Ecologically-Based Management of Rodent Pests

Farm Management,

Strategier til giftfri bekæmpelse af rotter og mus

I nærværende delprojekt er første fase en kortlægning, der identificerer de faktorer i systemer med udendørs svineproduktion i Danmark, som kan have betydning for forekomst af potentielle skadedyr og problemer i den forbindelse. Kortlægningen er blevet udført i form af en spørgeskemaundersøgelse. På grundlag af kortlægningen gennemføres efterfølgende en detaljeret beskrivelse af rotters (og eventuelle andre gnaveres) økologi i to udvalgte økologiske svinebedrifter, og der skal udarbejdes strategier til bekæmpelse af gnavere med fokus på rotter. I spørgeskemaet blev der spurgt om forekomst af og problemer med evt. skadedyr blandt pattedyr, fugle og insekter/mider. I denne rapport fokuseres på gnaverne og med hovedvægt på rotterne. Baggrunden for dette er, at der ifølge EU-bestemmelser kun må bruges gift, hvis det kan sikres, at den ikke indgår i fødekæden. Grise kan godt æde rotter og mus. Ifølge dansk lovgivning skal rotter bekæmpes overalt, og i øvrigt er bekæmpelsen et kommunalt anliggende (se Miljøbeskyttelsesloven 2001). Rotter og mus kan overføre smitte (f.eks. Salmonella, Leptospira, Yersinia, Erysipelothrix rhusiopathiae (rødsygebakterien) og Brachyspira hyodysenteria) (Feenstra., et al 2000; Gratz, 1994) til svinene, så alene af den grund kan der være en berettiget grund til at foretage bekæmpelse. Rottebekæmpelse skal udføres af autoriserede personer, mens musebekæmpelse kan udføres af landmanden selv. En stigende bestand af rotter (eller mus) vil utvivlsomt medføre betydelige risici for smitte med ovennævnte sygdomme. Traditionel bekæmpelse med gift er uønsket i økologisk husdyrproduktion. Det er derfor vigtigt, at der udvikles effektive, men giftfrie strategier til bekæmpelse af gnavere i økologisk svineproduktion. Viden om de faktorer, der påvirker niveauet af rotter i økologisk svineproduktion, er meget mangelfuld. I økologisk landbrug er brug af antikoagulanter til rottebekæmpelse tilladt under visse forudsætninger. Uanset hvem der udfører rotte- eller musebekæmpelse, er der en skjult konflikt, så snart der anvendes kemisk bekæmpelse

Livestock grazing intensity affects abundance of Common shrews (Sorex araneus) in two meadows in Denmark

<p>Abstract</p> <p>Background</p> <p>Current nature conservation in semi-natural grasslands often includes grazing and hay cutting, as well as the abandonment of draining. Semi-natural grassland and in particular meadows constitute important habitat type for a large number of animal species in today's fragmented and intensively cultivated landscape of Europe. Here we focus on the population characteristics of Common shrews <it>Sorex araneus </it>in relation to livestock grazing intensity in two wet meadows in western Denmark.</p> <p>Results</p> <p>High grazing intensity had a significant negative effect on Common shrew number compared to low grazing intensity and no grazing. Common shrew abundance was generally, but not significantly, higher on the low grazing intensity plots than on the ungrazed controls. No differences in body mass, sex ratio, or reproductive output between Common shrew individuals from the various grazing treatments were found.</p> <p>Conclusion</p> <p>No negative effects of low intensity grazing on Common shrew abundance were found compared to the ungrazed control. Low intensity grazing thus seems a suitable management regime for Common shrews, when grazing is needed as part of the meadow management scheme. High intensity grazing on the other hand is not a suitable management tool.</p

The Bioeconomics of Controlling an African Rodent Pest Species

The paper treats the economy of controlling an African pest rodent, the multimammate rat, causing major damage in maize production. An ecological population model is presented and used as a basis for the economic analyses carried out at the village level using data from Tanzania. This model incorporates both density-dependent and density-independent (stochastic) factors. Rodents are controlled by applying poison, and the economic benefits depend on the income from maize production minus the costs for maize production, fertiliser and poison. We analyse how the net present value of maize production is affected by various rodent control strategies, by varying the duration and timing of rodenticide application. Our numerical results suggest that, in association with fertiliser, it is economically beneficial to control the rodent population. In general the most rewarding duration of controlling the rodent population is 3-4 months every year, and especially at the end of the dry season/beginning of rainy season. The paper demonstrates that changing from todays practice of symptomatic treatment when heavy rodent damage is noticed to a practice where the calendar is emphasised, may substantially improve the economic conditions for the maize producing farmers. This main conclusion is quite robust and not much affected by changing prices and costs of the maize production.bio-economics; pest control; multimammate rat; crop production

Geographic distribution and ecological niche of plague in sub-Saharan Africa

<p>Abstract</p> <p>Background</p> <p>Plague is a rapidly progressing, serious illness in humans that is likely to be fatal if not treated. It remains a public health threat, especially in sub-Saharan Africa. In spite of plague's highly focal nature, a thorough ecological understanding of the general distribution pattern of plague across sub-Saharan Africa has not been established to date. In this study, we used human plague data from sub-Saharan Africa for 1970–2007 in an ecological niche modeling framework to explore the potential geographic distribution of plague and its ecological requirements across Africa.</p> <p>Results</p> <p>We predict a broad potential distributional area of plague occurrences across sub-Saharan Africa. General tests of model's transferability suggest that our model can anticipate the potential distribution of plague occurrences in Madagascar and northern Africa. However, generality and predictive ability tests using regional subsets of occurrence points demonstrate the models to be unable to predict independent occurrence points outside the training region accurately. Visualizations show plague to occur in diverse landscapes under wide ranges of environmental conditions.</p> <p>Conclusion</p> <p>We conclude that the typical focality of plague, observed in sub-Saharan Africa, is not related to fragmented and insular environmental conditions manifested at a coarse continental scale. However, our approach provides a foundation for testing hypotheses concerning focal distribution areas of plague and their links with historical and environmental factors.</p

Anti-erosion stone bunds influence rodent dynamics and crop damage in Ethiopian highlands

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Why Hantavirus Prevalence Does Not Always Increase With Host Density : Modeling the Role of Host Spatial Behavior and Maternal Antibodies

For wildlife diseases, one often relies on host density to predict host infection prevalence and the subsequent force of infection to humans in the case of zoonoses. Indeed, if transmission is mainly indirect, i.e., by way of the environment, the force of infection is expected to increase with host density, yet the laborious field data supporting this theoretical claim are often absent. Hantaviruses are among those zoonoses that have been studied extensively over the past decades, as they pose a significant threat to humans. In Europe, the most widespread hantavirus is the Puumala virus (PUUV), which is carried by the bank vole and causes nephropathia epidemica (NE) in humans. Extensive field campaigns have been carried out in Central Finland to shed light on this supposed relationship between bank vole density and PUUV prevalence and to identify other drivers for the infection dynamics. This resulted in the surprising observation that the relationship between bank vole density and PUUV prevalence is not purely monotonic on an annual basis, contrary to what previous models predicted: a higher vole density does not necessary result in a higher infection prevalence, nor in an increased number of humans reported having NE. Here, we advance a novel individual-based spatially-explicit model which takes into account the immunity provided by maternal antibodies and which simulates the spatial behavior of the host, both possible causes for this discrepancy that were not accounted for in previous models. We show that the reduced prevalence in peak years can be attributed to transient immunity, and that the density-dependent spatial vole behavior, i.e., the fact that home ranges are smaller in high density years, plays only a minor role. The applicability of the model is not limited to the study and prediction of PUUV (and NE) occurrence in Europe, as it could be easily adapted to model other rodent-borne diseases, either with indirect or direct transmission.Peer reviewe

Mycobacteria in Terrestrial Small Mammals on Cattle Farms in Tanzania

The control of bovine tuberculosis and atypical mycobacterioses in cattle in developing countries is important but difficult because of the existence of wildlife reservoirs. In cattle farms in Tanzania, mycobacteria were detected in 7.3% of 645 small mammals and in cow's milk. The cattle farms were divided into “reacting” and “nonreacting” farms, based on tuberculin tests, and more mycobacteria were present in insectivores collected in reacting farms as compared to nonreacting farms. More mycobacteria were also present in insectivores as compared to rodents. All mycobacteria detected by culture and PCR in the small mammals were atypical mycobacteria. Analysis of the presence of mycobacteria in relation to the reactor status of the cattle farms does not exclude transmission between small mammals and cattle but indicates that transmission to cattle from another source of infection is more likely. However, because of the high prevalence of mycobacteria in some small mammal species, these infected animals can pose a risk to humans, especially in areas with a high HIV-prevalence as is the case in Tanzania

Sympatric Occurrence of 3 Arenaviruses, Tanzania

To determine the specificity of Morogoro virus for its reservoir host, we studied its host range and genetic diversity in Tanzania. We found that 2 rodent species other than Mastomys natalensis mice carry arenaviruses. Analysis of 340 nt of the viral RNA polymerase gene showed sympatric occurrence of 3 distinct arenaviruses