Comparative genome sequencing to assess the genetic diversity and virulence attributes of 15 Vibrio anguillarum isolates

Vibrio anguillarum is the causative agent of vibriosis, a deadly haemorrhagic septicaemic disease affecting various marine and fresh/brackish water fish, bivalves and crustaceans. However, the diversity and virulence mechanisms of this pathogen are still insufficiently known. In this study, we aimed to increase our understanding of V. anguillarum diversity and virulence through comparative genome analysis of 15 V. anguillarum strains, obtained from different hosts or non‐host niches and geographical regions, among which 10 and 5 strains were found to be virulent and avirulent, respectively, against sea bass larvae. First, the 15 draft genomes were annotated and screened for putative virulence factors, including genes encoding iron uptake systems, transport systems and non‐ribosomal peptide synthetases. Second, comparative genome analysis was performed, focusing on single nucleotide polymorphisms (SNPs) and small insertions and deletions (InDels). Five V. anguillarum strains showed a remarkably high nucleotide identity. However, these strains comprise both virulent and avirulent strains towards sea bass larvae, suggesting that differences in virulence may be caused by subtle nucleotide variations. Clearly, the draft genome sequence of these 15 strains represents a starting point for further genetic research of this economically important fish pathogen.     

Epidemiological investigation of the buller steer syndrome (riding behaviour) in a western Canadian feedlot

Objective To describe the buller steer syndrome in a Western Canadian feedlot. Design A retrospective epidemiological study. Animals 78,445 male cattle that entered a 24,000-head feedlot in western Canada from 1991 to 1993. Procedure All cattle were given a hormonal growth promotant containing 20 mg oestradiol benzoate and 200 mg progesterone within 24 h of arrival at the feedlot. A ‘buller’ was a steer that was observed at daily pen checking to be ridden persistently by pen mates or had evidence of having been persistently ridden by pen mates. At the completion of the feeding period, animal health records for bullers were collected and analysed. Results The prevalence of bullers in the total population was 2139/78,445 (2.7%, range per pen 0 to 11.2%). The prevalence of bullers increased with increasing weight and age. The relapse risk after first treatment (three days in the feedlot hospital plus treatment for concurrent disease) was 30% on average (27 to 35%). Individual records from 9734 yearling steers that entered the feedlot in 1991 and 1992 showed that bullers were significantly (P < 0.05) heavier at processing than non-bullers. Bullers occurred as a point source epidemic with the cause occurring soon after cattle arrived at the feedlot and were mingled into pen groups. This gave a ‘days on feed’ distribution. The peak incidence of bullers occurred much sooner after arrival and dropped off much quicker in older cattle. The daily incidence of bullers was temporal, but was not related to season of the year, weather conditions or any other feedlot management practice. It was related to the seasonal arrival of cattle at the feedlot, their age at entry to the feedlot and the post arrival occurrence of bullers. Reimplantation with hormonal growth promotants and castration of intact bulls did not produce an epidemic of bullers. Conclusion The findings of this study support the theory that bullers are the result of agonistic interactions, which occur concurrent with the establishment and maintenance of a social hierarchy within pens of feedlot cattle.     

Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 4. Morphometric,microscopic and biomechanical properties of the digital tendons of the forelimb

AIM: To determine the weight, volume, density and cross-sectional area (CSA) of the digital flexor tendons, common digital extensor tendon (CDET) and suspensory ligament (SL) of the forelimb of young Thoroughbred horses in early training, and to assess the response to a training programme of known parameters of superficial digital flexor tendon (SDFT) tissue at mid-metacarpal level.

METHODS: The tendons of seven 2-year-old Thoroughbred horses in training were inspected, transected into segments of known length, and compared with those from seven untrained horses matched for age, sex and breed. The weight, volume, density and CSA of each segment, and the crimp angle, histological features, and biomechanical ultimate stress and stiffness of tendon samples from the mid-metacarpal region of the SDFT were determined.

RESULTS: There was no macroscopic evidence of swelling or discolouration in any of the tendon segments or cut surfaces. The volumes of SDFT and CDET segments of horses in the trained group were significantly greater than those in the untrained group (p=0.036 and p=0.039, respectively). A greater increase in volume than weight resulted in a lower density in the SDFT but not CDET in trained compared with untrained horses (p=0.038). CSA of these two tendons was significantly greater in the trained group (p=0.002 and 0.036, respectively), the percentage increase being greater in the CDET than the SDFT. The number of tenocytes at four sites in the mid-metacarpal SDFT region was less in trained than untrained horses (p=0.025). There was no histological evidence of inflammation, and no difference in crimp angle between groups. There was no significant between-group difference in stiffness or ultimate stress of tendon strips.

CONCLUSIONS: Volume and CSA of the SDFT and CDET were larger in trained than untrained horses. The SDFT was less dense in the trained group. Because no evidence of tendonitis was detected and training appeared to have no significant effect on crimp angle or biomechanical properties of tendon strips, the size and density changes were presumed to be adaptive and induced by the training.

CLINICAL RELEVANCE: Although evident in this in vitro study, the detection of adaptive from initial pathological increase in size of the SDFT is likely to be difficult in vivo.