Wild rodents as carriers of potential pathogens to pigs, chickens and humans

The aim of this thesis was to investigate the specific risks that rodents constitute for proliferation of pathogens and transmission of those to farm animals, and indirectly to humans. Rodents were captured in pig and chicken flocks, in wastewater treatment plants and other urban environments. The enteric pig pathogens Brachyspira hyodysenteriae and B. pilosicoli and the chicken pathogen B. intermedia were detected. Fingerprinting by Random Amplified Polymorphic DNA and Pulsed Field Gel Electrophoresis indicated cross-species transmission of B. pilosicoli, B. intermedia, B. innocens, and B. murdochii between rodents and farm animals. A phylogeny of murine brachyspiras was established. Three new genetic rodent variants of Brachyspira spp. were discovered, for which the provisional names ‘B. rattus’, ‘B. muridarum’ and ‘B. muris’ were suggested. Lawsonia intracellularis and encephalomyocarditis virus (EMCV) were detected in rodents trapped on pig farms. The clinical significance of leptospirosis in Sweden is reportedly minor. However, the detection of pathogenic leptospiras in mice, rats and a water vole indicated that rodents constitute a potential hazard to pigs and humans. Campylobacteriosis, salmonellosis and yersiniosis are the most frequently reported zoonosis in Europe. Rodents in the study carried C. jejuni, C. coli and C. upsaliensis. Identical isolates of the human pathogen Yersinia enterocolitica bioserotype 4/O:3 were isolated both from rodents and pigs on the same farm, indicating cross-species transmission. Salmonella enterica could not be detected by the applied real-time PCR, indicating a low sensitivity of this test. No zoonotic variants of Giardia spp. or Cryptosporidium spp. were detected. All samples were tested negative for Trichinella spp. indicating that trichinellosis is not a widespread infection in wild rodents in Sweden. No rodents were seropositive to Toxoplasma gondii. In conclusion, the results show that rodents could be a risk for the transmission of the pig pathogens Lawsonia intracellularis, Brachyspira hyodysenteriae, B. pilosicoli, pathogenic Leptospira spp. and EMCV, and zoonotic Campylobacter species and Yersinia enterocolitica 4/O:3 in Sweden

Biosecurity level and health management practices in 60 Swedish farrow-to-finish herds

Background: Biosecurity measures are important tools to maintain animal health in pig herds. Within the MINAPIG project, whose overall aim is to evaluate strategies to raise pigs with less antimicrobial use, biosecurity was evaluated in medium to large farrow-to-finish pig herds in Sweden. In 60 farrow-to-finish herds with more than 100 sows, the biosecurity level was evaluated using a previously developed protocol (BioCheck). In a detailed questionnaire, internal and external biosecurity was scored in six subcategories each. An overall score for biosecurity was also provided. Information regarding production parameters as well as gender and educational level of personnel working with the pigs was also collected. Descriptive statistics were used to examine the recorded data.Results: The median scores for external and internal biosecurity were 68 and 59, respectively, where 0 indicates total absence of biosecurity and 100 means maximal possible biosecurity. The subcategories for external and internal biosecurity that had the highest scores were "Purchase of animals" (external) and "Nursery unit"/"Fattening unit" (internal), while "Feed, water and equipment supplies" (external) and "Measures between compartments and equipment"/"Cleaning and disinfection" (internal) received the lowest scores. A female caretaker in the farrowing unit, a farmer with fewer years of experience and more educated personnel were positively associated with higher scores for some of the external and internal subcategories. In herds with < 190 sows, fattening pigs were mixed between batches significantly more often than in larger herds.Conclusions: The herds in this study had a high level of external biosecurity, as well as good internal biosecurity. Strong biosecurity related to the purchase of animals, protocols for visitors, the use of all-in, all-out systems, and sanitary period between batches. Still, there is room for improvement in preventing both the introduction of disease to herds (external) and the spread of infections within herds (internal). Systems for animal transport can be improved and with respect to internal biosecurity, there is especially room for improvement regarding hygiene measures in and between compartments, as well as the staff's working procedures between different groups of pigs

Experimental inoculation of Treponema pedis T A4 failed to induce ear necrosis in pigs

Ear necrosis is a syndrome affecting pigs shortly after weaning and is regarded as an animal welfare issue. The etiology is unknown but Treponema spp., predominantly Treponema pedis, are commonly detected in the lesions. Oral treponemes have been suggested as source of infection, transferred by biting and licking behavior. In this study, five pigs were intradermally inoculated with Treponema pedis strain T A4 with the aim of investigating if this strain would induce ear lesions. Three pigs served as controls. The inoculation was repeated after 29 days, and the study continued for 56 days. Serum samples were collected throughout the study and analyzed by ELISA for IgG antibodies towards T. pedis T A4 lysate. Skin biopsies were taken from the inoculation area at the end of the study. Gingival samples were collected and cultivated for treponemes, for comparison to the inoculation strain and to follow colonisation. The challenged pigs did not develop any clinical signs of infection and no spirochetes were detected in sections from skin biopsies. The number of Treponema-positive gingival samples increased during the study. In the challenge group, IgG towards the bacterial lysate peaked 7 days after each inoculation and decreased rapidly hereafter. In the control group a weak IgG response was observed after the second inoculation, possibly caused by the oral treponemes

Potential alternatives to antimicrobials in pig production based on perceived effectiveness, feasibility and return on investment

Based on a questionnaire returned by 111 pig health experts from six European countries a list of potential alternatives to antimicrobials was ranked. These althernatives provide input for further studies to find strategies to reduce the widely discussed use of antimicrobials and the potential risk from antimicrobial resistance

Effectiveness of alternative measures to reduce antimicrobial usage in pig production in four European countries

Background The reduction of antimicrobial usage (AMU) is in the focus in modern pig production. The objective of this study was to assess the effectiveness of alternatives to reduce AMU at herd level. In a prospective study, 68 farrow-to-finish pig herds located in Belgium, France, Germany and Sweden were recruited on a voluntary basis to implement tailor-made intervention plans to reduce their AMU. Alternative measures included improvement of biosecurity (n = 29 herds), vaccination (n = 30), changes of feeding schemes or drinking water quality (n = 45), improved pig health and welfare care (n = 21) as well as changes in stable climate and zootechnical measures (n = 14). Herds were followed for 1 year after implementation of measures. Annual antimicrobial expenditures or treatment records, as well as disease incidence scores were collected and compared to those of the year before intervention. AMU was measured as the treatment incidence and calculated by age category, antimicrobial class and administration route. Results Compliance with the intervention plans was high (median 93%). AMU was significantly reduced following the implementation of alternative measures: in the median herd of the four countries, pigs were treated before intervention 25% of their expected lifespan (200 days from birth to slaughter) and after intervention 16%. AMU of suckling and weaned pigs were significantly reduced by 37 and 54%, respectively. The usage of polymyxins and tetracyclines was significantly reduced by 69 and 49%, respectively. AMU via feed and water, as well as parenteral AMU were significantly reduced by 46 and 36%, respectively. Herds with a higher AMU level before intervention achieved a bigger reduction. The majority of disease incidence were similar before and after intervention, with a few exceptions of disorders related to the gastro-intestinal tract in suckling pigs (decreased) and in breeding pigs (increased). Conclusion Following tailor-made implementation of alternative measures, a substantial reduction of AMU in pig production was achievable without jeopardizing animal health. The AMU reduction in the youngest age categories (suckling and weaned pigs) and the reduction of group treatments via feed and water was in line with the recent European Guidelines on the prudent use of antimicrobials in veterinary medicine

Evaluation of the relationship between the biosecurity status, production parameters, herd characteristics and antimicrobial usage in farrow-to-finish pig production in four EU countries

Background: High antimicrobial usage and the threat of antimicrobial resistance highlighted the need for reduced antimicrobial usage in pig production. Prevention of disease however, is necessary to obtain a reduced need for antimicrobial treatment. This study aimed at assessing possible associations between the biosecurity level, antimicrobial usage and farm and production characteristics in order to advice on best practices for a low antimicrobial usage and maximum animal health and production. A cross-sectional study was conducted in 227 farrow-to-finish pig herds in Belgium, France, Germany and Sweden between December 2012 and December 2013. Associations between biosecurity status, antimicrobial usage, and production parameters were evaluated with multivariable general linear models, according to an assumed causal pathway. Results: The results showed that higher antimicrobial usage in sows tended to be associated with higher antimicrobial usage from birth until slaughter (p = 0.06). The antimicrobial usage from birth until slaughter was positively associated with the number of pathogens vaccinated against (p < 0.01). A shorter farrowing rhythm (p < 0.01) and a younger weaning age (p = 0.06) tended to be also associated with a higher antimicrobial usage from birth until slaughter whereas a better external biosecurity (p < 0.01) was related with a lower antimicrobial usage from birth until slaughter. Conclusion: Management practices such as weaning age and biosecurity measures may be important factors indirectly impacting on antimicrobial usage. We therefore promote a holistic approach when assessing the potential to reduce the need for antimicrobial treatments

Assigning defined daily doses animal: a European multi-country experience for antimicrobial products authorized for usage in pigs

Objectives To establish a consensus defined daily dose animal (DDDA) for each active substance (AS) and administration route for porcine veterinary antimicrobial products authorized in four European countries, thus allowing cross-country quantification and comparison of antimicrobial usage data. Methods All veterinary antimicrobial products authorized for porcine use in Belgium, France, Germany and Sweden were listed for each administration route. First, separate DDDAs for each product were defined based on the recommended dosing for the main indication. Second, a consensus DDDA was established by taking the mean of the DDDAs for each product within a certain category of AS plus administration route. Results One-hundred-and-fifty-nine, 240, 281 and 50 antimicrobial products were licensed in Belgium, France, Germany and Sweden, respectively, in February 2013. Large variations were observed for dosage and treatment duration recommendations between products and between countries for the same ASs. Only 6.8% of feed/water and 29.4% of parenteral AS groups had the same recommended dosage in the four countries. Conclusions This study presents a consensus DDDA list for use in the quantification and comparison of antimicrobial consumption. Four major recommendations have been formulated: (i) urgent need for harmonization of authorization and recommended summary of product characteristics (SPC) dosages; (ii) expand the developed preliminary DDDA list to include all authorized veterinary medicinal products in all EU member states and for all (food-producing) animal species; (iii) improved accessibility of country-specific SPC data would be preferable; and (iv) statement of the ‘long-acting' duration of a product in the SP

Streptococcus suisin Swedish grower pigs: occurrence, serotypes, and antimicrobial susceptibility

Background Streptococcus suisis a major cause of meningitis, arthritis, and pneumonia in pigs worldwide, and an emerging pathogen in humans. In Sweden, S. suishas previously received little attention but has in recent years become increasingly recognized as affecting the pig production. The aim of the present study was to investigate the occurrence, serotypes and antimicrobial susceptibility ofS. suisin Swedish grower pigs from herds with and without reported S. suis associated disease, as well as possible associations between S. suis associated disease and selected environmental and production factors. Swab samples were taken from the tonsils of clinically healthy 8-13-week-old grower pigs from ten case herds and ten control herds. Isolates were cultured, identified using MALDI-TOF MS, and serotyped using latex agglutination. The antimicrobial susceptibility of 188 isolates was tested using broth microdilution. Production data was gathered and environmental parameters were measured on the farms. Results Streptococcus suis was isolated from 95% of the sampled pigs in both the case and the control herds. Serotypes 3, 4, 5, 7, 9, 10, 11, 15, 16, and 17-34 were detected, although a majority of the isolates (81.5%) were non-typeable. There was less diversity among the serotypes isolated from the case herds than among those from the control herds; four and nine different serotypes, respectively. Isolates resistant to penicillin (3.8%) were reported for the first time in Sweden. Tetracycline resistance was common (88.4%). No association was noted between the production and the environmental factors investigated, and the carriership ofS. suis. Conclusions The carriership of S. suis was found to be higher in clinically healthy Swedish pigs than previously estimated, and for the first time, the presence of Swedish isolates resistant to penicillin was reported. Many of the most commonly disease-associated serotypes, e.g. serotypes 2, 9, 3, and 7, were detected in healthy grower pigs although further studies are needed to investigate the virulence of these isolates

Genome characteristics related to the virulence of Streptococcus suis in Swedish pigs

The impact of S. suis on Swedish pig production has increased in recent years, and characterization of the strains present in the pig population is needed to aid in surveillance and prevention. Therefore, the aim of this study was to identify and characterize differences in the genomes between Swedish S. suis isolates associated with disease and isolates from healthy animals. Isolates categorized as being pathogenic (n = 100) or non-pathogenic (n = 117) were whole-genome sequenced, serotyped in silico, and sequence-typed using traditional MLST and coregenome MLST, and a genome-wide association study was performed to identify virulence-associated genes. In decreasing order, serotypes 2, 1, and 7 were the most common in the pathogenic group, and serotypes 15 and 12 were the most common in the non-pathogenic group. Among the commonly disease-associated sequence types, ST28 and ST25 were identified, whereas ST1 was scarcely found. The majority of isolates belonged to novel sequence types, revealing differences between Swedish isolates and those reported from other countries. The genomes of the pathogenic isolates were on average smaller and less heterogenic as compared to those of the non-pathogenic isolates. Although a majority of the previously published virulence-associated genes included in the study were found in the genomes of both pathogenic and non-pathogenic isolates, several new, significantly virulence-associated genes were identified

Distribution of enteropathogenic Yersinia spp. and Salmonella spp. in the Swedish wild boar population, and assessment of risk factors that may affect their prevalence

Abstract Background Pure Eurasian wild boars and/or hybrids with domestic pigs are present in the wild on most continents. These wild pigs have been demonstrated to carry a large number of zoonotic and epizootic pathogens such as Salmonella spp., Yersinia enterocolitica and Y. pseudotuberculosis. Wild boar populations throughout Europe are growing and more and more wild boar meat is being consumed, the majority within the homes of hunters without having passed a veterinary inspection. The aim of this study was to investigate if factors such as population density, level of artificial feeding, time since establishment of a given population, and the handling of animal by-products from slaughtered animals could influence the presence of these pathogens in the wild boar. Results In total, 90 wild boars from 30 different populations in Sweden were sampled and analysed using a protocol combining pre-cultivation and PCR-detection. The results showed that 27% of the sampled wild boars were positive for Salmonella spp., 31% were positive for Y. enterocolitica and 22% were positive for Y. pseudotuberculosis. In 80% of the sampled populations, at least one wild boar was positive for one of these enteropathogens and in total, 60% of the animals carried at least one of the investigated enteropathogens. The presumptive risk factors were analysed using a case–control approach, however, no significant associations were found. Conclusion Human enteropathogens are commonly carried by wild boars, mainly in the tonsils, and can thus constitute a risk for contamination of the carcass and meat during slaughter. Based on the present results, the effect of reducing population densities and number of artificial feeding places might be limited