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Biomedical subjects

R L Walker

Publications and source records attributed to R L Walker.

At least 55 records · Page 3Linked to original sources
PubMed1995

Genotypic and phenotypic analysis of Salmonella strains associated with an outbreak of equine neonatal salmonellosis.

Isolates of Salmonella choleraesuis serotype ohio (S. ohio) recovered during an outbreak of equine neonatal salmonellosis on a Thoroughbred farm were compared with isolates of the same serotype from various animal, feed and environmental sources. Biochemical profiles, antimicrobial susceptibility patterns, phage susceptibility, plasmid profiles, restriction endonuclease analysis and ribotyping were used to compare relatedness of the strains. A total of 46 outbreak and non-outbreak associated isolates of S. ohio were studied. Differences in antimicrobial susceptibility patterns, phage susceptibility and plasmid profiles were useful for differentiating outbreak isolates from other equine isolates as well as bovine, porcine and some poultry isolates. Feed and other poultry isolates, most in geographic proximity to the outbreak, were indistinguishable from outbreak isolates by any of the methods employed. Investigative studies on the farm along with results of genotypic and phenotypic analysis of isolates suggested that contaminated feed was the most likely source of Salmonella in this outbreak.

Animals↗
PubMed1995

Spirochetes isolated from dairy cattle with papillomatous digital dermatitis and interdigital dermatitis.

Two groups of spirochetes were isolated from papillomatous digital dermatitis (PDD) lesions in dairy cattle. The two groups could be readily differentiated on the basis of morphologic and immunologic characteristics and enzymatic activity. A spirochete isolated from an interdigital dermatitis (IDD) lesion appeared morphologically and antigenically similar to spirochetes in one of the PDD groups and exhibited an identical enzyme activity pattern. The two groups of PDD spirochetes had characteristics most consistent with the genus Treponema. The PDD and IDD isolates differed morphologically from previously described bovine Treponema spp. Although spirochetes have been observed to be one of the predominant bacterial morphotypes in PDD and IDD and are found invading the stratum spinosum and dermal papillae in PDD lesions, the significance of these spirochetes in the etiopathogenesis of PDD and IDD is presently unknown.

Animals↗
PubMed1995

Renal function in the laboratory rat: a student exercise.

Because of the increased concern over use of human body fluids in physiology teaching laboratories, we developed an exercise in renal function that utilizes laboratory rats. The purpose is to demonstrate the role of the kidneys in the homeostatic control of extracellular fluid volume, plasma ionic concentrations, and osmolarity. Three treatment groups are utilized: a volume-expanded (access to 1 g/100 ml sucrose) group, a volume-expanded and salt-loaded (access to 0.9 g/100 ml NaCl) group, and a volume-depleted (water-deprived) group. A normovolemic control group (access to tap water) is also included. Rats are housed individually in metabolic cages that allow accurate measurement of fluid intake and urine output. Blood samples are removed via cardiac puncture. The animals recover from this procedure and can be reutilized within 2-3 wk. When class data are pooled, clear trends are seen that demonstrate the volume-, osmo-, and ionoregulatory abilities of the kidneys.

Animals↗
PubMed1993

Mycoplasma bovis associated with decubital abscesses in Holstein calves.

Between April of 1990 and March of 1992, calves on a Holstein calf ranch experienced subcutaneous decubital abscesses involving the brisket region, dorsal aspect of the carpus, and lateral aspect of the stifle joints. Fifty out of 2,500 (2%) Holstein calves between the ages of 3 and 12 weeks were affected. Needle aspirates of brisket abscesses from 8 calves and 6 live or dead calves with 1 or more decubital abscesses were submitted for examination. Two of the 6 calves in addition had bronchopneumonia. Mycoplasma bovis was isolated from all abscesses and 1 lung. Formalin fixed tissues taken from the affected areas also revealed M. bovis by immunoperoxidase staining. No evidence of joint involvement was apparent, and no mycoplasma was isolated from the joints adjacent to affected areas. Attempts to isolate mycoplasma from milk and environmental samples were unsuccessful.

Abscess↗
PubMed1992

Actinomycetales infections in slender-horned gazelles: six cases (1987-1989).

Disseminated Actinomycetales infections were diagnosed in 6 slender-horned gazelles at a zoologic park over a 17-month period. Nocardia and Mycobacterium spp were isolated. Possible predisposing causes leading to infection were investigated. Environmental contamination where the gazelles were housed was not high, and other breeds of gazelles at the park did not become infected, indicating that environmental exposure was not the sole factor involved. Information gathered from questionnaires sent to other zoologic parks and personnel communications indicated that this was not an isolated incident. Investigation into the genetic lineage of the gazelles revealed substantial inbreeding in prior generations. These findings suggested inbreeding may have been an important predisposing factor leading to infection. Careful scrutiny to ensure maximal heterozygosity of future breedings is warranted.

Actinomycetales Infections↗
PubMed1992

Bovine abortions attributable to Listeria ivanovii: four cases (1988-1990).

During a 3-year period, 4 cases of bovine abortion attributable to Listeria ivanovii were diagnosed from 243 bovine fetuses submitted for diagnostic evaluation. Listeria monocytogenes was isolated only once from a bovine fetus during this same time period. Pathologic findings were similar to those seen in abortions attributable to L monocytogenes. Consistent management factors were not recognized and breed susceptibility was not apparent. Listeria ivanovii is most often associated with abortions from sheep and is rarely reported from cattle. On the basis of findings in this study, L ivanovii must be included as a potential cause of bovine abortions.

Abortion, Veterinary↗
PubMed1991

Clostridium botulinum type-C intoxication associated with consumption of processed alfalfa hay cubes in horses.

An episode of nervous system dysfunction was observed in horses on 17 premises in 4 counties of southern California. Thirty-eight horses were affected, and 31 of those died. The common clinical signs of disease in the affected horses were: increased appetite; anxious attitude; rythmic, intermittent muscle tremors in the area of the tricep muscles; decreased palpebral tone; mydriasis; small hard fecal balls; and tendency to become sternally recumbent with the neck extended. The temporal distribution of cases on all 17 premises suggested a relationship between exposure to a common batch of alfalfa hay cubes and manifestations of similar clinical signs of disease in affected horses. Fifteen horses were submitted for necropsy. Diagnosis of botulism was established on the basis of detection of type-C1 toxin in the feed, in intestinal contents of 1 horse, and in the liver of the aforementioned horse and another horse. Toxigenic strains of Clostridium botulinum type-C were isolated from intestinal contents of 5 affected horses, one of which also contained type-C1 and type-C2 toxins. Seven of 10 horses treated with type-C antitoxin and plasma obtained from horses hyperimmunized with C botulinum type-C toxoids survived.

Animal Feed↗
PubMed1991

Comparison of an enzyme-linked immunosorbent assay to an indirect immunofluorescence assay for the detection of antibodies to Borrelia burgdorferi in the dog.

An enzyme-linked immunosorbent assay (ELISA) was compared to an indirect immunofluorescence assay (IFA) for detection of IgG antibodies to Borrelia burgdorferi in dog sera. The concordance of the two tests was 93.5% for sera from dogs from Maryland (n = 93), 98.0% for sera from dogs from North Carolina (n = 446), and 97.2% for the combined sample groups (n = 539). Twenty-five of the 27 samples with discordant or low positive results were tested, and showed immunoblot reactions to 1 to 10 different bands. Reaction patterns and intensity of the bands were quite variable, and did not explain a reason for the discordance.

Animals↗
PubMed1991

An outbreak of equine neonatal salmonellosis.

An outbreak of salmonellosis in foals occurred on a large Thoroughbred farm in California. Only foals less than 8 days of age exhibited clinical signs, which included depression, anorexia, and diarrhea. Three foals died from septicemia. The agent responsible was Salmonella ohio, which is rarely involved in salmonellosis in horses. During the course of the outbreak, S. ohio was isolated from 27 of 97 mares (27.8%) and 34 of 97 foals (35.1%). Mares were the presumed source of infection for foals. The absence of clinical signs in mares allowed for increased exposure of foals through environmental contamination. Although foals continued to become infected after strict control measures were adopted, none became ill. Salmonella serotypes of seemingly low virulence can produce serious disease outbreaks.

Animals↗
PubMed1990

Evaluation of four commercial anaerobic systems for identification of Eubacterium suis.

Four commercial anaerobic systems (CASs) were evaluated for usefulness in identification of Eubacterium suis. Twelve strains were evaluated in each system in triplicate, and results were interpreted independently by 5 individuals. Statistically significant differences (P less than 0.01) due to strain variation and reader interpretation accounted for discrepancies encountered. The reactivity, repeatability, and unique profiles generated made both CAS-1 and CAS-2 suitable adjuncts for identification of E. suis when colony morphology and Gram reaction were considered. Limited reactivity in CAS-3 limited its use as an aid in identification. Variability in test observations and the large number of numerical profiles generated precluded use of CAS-4.

Anaerobiosis↗
PubMed1990

Attenuation of Borrelia anserina by serial passage in liquid medium.

Borrelia anserina (Sakharoff) was successfully grown in a liquid medium (Barbour-Stoenner-Kelly) for 39 passages. By the 12th serial passage in medium, infectivity of B anserina for chicks was lost. Electron microscopy did not reveal structural differences between non-infective and infective cultured organisms. Changes in the protein profiles were found by electrophoresis as the organisms were passed in culture.

Animals↗
PubMed1989

Isolation of Eubacterium suis from sows with cystitis.

Eubacterium suis was isolated from the bladders of 3 of 64 sows (4.7%) examined at slaughter. Two of the sows had cystitis similar to other descriptions of E suis infections in sows. There was no histologic evidence of cystitis in the third sow from which E suis was recovered. In all 3 instances, a mixed infection was present. Other bacteria present were predominantly gram-positive organisms. Eubacterium suis cystitis may be more prevalent than previously suspected. The special culture conditions required to grow this organism may account for the paucity of reports in the United States.

Abattoirs↗