Effect of danofloxacin and tilmicosin on body temperatures of beef calves with pneumonia experimentally induced by inoculation with Mannheimia haemolytica

OBJECTIVE: To examine effects of danofloxacin and tilmicosin on continuously recorded body temperature in beef calves with pneumonia experimentally induced by inoculation of Mannheimia haemolytica. ANIMALS: 41 Angus-cross heifers (body weight, 160 to 220 kg) without a recent history of respiratory tract disease or antimicrobial treatment, all from a single ranch. PROCEDURE: Radiotransmitters were implanted intravaginally in each calf. Pneumonia was induced intrabronchially by use of logarithmic-phase cultures of M. haemolytica. At 21 hours after inoculation, calves were treated with saline (0.9% NaCl) solution, danofloxacin, or tilmicosin. Body temperature was monitored from 66 hours before inoculation until 72 hours after treatment. Area under the curve (AUC) of the temperature-time plot and mean temperature were calculated for 3-hour intervals and compared among treatment groups. RESULTS: The AUCs for 3-hour intervals did not differ significantly among treatment groups for any of the time periods. Analysis of the mean temperature for 3-hour intervals revealed significantly higher temperatures at most time periods for saline-treated calves, compared with temperatures for antimicrobial-treated calves; however, we did not detect significant differences between the danofloxacin- and tilmicosin-treated calves. The circadian rhythm of temperatures before exposure was detected again approximately 48 hours after bacterial inoculation. CONCLUSIONS AND CLINICAL RELEVANCE: Danofloxacin and tilmicosin did not differ in their effect on mean body temperature for 3-hour intervals but significantly decreased body temperature, compared with body temperature in saline-treated calves. Normal daily variation in body temperature must be considered in the face of respiratory tract disease during clinical evaluation of feedlot cattle.     

Comparison of the incidence of residual shunting between two surgical techniques used for ligation of patent ductus arteriosus in the dog

OBJECTIVE: To compare the incidence of residual patent ductus arteriosus (PDA) flow after ligation using 2 different dissection techniques: a standard dissection and a method described by Jackson and Henderson. STUDY DESIGN: A randomized, prospective study. ANIMALS: Thirty-five dogs admitted for surgical correction of a left to right shunting PDA. METHODS: Dogs were randomly assigned: 19 to a standard dissection technique (group S) and 16 to the Jackson and Henderson dissection group (group JH). RESULTS: Gender ratio, age at surgery, and diameter of the ductus were not statistically different between groups. Breed distribution was also similar. Because 1 dog had fatal intraoperative hemorrhage, only 34 dogs were available for residual flow comparisons. Twenty-one percent of group S dogs had residual flow compared with 53% in group JH. Whereas no intraoperative complications occurred in group S, 3 were encountered in group JH. CONCLUSIONS: The incidence of residual flow was higher when the Jackson and Henderson dissection was used for PDA ligation compared with a standard method of dissection. This was probably because of entrapment of loose connective tissue within the medial aspect of the ligature, impeding complete closure of the ductus. CLINICAL RELEVANCE: Ideal PDA closure should result in no residual ductal flow to prevent possible adverse long-term sequelae, such as recanalization and infective endocarditis.     

Congenital hypothyroidism with goiter in toy fox terriers

Congenital hypothyroidism with goiter was observed to segregate as a simple autosomal recessive trait in Toy Fox Terriers (TFTs). Neonatal affected pups exhibited inactivity, abnormal hair coat, stenotic ear canals, and delayed eye opening. Palpable ventrolateral cervical swellings were evident by 1 week of age. Serum thyroid hormone and thyroid-stimulating hormone concentrations were low and high, respectively. Histologic examination of the cervical masses disclosed cuboidal to columnar follicular epithelial cell hyperplasia with widely varying follicular size, shape, and amount of colloid. Oral thyroid hormone replacement therapy restored near-normal growth and development. At 8 weeks of age, radioiodine uptake and perchlorate discharge testing indicated an iodine organification defect. Biochemical analysis of thyroid tissue from affected dogs demonstrated enzymatic iodine oxidation deficiency and lack of sodium dodecyl sulfate-resistant thyroglobulin dimers, suggesting thyroid peroxidase deficiency. A nonsense mutation in the thyroid peroxidase gene of affected dogs was discovered and demonstrated to segregate with the disease. A DNA-based carrier test was developed and currently is used by TFT breeders to prevent this disorder.     

Evaluation of transcutaneous Doppler ultrasonography for the measurement of blood flow in the femoral artery of pigs

OBJECTIVE: To compare measurements of blood flow in the common femoral artery obtained by duplex Doppler ultrasonography (DDU) and a reference ultrasonic transit-time flow (TTF) method and to examine the impact of Doppler spectral waveform measurement techniques on volumetric estimates. ANIMALS: 5 healthy female pigs. PROCEDURES: Femoral arterial blood flow was measured simultaneously in anesthetized pigs by use of a TTF probe (left femoral artery) and transcutaneous DDU (right femoral artery). A range of flow states was induced pharmacologically by using xylazine, bradykinin, dobutamine, and isoflurane. Volumetric blood flow was calculated from DDU waveforms, using the product of the flow velocity integral (FVI), the cross-sectional vessel area, and heart rate. Three calculations of FVI were obtained by manually tracing the Doppler spectral envelopes at the outer envelope, the modal, and the inner envelope of the spectral dispersion pattern. Data analysis included calculation of Pearson correlation coefficients and Bland-Altman limits of agreement. RESULTS: Blood flow measured by DDU was more closely correlated with TTF measurements when the modal or inner envelope tracing method was used (r, 0.76 and 0.78; limits of agreement, -100 to 54.2 and -48.5 to 770 mL/min, respectively). Limits of agreement for the outer envelope tracing method were -238.5 to 64 mL/min. CONCLUSIONS AND CLINICAL RELEVANCE: Transcutaneous DDU is a reliable noninvasive technique for measuring blood flow in the femoral artery of pigs over a range of flow states. Tracing the inner envelope of the Doppler spectral dispersion pattern provided the best estimate of blood flow in this study.     

AORTO-CARDIAC FISTULAS IN SEVEN HORSES

This report describes the history, clinical, electrocardiographic and echocardiographic findings, treatment, outcome, and post-mortem findings in seven horses with aorto-cardiac fistula. Affected horses included 5 stallions, one gelding and one mare; 2 each of the Thoroughbred, Arabian and Standardbred breeds and one Thoroughbred-cross with a mean ± s.d. age of 12 ± 4 years, range 6–18 years. The presenting sings were acute distress (four horses), exercise intolerance (two horses) and the lesion was detected during a routine examination in one horse. Five horses had monomorphic ventricular tachycardia on admission and one other had a history of this arrhythmia. Five horses had a characteristic continuous murmur loudes in the right fourth intercostal space. Echocardiography (six horuses) and/or post-mortem examination (four horses) revealed the horses had aorto-cardiac fistulas arising from the right aortic sinus in all five horses in which the site was recorded. Two horses had ruptured aneurysmall dilatations of the aortic wall at this site. Fistulas extended into the right ventricle in four horses; the right atrium in two horses, the left ventricle in one horse, and five horses had dissecting tracts in the septal myocardium. Horses survived for periods ranging from 24th to 4 years. Aorto-cardiac fistula should be considered in the differential diagnosis for horses presenting with acute distress, bounding arterial pulse, a right-sided continuous murmur and/or monomorphic ventricular tachycardia, particularly in middle-aged or older stallions. Echocardiography is the technique of choice for confirming the diagnosis and demonstrating accompanying cardiac changes.     

Further evaluation of the efficacy of emamectin benzoate for treating Pseudocapillaria tomentosa (Dujardin 1843) in zebrafish Danio rerio (Hamilton 1822)

Pseudocapillaria tomentosa is a pathogenic nematode parasite, causing emaciation and severe inflammatory lesions in the intestines in zebrafish Danio rerio (Hamilton 1822). Emamectin benzoate is commercially available analogue of ivermectin used for treating salmon for sea lice, under the brand name SLICE^®, and we have used this for treating zebrafish with the P. tomentosa. Here, SLICE^®, 0.2 per cent active emamectin benzoate, was used for oral treatments at 0.35 mg emamectin benzoate/kg fish/day for 14 days starting at 7 days post‐exposure (dpe). Another experiment entailed initiating treatment during clinical disease (starting at 28 dpe). Early treatment was very effective, but delaying treatment was less so, presumably due to inappetence in clinically affected fish. We evaluated emamectin benzoate delivered in water, using Lice‐Solve? (mectinsol; 1.4% active emamectin benzoate) in two experiments. Application of four 24‐hr treatments, space over 7 days was initiated at 28 dpe at either 0.168 or 0.56 mg emamectin benzoate/L/bath, and both treatments completely eradicated infections. This was 3 or 10 times manufacture's recommended dose, but was not associated with clinical or histological side effects.     

Bioavailability of Iron to Pseudomonas fluorescens Strain A506 on Flowers of Pear and Apple

ABSTRACT The addition of 0.1 mM FeCl(3) to a defined culture medium induces the bacterial epiphyte Pseudomonas fluorescens strain A506 (A506) to produce an antibiotic toxic to the fire blight pathogen, Erwinia amylovora. Consequently, because A506 is registered and applied as a commercial product to suppress E. amylovora before floral infection of pear and apple, the relative availability of iron to A506 on surfaces of pear and apple flowers is of potential significance. An 'iron biosensor' construct of A506 was developed by transformation with an iron-regulated promoter (pvd) fused to a promoterless ice nucleation reporter gene (inaZ). This construct, A506 (pvd-inaZ), established high populations on pear and apple flowers, ranging from 10(4) to 10(6) CFU/flower. In seven trials on pear and apple trees, A506 (pvd-inaZ) expressed high ice nucleation activity (INA) on flowers, indicating limited iron bioavailability or a low-iron environment unlikely to induce antibiotic production by A506. A506 (pvd-inaZ) also colonized flowers when mixed with chemicals containing iron: FeSO(4) or the iron chelates ferric ethylenediaminedi-(o-hydroxyphenyl-acetic) acid (FeEDDHA) and ferric diethylenetriamine pentaacetate (FeDTPA). These compounds represent an array of commercial iron formulations applied to foliage to avert iron chlorosis. Treatment of flowers with a mixture of A506 (pvd-inaZ) and 3 mM FeEDDHA or FeDTPA significantly decreased INA compared with flowers treated with A506 (pvd-inaZ) in water. Lower concentrations (0.3 mM) of FeEDDHA, however, did not consistently suppress INA. These results indicate that apple and pear flowers represent an iron-limited environment to A506 and that treatment with 3 mM FeEDDHA is needed to increase significantly the level of iron available to this bacterium.