Individual and group antimicrobial usage rates on 34 farrow-to-finish swine farms in Ontario, Canada

Antimicrobial drug-use was assessed on 34 farrow-to-finish operations that marketed at least 500 hogs/yr. These operations either did not use any antimicrobials or used narrow-spectrum or broad-spectrum antimicrobials in rations of post-weaning pigs. Total antimicrobial use was measured for two months after obtaining inventories and records of all antimicrobials used. The collection of empty medication bottles and inventories of drugs on hand was convenient for producers and useful for estimating or validating recorded treatment rates, particularly for antimicrobials that were used only in one class of pig. Treatment records, however, underestimated by approximately 35% the amounts used for 27/29 farm–antimicrobial combinations. Rates of individual-pig treatment varied from 0–24.1 pigs treated/1000 pig-days, with a median of 5.29. Most individual animal treatments were given to piglets and sows at parturition and penicillin was the most commonly used antimicrobial. Gentamicin was administered to suckling piglets on 19 of the farms.     

Epididymitis Caused by Brucella ovis in a Southern Ontario Sheep Flock

Epididymitis was diagnosed in three rams in a commercial sheep flock in southern Ontario. The affected rams had palpably enlarged epididymides and two rams had semen which contained inflammatory cells and was of poor quality. Serum compliment fixation titers for Brucella ovis were 1:20, 1:80 and 1:90. Five other rams in the flock were clinically normal and without titers. Two of the affected rams had lesions similar to those produced by experimental infection with B. ovis. The infection in the rams had no apparent affect on ewe performance. The source of the infection remains unknown, but the rams were purchased from a flock which had imported ewes from the western U.S.A.     

An effect of rust (Uromyces viciae-fabae) on the yield of spring-sown field beans (Vicia faba) in the UK

Rust (Uromyces viciae-fabae) has recently been noted with increased frequency and earliness on spring-sown beans (Vicia faba) at Rothamsted. In 1982 an experiment was made to assess the damage and yield loss, if any, being caused by the disease. Plots received benomyl sprays to control chocolate spot (Botrytis fabae) or not, maneb plus mancozeb (protective) or propiconazole (systemic) fungicide applied twice or three times to control rust, or no fungicide at all. Rust was first found on 7 July and sprays were applied from 9 July but by 19 August plants of all treatments were dead. Fungicides controlled disease development during July and at harvest overall yields were 4·51 and 5·43 t/ha in unsprayed and sprayed treatments respectively. The difference was accounted for by the weight of individual grains and not by the number of pods per plant or grains per pod. Previously rust has been considered unimportant in the UK but its potential for damage is considerable.     

Detection of clusters of Salmonella in animals in Ontario from 1991 to 2001

The temporal patterns of Salmonella serovars isolated from animals in Ontario by 2 major laboratories between 1991 and 2001 were identified. Overall, the number of isolates remained relatively stable and the more frequent isolates were dominant, as in earlier surveys. However, the temporal patterns of specific isolates and the serovars isolated differed depending on the laboratory, species of animal, and reason for obtaining the culture (monitoring versus diagnostic sample). A number of temporal clusters were identified, but their dates of occurrence differed by laboratory. Whereas the laboratories serve an essential role for diagnosis and monitoring, the summary information should be interpreted cautiously. The importance of additional information, such as demographic source, specimen type, and appropriate denominator, when interpreting the data is discussed.     

Prevalence and characterization of verotoxin-producing escherichia coil (VTEC) in cattle from an Ontario abattoir

This study determined the prevalence of verotoxin (VT)-producing Escherichia coli (VTEC) in Ontario beef cattle at slaughter and characterized the isolates by serotype, virulence factors, virulence markers, and antimicrobial resistance. Cultures of rectal feces from 500 animals were screened for VT by an enzyme-linked immunosorbent assay (ELISA) and by polymerase chain reaction (PCR) for genes vt1, vt2, and eae. The VT-ELISA-positive samples were tested by a VT-immunoblot to isolate VTEC colonies. The prevalence rates of VTEC by VT-ELISA and PCR were 10.2% [95% confidence interval (CI), 7.8% to 13.2%] and 6.2% (95% CI, 4.4% to 8.7%), respectively. Colonies of VTEC were isolated from 27 (53%) of the 51 VT-ELISA-positive samples and belonged to 24 serotypes, which did not include O157:H7. Twelve of the serotypes have been implicated in disease in humans. Virulence profiling of the isolates by PCR revealed that 2 (8%) were eae-positive, 5 (21%) had vt1 only, and 19 (79%) had vt2, of which 3 had vt2 only, 7 had vt1 + vt2, 4 had vt2 + vt2c, 2 had vt2 + vt2c + vt2d, 2 had vt1 + vt2 + vt2c, and 1 had vt1 + vt2 + vt2c + vt2d. The distribution of selected plasmid-encoded putative virulence genes was as follows: ehxA, 63%; espP, 46%; saa, 67%; and subA, 54%. Nine of the 24 isolates were resistant to 1 or more antimicrobials. Major conclusions are that the VTEC prevalence of 10.2% was among the lower rates reported for beef cattle, a high proportion of the isolates had vt2 genes, the subA gene was reported for the 1st time in Canadian VTEC, and the absence of O157 VTEC likely reflects the use of a technique that detected all VTEC.     

A Proposed Role for VEGF Isoforms in Sex-Specific Vasculature Development in the Gonad

Many scientists have expended efforts to determine what regulates development of an indifferent gonad into either a testis or ovary. Expression of Sry and upregulation of Sox9 are factors that initiate formation of the testis-specific pathway to allow for both sex-specific vasculature and seminiferous cord formation. Migration of mesonephric precursors of peritubular myoid cells and endothelial cells into the differentiating testis is a critical step in formation of both of these structures. Furthermore, these events appear to be initiated downstream from Sry expression. Sertoli cell secretion of growth factors acts to attract these mesonephric cells. One hypothesis is that a growth factor specific for these cell linages act in concert to coordinate migration of both peritubular and endothelial cells. A second hypothesis is that several growth factors stimulate migration and differentiation of mesonephric 'stem-like' cells to result in migration and differentiation into several different cell lineages. While the specific mechanism is unclear, several growth factors have been implicated in the initiation of mesonephric cell migration. This review will focus on the proposed mechanisms of a growth factor, Vascular Endothelial Growth Factor, and how different angiogenic and inhibitory isoforms from this single gene may aid in development of testis-specific vascular development.     

Prevalence and antimicrobial resistance among Escherichia coli and Salmonella in Ontario smallholder chicken flocks

Surveillance is an important component of an overall strategy to address antimicrobial resistant bacteria in food animals and the food chain. The poultry market has many points of entry into the Canadian food chain, and some production practices are underrepresented in terms of surveillance. For example, pathogen carriage and antimicrobial resistance surveillance data are limited in smallholder chicken flocks raised for slaughter at provincially inspected abattoirs. In Canada, antimicrobial resistance in Escherichia coli and Salmonella isolated from commercial broiler chicken flocks, slaughtered at federally inspected abattoirs, is monitored by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS ). The objective of this study was to establish baseline information of antimicrobial resistance presence in E. coli and Salmonella isolated from smallholder flocks in Ontario, utilizing CIPARS collection and isolation methodologies, and to compare findings with CIPARS federally inspected abattoir data from Ontario, Canada. Five chickens per flock were sampled from 205 smallholder flocks. Of 1,025 samples, the E. coli prevalence was 99% (1,022/1,025), and 47% (483/1,022) of positive E. coli isolates were resistant to one or more of the 14 antimicrobials. Furthermore, as compared to results reported for the CIPARS commercial flocks, E. coli isolates from smallholder flocks had significantly lower resistance prevalence to six of 14 individual antimicrobials. Recovery of E. coli did not differ between federally inspected and provincially inspected flocks. Salmonella prevalence at the bird level in smallholder flocks was 0.3% (3/1,025), significantly lower (p  ? 0.0001, 95% CI 0.080%–0.86%) than federally inspected commercial flocks. The overall differences found between the commercial and smallholder flocks may be explained by differences in poultry husbandry practices and hatchery sources.