Prevalence of selected Shiga toxin-producing Escherichia coli vaccine antigen genes among two geographically distinct ruminant populations

Journal of Medical Microbiology · 2026-03-19

gene prevalence are likely due to the use of selective agars in isolation protocols.

Investigating the impacts of best management practices on fecal indicator bacteria, Giardia spp., and Cryptosporidium spp. in stream water from California meadows

Agriculture Ecosystems & Environment · 2026-03-03

The loss in number and function of wet meadow ecosystems in California is often associated with reduced drought tolerance and impaired water quality in watersheds. This research focused on investigating the improvement of meadow health and water quality by implementing best management practices (BMPs), particularly wildlife-friendly, cattle-exclusion fencing (allowing passage of wildlife) along streams, in a multi-use riparian wet meadow system. This longitudinal study followed the concentration of fecal indicator bacteria and fecal pathogens in the stream water from 2017 through 2022. Total coliforms, Escherichia coli , Giardia cysts, Cryptosporidium oocysts, and hydrologic parameters were monitored. The impact of the cattle exclusion fencing was evaluated using mixed-effect negative binomial and logistic regression models. Using EPA Method 1623, the overall prevalence of exceeding water quality standards for E. coli , Giardia spp., and Cryptosporidium spp. in the stream surface waters was 12.9%, 17.7%, and 27.1%, respectively. When the cattle exclusion fencing was present in a downstream location, E. coli in stream samples was reduced by 28 organisms/100 ml . Furthermore, significantly fewer water samples exceeded the regulatory thresholds set by the California State Water Resources Control Board when exclusion fencing was present. No statistically significant association was detected between fencing and the presence of Giardia spp. or Cryptosporidium spp. The hydrologic data revealed that the valley floor held more water over time, which was released more slowly throughout the year. This indicates that the wet meadow function is recovering, and suggests that using BMPs, including wildlife-friendly cattle exclusion fencing, in a multi-use wet meadow ecosystem that includes ranching, can help improve surface water quality and ecosystem health. • Protozoal pathogens in streams were detected throughout 5 years of meadow restoration. • Cattle exclusion fencing was associated with reduced freshwater stream E. coli concentrations. • Stream E. coli concentrations decreased by 28 organisms/100 ml at riparian fencing locations. • Cattle exclusion fencing was associated with improved water quality in California meadows.

The association between the use of dry cow therapy and bacteriological cure after calving and the development of phenotypic antimicrobial resistance on Egyptian dairy farms

PLoS ONE · 2026-04-01

Blanket dry cow therapy is a common practice on dairies to control mastitis, and when adopted, constitutes the majority of antimicrobial use on a dairy. The current study aimed to investigate the effect of dry cow therapy on the bacteriological cure and new infections after calving, and the association between dry cow therapy and antimicrobial resistance of Staphylococcus aureus isolated from milk samples of dairy cows after calving on Egyptian dairy farms. A randomized clinical trial was implemented on two Egyptian dairy farms. A total of 400 cows were randomized to one of four intramammary treatments at dry-off (Antibiotic, AB; Internal teat sealant, ITS; AB&ITS, or no treatment; Control). Composite milk samples were collected from enrolled cows at dry-off before receiving treatments and after calving. Bacterial culture and species identification were performed based on colony morphology, biochemical identification, and PCR using 16S rRNA. The Minimum Inhibitory Concentration (MIC) for each of the study Staphylococcus aureus (S. aureus) isolates was estimated using a commercial plate (CMV1AMAF Sensititre plate). Logistic regression models were used to estimate the effect of the different dry cow treatments on bacteriological cure and new infections. Parametric survival interval regression models were used to model the association between dry cow treatment and antimicrobial resistance after calving. Cows with a history of mastitis at the dry-off lactation had significantly higher odds (Odds Ratio, OR = 2.2, SE = 0.005, P < 0.01) of bacteriological cure compared to cows with no history of mastitis at the dry-off lactation. The highest percentage of resistance at dry-off was observed against penicillin (64%), sulfadimethoxine (54%), and erythromycin (30%) during the Spring/Summer season, while 37% was observed against penicillin and 30% for sulfadimethoxine during the Fall/Winter season. There was a significant increase in the MIC for ampicillin and ceftiofur in S. aureus isolated from cows that received AB and AB&ITS at dry-off in both study seasons. The current study revealed that more than 30% of subclinical mastitis cows were infected with S. aureus at dry-off and after calving, which requires future studies to evaluate the control measures of contagious mastitis implemented on Egyptian dairies before implementing the selective dry cow therapy algorithm.

Epidemiology of Antimicrobial Residues and Phenotypic Resistance of Bacterial Isolates from Waste Milk on California Dairies

Microorganisms · 2026-03-10

Waste milk (WM) on dairies is commonly fed to pre-weaned calves, raising concerns about antimicrobial drug (AMD) residues and their potential role in selecting for antimicrobial-resistant bacteria in their gut microbiota. The current observational study assessed AMD residue prevalence in WM and examined associations with AMR patterns in its bacterial isolates. Over a 10-month period, 40 WM samples were collected from eight dairies across Northern California, Northern San Joaquin Valley, and Greater Southern California. ELISA was used to detect six AMD residues, and bacterial isolates (n = 348), including coliforms, Streptococcus spp., Staphylococcus spp., and Staphylococcus aureus, were tested for AMR. Antimicrobial resistance was evaluated using the broth microdilution test, and associations with the presence of residues were analyzed via interval-censored accelerated failure time models. Ceftiofur was the most frequently detected residue (30%), followed by penicillin (5%), florfenicol (5%), and sulfadimethoxine (5%). Resistance varied by bacterial species, with significant associations observed between florfenicol residues and resistance in coliforms (MIC ratio = 2.12; p &lt; 0.01), and between ceftiofur residues and resistance in Streptococcus spp. (MIC ratio = 10.51; p = 0.03). These findings suggest that WM may contain low-level AMD residues linked to elevated AMR, highlighting the need for targeted antimicrobial stewardship practices to mitigate AMR dissemination in dairy calves.

Feeding preweaning Holstein calves a synbiotic supplement increases their energy-corrected milk yield as lactating cows

Journal of Dairy Science · 2026-02-06

Prebiotics and probiotics are feed additives that can benefit the host by modulating the gut microbiome, which is crucial in digestion, immunity, and overall animal health. This study aims to evaluate the effects of supplementing prebiotics, probiotics, or synbiotics to preweaning Holstein calves on their future milk yield. This study is a retrospective analysis of milk yield records from dairy cows that were randomized at birth to 1 of 4 twice-daily treatments administered during the preweaning period: (1) control, no additive (CON), (2) prebiotic (PRE; 7 mL of Saccharomyces cerevisiae yeast culture), (3) probiotic (PRO; Bacillus subtilis and Lactobacillus plantarum, delivering ∼1 billion and 250 million cfu per head per day, respectively), or (4) synbiotic (SYN; combination of both PRE and PRO at the same dosages as the PRE and PRO treatments). The study was conducted on a dairy farm in Fresno County, California, between 2019 and 2023, involving 1,296 Holstein cows over their first 3 lactations for a total of 2,735 lactations. Monthly test day records for milk yield, fat, and protein were used to calculate ECM, standardized to 4% fat and 3.3% protein, totaling 26,464 monthly test day milk records. A 2-piece splines mixed-effect regression model evaluated the effect of treatments on ECM yield. For the first lactation, ECM yield was estimated at 28.66 kg on the first DIM, peaked at 42.1 kg, and declined to 21.34 kg by 305 DIM. For parity ≥2, ECM yield was 41.06 kg at 1 DIM, peaked at 54.2 kg, and 33.74 kg at 305 DIM. The SYN treatment increased ECM yield by 1.00 kg/d compared with CON. This increase was primarily due to an increase in milk fat yield, with 0.048 kg/d more fat produced compared with the control group. No differences in ECM yield between PRE, PRO, or CON were observed. These findings suggest that supplementing SYN during the preweaning period increased milk, milk fat, and ECM yield across lactations 1, 2, and 3.

Rift Valley fever vaccines for animals and people: Envisioning One Health vaccination strategies

CABI One Health · 2026-02-05

Abstract Background: Rift Valley fever (RVF) is a zoonotic viral disease transmitted by mosquitoes, that causes significant impacts on animal health, public health, and socio-economic wellbeing in affected areas. Although RVF vaccines for livestock are available and human vaccines are currently under development, a coordinated One Health approach to vaccination has yet to be fully explored. This mini-review article aims to examine RVF vaccination strategies from a One Health perspective. Methods: Through a narrative literature review, evidence on RVF vaccination strategies for animals and humans was analyzed. Recurring themes relevant to decision making were identified and categorized into six interconnected decision domains, establishing a “One Health vaccination strategies” (OHVS) framework used to structure the synthesis and discussion of the evidence. Based on the available literature, as well as on strategies implemented for livestock and mathematical modeling studies, six joint scenarios combining livestock and human vaccination are suggested for future investigations. Results: Current evidence primarily supports preventive mass vaccination for livestock and indicates a targeted strategy for high-risk human populations. Conclusions: The expected synergistic benefits for affected communities, along with the balanced distribution of responsibilities and resources across sectors, make OHVS a valuable intervention framework. Once RVF human vaccines become available, this unified approach can strengthen collaboration among public health, veterinary, and environmental sectors, leading to a more effective, equitable, and sustainable intervention landscape. One Health impact statement Rift Valley fever (RVF) exemplifies the intricacies of environmental, human, and animal interconnections and interdependencies. Countries such as Tanzania where RVF is endemic have experienced decadal outbreaks in addition to a potential persistent transmission pattern, warranting implementation of vaccination programs that are effective in the context of complex disease ecosystem. This article explores the possibilities for vaccinating animals and humans as a critical component of a unified One Health approach to RVF prevention and control, drawing from existing literature and promising new research paths. It also outlines a practical decision making framework to help shape effective RVF vaccination strategies for both human and animal populations. By working closely with partners in Tanzania and the United States, this initiative demonstrates proof of concept for the importance of transdisciplinary collaboration and cross-sectoral coordination in disease prevention and control. This also provides actionable insights for both the scientific community and decision makers.

Assessing the impact of biosecurity compliance on farmworker and livestock health within a one health modeling framework

One Health · 2025-04-04 · 2 citations

Biosecurity compliance refers to adherence to protocols aimed at preventing infectious disease outbreaks and controlling antimicrobial resistance (AMR) across human, animal, and environmental interfaces. While many models focus solely on animal health, this study develops a One Health modeling framework to assess the impact of different compliance levels on both animal and farmworker health. The model integrates Ordinary Differential Equations (ODE) for pathogen transmission in animals and the environment with Stochastic Differential Equations (SDE) for disease spread among farmworkers. The next-generation matrix approach estimates the basic reproduction number R 0 i specific to each pathogen strain i , identifying thresholds for outbreaks or elimination of infection. Using literature-derived data on Salmonella transmission dynamics, the model is validated, and key parameters values are estimated. Using the calibrated model, we examine infection transmission in dairy cattle and zoonotic spillover to farmworkers with a focus on five key biosecurity measures: (1) animal movement control and quarantine, (2) disease monitoring and reporting, (3) hygiene and disinfection, (4) feeding and watering practices, and (5) antimicrobial stewardship. Simulations reveal that compliance with biosecurity measures that reduce host-to-host transmission in the animal population has the highest impact on the reduction of infection both in animal and farmworker populations. Further ODE-SDE model analysis indicates that full compliance with the other biosecurity measures is insufficient to prevent outbreaks in a dairy farm. These results are consistent with the local and global sensitivity analyses of the model. The One Health modeling framework developed in this study can also be applied to other zoonotic diseases as a guiding tool for decision making and optimal resource allocation to reduce the likelihood of spillover. • We examine the effects of varying biosecurity compliance on co-evolutionary dynamics of zoonotic disease spillover. • Controlling animal-to-animal disease transmission is crucial, but no single biosecurity measure can prevent outbreaks. • The One Health framework highlights the crucial role of farmworkers' efforts in mitigating zoonotic spillover risks on farms.

Antibiogram use on dairy cattle for bovine respiratory disease: Multidrug resistance in Pasteurella multocida and Mannheimia haemolytica in California dairies

Journal of Dairy Science · 2025-07-03 · 3 citations

Multidrug-resistant (MDR) bovine respiratory pathogens can significantly decrease treatment success and have an effect on dairy farm productivity. Although antibiograms have emerged as a tool to support empirical decision making for disease treatment, the prevalence of MDR isolates on a farm can have a negative effect on the selection of the best antibiotic treatment using antibiogram data. This study aimed to characterize the MDR profile of Pasteurella multocida and Mannheimia haemolytica isolates from the deep nasopharyngeal swabs of calves, heifers, and cows diagnosed with bovine respiratory disease (BRD) over 2 yr. For this purpose, animals were sampled in a repeated cross-sectional study from 3 large dairy farms in Northern California. From this study, a total of 146 P. multocida and 63 of M. haemolytica isolates were isolated and tested for antimicrobial susceptibility. Our results showed that, overall, a small fraction of the animals in the study had MDR P. multocida (15%) and M. haemolytica (17%). The prevalence of MDR P. multocida isolates was comparable between calves (14%), heifers (19%), and cows (12%), whereas MDR M. haemolytica was most prevalent in heifers (40%) followed by calves (4%). No MDR M. haemolytica was detected in the isolates from cows. Farm effect had the most significant association with MDR BRD pathogens, with 1 farm accounting for 94% of all MDR isolates of the study, while season had a minor association with MDR. The most common antimicrobial resistance drug classes across MDR pathogens were macrolides, phenicols, quinolones, and tetracyclines. Prevalence of resistant isolates to tetracyclines represented the greatest disparity between the 2 BRD pathogens evaluated, with P. multocida isolates having a higher percentage of resistance (71.8%) when compared with M. haemolytica (22.2%). In conclusion, there was a low prevalence of MDR in both P. multocida and M. haemolytica in the study, but farm management and the age of the animals increased the odds of MDR prevalence. These factors should be considered when generating antibiogram reports for BRD treatment to account for the potential prevalence of MDR isolates.

Antibiogram use on dairy cattle for bovine respiratory disease: Factors associated with bacterial pathogen identification and prediction of bacterial recovery using machine learning

Journal of Dairy Science · 2025-04-17 · 3 citations

Effective isolation of bacterial pathogens for bovine respiratory disease (BRD) is a critical step for accurate diagnosis of the agent associated with this disease on the dairy. Limited information is available on factors associated with herd-level bacterial pathogen recovery for BRD clinical cases, which are important data to help identify strategies to support the successful collection of a minimum number of each organism over time to generate cumulative antibiogram susceptibility testing reports. Our objective was to evaluate factors associated with the recovery of common pathobionts (Pasteurella multocida and Mannheimia haemolytica) in BRD clinical cases from preweaning calves, heifers, and cows at 3 California dairy farms over 2 yr. A second objective was to test the predictability of isolating these organisms in BRD clinical cases using the factors evaluated in the first objective utilizing machine learning (ML). During monthly herd visits, deep nasopharyngeal samples were collected from calves, heifers, and cows diagnosed with BRD over 2 yr. Samples were cultured in aerobic conditions, and pathogens were isolated through colony morphology and validated with MALDI-TOF MS. Evaluation of factors influencing bacterial recovery was initially tested for independence, followed by a logistic regression model and a stepwise logistic feature selection in SAS, and ML classifiers with leave-one-out cross-validation in Python packages. For our study, samples were collected from a total of 301 BRD clinical cases: 146 samples with a culture-positive for P. multocida, 63 samples with a culture-positive for M. haemolytica, and 3 samples with a culture-positive for Histophilus somni. For factors associated with the culture-positive of P. multocida in BRD clinical cases, an interaction between age and season was identified, where cows had overall lower odds of being culture-positive independently of the season when compared with calves in the spring and summer and heifers in the fall and winter. For factors associated with the culture-positive of M. haemolytica in BRD clinical cases, an interaction was also observed between age and season, but the farm further played a role in the odds of being culture-positive, with one farm having considerably greater odds than the remaining ones. Machine learning models with cross-validation showed a weak ability to distinguish positive from negative cases when using age, season, and farm for all scenarios according to F1-scores and receiver operating characteristic analysis. Differences in predictive abilities, factor importance, and the still limited number of predictors in these ML analyses further indicate a potential for building more robust future models once datasets are expanded and more robust algorithms are considered. Overall, correctly identifying factors that may be associated with the prevalence of BRD pathogens and, therefore, recovery of these pathogens is critical for the development of antibiogram programs for evaluation of the antimicrobial susceptibility of BRD pathogens.

Daily Milk Losses Associated with Dairy Cow Bunching, Cattle’s Protective Behavior Against Stable Flies (Stomoxys calcitrans) in California

Veterinary Sciences · 2025-10-26 · 1 citations

Cow bunching is a behavioral phenomenon where cattle aggregate in tight groups to protect themselves from biting by stable flies (Stomoxys calcitrans L.). The incidence of bunching varies between dairies and even among pens within the same dairy, as it is associated with the location-specific biting intensity of stable flies, which largely varies with dairy management and local environmental factors. Bunching may be associated with decreased feeding and laying times, as well as heat stress due to cattle aggregation. Thus, bunching may affect dairy cows’ milk production by reducing dry matter intake and rumination. To our knowledge, there are no previous studies specifically addressing the effect of cow bunching on milk production in lactating dairy cows. The objectives of our study were to estimate the economic impact of cow bunching against stable flies on milk production on a commercial California dairy and to estimate the economic losses associated with cow bunching and stable fly biting per cow per year. A longitudinal study was conducted from 1 May 2017 through 31 July 2017 on a 5000-cow Holstein herd housed in free stall pens in Tulare County, California. Pen-level cow bunching in four lactating cow pens was recorded weekly for 12 weeks. Bunching observations each day were matched to daily milk records for the study dairy. Two-piece spline linear mixed models were used to estimate the impact of cow bunching and stable fly counts on milk production. Cows in pens where bunching occurred experienced a significant milk reduction of 0.45 kg ± 0.104 (SE) per cow (p &lt; 0.01) on the day of bunching in comparison to cows in pens without bunching. There was a significant reduction of 0.6 kg/cow/day in milk production associated with each increase in one stable fly per cow leg (standard metric for recording stable fly biting activity) after adjusting for parity, temperature humidity index (THI), and days in milk (DIM). Based on the economic analysis conducted on weekly bunching and fly counts, modeled milk production losses were reported as weekly loss in milk revenue per cow. The estimated economic loss associated with cow bunching and stable fly counts was highest during the last week of May (USD 0.34/cow/week and USD 1.86/cow/week, respectively) and was lowest during the last week of July (USD 0.03/cow/week and USD 0.29/cow/week, respectively). To mitigate the most substantial economic loss, dairy producers should focus their efforts on controlling stable flies during the early stable fly season, when stable fly abundance tends to be highest.