Evaluation of factors associated with positive IgM capture ELISA results in equids with clinical signs compatible with West Nile virus infection: 1,017 cases (2003)

OBJECTIVE: To describe the prevalence of West Nile virus (WNV) infection and evaluate factors associated with positive IgM capture ELISA results in equids with clinical signs compatible with WNV infection. DESIGN: Retrospective case series. SAMPLE POPULATION: Laboratory submission forms from 1,104 equids tested for WNV in Colorado in 2003. PROCEDURES: Submission forms accompanying samples submitted for detection of WNV via IgM capture ELISA were obtained from the Colorado state veterinarian and diagnostic laboratories performing the tests. Data on signalment, clinical signs, history of vaccination against WNV, and assay results were collected from laboratory submission forms. Equids with clinical signs compatible with WNV infection in which IgM capture ELISA results were positive were considered as case equids. RESULTS: 1,104 equids were tested for WNV; 1,017 (92.1%) had clinical signs compatible with WNV infection. Among equids with clinical signs compatible with WNV infection, the odds of testing positive for WNV via IgM capture ELISA were lower in males and in vaccinated equids and higher in equids with moderate and severe illness, compared with females, unvaccinated equids, and equids with mild illness. CONCLUSIONS AND CLINICAL RELEVANCE: Among equids with clinical signs compatible with WNV infection, vaccination against WNV, severity of clinical signs, duration of illness, and region in Colorado were associated with increased risk of having a positive IgM capture ELISA result.     

Predisposing factors for small colon impaction in horses and outcome of medical and surgical treatment: 44 cases (1999-2004)

OBJECTIVE: To identify factors associated with development of small colon impaction in horses and with selection of medical versus surgical treatment and to determine the prognosis for affected horses following medical or surgical management. DESIGN: Retrospective case series. ANIMALS: 44 horses with primary impaction of the small colon. PROCEDURES: Medical records were reviewed for signalment, history, clinical findings, treatment (medical vs surgical), hospitalization time, and outcome. For comparison purposes, the same information was collected for 83 horses with primary impaction of the large colon. RESULTS: Diarrhea was the only factor found to be associated with development of small colon impaction. Horses with small colon impaction were 10.8 times as likely to have diarrhea at the time of initial examination as were horses with large colon impaction. Abdominal distension was the only factor associated with use of surgical versus medical treatment. Horses with small colon impaction that were treated surgically were 5.2 times as likely to have had abdominal distension at the time of admission as were horses with small colon impaction that were treated medically. Overall, 21 of 23 (91%) horses treated medically and 20 of 21 (95%) horses treated surgically survived to discharge. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that diarrhea may be a risk factor for development of small colon impaction and that horses with small colon impaction that have abdominal distension at the time of initial examination are more likely to require surgical than medical treatment.     

Foliar application of GA3 during terminal long-shoot bud development stimulates shoot apical meristem activity in Pinus sylvestris seedlings

The effect of exogenous gibberellin (GA3) on shoot apical meristem activity in conifer vegetative buds was investigated by spraying 0 or 0.1% GA3 on the foliage of first-year Scots pine (Pinus sylvestris L.) seedlings twice weekly for 9 weeks during development of the terminal long-shoot bud. Exogenous GA3 promoted mitotic activity in the apical zone, thereby increasing both the rate and duration of cataphyll formation and giving rise to a higher and wider apical meristem. The increase in number of cataphylls increased the number of axillary meristems, which developed as short-shoot buds.     

Fumonisin production and bioavailability to maize seedlings grown from seeds inoculated with Fusarium verticillioides and grown in natural soils

The fungus Fusarium verticillioides infects maize and produces fumonisins. The purpose of this study was to determine the ability of F. verticillioides to produce fumonisins in synthetic and natural soils and their biological availability to maize roots. Maize seeds were inoculated with a pathogenic strain of F. verticillioides (MRC826) and planted in synthetic and three different natural soils. There were statistically significant reductions in stalk weight and root mass and increased leaf lesions in the MRC826-treated seedlings in all soil types. Fumonisins were detected in all of the soils of seedlings grown from MRC826-inoculated seeds. The fumonisin produced in the soils was biologically available to seedlings as demonstrated by the statistically significant elevation of free sphingoid bases and sphingoid base 1-phosphates in their roots. These results indicate that F. verticillioides produced fumonisins in the autoclaved synthetic and natural soils and that the fumonisin produced is biologically available on the basis of evidence of inhibition of ceramide synthase.     

Evaluation of barcoded magnetic bead–based immunoassays for the simultaneous detection of feline leukemia virus antigen and antibody against feline immunodeficiency virus

Testing platforms that leverage automation, require minimal sample volume, and enable various tests to be performed simultaneously on a single sample have the potential to improve workflow and efficiency in veterinary diagnostic laboratories. We evaluated a barcoded magnetic bead (BMB) technology using established immunoassays for detection of feline leukemia virus (FeLV) p27 antigen and antibody against feline immunodeficiency virus (FIV). Analytical sensitivity, limit of blank, and limit of detection were used to establish a functional sensitivity of 1.00 ng/mL of inactivated FeLV antigen and 35.7 ng/mL of anti-FIV monoclonal antibody. Common interferents, such as hemoglobin, lipid, and bilirubin, were not found to interfere with the performance of the assay. Intra- and inter-assay CVs were <13% for both assays using manufactured samples. Using a set of 116 feline samples, the diagnostic accuracy of our multiplex assay was 100% compared to reference assays. Performance in a convenience set of 1,000 feline samples submitted to a commercial diagnostic laboratory revealed a proportion of positive results of 1.3% for FeLV and 3.7% for FIV. BMB technology should enable rapid screening of samples for various markers in a single immunoassay well.     

Cyclic hematopoiesis in a mixed-breed dog: case report and brief review

An 8-wk-old, male, mixed-breed puppy was adopted from a rescue organization. From the time of adoption, the puppy suffered episodes of illness affecting various organ systems, which resolved with supportive therapy but relapsed once medical therapy was discontinued. Review of the hematologic data revealed cyclic fluctuations in circulating blood cells. Cyclicity was most prominent in neutrophils, with recurrent severe neutropenia. Neutropenic episodes lasted 5–6 d, with regular cycles of 11–14 d between nadir neutrophil counts. Genetic testing determined that the patient was homozygous mutant for the frameshift mutation in the adaptor protein complex 3 β-subunit (AP3B1) gene, originally identified in gray collies with cyclic hematopoiesis (CH). Pedigree information was not available, but the patient’s features were phenotypically distinct from those of collies. We describe here a case of the AP3B1 mutation in a mixed-breed dog that did not resemble a collie, undescribed previously, to our knowledge. Our findings indicate that the AP3B1 mutation and CH are present within the general canine population and are not restricted to collies.     

Hypersensitive-like reaction conferred by the Mex-1 resistance gene against Meloidogyne exigua in coffee

The response of a susceptible coffee cultivar (Caturra) to infection by the root-knot nematode Meloidogyne exigua was compared histologically with that of cv. Iapar 59 possessing the recently identified Mex-1 resistance gene. The reproductive behaviour of the nematode was also compared in the two cultivars. Penetration and development in resistant plants were reduced in comparison with susceptible plants. Several cell features, including dark-stained cytoplasm and altered organelle structure, were observed in the resistant cultivar, indicating a hypersensitive-like (HR) response of the infested host cells. Features of giant cells were sometimes found beside necrotic-like areas, but the corresponding feeding sites were frequently associated with nematodes displaying abnormal shape. Six weeks after inoculation, root systems of cv. Caturra contained significantly more nematodes than those of cv. Iapar 59 (mean values 1574 and 41, respectively). The susceptible cultivar presented a minimum of 11 galls per plant, compared with only one or two galls per plant in the resistant cultivar. The findings are discussed in the context of plant–pathogen interactions.     

Optimizing livestock manure applications to reduce nitrate and ammonia pollution:scenario analysis using the MANNER model

Abstract. Measures to reduce ammonia (NH₃) emissions by incorporating livestock manures into the soil may increase the potential for nitrate (NO₃^‐) leaching. The Manure Evaluation Routine (MANNER) model estimates the amount of N available to crops following livestock manure applications after calculating losses due to NH₃ volatilization and NO₃^‐ leaching. The main objective of this study was to use the MANNER model to quantify the impact on NO₃^‐ leaching of introducing measures to reduce NH₃ emissions, following application of livestock manures. The data produced were also used to make preliminary estimates of the likely effect of selected NH₃ abatement techniques on the potential for nitrous oxide (N₂O) emissions. At typical UK rates of application, the potential for increased NO₃^‐ leaching following either injection of slurry or rapid incorporation of solid manures was greatest for broiler/turkey manure (22–58 kg N ha^–1) and least for straw‐based cattle manure (6–10 kg N ha^–1). The results suggest that in order to avoid substantially increasing the potential for NO₃^‐ leaching as a consequence of NH₃ abatement, livestock manures should not be applied by low NH₃ emission techniques prior to autumn‐sown crops in the UK. Instead, low‐emission applications should be made from October onwards to grassland and where possible, late autumn‐sown combinable crops or to arable land which will be planted in the spring. However, in several areas of England and Wales there is currently insufficient land planted to spring crops on which to incorporate the livestock manures produced in those areas.     

Susceptibility of Eucalyptus globulus ssp. globulus to sawfly (Perga affinis ssp. insularis) attack and its potential impact on plantation productivity

Sawflies (Perga species) are leaf-damaging pests of the major plantation tree species Eucalyptus globulus ssp. globulus. This work describes the patterns of quantitative genetic variation in susceptibility to attack by Perga affinis ssp. insularis, based on data from a large open-pollinated trial containing genetic material from throughout the geographic range of E. globulus ssp. globulus. Forty three per cent of the trees in the trial exhibited damage from sawflies in either their sixth or seventh growth seasons. The incidence of damage was genetically based, with significant variation between geographic races of E. globulus ssp. globulus and highly heritable (h²=0.43±0.05) variation in damage incidence within races. Susceptibility to sawfly damage significantly affects plant fitness with both genetic and environmental correlations demonstrating that sawfly damage causes slow growth and increased mortality of trees. Mild and severe sawfly damage resulted in 16 and 31% reduction in the basal area of surviving trees, and the effect was consistent across races and families. Based on this data, we propose a model predicting relative plantation productivity of races of different susceptibility under different infestation regimes.     

High resolution temporal variation in wood properties in irrigated and nonirrigated Eucalyptus globulus

? Environmental determinants of wood properties variation were examined in Eucalyptus globulus, a globally important hardwood plantation species, in southern Tasmania, Australia.

? Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees.

? Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees.

? Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated.