Host surveys, ixodid tick biology and transmission scenarios as related to the tick-borne pathogen, Ehrlichia canis     

Stich RW  Schaefer JJ  Bremer WG  Needham GR  Jittapalapong S 《Veterinary parasitology》2008,158(4):256-273

The ehrlichioses have been subject to increasing interest from veterinary and public health perspectives, but experimental studies of these diseases and their etiologic agents can be challenging. Ehrlichia canis, the primary etiologic agent of canine monocytic ehrlichiosis, is relatively well characterized and offers unique advantages and opportunities to study interactions between a monocytotropic pathogen and both its vertebrate and invertebrate hosts. Historically, advances in tick-borne disease control strategies have typically followed explication of tick-pathogen-vertebrate interactions, thus it is reasonable to expect novel, more sustainable approaches to control of these diseases as the transmission of their associated infections are investigated at the molecular through ecological levels. Better understanding of the interactions between E. canis and its canine and tick hosts would also elucidate similar interactions for other Ehrlichia species as well as the potential roles of canine sentinels, reservoirs and models of tick-borne zoonoses. This article summarizes natural exposure studies and experimental investigations of E. canis in the context of what is understood about biological vectors of tick-borne Anaplasmataceae.  相似文献   

Ribosomal RNA-based analysis of the bacterial flora from the conjunctivae of cattle with bovine keratoconjunctivitis (BKC)     

Hare WR  Hoyt PG  Hohn C  Higgins JA 《Veterinary microbiology》2008,131(3-4):358-368

Bovine keratoconjunctivitis (BKC), colloquially referred to as 'pinkeye', is a disease affecting cattle worldwide; it costs cattle producers millions of dollars in economic loss annually. While Moraxella spp. are the primary etiologic agent of pinkeye, surveys of flora from the conjunctivae of livestock from around the world have indicated that a variety of bacterial commensals occupy this niche. We used molecular biology-based methods to determine the composition of bacterial flora in the conjunctivae of normal dairy and beef cattle from Maryland (n=113), and beef cattle with clinical BKC from Louisiana (n=42). Three regimens were used: 16S rRNA PCR and DGGE analysis of amplicons; 16S rRNA PCR and cloning of amplicons into Escherichia coli followed by screening and sequencing of clones harboring inserts; and culture of bacteria on chromogenic agar followed by 16S rRNA PCR and sequencing. Most taxa were comprised of saprophytes found in the environment, such as Bacillus, Pantoea, E. coli, and Exiguobacterium. Moraxella spp. were infrequently observed. Some species, such as Propionibacterium acnes, represent taxa not previously associated with the conjunctivae. Bacillus pumilus and Bacillus licheniformis isolates from the conjunctivae of Maryland cattle were genetically distinct from isolates previously implicated in septic infections in cattle at the same location. We conclude that employing 16S rRNA-based methods for bacterial identification can be useful in defining the flora present in the conjunctivae of normal cattle, and those with BKC.  相似文献   

Characterization of a parainfluenza virus isolated from a bottlenose dolphin (Tursiops truncatus)     

Nollens HH  Wellehan JF  Saliki JT  Caseltine SL  Jensen ED  Van Bonn W  Venn-Watson S 《Veterinary microbiology》2008,128(3-4):231-242

A novel member of the parainfluenza virus family was identified in a bottlenose dolphin with respiratory disease. The case animal was a 19-year old male Atlantic bottlenose dolphin (Tursiops truncatus) that presented with signs of respiratory illness, including raspy, foul-odored breaths and cream-colored exudate from the blowhole. Focally extensive pyogranulomatous bronchointerstitial pneumonia with moderate numbers of intralesional yeast organisms was identified on histopathological examination. Other significant microscopic findings included multifocal erosive and ulcerative tracheitis and laryngitis consisting of active laryngeal lymphatic tissue and dilated glands with eosinophilic fluid. The cause of death was attributed to respiratory disease of unknown etiology. In addition to the postmortem isolation of Candida glabrata and mixed bacteria from lung tissue, a virus was isolated from two antemortem affected lung aspirates collected over a 2-month period and two postmortem samples (mediastinal lymph node and left lung tissue homogenate). The morphology of the virions on negative staining and transmission electron microscopy was consistent with that of paramyxoviruses. Two genomic fragments, comprising 532 and 419 nucleotides from the open reading frames that code for the viral polymerase and fusion protein, respectively, were amplified by polymerase chain reaction using degenerate primers. Phylogenetic analyses of the two viral RNA segments showed that the isolate comprised a novel virus strain, tentatively named T. truncatus parainfluenza virus type 1 (TtPIV-1). The virus is monophyletic with, but genetically distinct from, the various bovine parainfluenza virus type 3 strains.  相似文献   

Protein Content of Bulk Wheat from Near‐Infrared Reflectance of Individual Kernels     

Stephen R. Delwiche  William R. Hruschka 《Cereal Chemistry》2000,77(1):86-88

Protein content of wheat by near‐infrared (NIR) reflectance of bulk samples is routinely practiced. New instrumentation that permits automated NIR analysis of individual kernels is now available, with the potential for rapid NIR‐based determinations of color, disease, and protein content, all on a single kernel (sk) basis. In the event that the protein content of the bulk sample is needed rather than that of the individual kernels, the present study examines the feasibility of estimating bulk sample protein from sk spectral readings. On the basis of 318 wheat samples of 10 kernels per sample, encompassing five U.S. wheat classes, the study demonstrates that with as few as 300 kernels bulk sample protein content may be estimated by sk NIR reflectance spectra at an accuracy equivalent to conventional bulk kernel NIR instrumentation.  相似文献   

Delta Society identifies with one-health concept     

McCulloch WF  Norvell LJ 《Journal of the American Veterinary Medical Association》2007,231(8):1197

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Resistance management strategies in malaria vector mosquito control. A large-scale field trial in Southern Mexico     

Janet Hemingway  R. Patricia Penilla  Americo D. Rodriguez  Bronwen M. James  William Edge  Hilary Rogers  Mario H. Rodriguez 《Pest management science》1997,51(3):375-382

A resistance management programme comparing rotations, mosaics and single use of insecticides for residual house-spraying against the insect vectors of malaria is being carried out in Southern Mexico. The area was chosen because of its prior history of insecticide use, relatively sedentary vector, and physical features of the area which limit inward migration of insects to the study area. A high level of resistance to DDT and low levels of organophosphorus (OP), carbamate and pyrethroid resistance were detected by WHO discriminating-dose assays in field populations of Anopheles albimanus in the pre-spray period in the region where this resistance management project is being undertaken. After the first year of spraying, resistance, as measured by a discriminating-dose assay, was still at a high level for DDT and had risen for all the other insecticides. Biochemical assays showed that DDT resistance was primarily caused by elevated levels of glutathione S-transferase (GST) activity leading to increased rates of metabolism of DDT to DDE. The numbers of individuals with elevated GST and DDT resistance were well correlated, suggesting that this is the only major DDT resistance mechanism in this population. The carbamate resistance in this population was conferred by an altered acetylcholinesterase (AChE) mechanism. The level of resistance in bioassays correlated well with the frequency of individuals homozygous for the altered AChE allele. This suggests that the level of resistance conferred by this mechanism in its heterozygous state is below the level of detection of the bioassay. The low levels of OP and pyrethroid resistance could be conferred by either the elevated esterase or monooxygenase enzymes. The esterases, however, are elevated only with p-nitrophenyl acetate (PNPA), and are unlikely to be causing broad-spectrum OP resistance. The altered AChE mechanism may also be contributing to the OP but not the pyrethroid resistance. There were significant differences in some resistance gene frequencies for insects obtained by different indoor and outdoor trapping methods. To determine whether the different sampling methods were effectively sampling the same interbreeding population, RAPD analysis of insects obtained by different collection methods in different villages was undertaken. There was no observed variability in the RAPD patterns for the different mosquito samples with a number of primers. ©1997 SCI  相似文献   

Neonatal lamb mortality: major risk factors and the potential ameliorative role of melatonin     

Tom Flinn  David O.Kleemann  Alyce M.Swinbourne  Jennifer M.Kelly  Alice C.Weaver  Simon K.Walker  Kathryn L.Gatford  Karen L.Kind  William H.E.J.van Wettere 《畜牧与生物技术杂志(英文版)》2021,(2):451-461

High incidences of pre-weaning mortality continue to limit global sheep production, constituting a major economic and welfare concern. Despite significant advances in genetics, nutrition, and management, the proportion of lamb deaths has remained stable at 15–20% over the past four decades. There is mounting evidence that melatonin can improve outcomes in compromised ovine pregnancies via enhanced uterine bloodflow and neonatal neuroprotection. This review provides an overview of the major risk factors and underlying mechanisms involved in perinatal lamb mortality and discusses the potential of melatonin treatment as a remedial strategy. Supplementing pregnant ewes with melatonin enhances uterine bloodflow and fetal oxygenation, and potentially birthweight and neonatal thermogenic capacity. Melatonin freely crosses the ovine placenta and blood-brain barrier and provides neuroprotection to the fetal lamb during periods of chronic and acute hypoxia throughout gestation, with improved behavioural outcomes in hypoxic neonates. The current literature provides strong evidence that maternal melatonin treatment improves outcomes for lambs which experience compromised in utero development or prolonged parturition, though to date this has not been investigated in livestock production systems. As such there is a clear basis for continued research into the effects of maternal melatonin supplementation during gestation on pre-weaning survival under extensive production conditions.  相似文献   

A TECHNIQUE FOR MAGNETIC RESONANCE IMAGING OF EQUINE CADAVER SPECIMENS     

William R.  Widmer  DVM  MS  Kenneth A.  Buckwalter  MD MS  Michael A.  Hill  B. Vet.Med.  PhD  MRCVS  John F.  Fessler  DVM MS  Susan  Ivancevich  MD 《Veterinary radiology & ultrasound》1999,40(1):10-14

We tested an adaptation of a technique for performing magnetic resonance (MR) imaging of human cadaver limbs in the horse. The forelimbs from a normal horse were collected, frozen, and sealed with a paraffin-polymer combination prior to imaging with either a high- or midfield magnetic resonance scanner. Each forelimb was defrosted, scanned, and refrozen on two separate occasions. A five-point scale was used to evaluate the quality of each set of sagittal and transverse, T1-weighted images of each digit. There was no difference in image quality between first and second scans of either specimen (p > 0.05). We conclude that this technique allows investigators to bank tissue specimens for future magnetic resonance imaging without significant loss of image quality.  相似文献   

Using Economic Base Models to Explain New Trends in Rural Income     

Peter B. Nelson  William B. Beyers 《Growth and change》1998,29(3):295-318

The economics or urban and rural areas in the United States continue to experience change in their structure, leading to changes in their economic base. This paper argues that nontraditional sources of income, employment, and business activity have become more important in the economic base of rural areas. Current trends in rural parts of the western United States are used to document this argument. In spite of the decline in the relative or absolute important of traditional natural-resource-oriented industries in the rural West, in the 1990s this region is experiencing population growth rates well above those of the nation as whole. This reversal of development experience from the 1990s is analyzed empirically, and extended economic base models are proposed to capture forces which now are found to be of growing significance in explaining current development trends in western rural economics.  相似文献   

Factors and Correlates of Employment Growth in the Canadian Urban System, 1971–1991     

William J. Coffey  Richard G. Shearmur 《Growth and change》1998,29(1):44-66

The objective of this paper is to examine a number of hypotheses concerning the factors or correlates of employment growth in the Canadian urban system—a set of 152 urban areas having populations of more than ten thousand inhabitants which comprises 77.4 percent of the national population. Do observed patterns of sectoral employment growth obey some sort of underlying logic? More specifically, do the rates of employment growth that are found in individual urban areas vary significantly according to one or more of the following attributes of an urban area: a) the region in which it is located; b) its population size; c) its relative proximity to a major metropolitan area; d) its socioeconomic characteristics? While approaches involving a, e and f yield promising results, it is clear that there are few immutable laws that permit one to predict where employment growth will occur within the urban system. Perhaps the most fundamental characteristic of the analyses conducted involves the instability of the results from one decade to another; one decade’s category of winners is often the other decade’s category of losers.  相似文献