Dysentery caused by Escherichia coli (S102-9) in calves: natural and experimental disease

A dysentery syndrome was recognized among the Institute's calves at 18 to 21 days of age. It was reproduced experimentally in gnotobiotic calves with an atypical Escherichia coli (S102-9) isolated from the affected calves. In both natural and experimental disease the calves passed copious bright red blood in the feces and developed diarrhea. Walls of the colon and rectum were thickened, and the mucosa was reddened and covered by an exudate that contained mucus and blood clots. Bacteria were seen closely adherent to the luminal surfaces of enterocytes, often in cup-shaped depressions or on cytoplasmic pedestals. Microvilli were distorted, disorientated or absent. There was exfoliation of infected enterocytes and a mild acute inflammation of the underlying lamina. In two of five calves with natural disease, the adherent bacteria did not stain by the immunoperoxidase method with antisera raised against E. coli (S102-9). This indicated that there was possibly more than one bacterial cause of the syndrome. Lesions in experimentally infected calves were indistinguishable from those produced by some E. coli which are enteropathogenic for man, rabbits, and pigs.     

Validation of a radioassay for the determination of serum folate and cobalamin concentrations in dogs

Determinations of serum folate and cobalamin concentrations in dogs have proved of considerable value for the identification and characterisation of chronic small intestinal disorders, but the microbiological assays used are time-consuming and technically demanding. Dual isotope radio-assays are more convenient and have been developed for the determination of folate and cobalamin in human beings. This study has evaluated such an assay for the determination of serum folate and cobalamin concentrations in dogs by direct comparison with microbiological assays used previously. Assays were performed on samples from 77 dogs, including controls and animals with confirmed or suspected chronic small intestinal disease. Regression analysis demonstrated a significant relationship between the two assays for serum folate concentrations (R=0–85; P=0–0001) and a definite trend for radioassay to give lower results than bioassay. There was also a significant relationship between bioassay and radioassay data for serum cobalamin (R=0–91; P=0–0001) with comparable absolute values for these two assays. Radioassay of serum samples from 31 clinically healthy dogs gave control ranges of 3–7 to 8-8 4mUg/litre for folate and 205 to 490 ng/litre for cobalamin. These ranges were similar to those calculated by comparison with the established ranges for bioassay using regression analysis, which predicted ranges of 4-4 to 8-4 μg/litre and 217 to 398 ng/litre for radioassay of serum folate and cobalamin, respectively. These data indicate that a dual isotope radioassay of serum folate and cobalamin may be used for dogs, and emphasise the need for laboratories to validate and establish their own control ranges for different assays.     

Neurologic manifestations of trypanosomiasis in a dog

A 13-month-old Doberman Pinscher was evaluated because of slowly progressive paraparesis and signs of depression. The dog had temporal, supraspinatus, and infraspinatus muscle atrophy, bilateral enophthalmos, superficial inguinal lymphadenopathy, tachycardia with pulse deficits, and lesions of active and inactive chorioretinitis. Neurologic abnormalities included hyperreflexic patellar reflexes, lack of conscious proprioception, signs of superficial pain in the hind limbs, and depressed hopping reflexes in the forelimbs. Cranial nerve abnormalities included decreased sensation in the left nostril and a delayed gag reflex. Results of cerebrospinal fluid analysis were characteristic of nonsuppurative inflammation. A diagnosis of multifocal neurologic disease was made. The dog did not have serum titers for fungal diseases, canine distemper, Ehrlichia canis infection, borreliosis, Rocky Mountain spotted fever, or toxoplasmosis. The dog did not respond to various antimicrobial treatments, and only slightly responded to corticosteroid treatment. The dog died during an anesthetic procedure. The postmortem diagnosis of Trypanosoma cruzi infection (canine Chagas disease) was made on identification of the amastigote form of the organism in sections of brain, spinal cord, and myocardium.     

EX VIVO MAGNETIC RESONANCE IMAGING OF THE DISTAL ROW OF EQUINE CARPAL BONES: ASSESSMENT OF BONE SCLEROSIS AND CARTILAGE DAMAGE

The distal row of carpal bones (C2, C3, and C4) from eight left intercarpal joints--four from Standardbred Trotters and four from Swedish Warmblood horses--were used to assess the potential of magnetic resonance (MR) imaging to detect cartilage and bone lesions. The joints used in the study were classified by macroscopic and radiographic examinations as having normal, mild, moderate, or severe articular cartilage lesions and bone sclerosis. Those classifications correlated well with the appearance of the MR images. Bone sclerosis in the MR images was observed as regions of decreased signal intensity. Upon quantitative analysis of the MR images there was a significant difference (p < 0.0001) in the MR signal intensity from areas where radiographic bone sclerosis was observed compared to areas of radiographic nonsclerotic bone. In addition, the MR images were used to pilot the location of histology slices through areas of interest that were then examined microscopically; hence, the lesions found from the MR imaging examination were verified microscopically. It was concluded that cartilage lesions and cartilage loss are related to the sclerotic state of the underlying bone. The MR protocols developed in this study were applied on five intact cadaveric carpal joints, and it was concluded that MR imaging could successfully be used in the intact joint to detect minor cartilage and bone lesions not visualized by either radiography or macroscopic examination. Hence, MR imaging can be used to delineate interactions between articular cartilage and subchondral bone over time and in vivo.     

A method to measure the susceptibility of pasture soils to poaching by cattle

Abstract. A new method of measuring susceptibility to poaching is described, based on the concept that poaching is caused by a progressive loss of soil strength during repeated treading in wet weather. Susceptibility was measured by the rate of loss of strength in response to concurrent treading and irrigation at standard rates. The pressures exerted on the ground by a walking dairy cow were simulated by a purpose-built penetrometer, whilst water was applied via a network of plastic pipes fitted with syringe needles. Measurements were performed on four pasture soils having a range of clay contents and compared in relation to a mechanism proposed for the process. The results show susceptibility to be a property not wholly determined by the clay content of the soil, but suggest that it is influenced by bulk density and the strength of the sward, which will van, according to weather and pasture management.     

A Biomechanical Comparison of Headless Tapered Variable Pitch and AO Cortical Bone Screws for Fixation of a Simulated Lateral Condylar Fracture in Equine Third Metacarpal Bones

OBJECTIVE: To compare drilling, tapping, and screw-insertion torque, force, and time for the 4.5-mm AO and 6.5-mm Acutrak Plus (AP) bone screws, and to compare the mechanical shear strength and stiffness of a simulated complete lateral condylar fracture of the equine third metacarpal bone (MC3) stabilized with either an AO or AP screw. STUDY DESIGN: In vitro biomechanical assessment of screw-insertion variables, and shear failure tests of a bone-screw-stabilized simulated lateral condylar fracture. SAMPLE POPULATION: Eight pairs of cadaveric equine MC3s METHODS: Metacarpi were placed in a fixture and centered on a biaxial load cell in a materials-testing system to measure torque, compressive force, and time for drilling, tapping, and screw insertion. Standardized simulated lateral condylar fractures were stabilized by either an AO or AP screw and tested in shear until failure. A paired t test was used to assess differences between screws, with significance set at P < .05. RESULTS: Insertion and mechanical shear testing variables were comparable for AO and AP insertion equipment and screws. CONCLUSION: The 6.5-mm tapered AP screw can be inserted in equine third metacarpal condyles and is mechanically comparable with the 4.5-mm AO screw for fixation of a simulated lateral condylar fracture. CLINICAL RELEVANCE: Considering the comparable mechanical behavior, the potential for less-persistent soft-tissue irritation with the headless design, and the ability to achieve interfragmentary compression by inserting the screw in one hole drilled perpendicular to the fracture plane, the 6.5-mm tapered AP screw may be an attractive alternative for repair of incomplete lateral condylar fractures in horses.     

Polymerase chain reaction and DNA sequencing for detection of ovine herpesvirus 2 in American bison (Bison bison).

Serum samples were collected at slaughter from 226 24-30-month-old ranch-raised, clinically normal American bison (Bison bison) bulls from North Dakota, Minnesota, Kansas, and Manitoba to assess the presence of antibodies to ovine herpesvirus 2 (OHV-2). Antibodies to OHV-2 were detected by competitive inhibition enzyme-linked immunosorbent assay in 10 of 226 (4.40%) samples. Polymerase chain reaction (PCR) analysis of sera positive for OHV-2 DNA demonstrated a 238 kilobase fragment. The nucleotide sequence of the PCR-positive samples in comparison to the reported OHV-2 nucleotide sequence resulted in a homology range of 82.8-95.4%.     

Effects of medetomidine premedication on propofol infusion anaesthesia in dogs

Observations of cardiovascular and respiratory parameters were made on six dogs anaesthetized on two separate occasions for 120 minutes with a propofol infusion, once without premedication and once following premedication with 10 μg kg-¹ of intramuscular medetomidine. During anaesthesia the heart rate and cardiac index tended to be lower following medetomidine premedication, while the mean arterial pressure was significantly greater (p<0.05). Although the differences were not statistically significant, the systemic vascular resistance, pulmonary vascular resistance and stroke volume index were also greater in dogs given medetomidine. The mean arterial oxygen and carbon dioxide tensions were similar under both regimens, but in 2 dogs supplementary oxygen had to be administered during anaesthesia to alleviate severe hypoxaemia on both occasions they were anaesthetized. Minute and tidal volumes of respiration tended to be greater in dogs not given medetomidine but medetomidine premedication appeared to have no effect on venous admixture. Dogs given medetomidine received intramuscular atipamezole at the end of the 120 min. propofol infusion; the mean time from induction of anaesthesia to walking without ataxia was 174. min in the unpremedicated dogs and 160 min. in the dogs given atipamezole. The mean blood propofol concentration at which the dogs walked without ataxia was higher in the unpremedicated animals (2.12 ± 0.077 μg. ml-¹ compared with 1.27 ± 0.518 μg. ml-¹ in the premedicated dogs). The oxygen delivery to the tissues was lower after medetomidine premedication (p = 0.03) and the oxygen consumption was generally lower after medetomidine premedication but the difference did not achieve statistical significance. No correlation could be demonstrated between blood propofol concentration and cardiac index, systemic or pulmonary vascular resistance indices, systolic, diastolic or mean arterial blood pressures.     

Diagnosis of right coronary artery to right atrial fistula in a dog using two-dimensional echocardiography

A five-year-old boxer dog developed cardiac murmurs, complete heart block and car-diomegaly associated with vegetative bacterial endocarditis. Using two-dimensional echocardiography, vegetative lesions of the aortic valves and extension of the vegetations into the proximal right coronary artery and adjacent atrial septum were identified. The vegetation within the atrial septum appeared as a cavitated mass which protruded into the right atrium. Fistulae within the atrial septal vegetation permitting communication between the coronary artery and right atrium were observed with colour Doppler echocardiography. The dog died despite medical treatment. Post mortem examination confirmed the echo-cardiographic findings. Vegetative endocarditis with invasion into the right coronary artery and atrial septum producing fistulae and communication with the right atrium has not been reported previously in dogs. Doppler echocardiography proved useful in demonstrating the abnormal anatomy, intraluminal fistular blood flow and its communication with the right atrium.