Search Results (29)

Background/Objectives: Bovine respiratory disease complex (BRDC) is commonly treated empirically, as etiological diagnosis is often impractical under field conditions. Comparative evidence on antimicrobial efficacy in undifferentiated BRDC remains limited. This study aimed to compare the therapeutic efficacy of tulathromycin and ceftiofur for treating undifferentiated BRDC in dairy cattle and to describe hematological and biochemical responses following a tulathromycin metaphylaxis program implemented during the seasonal high-PM2.5 period in northern Thailand. Methods: Thirty-eight Holstein–Friesian cattle with clinical BRDC were randomly assigned to receive tulathromycin (2.5 mg/kg, single subcutaneous dose; n = 20) or ceftiofur (2.2 mg/kg, intramuscularly for three consecutive days; n = 18). The clinical parameters of the surviving cattle were monitored for 5 days, and hematological and biochemical profiles were assessed on Days 1 and 5 in the surviving cattle. In addition, 87 pregnant dairy heifers were enrolled in a metaphylaxis trial and allocated to no injection, one tulathromycin injection, or two injections administered one month apart. Results: Cure rates were comparable between the tulathromycin and ceftiofur groups (90.0% vs. 88.9%), with similar case fatality rates (10.0% vs. 11.1%). No significant between-group differences were observed for clinical, hematological, or biochemical parameters. Both treatments resulted in significant within-group clinical and hematological improvement. During the metaphylaxis trial, no animals developed clinical BRDC; however, significant differences were observed in selected hematological parameters among injection groups. Conclusions: Tulathromycin and ceftiofur demonstrated comparable efficacy for treating undifferentiated BRDC in dairy cattle under field conditions. In the metaphylaxis component, conducted during the seasonal high-PM2.5 period, the absence of clinical BRDC cases did not allow for evaluation of preventive efficacy. Nevertheless, differences in selected blood parameters were observed among injection groups and should be interpreted cautiously, warranting further investigation in studies incorporating low- and high-PM2.5 comparisons. Full article

Background/Objectives: The expansion of intensive swine production in Córdoba, Argentina, underscores the need to assess the risks associated with antimicrobial (AM) use, whose extensive application has driven antimicrobial resistance, a major global threat within the One Health framework. This study aimed to characterize AM use practices and evaluate the epidemiological resistance profiles (non-wild-type phenotypes, NWT) of commensal Escherichia coli of fecal origin from swine farms, using epidemiological cut-off values (ECOFFs) as a surveillance criterion. Methods: An observational cross-sectional study was conducted in 19 farrow-to-finish farms in Córdoba during 2023. Information on AM use (prophylaxis, metaphylaxis, treatment) across production categories was collected. A total of 437 E. coli isolates were obtained from fecal samples, and minimum inhibitory concentrations (MICs) were determined for 10 AMs of critical importance for human and animal health. NWT phenotypes were classified according to EUCAST ECOFFs, and multidrug resistance (MDR) was assessed. Results: AM use was frequent and predominantly prophylactic (89.5% of farms), mainly through mass medication (66.3%), with macrolides and amoxicillin being the most commonly administered AMs. NWT proportions were extremely high (90–92%) for ampicillin, tetracyclines, and chloramphenicol and substantial for ciprofloxacin (50.6%), sulfamethoxazole (68.2%), and trimethoprim (44.9%). Extended-spectrum β-lactamase (ESBL)-producing phenotypes were detected. Alarmingly, 92% of isolates were classified as MDR E. coli, with homogeneous distribution across production categories. Conclusions: Findings reveal intensive and largely empirical AM use that has consolidated a stable intestinal resistome in the swine population. High MDR levels, even in categories with limited direct AM exposure or involving banned compounds, suggest that co-selection and horizontal gene transfer are key drivers of resistance. This scenario highlights the urgent need to strengthen integrated surveillance and promote prudent AM use strategies under the One Health approach to preserve therapeutic efficacy. Full article

Background/Objectives: Long-read metagenomic sequencing can detect bacteria and antimicrobial resistance genes (ARGs) from bovine respiratory samples, providing an alternative to culture and antimicrobial susceptibility testing (C/S). This study applied Bayesian latent class models (BLCMs) to estimate the sensitivity (Se) and specificity (Sp) of long-read metagenomic sequencing compared to C/S for detecting Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni, as well as associated macrolide and tetracycline resistance potential. Methods: Deep nasopharyngeal swabs were collected from fall-placed feedlot calves at arrival, 13, and 36 days on feed across two years and two metaphylaxis protocols. Samples underwent C/S and long-read metagenomic sequencing. BLCMs were used to estimate Se and Sp for the detection of bacteria and potential for antimicrobial resistance (AMR). Results: Se and Sp for detecting respiratory bacteria by metagenomics were not significantly different than culture, with four exceptions. For the 2020 samples, Se for M. haemolytica was lower than culture, and Sp for H. somni was lower, while in both 2020 and 2021 samples, Se for P. multocida was higher for metagenomics than culture. The estimated Se and Sp of metagenomics for the detection of msrE-mphE, EstT, and tet(H) within bacterial reads were either not significantly different or were lower than AST, with Sp > 95% with one exception. Conclusions: This study provided BLCM-based estimates of clinical Se and Sp of metagenomics and C/S without assuming a gold standard in a large pen research setting. These findings demonstrate the potential of long-read metagenomics to support bovine respiratory disease diagnostics, AMR surveillance, and antimicrobial stewardship in feedlot cattle. Full article

Antimicrobial resistance (AMR) in livestock production systems has emerged as a major global health concern, threatening not only animal welfare and agricultural productivity but also food safety and public health. The widespread, and often poorly regulated, use of antimicrobials for growth promotion, prophylaxis, and metaphylaxis has accelerated the emergence and dissemination of resistant bacteria and resistance genes. These elements circulate across interconnected animal, environmental, and human ecosystems, driven by mobile genetic elements and amplified through the food production chain. It is estimated that more than two-thirds of medically important antimicrobials are used in animals, and AMR could cause millions of human deaths annually by mid-century if unchecked. In some livestock systems, multidrug-resistant E. coli prevalence already exceeds half of isolates, particularly in poultry and swine in low- and middle-income countries (LMICs). This narrative review provides a comprehensive overview of the molecular epidemiology, ecological drivers, and One Health implications of AMR in food-producing animals. We highlight key zoonotic and foodborne bacterial pathogens—including Escherichia coli, Salmonella enterica, and Staphylococcus aureus—as well as underappreciated reservoirs in commensal microbiota and livestock environments. Diagnostic platforms spanning phenotypic assays, PCR, MALDI-TOF MS, whole-genome sequencing, and CRISPR-based tools are examined for their roles in AMR detection, surveillance, and resistance gene characterization. We also evaluate current antimicrobial stewardship practices, global and regional surveillance initiatives, and policy frameworks, identifying critical implementation gaps, especially in low- and middle-income countries. Emerging sectors such as aquaculture and insect farming are considered for their potential role as future AMR hotspots. Finally, we outline future directions including real-time genomic surveillance, AI-assisted resistance prediction, and integrated One Health data platforms as essential innovations to combat AMR. Mitigating the threat of AMR in animal agriculture will require coordinated scientific, regulatory, and cross-sectoral responses to ensure the long-term efficacy of antimicrobial agents for both human and veterinary medicine. Full article

Antimicrobial resistance (AMR) is a major public health concern influenced by antimicrobial use (AMU) in animal production systems. In swine, metaphylactic treatments may contribute to the emergence and dissemination of resistance genes. In this study, we isolated bacteria from the nasal cavities of 50 sows across 10 farms in the Federal District, Brazil. A total of 132 bacterial isolates were obtained and tested for phenotypic resistance to 23 antimicrobials using the disk diffusion method. Resistance was detected against all tested antimicrobials, with an overall resistance rate of 55.6% (1605/2888 tests). The highest resistance rates were observed for bacitracin (92.4%) and penicillin (79.2%), while lower resistance rates were found for aminoglycosides. Most isolates exhibited multidrug resistance to 7–9 classes of antimicrobials, including strains of Staphylococcus, Escherichia coli, and Klebsiella—all of which are relevant in the context of One Health. Actinobacillus suis showed the highest resistance levels among all identified species. AMR was positively correlated with both the duration and the number of antimicrobial agents used in feed, reinforcing the need for prudent AMU practices. The use of autogenous vaccines against Pasteurella multocida was associated with reduced lung lesions, underscoring the value of vaccination in disease control. AMR surveillance programs may benefit from including bacterial colonizers from the microbiota, though further studies are necessary to better understand the resistance dynamics of these commensals. Full article

Metaphylaxis or treating the entire population of cattle at arrival with an antimicrobial has been studied extensively in the cattle industry; however, little information is available on the impacts of treating only a proportion of the population with antimicrobials at arrival. The study objective was to determine potential associations between the proportion of animals in a pen treated with antimicrobial therapy with pen performance and nasopharyngeal microbiome. Yearling steers (n = 160) were randomly allocated to study pens (n = 40) and pens were systematically randomized to one of two antimicrobial treatments (META: all four head received tulathromycin; MIXED: two of four head randomly selected to receive tulathromycin). The study was conducted in conjunction with an essential oil feeding trial. Deep nasal pharyngeal (DNP) swabs were collected from every steer at Days 0, 14, 28, and 56. All DNP swabs were individually cultured for Pasteurella multocida and Mannheimia haemolytica. Samples of DNA were extracted from DNP swabs, pooled by pen, and analyzed by metagenomic shotgun sequencing to compare nasopharyngeal microbiome composition and quantity of resistance genes between test groups. Neither antimicrobial nor essential oil treatment groups had any significant associations with performance or DNP microbiome. Sampling day was significantly associated with alpha and beta diversity at the species level. Shannon’s diversity and Inverse Simpson diversity were significantly lower on Day 14 versus both Day 0 and Day 56. These data indicated a shift in microbial populations across study days; however, the microbiome diversity and relative abundance were not significantly different between antimicrobial treatment groups. Full article

Our study aimed to compare Bovine Respiratory Disease (BRD) morbidity, mortality, and growth in dairy and dairy beef cross-bred calves during the commingle period, 81–120 days of age, using two different BRD prevention strategies. The calves (n = 1799) were randomly assigned into groups: (1) Control (CON; received no vaccine or metaphylaxis); (2) Tulathromycin metaphylaxis (TUL; Increxxa^TM, Elanco Animal Health Inc., Greenfield, IN, USA); and (3) Mannheimia haemolytica vaccine (VACC; Nuplura^® PH, Elanco Animal Health Inc., Greenfield, IN, USA). Calves were individually weighed three times during the study to estimate average daily gain (ADG). Deep nasopharyngeal swabs, thoracic ultrasonography, health scores, and treatment records were collected during the study. Ultrasound and health score results were not different across treatments. In this study, the TUL group had a lower cumulative BRD incidence than CON. The cumulative incidence and 95% CI of BRD during the commingle period, 81–120 days of age for CON, TUL, and VACC were 0.43 (0.38 to 0.47), 0.36 (0.38 to 0.40), and 0.39 (0.35 to 0.43), respectively. The ADG for CON, TUL, and VACC were 0.25 ± 0.15, 0.32 ± 0.15, and 0.17 ± 0.15 kg, respectively. There was no difference among the treatment groups for ADG. Management and environmental conditions were variable at this operation throughout the study period and likely impacted the calves. Earlier interventions may be needed when the BRD incidence is elevated in high-risk calves. Full article

Metaphylactic antibiotic use in feeder cattle is a common practice to control respiratory disease. Antimicrobial stewardship is important to ensure continued efficacy and to protect animal welfare. The objective of this study is to identify characteristics of cohorts of cattle that had not received metaphylaxis that would have benefited economically from the use of metaphylaxis. Cohorts (n = 12,785; 2,206,338 head) from 13 feedlots that did not receive metaphylaxis were modeled using an economic model to estimate net returns for three metaphylactic options. Logistic regression models with covariates for entry weight, sex, average daily weight gain, number of animals per cohort, and days on feed, with feedlot as a random effect, were used to determine the model-adjusted probability of cohorts benefiting economically from metaphylaxis. Most (72%) cohorts in this data set that had not received metaphylaxis at arrival would not economically benefit from metaphylaxis. Sex, entry weight category, number of cattle in the cohort, and average daily weight gain were associated with the likelihood of benefitting economically from metaphylaxis. The results illustrated that cattle cohort demographics influenced the probability that cohorts would benefit economically from metaphylaxis and the type of metaphylaxis utilized, and integrating this information has the potential to influence the metaphylaxis decision. Full article

Antimicrobials are crucial for treating bovine respiratory disease (BRD) in beef feedlots. Evidence is needed to support antimicrobial use (AMU) decisions, particularly in the early part of the feeding period when BRD risk is highest. The study objective was to describe changes in prevalence and antimicrobial susceptibility of BRD bacterial pathogens at feedlot processing (1 day on feed (1DOF)), 12 days later (13DOF), and for a subset at 36DOF following metaphylactic antimicrobial treatment. Mixed-origin steer calves (n = 1599) from Western Canada were managed as 16 pens of 100 calves, receiving either tulathromycin (n = 1199) or oxytetracycline (n = 400) at arrival. Deep nasopharyngeal swabs collected at all time points underwent culture and antimicrobial susceptibility testing (AST). Variability in the pen-level prevalence of bacteria and antimicrobial susceptibility profiles were observed over time, between years, and metaphylaxis options. Susceptibility to most antimicrobials was high, but resistance increased from 1DOF to 13DOF, especially for tetracyclines and macrolides. Simulation results suggested that sampling 20 to 30 calves per pen of 200 reflected the relative pen-level prevalence of the culture and AST outcomes of interest. Pen-level assessment of antimicrobial resistance early in the feeding period can inform the evaluation of AMU protocols and surveillance efforts and support antimicrobial stewardship in animal agriculture. Full article

A population of burrowing owls (Athene cunicularia) under professional care at Zoomarine Portugal presented with sudden respiratory clinical signs. Clinical management included a thorough diagnosis plan, including in-house fecal analysis that revealed the presence of ovoid unioperculate eggs. In the postmortem examination of one hyperacute dyspneic specimen, adult nematode parasites were collected and identified based on their morphology as Cyathostoma (Hovorkonema) americana. Even after a broad-spectrum deworming protocol as part of the treatment and metaphylaxis approach, the incidence of parasitic reinfection was high. The complete clinical resolution was only accomplished after the identification and management of the possible focus of infection, a wild population of cattle egrets (Bubulcus ibis) that frequently congregated above the owls’ habitat. To the authors’ best knowledge, this is the first report of infection by Cyathostoma (Hovorkonema) americana in burrowing owls. Although nematodes of the family Syngamidae are not commonly included in the differential diagnosis of infectious respiratory agents of birds of the order Strigiformes, this report highlights the possibility of opportunistic parasitism in a zoological context, especially where there is a continued proximity to free-ranging avifauna. Full article

Emerging, re-emerging and zoonotic viral pathogens represent a serious threat to human health, resulting in morbidity, mortality and potentially economic instability at a global scale. Certainly, the recent emergence of the novel SARS-CoV-2 virus (and its variants) highlighted the impact of such pathogens, with the pandemic creating unprecedented and continued demands for the accelerated production of antiviral therapeutics. With limited effective small molecule therapies available for metaphylaxis, vaccination programs have been the mainstay against virulent viral species. Traditional vaccines remain highly effective at providing high antibody titres, but are, however, slow to manufacture in times of emergency. The limitations of traditional vaccine modalities may be overcome by novel strategies, as outlined herein. To prevent future disease outbreaks, paradigm shift changes in manufacturing and distribution are necessary to advance the production of vaccines, monoclonal antibodies, cytokines and other antiviral therapies. Accelerated paths for antivirals have been made possible due to advances in bioprocessing, leading to the production of novel antiviral agents. This review outlines the role of bioprocessing in the production of biologics and advances in mitigating viral infectious disease. In an era of emerging viral diseases and the proliferation of antimicrobial resistance, this review provides insight into a significant method of antiviral agent production which is key to protecting public health. Full article

Apart from increased fluid intake, patients with kidney stone disease (KSD) due to renal phosphate wasting require specific metaphylaxis. NaPi2a, NaPi2c, and NHERF1 regulate plasma phosphate concentration by reabsorbing phosphate in proximal kidney tubules and have been found altered in monogenic hypophosphatemia with a risk of KSD. In this study, we aimed at assessing the combined genetic alterations impacting NaPi2a, NaPi2c, and NHERF1. Therefore, we screened our hereditary KSD registry for cases of oligo- and digenicity, conducted reverse phenotyping, and undertook functional studies. As a result, we identified three patients from two families with digenic alterations in NaPi2a, NaPi2c, and NHERF1. In family 1, the index patient, who presented with severe renal calcifications and a bone mineralization disorder, carried digenic alterations affecting both NaPi transporter 2a and 2c. Functional analysis confirmed an additive genetic effect. In family 2, the index patient presented with kidney function decline, distinct musculature-related symptoms, and intracellular ATP depletion. Genetically, this individual was found to harbor variants in both NaPi2c and NHERF1 pointing towards genetic interaction. In summary, digenicity and gene dosage are likely to impact the severity of renal phosphate wasting and should be taken into account in terms of metaphylaxis through phosphate substitution. Full article

Antimicrobial resistance (AMR) is a global public health threat that jeopardizes efficacy of antibiotics in veterinary and human medicine. Antibiotics are commonly administered to target the bacterial component of bovine respiratory disease (BRD). The objectives of this study were to obtain a better understanding of antibiotic resistance in BRD-associated bacteria (Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni), investigate the clinical significance of AMR by monitoring clinical outcomes, and determine if regional differences exist in AMR trends. Deep pharyngeal swabs were used to sample beef cattle at initial BRD diagnosis (n = 453) from US feedlots representing three geographic regions. Organisms were identified by bacterial culture and subjected to broth microdilution antimicrobial susceptibility testing. Bacterium prevalence include P. multocida (36.0%), M. haemolytica (32.7%), and H. somni (28.5%). Of the Histophilus isolates, 39.5% were resistant to at least one antimicrobial, compared to 11.7% and 8.8% Pasteurella and Mannheimia, respectively. Non-susceptibility across all organisms was 5.7 X more likely in animals that received metaphylaxis, than those that did not (p < 0.0001; OR 5.7; CI 2.6–12.5). During days on feed 21–40, non-susceptibility of Histophilus was 8.7 X more likely than Mannheimia (p = 0.0002; OR 8.7; CI 2.8 to 27.4) and 6 X more likely than Pasteurella (p = 0.0016; OR 6.0; CI 2.0–18.0). Full article

The objectives were to evaluate the effects of metaphylaxis (META) and pull-and-treat (PT) programs on health, antimicrobial use, beef production, economics, and greenhouse gas emissions in cattle at medium risk for bovine respiratory disease (BRD). A randomized complete block design was used at two US commercial feedlots. Steers and heifers [2366 total; 261 (±11.0) kg initial weight] were blocked by sex and feedlot arrival, and allocated to one of two pens within a block (16 pens total, eight blocks). Pens were randomly assigned to treatment: META, tulathromycin injection at initial processing; or PT, tulathromycin injection only for first clinical BRD treatment. Data were analyzed with linear and generalized linear mixed models. There was greater BRD morbidity in PT than META cattle (17.2% vs. 7.3% respectively; p < 0.01), and greater total mortality (2.5% vs. 1.1% respectively; p = 0.03). Per animal enrolled, 1.1 antimicrobial doses were used for META compared to 0.2 for PT (p < 0.01). Per animal enrolled, final live (p = 0.04) and carcass (p = 0.08) weights were greater for META than PT; however, net returns ($/animal) were not significantly different (p = 0.71). Compared to PT, total lifetime estimated CO₂ equivalent emissions from production were reduced by 2% per unit of live weight for META (p = 0.09). While antimicrobial use was reduced with PT, there may be substantial negative impacts on other outcomes if META was not used in this type of cattle population. Full article

Oxidized β-carotene (OxBC), a phytochemical that occurs naturally in plants, is formed by the spontaneous reaction of β-carotene with ambient oxygen. Synthetic OxBC, obtained by full oxidation of β-carotene with air, shows considerable promise as an in-feed antimicrobial alternative additive that enhances health and performance in livestock. OxBC is predominantly composed of β-carotene-oxygen copolymers that have beneficial immune-modulating effects that occur within the innate immune system by priming it to face microbial challenges and by mitigating the inflammatory response. OxBC does not have any direct anti-bacterial activity. Further, unlike traditional immune stimulants, OxBC modulates but does not stimulate and utilize the animal’s energy stores unless directly stress-challenged. These immune effects occur by mechanisms distinct from the provitamin A or antioxidant pathways commonly proposed as explanations for β-carotene’s actions. Trials in poultry, swine, and dairy cows with low parts-per-million in-feed OxBC supplementation have shown performance benefits over and above those of feeds containing regular vitamin and mineral premixes. Through its ability to enhance immune function, health, and performance, OxBC has demonstrated utility not only as a viable alternative to in-feed antimicrobials but also in its ability to provide tangible health and performance benefits in applications where antimicrobial usage is precluded. Full article