The role of transportation in the spread of Brachyspira hyodysenteriae in fattening farms

Presence of Porcine Circovirus Type 2 in the Environment of Farm Facilities without Pigs in Long Term-Vaccinated Farrow-to-Wean Farms

Vaccination against Porcine Circovirus Type 2 (PCV2) even over several years has proven as an insufficient measure to eradicate the infection from farms, possibly due to not producing sterilizing immunity. Viral persistence in the farm environment has been proposed as a possible cause of reinfection, and for that reason, the main objective of this study was to identify potential critical points where PCV2 could persist in farrow-to-wean farms which had been vaccinating piglets for years. Surface samples were collected from different farm facilities with and without animals and analyzed by qPCR to detect and quantify the viral load. Most of the samples taken in animal housing facilities tested negative (96.6%); however, PCV2 was more frequently detected in samples from the offices (37.5%), the farm staff (25%) and the perimeter (21%). These results indicate that PCV2 contamination is frequent in facilities despite the long-term use of vaccination programs. Therefore, PCV2 control programs should include more exhaustive cleaning and disinfection protocols in non-animal facilities, as well as the implementation of specific biosecurity measures in these areas to minimize the risk of PCV2 introduction from external sources.

Transmission of antimicrobial resistance (AMR) during animal transport

The transmission of antimicrobial resistance (AMR) between food-producing animals (poultry, cattle and pigs) during short journeys (< 8 h) and long journeys (> 8 h) directed to other farms or to the slaughterhouse lairage (directly or with intermediate stops at assembly centres or control posts, mainly transported by road) was assessed. Among the identified risk factors contributing to the probability of transmission of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs), the ones considered more important are the resistance status (presence of ARB/ARGs) of the animals pre-transport, increased faecal shedding, hygiene of the areas and vehicles, exposure to other animals carrying and/or shedding ARB/ARGs (especially between animals of different AMR loads and/or ARB/ARG types), exposure to contaminated lairage areas and duration of transport. There are nevertheless no data whereby differences between journeys shorter or longer than 8 h can be assessed. Strategies that would reduce the probability of AMR transmission, for all animal categories include minimising the duration of transport, proper cleaning and disinfection, appropriate transport planning, organising the transport in relation to AMR criteria (transport logistics), improving animal health and welfare and/or biosecurity immediately prior to and during transport, ensuring the thermal comfort of the animals and animal segregation. Most of the aforementioned measures have similar validity if applied at lairage, assembly centres and control posts. Data gaps relating to the risk factors and the effectiveness of mitigation measures have been identified, with consequent research needs in both the short and longer term listed. Quantification of the impact of animal transportation compared to the contribution of other stages of the food-production chain, and the interplay of duration with all risk factors on the transmission of ARB/ARGs during transport and journey breaks, were identified as urgent research needs.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Brachyspira hyodysenteriae in swine

Brachyspira hyodysenteriae (B. hyodysenteriae) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for swine in a previous scientific opinion. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9, and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR B. hyodysenteriae can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (33-66% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 3 (Categories A, B and C; 1-10%, 10-33% and 10-33% probability of meeting the criteria, respectively) and the AHAW Panel was uncertain whether it meets the criteria in Sections 4 and 5 (Categories D and E, 50-90% and 33-66% probability of meeting the criteria, respectively). The main animal species to be listed for AMR B. hyodysenteriae according to Article 8 criteria are pigs and some species of birds, such as chickens and ducks.

Combined in-vitro and on-farm evaluation of commercial disinfectants used against Brachyspira hyodysenteriae

BACKGROUND

Swine dysentery (SD) is a severe infectious disease with a relevant impact on pig production usually caused by Brachyspira hyodysenteriae, although B. hampsonii causes an identical clinical picture. SD control relies on antimicrobials, good management practices and strict biosecurity with cleaning and disinfection as crucial tools to avoid the pathogen transmission. This study evaluates the in-vitro efficacy of an array of commercial disinfectants against a collection of B. hyodysenteriae isolates using broth tests. The efficacy of cleaning and disinfection protocols was also evaluated on two farms with endemic SD using surface swabs collected in emptied pens before and after cleaning and disinfection procedures, using both real-time PCR and bacterial microbiological culture.

RESULTS

Most of the commercial disinfectants evaluated were effective against all B. hyodysenteriae isolates tested, with a reduction of more than 5.00 log10 CFU/mL (bactericidal efficacy of 99.999%). However, some isolates exhibited reduced susceptibility to Virkon-S and Limoseptic disinfectants. The evaluation of cleaning and disinfection protocols on farms with SD outbreaks showed that approximately half the pens tested (n = 25) were positive by real-time PCR after pigs removal (mean B. hyodysenteriae counts 5.72 ± 1.04 log10 CFU/mL) while almost 20% of the pens remained positive after cleaning (n = 7) and disinfection (n = 5) procedures although with significantly lower, mean estimates (4.31 ± 0.43 log10 CFU/mL and 4.01 ± 0.55 log10 CFU/mL, respectively).

CONCLUSIONS

These results show the efficacy of disinfectants against B. hyodysenteriae but also stress the need to implement adequately the cleaning and disinfection protocols on pig farms and review and revise their efficiency periodically.

Viral Metagenome-Based Precision Surveillance of Pig Population at Large Scale Reveals Viromic Signatures of Sample Types and Influence of Farming Management on Pig Virome

Pigs are a major meat source worldwide and a pillar of Chinese animal husbandry; hence, their health and safety are a prioritized concern of the national economy. Although pig viruses have been continuously investigated, the full extent of the pig virome has remained unknown and emerging viruses are still a major threat to the pig industry. Here, we report a comprehensive study to delineate the pig virome of 1,841 healthy weaned pigs from 45 commercial farms collected from 25 major pig-producing regions across China. A viromic sequence data set, named Pigs_VIRES, which matched 96,586 viral genes from at least 249 genera within 66 families and which almost tripled the number of previously published pig viromic genes, was established. The majority of the mammalian viruses were closely related to currently known ones. A comparison with previously published viromes of bovines, avians, and humans has revealed the distinct composition of Pigs_VIRES, which has provided characteristic viromic signatures of serum, pharyngeal, and anal samples that were significantly influenced by farming management and disease control measures. Taken together, Pigs_VIRES has revealed the most complete viromic data set of healthy pigs to date. The compiled data also provide useful guidance to pig viral disease control and prevention and the biosafety management of pig farms. Especially, the established viromic protocol has created a precision surveillance strategy to potentially innovate currently used surveillance methods of animal infectious diseases, particularly by making precision surveillance available to other animal species on a large scale or even during a nationwide surveillance campaign.

IMPORTANCE Pigs are deeply involved in human lives; hence, their viruses are associated with public health. Here, we established the most comprehensive virome of healthy piglets to date, which provides a viromic baseline of weaned pigs for disease prevention and control, highlighting that longitudinal viromic monitoring is needed to better understand the dynamics of the virome in pig development and disease occurrence. The present study also shows how high standards of animal farm management with strict biosafety measures can significantly minimize the risk of introduction of pathogenic viruses into pig farms. Particularly, the viromic strategy established, i.e., high-throughput detection and analyses of various known and unknown pathogenic viruses in a single test at large scale, has completely innovated current surveillance measures in provision of timely and precise detection of all potentially existing pathogenic viruses and can be widely applied in other animal species.

Postweaning mortality in commercial swine production. I: review of non-infectious contributing factors

Postweaning mortality is a complex causal matrix involving animal, environment, and infectious etiologic factors. Despite advances in swine productivity such as total pigs born, growth rate, feed intake, and efficiency, there have been modest to no improvements in postweaning mortality rates over the last several years. Industry averages for postweaning mortality range from four to eight percent for each the nursery, grow-finish, or wean-finish stages. Retrospective mortality causal analyses of individual databases have been performed. However, little information derived from meta-analysis, systematic review, or comprehensive literature reviews are available. In order to develop and evaluate strategies to comprehensively manage and reduce postweaning mortality, addressing the complexity and range of impact that factors have on mortality is necessary to identify and prioritize such contributing factors. Our objective is to describe the current state of knowledge regarding non-infectious causes of postweaning mortality, focusing on estimates of frequency and magnitude of effect where available. Postweaning mortality can be generalized into non-infectious and infectious causes, with non-infectious factors further classified into anatomic abnormalities, toxicity, animal factors, facility factors, nutritional inadequacies, season, and management factors. Important non-infectious factors that have been identified through review of literature include birth weight, pre-weaning management, weaning age and weight, and season. Additionally, reasons for mortality with a low incidence but a high magnitude include abdominal organ torsion/volvulus, sodium ion or ionophore toxicosis, or dietary imbalance due to feed formulation or manufacture error. Many interactive effects are present between and among infectious and non-infectious factors, but an important trend is the impact that non-infectious factors have on the incidence, severity, and resolution of infectious disease. Strategies to reduce postweaning mortality must consider the dynamic, complex state that forms the causal web. Control of postweaning mortality through understanding of the complexity, evaluation of mortality reduction strategies through rigorous scientific evaluation, and implementation remains an area of opportunity for continued growth and development in the global swine industry.

Multilayer network analysis unravels haulage vehicles as a hidden threat to the British swine industry

When assessing the role of live animal trade networks in the spread of infectious diseases in livestock, attention has focused mainly on direct movements of animals between premises, whereas the role of haulage vehicles used during transport, an indirect route for disease transmission, has largely been ignored. Here, we have assessed the impact of sharing haulage vehicles from livestock transport service providers on the connectivity between farms as well as on the spread of swine infectious diseases in Great Britain (GB). Using all pig movement records between April 2012 and March 2014 in GB, we built a series of directed and weighted static multiplex networks consisting of two layers of identical nodes, where nodes (farms) are linked either by (a) the direct movement of pigs and (b) the shared use of haulage vehicles. The haulage contact definition integrates the date of the move and the duration Δ s that lorries are left contaminated by pathogens, hence accounting for the temporal aspect of contact events. For increasing Δ s , descriptive network analyses were performed to assess the role of haulage on network connectivity. We then explored how viruses may spread throughout the GB pig sector by computing the reproduction number R . Our results showed that sharing haulage vehicles increases the number of contacts between farms by >50% and represents an important driver of disease transmission. In particular, sharing haulage vehicles, even if Δ s  < 1 day, will limit the benefit of the standstill regulation, increase the number of premises that could be infected in an outbreak, and more easily raise R above 1. This work confirms that sharing haulage vehicles has significant potential for spreading infectious diseases within the pig sector. The cleansing and disinfection process of haulage vehicles is therefore a critical control point for disease transmission risk mitigation.

Risk factors for the infection with Brachyspira hyodysenteriae in pig herds

Swine dysentery (SD), caused by infection with Brachyspira hyodysenteriae, is a serious disease in pig production worldwide. Quantitative risk factors triggering the occurrence of infection are unknown. The present case-control study aimed at identifying major risk factors related to presence of B. hyodysenteriae in pig herds. Twenty case herds and 60 randomly selected control herds with a minimum herd size of '10 sows/ 80 fattening pigs' were examined by means of a questionnaire-based interview and a herd examination. Herds with previous eradication of SD were excluded. Logistic regression models revealed that the 'positive/suspicious SD status of source herds', the regular application of treatment, purchasing more than 4 batches/ year, contact to foxes, diagnostics performed during last 12 months, liquid feeding systems, rats on farm, and >250 fatting places were associated with higher chances of a herd to be infected. On the contrary, having different sources of grower pigs within one batch, the presence of raptor birds and the presence of martens in the region were associated with fewer chances of being infected. The final multivariable logistic regression model identified purchasing more than 4 batches/ year (OR = 7.5, 95 % CI 1.8-54.3) and contact to foxes (OR = 5.9; 97.5 % CI 1.2-34.6) as the two main risk factors in our study. 'More than 4 batches/ year' implies continuous herd management supporting persistence of B. hyodysenteriae in an infected herd, but also increased number of purchases each increasing the risk of B. hyodysenteriae introduction by carrier pigs or transport vehicles. Foxes might be infected with B. hyodysenteriae by feeding on positive piglets and rodents. Besides, 'contact to foxes' might represent a lack in biosecurity. In conclusion, the risk factors detected underline the importance of biosecurity in SD prevention and control.

The pig transport network in Switzerland: Structure, patterns, and implications for the transmission of infectious diseases between animal holdings

The topology of animal transport networks contributes substantially to how fast and to what extent a disease can transmit between animal holdings. Therefore, public authorities in many countries mandate livestock holdings to report all movements of animals. However, the reported data often does not contain information about the exact sequence of transports, making it impossible to assess the effect of truck sharing and truck contamination on disease transmission. The aim of this study was to analyze the topology of the Swiss pig transport network by means of social network analysis and to assess the implications for disease transmission between animal holdings. In particular, we studied how additional information about transport sequences changes the topology of the contact network. The study is based on the official animal movement database in Switzerland and a sample of transport data from one transport company. The results show that the Swiss pig transport network is highly fragmented, which mitigates the risk of a large-scale disease outbreak. By considering the time sequence of transports, we found that even in the worst case, only 0.34% of all farm-pairs were connected within one month. However, both network connectivity and individual connectedness of farms increased if truck sharing and especially truck contamination were considered. Therefore, the extent to which a disease may be transmitted between animal holdings may be underestimated if we only consider data from the official animal movement database. Our results highlight the need for a comprehensive analysis of contacts between farms that includes indirect contacts due to truck sharing and contamination. As the nature of animal transport networks is inherently temporal, we strongly suggest the use of temporal network measures in order to evaluate individual and overall risk of disease transmission through animal transportation.