A systematic review and meta-analysis were conducted to determine the efficacy of selective dry-cow antimicrobial therapy compared to blanket therapy (all quarters/all cows). Controlled trials were eligible if any of the following were assessed: incidence of clinical mastitis during the first 30 DIM, frequency of intramammary infection (IMI) at calving, or frequency of IMI during the first 30 DIM. From 3480 identified records, nine trials were data extracted for IMI at calving. There was an insufficient number of trials to conduct metaanalysis for the other outcomes. Risk of IMI at calving in selectively treated cows was higher than blanket therapy (RR = 1.34, 95% CI = 1.13, 1.16), but substantial heterogeneity was present (I 2 = 58%). Subgroup analysis showed that, for trials using internal teat sealants, there was no difference in IMI risk at calving between groups, and no heterogeneity was present. For trials not using internal teat sealants, there was an increased risk in cows assigned to a selective dry-cow therapy protocol, compared to blanket treatment, with substantial heterogeneity in this subgroup. However, the small number of trials and heterogeneity in the subgroup without internal teat sealants suggests that the relative risk between treatments may differ from the determined point estimates based on other unmeasured factors.

Infections due to Campylobacter, Escherichia coli and Salmonella pose a significant health burden in Canada, resulting in major costs to the health care system and economic impacts due to lost productivity resulting from illness. Recent literature suggests that climate may play a role in the prevalence of these pathogens along the food chain. This study used integrated surveillance data to examine associations between weather variables, serving as a proxy for climate, in agricultural areas and Campylobacter, generic E. coli and Salmonella contamination on samples of beef, poultry and swine meat products in Canada. Various temperature metrics (average, maximum and variability) were correlated with Campylobacter prevalence along the food chain. The prevalence of E. coli and Salmonella was correlated with both precipitation and temperatures metrics; however, analysis for E. coli was limited to beef and swine meats at retail settings, because prevalence in other combinations approached 100%, which obviated further analysis. Campylobacter contamination in poultry and swine at abattoir and retail settings demonstrated a seasonal trend, with increased prevalence generally from June or July through November, compared to the baseline month of December. Based on these analyses, Campylobacter is the most likely foodborne bacteria studied whose occurrence in meat products is affected by climatic changes in Canada. An exploratory analysis of data at the provincial scale, using Ontario as an example, revealed similar directional relationships between climate and bacterial prevalence.

Coxiella burnetii is a zoonotic bacterium that causes Q fever, a potentially severe disease of humans. The objectives of this study were to determine the seroprevalence and risk factors for C. burnetii exposure in sheep and goat farm workers in Ontario, Canada. Between August 2010 and March 2012, 172 farm workers from 78 sheep and goat farms were surveyed regarding demographics, lifestyle, farm practices, and medical history. Sera from these people were collected and analyzed for Q fever titers using the immunofluorescence assay. A mixed multivariable logistic regression model was constructed to identify risk factors for seropositivity. Individual-level and farm-level seroprevalence for C. burnetii were 64.5% (111/172, 95% CI = 57.2-71.4) and 74.4% (58/78, 95% CI = 63.2-83.6), respectively. Farm worker seropositivity was positively associated with an increasing proportion of seropositivity of sheep/goats on farm (odds ratio [OR] = 1.04; 95% CI 1.02-1.07). A higher odds of seropositivity was also observed for people working on dairy goat farms compared to the odds on dairy sheep (OR = 0.04; 95% CI 0.003-0.53) or meat goat (OR = 0.09; 95% CI 0.01-0.67) farms. Coxiella burnetii seropositivity was common in workers on sheep and goat farms in Ontario. Given the significant risk of morbidity associated with this infection, early recognition and treatment of Q fever are important. The risk factors identified provide insight into disease transmission between animals and people, which is particularly important for farmers, researchers, medical doctors, veterinarians, and public health professionals. Physicians practicing in rural areas should consider Q fever infection when patients present with atypical pneumonia and suggestive risk factors.

Coxiella burnetii is a zoonotic bacterium, and infection in goats with this bacterium can result in abortion, stillbirth or birth of non-viable kids. A cross-sectional study was conducted to identify the seroprevalence and risk factors for C. burnetii exposure in Ontario goats. Sera were collected between August 2010 and February 2012, and tested for C. burnetii specific antibodies using an enzyme-linked immunosorbent assay (IDEXX). Overall, 63.2% (48/76, 95% CI=51.9-73.4) of farms had one or more seropositive goats. A higher farm-level seroprevalence of 78.6% (33/42) was found on dairy goat farms, compared to 44.1% (15/34) on meat goat farms (p<0.01). At the overall individual-animal level, 32.5% (714/2195, 95% CI=30.6-34.5) of goats were seropositive. Similarly, a higher individual-level seroprevalence was identified for dairy goats (43.7%, 633/1447) compared to meat goats (10.8%, 81/748) (p<0.001). A mixed multivariable logistic model that controlled for farm-level clustering identified risk factors associated with seropositivity (p<0.05). Increases in the female herd size (logarithmic scale) were associated with increased odds of seropositivity, while increases in male herd size had a negative association with seropositivity. If other sheep or goat farms were located in a 5-km radius, goats had 5.6 times (95% CI=1.01-30.8) times the odds of seropositivity compared to those that were not. Relative to goats from farms where all kidding pen hygiene was practiced (adding bedding, removing birth materials and disinfection after kidding), goats from farms which only added bedding and removed birth materials had a higher odds of seropositivity (OR=19.3, 95% CI=1.1-330.4), as did goats from farms which practiced none of these measures (OR=161.0, 95% CI=2.4-10822.2). An interaction term revealed kidding outdoors when there were no swine on farm had a protective effect on seropositivity compared to kidding indoors, or kidding outdoors with swine on the farm. These results can inform strategies to mitigate exposure to C. burnetii in Ontario.

A systematic review and network meta-analysis were conducted to assess the relative efficacy of antimicrobial therapy given to dairy cows at dry-off. Eligible studies were controlled trials assessing the use of antimicrobials compared to no treatment or an alternative treatment, and assessed one or more of the following outcomes: incidence of intramammary infection (IMI) at calving, incidence of IMI during the first 30 days in milk (DIM), or incidence of clinical mastitis during the first 30 DIM. Databases and conference proceedings were searched for relevant articles. The potential for bias was assessed using the Cochrane Risk of Bias 2.0 algorithm. From 3480 initially identified records, 45 trials had data extracted for one or more outcomes. Network meta-analysis was conducted for IMI at calving. The use of cephalosporins, cloxacillin, or penicillin with aminoglycoside significantly reduced the risk of new IMI at calving compared to non-treated controls (cephalosporins, RR = 0.37, 95% CI 0.23–0.65; cloxacillin, RR = 0.55, 95% CI 0.38–0.79; penicillin with aminoglycoside, RR = 0.42, 95% CI 0.26–0.72). Synthesis revealed challenges with a comparability of outcomes, replication of interventions, definitions of outcomes, and quality of reporting. The use of reporting guidelines, replication among interventions, and standardization of outcome definitions would increase the utility of primary research in this area.