Differential Responses to Pea Bacterial Blight in Stems, Leaves and Pods Under Glasshouse and Field Conditions

Resistance to pea bacterial blight (Pseudomonas syringae pv. pisi) in different plant parts was assessed in 19 Pisum sativum cultivars and landraces, carrying race-specific resistance genes (R-genes) and two Pisum abyssinicum accessions carrying race-nonspecific resistance. Stems, leaves and pods were inoculated with seven races of P. s. pv. pisi under glasshouse conditions. For both race-specific and nonspecific resistance, a resistant response in the stem was not always associated with resistance in leaf and pod. Race-specific genes conferred stem resistance consistently, however, there was variability in the responses of leaves and pods which depended on the matching R-gene and A-gene (avirulence gene in the pathogen) combination. R2 generally conferred resistance in all plant parts. R3 or R4 singly did not confer complete resistance in leaf and pod, however, R3 in combination with R2 or R4 enhanced leaf and pod resistance. Race-nonspecific resistance conferred stem resistance to all races, leaf and pod resistance to races 2, 5 and 7 and variable reactions in leaves and pods to races 1, 3, 4 and 6.Disease expression was also studied in the field under autumn/winter conditions. P. sativum cultivar, Kelvedon Wonder (with no R genes), and two P. abyssinicum accessions, were inoculated with the most frequent races in Europe under field conditions (2, 4 and 6). Kelvedon Wonder was very susceptible to all three races, whereas P. abyssinicum was much less affected. The combination of disease resistance with frost tolerance in P. abyssinicum enabled plants to survive through the winter. A breeding strategy combining race-nonspecific resistance derived from P. abyssinicum with race-specific R-genes should provide durable resistance under severe disease pressure.     

Putative uremic encephalopathy in horses: five cases (1978-1998)

OBJECTIVE: To determine historical, physical examination, clinicopathologic, and postmortem findings in horses with putative uremic encephalopathy. Design-Retrospective study. Animals-5 horses with renal failure and neurologic disease not attributable to abnormalities in any other organ system. PROCEDURE: Medical records from 1978 to 1998 were examined for horses with renal disease and neurologic signs not attributable to primary neurologic, hepatic, or other diseases. Signalment, history, physical examination findings, clinicopathologic data, renal ultrasonographic findings, and postmortem data were reviewed. RESULTS: Of 332 horses with renal disease, 5 met selection criteria. Historical findings, physical examination findings, clinicopathologic data, ultrasonographic data, and postmortem findings were consistent with chronic renal failure. Swollen astrocytes were detected in all 4 horses examined at necropsy. CONCLUSIONS AND CLINICAL RELEVANCE: A single criterion was not determined to be pathognomonic for uremic encephalopathy in horses. Uremic encephalopathy should be considered as a differential diagnosis in horses with evidence of chronic renal failure and encephalopathic neurologic sign not attributable to other causes. Astrocyte swelling, which was common to all 4 horses examined at necropsy, may serve as a microscopic indicator of uremic encephalopathy in horses.     

Population-based study of fecal shedding of Clostridium perfringens in broodmares and foals

OBJECTIVE: To determine the percentage of broodmares and foals that shed Clostridium perfringens in their feces and classify the genotypes of those isolates. DESIGN: Prospective cross-sectional study. ANIMALS: 128 broodmares and their foals on 6 equine premises. PROCEDURES: Anaerobic and aerobic bacteriologic cultures were performed on feces collected 3 times from broodmares and foals. All isolates of C. perfringens were genotyped. RESULTS: Clostridium perfringens was isolated from the feces of 90% of 3-day-old foals and 64% of foals at 8 to 12 hours of age. A lower percentage of broodmares and 1- to 2-month-old foals shed C. perfringens in their feces, compared with neonatal foals. Among samples with positive results, C. perfringens type A was the most common genotype identified (85%); C. perfringens type A with the beta2 toxin gene was identified in 12% of samples, C. perfringens type A with the enterotoxin gene was identified in 2.1% of samples, and C. perfringens type C was identified in < 1% of samples. CONCLUSIONS AND CLINICAL RELEVANCE: Clostridium perfringens was identified from the feces of all but 6 foals by 3 days of age and is likely part of the normal microflora of neonatal foals. Most isolates from broodmares and foals are C. perfringens type A; thus, the clinical relevance of culture results alone is questionable. Clostridium perfringens type C, which has been associated with neonatal enterocolitis, is rarely found in the feces of horses.     

Effects of dietary flaxseed oil supplementation on equine plasma fatty acid concentrations and whole blood platelet aggregation

An 18-week feeding trial was performed to investigate the effects of an omega-3 (n-3) fatty acid-enriched ration on plasma fatty acid concentrations and platelet aggregation in healthy horses. Flaxseed oil served as the source of the n-3 fatty acid alpha-linolenic acid (ALA). Twelve horses were fed dietary maintenance requirements using a complete pelleted ration (80%) and timothy grass hay (20%) for a 2-week acclimation period before being randomly assigned either to a treatment (group 1) or control (group 2) group. Group 2 horses (n = 6) were fed the diet described in the acclimation period, whereas group I horses (n = 6) were fed a 10% flaxseed oil-enriched complete pellet (80%) and grass hay (20%). Biological samples and physical measurements were collected at one point during the acclimation period (week 0) and every 4 weeks thereafter (weeks 4, 8, 12, and 16). Body weight, CBC (including platelet count), plasma fibrinogen. electrolyte (Na, K, and Cl) concentrations, and biochemical profile enzyme activities (aspartate aminotransferase, alkaline phosphatase, gamma-glutamyltransferase, and creatine kinase) did not change markedly with diet. Platelet aggregation was not altered by the supplementation of flaxseed oil in these healthy horses, although increases in plasma cis-polyunsaturated 18-carbon fatty acids C18:3; n-3 (ALA) and C18:2; n-6 (linoleic acid), biologically active C20:5; n-3 (eicosapentaenoic acid [EPA]), and malondialdehyde (MDA) were evident. There were no marked decreases in C20:4; n-6 (arachidonic acid [AA]) or increases in C22:6; n-3 (docosahexaenoic acid [DHA]), signifying that flaxseed oil may have had a high percentage of omega-6 (n-6) fatty acids as well as n-3 fatty acids, and this relatively high n-6: n-3 fatty acid ratio may have affected the biochemical effect of n-3 fatty acids. In healthy horses supplemented with flaxseed oil, platelet aggregation was not altered, which may have been due to the limited biologic effect in healthy subjects or the inability of flaxseed oil to induce the necessary biochemical effect of replacing n-6 fatty acids with n-3 types.     

An introduction to biosecurity of cattle operations.

Recent world events have heightened awareness for the need to safeguard our livestock industries from disease agents. Biosecurity is the outcome of all activities undertaken to preclude introduction of disease agents into an animal population. The concepts of biosecurity are not new. Activities directed at ensuring biosecurity include controlling exposure and optimizing resistance. Programs for biosecurity must be individually tailored to specific situations to account for varying risks and perceptions of risk by decision makers. It is important for practitioners to take a holistic approach to disease control, considering the epidemiology of the disease in addition to the available vaccines and therapeutics.     

Equine viral arteritis at a veterinary teaching hospital

An outbreak of equine viral arteritis (EVA) occurred at a veterinary teaching hospital in the summer and autumn of 1984. Clinical signs were observed in 16 out of 61 hospitalized horses and included ventral, limb and preputial edema, mild conjunctivitis with lacrimation, pyrexia and increased respiratory and heart rates. Of 16 clinically affected horses, 13 were undergoing experimental abdominal surgery and/or were involved in digestion experiments; 9 of the 13 were > 20 years of age. The three other clinically affected horses were client animals. Thirteen client horses developed serologic titers to equine arteritis virus in the absence of clinical signs. The risk of infection was associated with close contact, involvement in the experimental studies being conducted and length of hospitalization. The disease was mild, limited in spread and successfully controlled by quarantine.     

Immune-mediated hemolytic anemia and thrombocytopenia in a foal

A one-month-old Quarter Horse filly had unilateral epistaxis, hyphema, icterus, petechial hemorrhages in the oral, nasal, conjunctival, and vulvar mucous membranes, anemia, thrombocytopenia, negative antinuclear test result, and a positive direct Coombs' test result. Megakaryocytes or cell-associated IgG (fluorescent antibody and immunoperoxidase stains) were not found in bone marrow biopsy specimens. Treatment consisted of glucocorticoids, antibiotics, and a single whole blood transfusion. The foal responded well to treatment, did not develop relapses of the disease, and was clinically normal one year after treatment.