Animal Health Research Reviews最新文献

Bovine respiratory disease (BRD) is one of the most common and costly diseases of beef cattle. Much research has been conducted to understand prevention, treatment, and economic impacts of this syndrome. Impacts from BRD occur in multiple phases of the beef industry including both pre- and post-weaned calves. This disease causes negative impacts due to production losses, treatment costs, and cattle mortality. The large scope of BRD impacts merits further research on effective prevention and intervention technologies to limit deleterious impacts to the cattle industry.

Bovine respiratory disease (BRD) treatment failure occurs when animals receiving a treatment regimen for BRD fail to directly return to health, resulting in chronic illness and a requirement for repeated treatments, sale for salvage slaughter, euthanasia or death. BRD treatment failure has both direct and indirect impacts. Direct impacts include costs to manage chronically ill animals, including those associated with BRD relapse treatment; reduced returns from animals sent for salvage slaughter, loss of the initial investment to purchase the animal and feed and other accumulated expenses to death, and costs associated with carcass disposal. Indirect impacts include costs of infrastructure requirements, and negative effects on animal welfare and employee morale.

In 1991, USDA's National Animal Health Monitoring System (NAHMS) conducted its first dairy study, a baseline assessment that focused on the health and management of heifer calves. During the study, producers ranked respiratory disease among the top two most common health problems affecting dairy calves. Over the last 25 years, U.S. dairy producers have participated in six NAHMS studies, yielding a rich repository of information that has helped identify needs for research, extension, and education in the dairy industry. NAHMS' most recent dairy study, conducted in 2014, provides the latest estimates on dairy cattle health and includes another in-depth look at heifer-calf health. While overall mortality in calves has decreased, bovine respiratory disease (BRD) remains an important cause of morbidity in calves. This raises the concern that BRD mitigation may be at a standstill on dairies. Research and on-farm experience have done much to elucidate the challenges associated with detection and perceived impacts of this complex disease. Continued development and implementation of new methods for monitoring health and detecting disease will provide additional tools to upend stalemating factors associated with BRD control, helping the dairy industry 'turn a corner' on this important disease.

Genomic variation exists in cattle that affects their susceptibility to the complex of pathogens responsible for bovine respiratory disease (BRD). Heritability estimates and genome-wide association analyses (GWAA) support the role of host genomic variation in BRD susceptibility. Heritability estimates for BRD susceptibility range from 0.02 to 0.29 depending on the population, the definition of the disease, and the accuracy of diagnosis. GWAA have identified genomic regions (loci) associated with BRD in beef and dairy cattle based on a variety of BRD diagnostic criteria. National standards need to be developed for BRD diagnostics and reporting to facilitate selection. Commercial genotyping is available to predict BRD susceptibility in dairy cattle and for the selection of replacement animals. Disease pathogen profiles vary by region and can result in genetic heterogeneity where different loci are important for susceptibility to different BRD pathogens. Although the identification of the BRD pathogens may not be critical for treatment, it is of paramount importance in identifying loci that render cattle susceptible to the disease. Identification of loci associated with host susceptibility to BRD provides a foundation for genomic selection to reduce disease and opens the possibilities to a better understanding of how the host defends itself.

Advances in molecular and proteomic technologies and methods have enabled new diagnostic tools for bovine respiratory pathogens that are high-throughput, rapid, and extremely sensitive. Classically, diagnostic testing for these pathogens required culture-based approaches that required days to weeks and highly trained technical staff to conduct. However, new advances such as multiplex hydrolysis probe-based real-time PCR technology have enabled enhanced and rapid detection of bovine respiratory disease (BRD) pathogens in a variety of clinical specimens. These tools provide many advantages and have shown superiority over culture for co-infections/co-detections where multiple pathogens are present. Additionally, the integration of matrix-assisted laser desorption ionization time of flight mass spectrometry (MS) into veterinary diagnostic labs has revolutionized the ability to rapidly identify bacterial pathogens associated with BRD. Recent applications of this technology include the ability to type these opportunistic pathogens to the sub-species level (specifically Mannheimia haemolytica) using MS-based biomarkers, to allow for the identification of bacterial genotypes associated with BRD versus genotypes that are more likely to be commensal in nature.

Assessment of behavior is a longstanding strategy to assist the diagnosis of clinical bovine respiratory disease (BRD) in beef cattle. Cattle with systemic inflammation caused by infectious pathogen(s) display predictable behavioral adaptations compared to healthy cohorts. Behavioral alterations in BRD-affected cattle include lethargy, social isolation, and anorexia. However, behavior assessment to support BRD case definition in the production setting is challenging because: (1) other bovine diseases cause behavior alterations similar to BRD; (2) cattle have inherent prey instinct to disguise sickness behavior during human evaluation; (3) labor constraints dictate very brief observation of animal behavior; and (4) traditional behavior assessment is subjective and agreement is often poor. Some of these challenges may be overcome with the use of advanced technologies that allow continuous, remote, and objective behavior assessment of individual cattle. Automated methodologies for behavior assessment include three-axis accelerometers that quantify physical behaviors, systems that document feeding/watering behavior, and triangulation systems that document spatial behavior. Each of these behavior-monitoring approaches generates unique information and may facilitate early detection of BRD compared to traditional methods. Nevertheless, adoption of behavior assessment technologies for BRD diagnosis in beef operations hinges upon improved detection, positive return on investment, and successful integration within existing BRD management practices.

Bovine respiratory disease (BRD) is one of the most common indications for antimicrobial therapy in beef cattle production and research trials demonstrate that antibiotic therapy greatly improves clinical outcome for BRD. These trials also show that BRD treatment success rates are less than 100% and that there are opportunities to optimize antimicrobial prescribing and improve clinical outcomes if the underlying cause(s) of BRD treatment failures can be identified and addressed. As the etiology of BRD in an individual animal is frequently multi-factorial in nature; it is likely that BRD treatment failures also result from complex interactions between the drug, drug administrator, animal host, pathogens, and the environment. This review will focus specifically on the pharmacological aspects, specifically the interactions between the host and the drug and the drug and the drug administrator, of BRD treatment failures and the actions that veterinary practitioners can take to investigate and mitigate therapeutic failures in future cases.

Bovine respiratory disease (BRD) is the leading natural cause of death in US beef and dairy cattle, causing the annual loss of more than 1 million animals and financial losses in excess of $700 million. The multiple etiologies of BRD and its complex web of risk factors necessitate a herd-specific intervention plan for its prevention and control on dairies. Hence, a risk assessment is an important tool that producers and veterinarians can utilize for a comprehensive assessment of the management and host factors that predispose calves to BRD. The current study identifies the steps taken to develop the first BRD risk assessment tool and its components, namely the BRD risk factor questionnaire, the BRD scoring system, and a herd-specific BRD control and prevention plan. The risk factor questionnaire was designed to inquire on aspects of calf-rearing including management practices that affect calf health generally, and BRD specifically. The risk scores associated with each risk factor investigated in the questionnaire were estimated based on data from two observational studies. Producers can also estimate the prevalence of BRD in their calf herds using a smart phone or tablet application that facilitates selection of a true random sample of calves for scoring using the California BRD scoring system. Based on the risk factors identified, producers and herd veterinarians can then decide the management changes needed to mitigate the calf herd's risk for BRD. A follow-up risk assessment after a duration of time sufficient for exposure of a new cohort of calves to the management changes introduced in response to the risk assessment is recommended to monitor the prevalence of BRD.