Annette Backhans

The enteropathogenic Yersinia genus is commonly detected in wildlife including wild boars. Difficulties in its cultivation may hamper subsequent epidemiological studies and outbreak investigations. Multiple-locus variable-number tandem repeat analysis (MLVA) of Yersinia (Y.) enterocolitica and Y. pseudotuberculosis has proven useful in source attribution and epidemiological studies but has hitherto relied on the analysis of isolates. In the present study, MLVA profiles generated from 254 isolates of Y. enterocolitica indicated similarities between human, pig and rodent isolates. Further, MLVA analyses of 13 Y. pseudotuberculosis pure-cultured isolates were compared to MLVA analyses performed directly on the 14 PCR-positive enrichment broths from which the isolates originated, which showed matching MLVA profiles. This indicates that MLVA analysis performed directly on enrichment broths could be a useful method for molecular epidemiological investigations. In addition, 10 out of 32 samples of wild boar minced meat obtained from private hunters and from approved wild-game-handling establishments were PCR-positive for the presence of Y. enterocolitica and may indicate a risk for public health.

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 reportedS. suisassociated disease, as well as possible associations betweenS. suisassociated 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 suiswas 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 ofS. suiswas 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.

Periodontal disease is common in dogs and is initiated by gingival plaque composed of several hundred bacterial species. Some of these species have specifically been pointed out as potential periodontal pathogens, such as Treponema spp. Treponema spp. are difficult to culture and therefore the majority have been detected by culture-independent methods, such as PCR (Polymerase Chain Reaction). This leaves many Treponema spp. uncharacterized and unnamed. In this study, treponemes were investigated in gingival plaque from dogs with varying degree of periodontal disease with the aim to describe their occurrence and diversity in dogs. The methods used were culture, phase-contrast microscopy, PCR targeting the 16SrRNA-tRNA^Ile intergenic spacer region (ISR2), sequencing of the ISR2 and phylogenetic analysis. Treponema spp. were detected in samples from 10 out of 11 dogs and isolates were obtained from six dogs. Both healthy and periodontitis affected dogs were Treponema positive. Phylogenetic analysis, based on ISR2 sequences, revealed a large diversity of treponemes in the study population that were found to be distributed mainly in two groups, corresponding to the human oral treponeme phylogroups II (Treponema denticola) and IV (Treponema maltophilum) genetic groups. They were generally more distantly related to other treponemes in these groups. Treponemes from dogs with periodontitis and dogs with mild gingivitis without periodontitis did not differ in any obvious way. The results indicate that several phylotypes of oral treponemes are common in dogs regardless of periodontal status.

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. 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. 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.

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.

Antimicrobial resistance is an increasing problem and reducing AM use is critical in limiting its severity. The underlying causes of antimicrobial use at pig farm level must be understood to select effective reduction measures. We previously showed that antimicrobial use on Swedish pig farms is comparatively low but varies between farms, although few farms are high users. In the present survey of a convenience sample of 60 farrow-to-finish herds in Sweden, we investigated farmers’ attitudes to antimicrobials and the influence of information provided by veterinarians about antimicrobial resistance. Farm characteristics were also recorded. We had previously quantified antimicrobial use for different age categories of pigs during one year, as well as external and internal biosecurity. Risk factors based on hypothetical causal associations between these and calculated treatment incidence (TI) for the different age categories were assessed here in a linear regression model. There were no significant associations between biosecurity and TI for any pig age category. Increasing farmer age was associated with higher TI for suckling piglets and fatteners. For suckling piglets, the age group with the highest frequency of treatment, TI was also significantly associated with farmer and education of the staff, where female farmers, and university educated staff was associated with a higher TI. Larger farms were associated with a higher TI in fatteners. In the investigated Swedish pig farms, factors that influenced antimicrobial usage were more related to characteristics of the individual farmer and his/her staff than to biosecurity level, other management factors or farmers’ attitudes to antimicrobials.

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. 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. 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.

SUMMARY: A total of 207 wild rodents were caught on nine pig farms, five chicken farms and five non-farm locations in Sweden and surveyed for a selection of bacteria, parasites and viruses.Lawsonia intracellulariaand pathogenicYersinia enterocoliticawere only detected in rodents on pig farms (9% and 8% prevalence, respectively) which indicate that these agents are more likely to be transmitted to rodents from pigs or the environment on infected farms.Brachyspira hyodysenteriae(1%),Brachyspira intermedia(2%),Campylobacter jejuni(4%),Campylobacter upsaliensis(2%), leptospires (7%) and encephalomyocarditis virus (9%) were also detected from rodents not in contact with farm animals.GiardiaandCryptosporidiumspp. were common, although no zoonotic types were verified, andSalmonella entericawas isolated from 1/11 mice on one farm but not detected by PCR from any of the rodents.Trichinellaspp. andToxoplasma gondiiwere not detected.