijnenpopulaties
Drees, J.M. ; Dekker, J.J.A. ; Lavazza, A. ; Cappucci, L. - \ 2007
Arnhem : Zoogdiervereniging VZZ (Rapport / Zoogdiervereniging VZZ nr. 2007.17)
konijnen - konijnenziekten - zoogdieren - knaagdieren - myxomatose - rabbit hemorrhagic disease virus - rabbits - rabbit diseases - mammals - rodents - myxomatosis - rabbit hemorrhagic disease virus
De sterke achteruitgang van het konijn in Nederland sinds 1990 is waarschijnlijk vooral een gevolg van (meer)jaarlijks terugkerende epidemieën van Rabbit Hemorrhagic Disease (RHD, in het Nederlands VHS genoemd) een dodelijke konijnenziekte, waaraan het dier heel plots sterft. Doordat het merendeel ondergronds doodgaat en er geen zieke dieren rondlopen, is het eerste optreden van RHD vaak onopgemerkt, maar de achteruitgang in de aantallen is overduidelijk. Dit onderzoek betreft het vóórkomen en de verspreiding van de rabbit haemorrhagic disease en myxomatose in Nederland.
Role of Rodents in transmission of Salmonella and Campylobacter
Meerburg, B.G. ; Kijlstra, A. - \ 2007
Journal of the Science of Food and Agriculture 87 (2007)15. - ISSN 0022-5142 - p. 2774 - 2781.
biologische landbouw - biologische voedingsmiddelen - voedselveiligheid - pathogenen - knaagdieren - knaagdierenbestrijding - organic farming - organic foods - food safety - pathogens - rodents - rodent control - infected poultry units - broiler flocks - risk-factors - enteritidis infection - mus-musculus - layer farms - house mouse - jejuni - mice - pigs
Salmonella and Campylobacter are generally regarded as the most important food-borne pathogens in the world. Reduction or elimination of these pathogens in the first part of the food chain (on the farm) is important to prevent disease among consumers of animal products. In organic farming, elimination becomes more difficult, as food animals are allowed outdoors and have easy access to potential sources of hazardous pathogens. Whilst rodents are often associated by organic farmers with infrastructural damage and eating or spoiling of stored feed and products, their zoonotic risks are frequently underestimated. They can amplify the number of pathogens in the environment and transfer them to food animals. Thus organic farmers should be aware of the need for rodent control from a food safety perspective. Preferably, rodent control should form an integral part of a total package of hygiene measures to prevent transfer of food-borne pathogens. These should also include e.g. control of wild birds and flies and obligatory disinfection of boots/clothes and equipment for farm workers and visitors.
Kleine zoogdieren op biologische varkensbedrijven: voedselveiligheidsrisisco
Meerburg, B.G. - \ 2006
Dierplagen informatie 2006 (2006)3. - ISSN 1388-137X - p. 16 - 17.
biologische landbouw - knaagdieren - knaagdierenbestrijding - voedselveiligheid - varkenshouderij - organic farming - rodents - rodent control - food safety - pig farming
Spitsmuizen en andere knaagdieren op het boerenbedrijf kunnen bijdragen aan de biodiversiteit op het bedrijf. Maar ze kunnen ook ziekten als Salmonella, Campylobacter en Toxoplasma Gondii overdragen op andere zoogdieren.
|Zoonotische risico's van knaagdieren in de veehouderij = Zoonotic risk of rodents in livestock production
Meerburg, B.G. ; Kijlstra, A. - \ 2006
Tijdschrift voor Diergeneeskunde 131 (2006)12. - ISSN 0040-7453 - p. 445 - 447.
salmonella - campylobacter - toxoplasma gondii - ziektedistributie - knaagdieren - ziekteoverdracht - knaagdierenbestrijding - veehouderijbedrijven - dierenwelzijn - disease distribution - rodents - disease transmission - rodent control - livestock enterprises - animal welfare - toxoplasma-gondii
Besides causing economic losses, rodents (rats and mice) in animal farms can transfer pathogens to food animals. In turn, these pathogens can be transferred to humans by food animals, which can cause hazards for food safety. This article describes the risks of rodent presence on-farm and transfer of the bacteria Salmonella and Campylobacter and the parasite Toxoplasma gondii. Attention is also paid to ethical aspects of rodent control.