Table of Contents and AbstractsJuly 2018, Vol. 82, No. 3


Changes in antimicrobial resistance levels among Escherichia coli, Salmonella, and Campylobacter in Ontario broiler chickens between 2003 and 2015

Agnes Agunos, Richard K. Arsenault, Brent P. Avery, Anne E. Deckert, Sheryl P. Gow, Nicol Janecko, David F. Léger, E. Jane Parmley, Richard J. Reid-Smith, Scott A. McEwen (page 163)

Poultry has been identified as a reservoir of foodborne enteric pathogens and antimicrobial resistant bacteria. The objective of this study was to describe and compare antimicrobial resistant isolates from an Ontario broiler chicken farm-level baseline project (2003 to 2004) to the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) Ontario abattoir and retail surveillance data from 2003, and to the most recent (2015) CIPARS Ontario chicken surveillance data in order to assess the impact of an industry-wide policy change in antimicrobial use. Ceftiofur resistance (TIO-R) prevalence in Salmonella decreased by 7% on farm between 2003 and 2004 and 2015. During the same timeframe, TIO-R E. coli prevalence decreased significantly by 16%, 11%, and 8% in farm, abattoir, and retail samples, respectively. Gentamicin resistant (GEN-R) E. coli, however, increased by 10% in farm and 15% in retail-derived isolates, and trimethoprim-sulfamethoxazole resistant (TMSm-R) E. coli increased significantly by 20%, 18%, and 5% in farm, abattoir, and retail isolates, respectively. Similarly, ciprofloxacin-resistant (CIP-R) Campylobacter spp. significantly increased in retail isolates by 11% and increased in farm (33%) and abattoir isolates (7%). The decrease in TIO-R Salmonella/E. coli in recent years is consistent with the timing of an industry-led intervention eliminating the preventive use of ceftiofur, a third generation cephalosporin and class of antimicrobials deemed critically important to human medicine. The rise in GEN-R and TMSm-R prevalence is indicative of recent shifts in antimicrobial use. Our study highlights the importance of integrated surveillance in detecting emerging trends and determining the efficacy of interventions to improve food safety.

Pharmacokinetics of cannabidiol administered by 3 delivery methods at 2 different dosages to healthy dogs

Lisa R. Bartner, Stephanie McGrath, Sangeeta Rao, Linda K. Hyatt, Luke A. Wittenburg (page 178)

The purpose of this study was to determine the pharmacokinetics of cannabidiol (CBD) in healthy dogs. Thirty, healthy research dogs were assigned to receive 1 of 3 formulations (oral microencapsulated ?oil beads, ?oral CBD-infused oil, or ?CBD-infused transdermal cream), at a dose of 75 mg or 150 mg q12h for 6 wk. Serial cannabidiol plasma concentrations were measured over the first 12 h and repeated at 2, 4, and 6 wk. Higher systemic exposures were observed with the oral CBD-infused oil formulation and the half-life after a 75-mg and 150-mg dose was 199.7 ± 55.9 and 127.5 ± 32.2 min, respectively. Exposure is dose-proportional and the oral CBD-infused oil provides the most favorable pharmacokinetic profile.

Does antimicrobial therapy improve outcomes in horses with severe equine asthma and a positive tracheal wash bacterial culture?

Michelle L. Husulak, Stephen T. Manning, Melissa D. Meachem, Hilary J. Burgess, Tasha Y. Epp, Julia B. Montgomery (page 184)

The objective of this study was to observe the outcomes of adding an antimicrobial treatment to a conventional treatment regime in horses with severe equine asthma in a clinical setting. Eleven client-owned horses with a history consistent with severe equine asthma, increased respiratory effort and nostril flaring, ≥ 20% neutrophils on bronchoalveolar lavage (BAL), and a positive tracheal wash (TW) bacterial culture were treated with environmental management, corticosteroids, and bronchodilators. Six horses were also treated with an antimicrobial (principal group), while the other 5 were administered saline as a placebo (control group). Treatment with antimicrobials significantly improved the post-treatment clinical score of the principal group compared with the pre-treatment score, whereas no significant difference occurred in the control group. The principal group also had significantly less neutrophil myeloperoxidase (MPO) activity post-treatment than pre-treatment, with a median difference of −0.39 units/[protein] in the principal group and a median difference of −0.21 units/[protein] in the controls. There was no difference in MPO activity pre- versus post-treatment in the control group. No differences were noted in the intra-group comparisons of pre- versus post-treatment BAL neutrophil counts, mucus scores, and concentrations of interleukin-8 (IL-8) or tumor necrosis factor-alpha (TNF-α) in bronchoalveolar lavage fluid (BALF) in either group. There were no differences found in the inter-group comparisons of the principal versus controls for each of the pre- and post-treatment time periods for BAL neutrophil count, mucus score, clinical scores, MPO activity, and IL-8 or TNF-α concentrations. The role of airway bacteria in horses with severe equine asthma requires further investigation as antimicrobial therapy improved post-treatment clinical scores and decreased MPO activity in the group of horses studied, but did not affect other measures of airway inflammation.

Impact of a trap-neuter-return event on the size of free-roaming cat colonies around barns and stables in Quebec: A randomized controlled trial

Valérie Bissonnette, Bertrand Lussier, Béatrice Doizé, Julie Arsenault (page 192)

The objective of this study was to evaluate the impact of a trap-neuter-return (TNR) event on the size of free-roaming rural cat colonies in Quebec. This prospective randomized, controlled study included 18 cat colonies around barns and stables that were randomly assigned to either a TNR group (10 colonies of 7 to 27 cats; 14.3 cats on average) or a control group (8 colonies of 7 to 26 cats; 14.5 cats on average). The number of cats in each colony was calculated from the images obtained by camera-trapping at: baseline (T0), 7.5 mo (T7), and 12 mo (T12). At baseline, the TNR group was subjected to a TNR event. When taking into account adults only, a significant growth difference was observed in the number of cats between the TNR group and the control group at T7 (P = 0.03). When including kittens as well as adults, a trend towards a lower growth of the TNR group compared to the control group was noted at T7 (P = 0.06). There was no difference in the number of kittens between the 2 groups at T7 (P = 0.49) or at T12 (P = 0.36). There was a trend towards more emigration in the control group at T12 (P = 0.095). Isolated TNR events have a low and temporary impact on colony size in Quebec's rural cat colonies.

Cardiac weights and weight ratios as indicators of cardiac lesions in pigs: A study of pig hearts from an Ontario abattoir

Kathy Zurbrigg, Tony van Dreumel, Max F. Rothschild, David Alves, Robert Friendship, Terri L. O'Sullivan (page 198)

Clinically healthy pigs used in research are assumed to have normal cardiac structure and function. Subclinical cardiac abnormalities may adversely affect the responses being measured in these experiments. The gross and histologic lesions observed in hearts collected from a Canadian abattoir between 2012 and 2015 indicated an unexpectedly high prevalence of cardiac abnormalities: 75% (297/396) of the hearts examined had such lesions. The ratios of total heart weight to body weight and of right ventricle weight to body weight were significantly greater for the hearts with lesions than for the hearts with no lesions, which suggests that cardiac remodeling, particularly hypertrophy, had occurred. The large percentage of hearts with cardiac remodeling from asymptomatic market pigs demonstrates an increased probability that subclinical cardiac abnormalities may exist in research pigs, especially those accessed through commercial channels. Researchers should be aware of this likelihood if subclinical cardiac abnormalities could adversely affect their experimental findings.

Effects of a single intravenous bolus injection of alfaxalone on canine splenic volume as determined by computed tomography

Michelle M.M. Hasiuk, Fernando L. Garcia-Pereira, Clifford R. Berry, Gary W. Ellison (page 203)

The purpose of this study was to evaluate the effects of a single intravenous dose of alfaxalone on canine splenic volume. In 6 adult beagle dogs the splenic volume [mean ± standard error (SE)] was determined by computed tomography to be 0.17 ± 0.02 L before alfaxalone administration and 0.24 ± 0.02 L (P = 0.0091) and 0.23 ± 0.02 L (P = 0.0268) 15 and 30 min, respectively, after alfaxalone administration. Hematocrits (mean ± SE) obtained at the same times were, respectively, 46.3% ± 1.3%, 40.6% ± 1.3% (P = 0.0015), and 41.7% ± 1.3% (P = 0.0057). In conclusion, alfaxalone caused relaxation of the canine splenic capsule and an increase in the splenic volume, along with a decrease in the hematocrit in these dogs.

Intraocular pressure measurements in cattle, sheep, and goats with 2 different types of tonometers

Nina Peche, Johanna Corinna Eule (page 208)

The aim of this study was to investigate normal intraocular pressure (IOP) values of cattle, sheep, and goats with a rebound tonometer [TonoVet (TV)] and an applanation tonometer [Tono-Pen AVIA (TPA)] and to determine correction functions for the 2 devices. A total of 60 healthy cattle, sheep, and goats (20 of each) underwent slit-lamp biomicroscopy. Intraocular pressure (IOP) readings were taken from both eyes with the 2 different tonometers and statistically analyzed. For calibration purposes, the IOP was preset on each instrument at 5 to 60 mmHg using 5 mmHg increments in 10 bovine, 8 ovine, and 6 caprine freshly enucleated eyes. Readings were taken with both tonometers at each interval and compared to the manometrically controlled IOP (Mann-Whitney U-test, P ≤ 0.05; Bland-Altman plot, and regression analysis). The median IOP measurements (min to max) obtained with the TV were 23 mmHg (12 to 40 mmHg), 11 mmHg (7 to 20 mmHg), and 23 mmHg (9 to 37 mmHg) for cattle, sheep, and goats, respectively. Using the TPA, the median IOP measurements were 16 mmHg (8 to 27 mmHg), 10 mmHg (5 to 18 mmHg), and 13 mmHg (4 to 25 mmHg) for cattle, sheep, and goats, respectively. There were statistically significant differences between the readings taken with the TV and the TPA in all species (Wilcoxon-test, P ≤ 0.05). All measurements obtained with the TV and the TPA during the calibration procedure differed statistically significantly from the manometrically controlled IOP measurements (Mann-Whitney U-test, P ≤ 0.05). For both instruments, regression formulas were calculated to correct the measurements. Both tonometers can be used effectively to assess intraocular pressure in ruminants, using the specific regression formulas.

The biological characteristics of sheep umbilical cord mesenchymal stem cells

Fenghao Chen, Chenqiong Zhao, Yuhua Zhao, Li Li, Shi Liu, Zhiqiang Zhu, Weijun Guan (page 216)

Although mesenchymal stem cells (MSCs) are now regarded as a promising cell resource for tissue repair and regeneration, the optimal source of MSCs has not yet been determined. The objective of this study was to provide a theoretical basis for the clinical application of umbilical cord mesenchymal stem cells (UCMSCs) in the future. Umbilical cord is an easily obtainable tissue resource, which is one reason that it has become a candidate resource for mesenchymal stem cells. In this study, we analyzed the biological characteristics of UCMSCs, such as their multiple differentiation and clone-forming ability, through morphological observation, reverse transcription polymerase chain reaction (RT-PCR), growth curve, positive rate test, and immunophenotype. Umbilical cord MSCs were successfully isolated and passaged to 29 generations. The results from RT-PCR showed that UCMSCs were positive for CD29, CD44, CD73, but negative for CD34. The expression of the stem cell marker nucleostemin and tenocyte-related markers showed similar positive results with CD44, CD73, and CD90. In addition, UCMSCs can be induced to differentiate into osteoblasts, adipocytes, or chondrocytes. Our study showed that UCMSCs not only have the ability to self-renew, but also have the potential to differentiate into multiple lineages. In general, we concluded that UCMSCs are a reliable source for use in cell therapy.

Isolation, culture, and characterization of chicken lung-derived mesenchymal stem cells

Fenghao Chen, Chenqiong Zhao, Yuhua Zhao, Li Li, Shi Liu, Zhiqiang Zhu, Weijun Guan (page 225)

Using lung tissues separated from 12-day-old chicken embryos, we attempted to obtain a novel population of stem cells, namely, chicken lung-derived mesenchymal stem cells (LMSCs), which exhibit spindle-like morphology.

The results of colony-forming assay and population doubling assay demonstrated that LMSCs had enormous colony-forming, self-renewal, and proliferative potential. When appropriately induced, LMSCs could differentiate into osteoblasts, adypocytes, chondrocytes, and neurons; in other words, LMSCs had cross-embryonic layer differentiation potential under corresponding induction conditions. Aside from colony-forming, self-renewal, and multilineage differentiation capabilities, LMSCs were characterized by specific cell phenotypes. The results of immunohistochemistry and flow cytometry demonstrated that LMSCs consistently expressed OCT-4 — a specific gene marker expressed in pluripotent stem cells — and markers associated with MSCs such as CD29, CD73, CD90, and CD105. However, LMSCs lacked hematopoietic cell surface molecules such as CD34 and CD45. Primary LMSCs could be subcultured to passage 24 at most in vitro and karyotype analysis demonstrated that LMSCs possessed genomic stability.

These unique characteristics were consistent with the characteristics of MSCs, which had been isolated from other tissues. This provides a foundation for LMSCs as a promising avenue for cellular transplantation therapy, regenerative medicine, and tissue engineering.

Brief Communications

ACTN3 gene variants as potential phenotype and performance biomarkers in Brazilian sport horses training for eventing in a tropical climate

Felipe Gomes Ferreira Padilha, Kênia Balbi El-Jaick, Liane de Castro, Aline dos Santos Moreira, Fernando Queiroz de Almeida, Ana Maria Reis Ferreira (page 236)

The aim of this study was to look for mutations in the equine ACTN3 gene and to identify sequence variants that might be associated with the phenotype and performance of Brazilian sport horses training for events in a tropical climate. Among 17 such horses direct DNA sequencing and mutation analysis of the exon 15 and the intron–exon boundaries of ACTN3 revealed 2 new sequence variants in the ACTN3 intron 14–15, designated c.1681–86G > A and c.1681–129delA. Wild-type/deletion heterozygotes (A/del) had a lower mean subcutaneous fat layer in the region of the gluteus medius, as measured by ultrasonography, than the del/del homozygotes; the correlation was significant (P = 0.017). This single base-pair deletion in ACTN3 intron 14–15 may have resulted in metabolic changes that led to increased deposition of body fat in the homozygous state. However, neither sequence variant was correlated with the time to fatigue in a test on a high-speed treadmill with an incremental-speed protocol.

Effect of piglet separation from dam at birth on colostrum uptake

Rodrigo Manjarín, Yanisse A. Montano, Roy N. Kirkwood, Darin C. Bennet, Kiro R. Petrovski (page 239)

The objective of this study was to determine whether birth order influences piglet survival because of reduced uptake of maternal antibodies by the piglets born later in large litters. Forty-five litters were serially allocated to one of 2 study groups. The crèche group consisted of 18 litters for which the 205 piglets were removed to a warm box to prevent suckling until 4 h after delivery of the first pig, and the control group of 27 litters for which 306 piglets were allowed to suckle from birth. The protein content of piglet blood and sow colostrum was determined with Brix refractometers. Parity, farrowing duration, liveborn litter size, litter size at 12 d, and piglet weight at birth and at 24 h and 12 d of age did not differ between the 2 treatment groups (P > 0.1). There were also no significant differences (P > 0.1) at any time point in weight or in the mean percent protein in plasma between the first 3 and the last 3 piglets born to an individual sow. However, the mean percent protein in plasma was significantly higher in the control group than in the crèche group at both 24 h (P ≤ 0.05) and day 12 (P ≤ 0.01) postpartum. The lack of differences in plasma protein levels between the first and last pigs born along with the lower percent plasma protein in the piglets that were prevented from suckling immediately after birth militate against the use of this technique as a way to equalize the opportunity for adequate transfer of maternal antibodies.