Purification of lily symptomless virus. Use and value of antisera against intact and pyrrolidine-degraded virus for testing lilies and tulips

Lily symptomless virus (LSV) was purified by clarification with chloroform, precipitation with polyethylene glycol and NaCl, and differential centrifugation. The influence of the source material and some buffers on virus yields were determined.Antisera were prepared against intact and pyrrolidine degraded LSV. It was concluded that intact and degraded LSV have very few antigenic determinants in common or none at all. The sensitivities of the micro-precipitin test and the single immunodiffusion drop test were about the same, but lower than that of electron microscopy.In the testing of lilies for LSV the most reliable results in leaves were obtained during the period from two weeks after flowering until close to the end of the growing season, and in leaves growing at a level about one-fourth of the distance from the top of the stem. In contrast to secondary infections, primary infections were detected more successfully in stored bulbs than in leaves taken from plants in the preceding growing season.In the testing of tulips, LSV was detected better in flowers than in leaves. Detection of primary infections was almost impossible. Except for those with a pink flower, experimentally infected tulips remained symptomless.Samenvatting Het symptoomloos lelievirus (LSV) were gezuiverd door klaring met chloroform, precipitatie met polyethyleenglycol en NaCl en differentieel centrifugeren. Het effect van het uitgangsmateriaal en enkele buffers op de virusopbrengst werd nagegaan.Antisera werden bereid tegen intact en met pyrrolidine afgebroken LSV. Geconcludeerd were dat intact en afgebroken LSV geen of slechts enkele antigene determinanten gemeenschappelijk hebben.De gevoeligheid van de microprecipitatietoets en de enkele immuno-diffusiedruppeltoets is ongeveer gelijk. Met het elektronenmicroscoop kunnen echter lagere virusconcentraties worden aangetoond.Het toetsen van lelies op LSV gaf de betrouwbaarste resultaten met bladeren die op ongeveer driekwart hoogte van de stengel groeien en in de periode tussen 2 weken na de bloei en vrijwel het einde van het groeiseizoen worden geplukt. Primaire infecties konden, in tegenstelling tot secundaire infecties, beter worden vastgesteld aan bolmateriaal tijdens de bewaring dan aan bladeren in het voorafgaande groeiseizoen.Bij het toetsen van tulpen werd het LSV met grotere zekerheid vastgesteld in bloemen dan in bladeren. Het vaststellen van primaire infecties was bijna niet mogelijk. Na infectie van tulpen met LSV vertoonden alleen die met een rose bloemkleur symptomen.     

Evaluation of the effects of animal age, concurrent bacterial infection, and pathogenicity of porcine reproductive and respiratory syndrome virus on virus concentration in pigs

OBJECTIVE: To evaluate the influences of animal age, bacterial coinfection, and porcine reproductive and respiratory syndrome virus (PRRSV) isolate pathogenicity on virus concentration in pigs. ANIMALS: Twenty-one 2-month-old pigs and eighteen 6-month-old pigs. PROCEDURE: Pigs were grouped according to age and infected with mildly virulent or virulent isolates of PRRSV. The role of concurrent bacterial infection was assessed by infecting selected pigs with Mycoplasma hyopneumoniae 21 days prior to inoculation with PRRSV. On alternating days, blood and swab specimens of nasal secretions and oropharyngeal secretions were collected. On day 21 after inoculation with PRRSV, selected tissues were harvested. Concentrations of PRRSV were determined by use of quantitative real-time PCR and expressed in units of TCID(50) per milliliter (sera and swab specimens) or TCID(50) per gram (tissue specimens). RESULTS: Concentrations of virus were higher in blood and tonsils of pigs infected with virulent PRRSV. Pigs infected with virulent PRRSV and M hyopneumoniae had significantly higher concentrations of viral RNA in lymphoid and tonsillar tissue. Coinfection with M hyopneumoniae resulted in a higher viral load in oropharyngeal swab specimens and blood samples, independent of virulence of the PRRSV isolate. Two-month-old pigs had significantly higher viral loads in lymph nodes, lungs, and tracheal swab specimens than did 6-month-old pigs, independent of virulence of the PRRSV isolate. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple factors affect PRRSV concentration in pigs, including pathogenicity of the PRRSV isolate, age, and concurrent infection with M hyopneumoniae.     

Metapopulation dynamics and a landscape approach to conservation of lowland water voles (<Emphasis Type="Italic">Arvicola amphibius</Emphasis>)

Effective conservation management for species that function as metapopulations requires an understanding of population dynamics at the landscape scale. The water vole, Arvicola amphibius, is one such species. Water voles have recently undergone a significant decline in the UK, as a result of habitat loss and predation from the introduced American mink, Neovison vison. Large reed bed and grazing marsh sites can provide refuge habitats for water voles from mink predation, in which case populations within these sites could sustain metapopulations in the surrounding landscape where conditions are less favourable. We carried out a study using a stochastic patch occupancy model to determine the long term viability of water vole metapopulations in the wider landscape around a series of extensive reed bed and grazing marsh sites designated as National Key Sites for water voles. The results of our model simulations show that a large protected core site, or mainland, is essential in maintaining the long term viability of these systems. Our results also show how these metapopulations could be enhanced by increasing patch numbers through habitat creation and/or restoration and suggest what the minimum effective size of created or restored patches should be. The study shows how population modelling can provide insight into some effective practical ways of enhancing the viability of water vole metapopulations at the landscape scale. Furthermore it demonstrates that extensive wetlands are an appropriate focus for water vole conservation measures.     

Predictors of Extreme Negative Feelings Toward Coyote in Newfoundland

Human–coyote interactions have occurred since the arrival of the species to the island of Newfoundland in 1985. A mail survey (N = 786) of Newfoundland residents was conducted in 2008. The survey explored negative feelings toward coyotes. A four stage hierarchical multiple regression model examined how the dependent variable, “feelings,” was influenced by four independent blocks of variables: “existence beliefs,” “impact beliefs,” “fear,” and “experience and demographic characteristics.” Together the predictors explained 50% of the variability, with existence beliefs accounting for most of the variation (ΔR² = . 45), followed by impact beliefs (ΔR² = .024) and fear (ΔR² = .018). The experience-demographic block of variables accounted for minimal influence (ΔR² = .003) and was not statistically significant. The remaining variability might be explained by emotions. When exploring human–wildlife interactions it is important to understand the role of affect in the formation of attitudes as feelings influence the tolerance and ultimately the willingness to coexist with wildlife.     

Dental microwear of sympatric rodent species sampled across habitats in southern Africa: Implications for environmental influence

Dental microwear textures have proven to be a valuable tool for reconstructing the diets of a wide assortment of fossil vertebrates. Nevertheless, some studies have recently questioned the efficacy of this approach, suggesting that aspects of habitat unrelated to food preference, especially environmental grit load, might have a confounding effect on microwear patterning that obscures the diet signal. Here we evaluate this hypothesis by examining microwear textures of 3 extant sympatric rodent species that vary in diet breadth and are found in a variety of habitat types: Mastomys coucha, Micaelamys namaquensis and Rhabdomys pumilio. We sample each of these species from 3 distinct environmental settings in southern Africa that differ in rainfall and vegetative cover: Nama‐Karoo shrublands (semi‐desert) and Dry Highveld grasslands in the Free State Province of South Africa, and Afromontane (wet) grasslands in the highlands of Lesotho. While differences between habitat types are evident for some of the species, inconsistency in the pattern suggests that the microwear signal is driven by variation in foods eaten rather than grit‐level per se. It is clear that, at least for species and habitats sampled in the current study, environmental grit load does not swamp diet‐related microwear signatures.     

A novel method to identify herds with an increased probability of disease introduction due to animal trade

In the design of surveillance, there is often a desire to target high risk herds. Such risk-based approaches result in better allocation of resources and improve the performance of surveillance activities. For many contagious animal diseases, movement of live animals is a main route of transmission, and because of this, herds that purchase many live animals or have a large contact network due to trade can be seen as a high risk stratum of the population. This paper presents a new method to assess herd disease risk in animal movement networks. It is an improvement to current network measures that takes direction, temporal order, and also movement size and probability of disease into account. In the study, the method was used to calculate a probability of disease ratio (PDR) of herds in simulated datasets, and of real herds based on animal movement data from dairy herds included in a bulk milk survey for Coxiella burnetii. Known differences in probability of disease are easily incorporated in the calculations and the PDR was calculated while accounting for regional differences in probability of disease, and also by applying equal probability of disease throughout the population. Each herd's increased probability of disease due to purchase of animals was compared to both the average herd and herds within the same risk stratum. The results show that the PDR is able to capture the different circumstances related to disease prevalence and animal trade contact patterns. Comparison of results based on inclusion or exclusion of differences in risk also highlights how ignoring such differences can influence the ability to correctly identify high risk herds. The method shows a potential to be useful for risk-based surveillance, in the classification of herds in control programmes or to represent influential contacts in risk factor studies.