Improvements in swine herd biosecurity reduce the incidence risk of porcine reproductive and respiratory syndrome virus in breeding herds in the Midwestern United States

OBJECTIVE

Porcine reproductive and respiratory syndrome (PRRS) is a significant disease of swine. The purpose of this study was to determine whether application of a comprehensive, science-based approach to breeding herd biosecurity, known as next-generation biosecurity (NGB), could reduce PRRS incidence risk across a large commercial production company.

ANIMALS

Pigs (381,404 sows across 76 breeding herds).

METHODS

From 2009 to 2020, the annual incidence risk of PRRS in sow farms managed by the same company averaged 33%, ranging from 20% to 50%. To measure the effect of NGB on PRRS incidence risk, a retrospective cohort study was conducted from July 1, 2021, to June 30, 2023, across breeding herds managed by the same company. During the analysis, 2 groups of herds emerged: those that implemented protocols for all phases of NGB (NGB COMPLETE), and those that implemented all described protocols of biosecurity except for air filtration (NGB INCOMPLETE).

RESULTS

During the 2-year assessment period, 56 breeding herds were classified as NGB COMPLETE, while 20 herds were NGB INCOMPLETE. The PRRS incidence risk in NGB COMPLETE herds was 8.9% as compared to 40.0% in NGB INCOMPLETE herds. From disease year 1 (July 1, 2021, to June 30, 2022) and disease year 2 (July 1, 2022, to June 30, 2023), system-wide PRRS incidence risk was 8.6% and 9.2%, respectively. The association between NGB status and PRRS incidence risk for the 2-year period was statistically significant at a P value of .006.

CLINICAL RELEVANCE

Results of the present report provided evidence that improvements in biosecurity result in lower PRRS incidence risk under large-scale commercial swine production conditions.

Will swine veterinarians lead by meeting the next-generation needs of our industry?

The US swine industry is currently challenged by the potential of transboundary animal disease (eg, African swine fever) entry to the national herd and the relentless pressures of domestic diseases (eg, porcine reproductive and respiratory syndrome). The task of the swine veterinarian is to biosecure both the national herd and their customers' local farms to mitigate these risks. This Viewpoint raises 4 questions that swine veterinarians, including practicing (private and corporate), industry, research, academic, and regulatory (state and federal) veterinarians who spend a portion of their time controlling, treating, preventing, or eradicating diseases of swine, must answer to meet the needs of their farms to compete globally and survive. In addition, it appears that there is sufficient science-based information to move forward in a collaborative manner and that the goals of prevention of African swine fever and elimination of porcine reproductive and respiratory syndrome virus are technically possible. Therefore, as previous generations of swine veterinarians led the US industry in the elimination of foot-and-mouth disease virus, classical swine fever virus, and pseudorabies virus from the national herd, the central challenge is whether the next generation of veterinarians will provide the necessary leadership to deal with the current industry and its next-generation challenges.

Evaluating the effect of temperature on viral survival in plant-based feed during storage

Viruses of veterinary significance are known to survive for extended periods in plant-based feed ingredients imported into North America. To reduce the likelihood of virus introduction, high-risk ingredients, such as oil seed meals, are stored in designated facilities for extended periods under controlled environmental conditions to minimize viral infectivity prior to use in diets. While 30 days has become a standard storage period, the required ambient temperature to inactivate viruses during this time is not known. To address the question, 1-metric tonne totes of conventional soybean meal were inoculated with PRRSV 144 lineage 1C variant and SVA prior to storage for 30 days at 23.9°C, 15.5°C or 10°C, and feeding to pigs. Virus infectivity was evaluated through detection of viral RNA in oral fluid samples, along with clinical signs. Results indicated that inactivation of both viruses occurred in soy stored at 23.9°C. In contrast, SVA infectivity was observed in soy stored at both 15.5°C and 10°C, while PRRSV 144 L1C variant infectivity was only observed in soy stored at 10°C. These results suggest that a storage period of 30 days and a temperature of 23.9°C may assist in the reduction of the risk of virus contaminated plant-based feed ingredients, such as soybean meal.

Evaluation of a General Practitioner with Special Interest model: lessons learned from staff experiences

BACKGROUND

The integration of general practitioners into specialist outpatient clinics is associated with improved access to care; however, little is understood about the organisation-level factors that affect successful implementation. We aimed to identify factors that were facilitators or barriers to the implementation of a General Practitioner with Special Interest (GPwSI) model of care across a range of specialties.

METHODS

Semi-structured, in-depth interviews were conducted with 25 stakeholders at 13 GPwSI clinics in operation within a Queensland public health service. A deductive content analysis was conducted using the Consolidated Framework for Implementation Research (CFIR).

RESULTS

Stakeholders generally supported the GPwSI model and saw advantages to patients and specialist medical practitioners in terms of waiting lists, workload, and improving clinician self-efficacy and knowledge. A number of factors were identified as being crucial to the success of the program, such as adequate support and planning for the implementation, appropriate funding and advocacy.

CONCLUSIONS

Our evaluation indicates that a GPwSI model can be a beneficial resource for improving care to patients and reducing wait lists, dependent upon adequate planning, training, and support.

Evaluation of the US Army Institute of Public Health Destination Monitoring Program, a food safety surveillance program

The Destination Monitoring Program, operated by the US Army Public Health Command (APHC), is one component that supports the APHC Veterinary Service's mission to ensure safety and quality of food procured for the Department of Defense (DoD). This program relies on retail product testing to ensure compliance of production facilities and distributors that supply food to the DoD. This program was assessed to determine the validity and timeliness by specifically evaluating whether sample size of items collected was adequate, if food samples collected were representative of risk, and whether the program returns results in a timely manner. Data was collected from the US Army Veterinary Services Lotus Notes database, including all food samples collected and submitted from APHC Region-North for the purposes of destination monitoring from January 1, 2013 to December 31, 2013. For most food items, only one sample was submitted for testing. The ability to correctly identify a contaminated food lot may be limited by reliance on test results from only one sample, as the level of confidence in a negative test result is low. The food groups most frequently sampled by APHC correlated with the commodities that were implicated in foodborne illness in the United States. Food items to be submitted were equally distributed among districts and branches, but sections within large branches submitted relatively few food samples compared to sections within smaller branches and districts. Finally, laboratory results were not available for about half the food items prior to their respective expiration dates.

ATP-dependent chromatin remodeling activities

Genetic and biochemical approaches have indicated that the packaging of DNA into chromatin can be repressive to transcription. ATP-dependent chromatin remodelling activities can facilitate transcription from chromatin templates. Consistent with this, biochemical assays have shown that the action of ATP-dependent chromatin remodelling activities increase the accessibility of DNA within chromatin templates. However more recent functional studies suggest that many ATP-dependent chromatin remodelling activities can also function as repressors of transcription. Here we review recent advances to our understanding of the biological function of these complexes. We then consider some of the mechanisms by which ATP-dependent chromatin remodelling activities together with other forms of chromatin remodelling or modifying enzymes may act to regulate genomic accessibility either positively or negatively.

Mechanisms for ATP-dependent chromatin remodelling

Gene regulation involves the generation of a local chromatin topology that is conducive to transcription. Several classes of chromatin remodelling activity have been shown to play a role in this process. ATP-dependent chromatin-remodelling activities use energy derived from the hydrolysis of ATP to alter the structure of chromatin, making it more accessible for transcription factor binding. The yeast SWI-SWF complex is the founding member of this family of ATP-dependent chromatin-remodelling activities. We have developed a model system to study the ability of the SWI-SWF complex to alter chromatin structure. Using this system, we find that SWI-SWF is able to alter the position of nucleosomes along the DNA. This is consistent with recent reports that other ATP-dependent chromatin-remodelling activities can alter the positions of nucleosomes along DNA. This suggests that nucleosome mobilization may be a general feature of the activity of ATP-dependent chromatin-remodelling activities. Some of the mechanisms by which nucleosomes may be moved along DNA are discussed.

Generation of superhelical torsion by ATP-dependent chromatin remodeling activities

ATP-dependent chromatin remodeling activities participate in the alteration of chromatin structure during gene regulation. All have DNA- or chromatin-stimulated ATPase activity and many can alter the structure of chromatin; however, the means by which they do this have remained unclear. Here we describe a novel activity for ATP-dependent chromatin remodeling activities, the ability to generate unconstrained negative superhelical torsion in DNA and chromatin. We find that the ability to distort DNA is shared by the yeast SWI/SNF complex, Xenopus Mi-2 complex, recombinant ISWI, and recombinant BRG1, suggesting that the generation of superhelical torsion represents a primary biomechanical activity shared by all Snf2p-related ATPase motors. The generation of superhelical torque provides a potent means by which ATP-dependent chromatin remodeling activities can manipulate chromatin structure.