Table of Contents and Abstracts

The objective of this study was to characterize respiratory clinical signs, other than panting and respiratory distress, as well as thoracic radiographic abnormalities, in dogs with hypercortisolism. Although there have been case reports and studies evaluating the results of pulmonary scintigraphy, no studies have yet reviewed respiratory clinical signs and radiograph results in dogs with hypercortisolism. This study addresses this gap. A case series was evaluated and the dogs’ clinical histories were obtained, including clinical signs and physical examination. Digital thoracic radiographs were analyzed to consider such parameters as the diameter of the main bronchi, lung patterns, and the size of the pulmonary trunk. The most common respiratory symptoms were snoring (61.9%), coughing (57.1%), and fatigue (52.4%). Physical examination revealed a high frequency of changes on lung auscultation (95.2%). The body condition score (BCS) was high in 95% of dogs and a significant correlation was observed between the presence of cyanosis and changes in lung auscultation, both of which present similar risk factors. Furthermore, body weight showed a moderate correlation with respiratory rate (RR = 0.571). Radiographic changes were evident in 47.5% of dogs, with the bronchial pattern being the most common (70%). Based on these results, it was observed that respiratory and radiographic abnormalities are frequent in dogs with spontaneous hypercortisolism and a high body condition score was relevant for exacerbating clinical respiratory signs, such as cyanosis and tachypnea.

Growth-promoting antibiotics have been used in cattle, but concern about antimicrobial overuse has prompted a re-evaluation of this practice. To evaluate changes in the ruminal microbiota of feedlot cattle by virginiamycin, a total of 76 crossbreed beef cattle from 2 batches of cattle at different sampling periods (B1 and B2) were divided into 2 groups: one receiving virginiamycin in their diet (ATB) and the other receiving the same diet without any growth promoter (CON). The use of virginiamycin was associated with significant changes in the diversity and composition of the ruminal microbiota of cattle in B1, but not in cattle in B2. Several bacterial taxa were significantly more abundant in samples from CON, e.g., an unclassified genus of the TM7 phylum, whereas others were associated with the use of virginiamycin, e.g., Holdemania and Selenomonas spp. In conclusion, virginiamycin can affect bacterial diversity and composition in the rumen of feedlot cattle, but its effect is inconsistent in different seasons of the year.

Ergot alkaloids are known to cause devastating effects in livestock. The objectives of this study were to evaluate the effects of prolonged ergot exposure on selected vasculature in pregnant sheep and to examine the role of alpha-1 adrenergic receptors in mediating these effects. Twelve 60-day pregnant sheep were randomly placed into control and exposure groups (n = 6/group). Ergot-contaminated feed pellets were given orally once a day for 45 d to the exposure group [46.6 µg/kg body weight (BW) total ergot alkaloids]. The control group (Ctl) received ergot-free pellets. The maternal pedal artery from the left hindlimb and the umbilical artery and vein were dissected and mounted in a tissue bath. The vascular contractile response to a cumulatively increasing dose of phenylephrine (PE) in the exposure group (Exp) was compared with the control groups. Chronic exposure to ergot alkaloids resulted in a 70.6% and 91.3% increase in PE contractile response in the umbilical artery (Ctl EC₅₀ = 3.962 × 10^-6; Exp EC₅₀ = 1.161 × 10^-6, P < 0.0001) and the umbilical vein (Ctl EC₅₀ = 7.889 × 10^-6; Exp EC₅₀ = 6.801 × 10^-7, P < 0.0001), respectively, but there was no increase in the pedal artery (P = 0.3927), when compared to the control group. Fetal weight in the ergot-exposed group was significantly lower than in the control group (Ctl 3.3 ± 0.17 kg; Exp 2.07 ± 0.13 kg, P = 0.0002). The increase in contractile response in the umbilical vein may result in decreased blood supply to the fetus causing decreased fetal weight. Negative impact was seen at significantly lower levels of ergot alkaloids than what is currently allowed by Canadian standards, which suggests that these limits should be reevaluated to ensure livestock safety.

The objective of this field trial was to determine the efficacy of a recombinant toxoid vaccine against Shiga toxin 2e (Stx2e) in piglets suffering from edema disease (ED). Three farms with confirmed ED cases were selected for the field trials. On each farm, a total of 40 4-day-old pigs were randomly allocated to either the vaccinated or unvaccinated group, with 20 pigs per group (10 males and 10 females). A 1.0-mL dose of the recombinant toxoid vaccine was administered intramuscularly to pigs in the vaccinated groups in accordance with the manufacturer’s recommendations at 4 d of age. A single 2.0-mL dose of phosphate-buffered saline was administered to unvaccinated pigs at the same age. Clinical signs of ED were observed in 12 piglets in the unvaccinated groups and 7 unvaccinated pigs died as a result of ED out of the total number of piglets on Farms A, B, and C. Vaccination had a positive effect on pig growth performance compared to that of unvaccinated pigs on 2 of the 3 farms. Seroconversion of neutralizing antibodies against Stx2e occurred in 70% of piglets in the vaccinated group on Farm A, 75% of vaccinated piglets on Farm B, and 55% of vaccinated piglets on Farm C, when detectable antibodies were measured at 17 d post-vaccination (dpv). Detectable antibodies were measured in 85% of vaccinated piglets on Farms A and B and in 90% of these piglets on Farm C at 37 dpv. These field trials determined that the ED recombinant toxoid vaccine successfully reduced clinical signs and mortality, improved average daily weight gain, and resulted in the production of neutralizing antibodies against Stx2e in pigs.

Alpha toxin has become the subject of research in recent years. The objective of this article was to review and summarize recent research on the molecular structure and biological function of the alpha toxin of Clostridium perfringens. This includes the work of our research team, as well as that of other researchers. Clostridium perfringens is an anaerobic, spore-forming, Gram-positive bacillus. It can cause various intestinal diseases, such as gas gangrene, food poisoning, non-foodborne diarrhea, and enteritis. Clostridium perfringens can be classified into 5 toxinotypes A, B, C, D, and E, based on the production of major toxins. Each type of C. perfringens produces alpha toxin, which is one of the most important lethal and dermonecrotic toxins and is considered a primary virulence factor. Alpha toxin is a multifunctional metalloenzyme with phospholipase C and sphingomyelinase activities that simultaneously hydrolyze phosphatidylcholine and sphingomyelin. It can therefore destroy the integrity of cell membranes and eventually cause cell lysis. The clinical effects of alpha toxins are characterized by cytotoxicity, hemolytic activity, lethality, skin necrosis, platelet aggregation, and increased vascular permeability. Future research will concentrate on the pathogenesis of alpha toxin exposure, clarifying the interaction between alpha toxin and the cell membrane and investigating the mechanism of activating platelet function. This research will have substantial theoretical and practical value in controlling disease progression, identifying targeted therapeutic sites, and reducing the toxic effects of vaccines.