Experimental Infection of Mink Enforces the Role of Arcanobacterium phocae as Causative Agent of Fur Animal Epidemic Necrotic Pyoderma (FENP)

Comparative Genomics of 42 Arcanobacterium phocae Strains

For the last 13 years, the fur industry in Europe has suffered from epidemic spouts of a severe necrotizing pyoderma. It affects all species currently farmed for fur and causes animal welfare problems and significant losses to the farmers. The causative agent of this disease was identified as Arcanobacterium phocae. Previously, this bacterium has been isolated from seals and other marine mammals, apparently causing wound and lung infections. Attempts at antibiotic treatment have been unsuccessful and the current advice on preventing the disease is to cull all animals with clinical signs. This poses an urgent question regarding possible vaccine development, as well as the need for further understanding of the pathogenicity of this organism. This study compared the whole genomes of 42 A. phocae strains isolated from seals, blue foxes, finnraccoons, mink and otter. The sequences were created using the Illumina technology and annotations were done using the RAST pipeline. A phylogenetic analysis identified a clear separation between the seal strains and the fur-animal-derived isolates, but also indicated that the bacterium readily adapts to new environments and host species with reasonable diversity. A pan- and core-genome was created and analyzed for proteins. A further analysis identified several virulence factors as well as multiple putative and secreted proteins of special interest for vaccine development.

Association between Fur Animal Necrotizing Pyoderma in breeding farm mink (Neovison vison) and reduced fertility

BACKGROUND

The disease Fur Animal Necrotizing Pyoderma (FNP) has since 2000 been reported in many fur producing countries including Canada, Finland and Denmark. Development of FNP is characterised by rapidly forming treatment-resistant wounds on paws and in the head region. Economic losses related to FNP have been associated with mortality and decreased fur quality as well as increased veterinary costs. Also it has been suggested that FNP may be associated with reduced production results for breeding mink. The aim of this study was to evaluate if there is an association between FNP lesions in breeding animals and reduced production results based on a retrospective cohort study.

RESULTS

1465 breeding animals (244 males and 1221 females) were followed during the breeding season 2019 on five Danish mink farms. Two farms were removed from the analysis since no occurrence of FNP appeared in the observation group. After exclusion, 846 breeding animals (148 males and 698 females) remained in the analysis and were divided into two groups: exposed (EXP) or non-exposed (N-EXP) depending on the disease history of the males during mating. Females exposed to FNP positive males during breeding in average produce 14% fewer kits (P = 0.032) and these females were also more than double as likely to produce small litters (N ≥ 3) than N-EXP females. Female's from the EXP group were introduced more times to males than females in the N-EXP group (P = 0.0001, 2.5 more times in average). Females in the EXP group did not have a statistically higher risk of becoming barren (P = 0.138) though the relative risk of becoming barren was 77% higher after encountering a FNP male.

CONCLUSIONS

This study shows that FNP has more economic losses for the farms than direct loss of animals. Females in contact with males with FNP lesion during breeding have a higher risk of becoming barren, and produce significantly fewer kits compared to females whom haven't been in contact with a FNP positive male.

Comparison of Streptococcus halichoeri isolates from canine and fur animal infections: biochemical patterns, molecular characteristics and genetic relatedness

Background

Streptococcus halichoeri infections have been reported in grey seals, a European badger, a Stellar sea lion and humans, but its presence in companion and fur animals is unknown. Since 2010, S. halichoeri-like bacteria (SHL) have been isolated from fur animals and dogs in Finland. Our aim was to retrospectively investigate laboratory records for SHL from canine and fur animal infections, characterize the isolates and compare their genetic relatedness in relation to three reference strains: CCUG 48324^T, originating from a grey seal, and strains 67100 and 61265, originally isolated from humans.

Results

A total of 138 and 36 SHLs from canine and fur animal infections, respectively, were identified in the laboratory records. SHL was commonly associated with skin infections, but rarely as the only species. A set of 49 canine and 23 fur animal SHLs were further characterized. MALDI-TOF confirmed them as being S. halichoeri. The growth characteristics were consistent with the original findings, but isolates were catalase positive. In total, 17 distinct API 20 Strep patterns were recorded among all 75 isolates tested, of which pattern 5563100 was the most common (n = 30). Antimicrobial resistance to erythromycin and clindamycin was common in canine isolates, but rare in fur animal isolates. Three clusters were observed by PFGE, and 16S rRNA sequencing revealed 98.1–100% similarities with the human strains and 98.1–99.5% with the seal strain. A phylogenetic tree of concatenated 16S rRNA and rpoB revealed closely related isolates with two clades. Fifteen canine isolates were identical to the human strains based on concatenated 16S rRNA and rpoB sequencing.

Conclusions

Streptococcus halichoeri appears to be quite a common bacterial species in the skin of dogs and fur animals. The clinical significance of S. halichoeri is uncertain, as it was rarely isolated as a monoculture. No apparent temporal or spatial clustering was detected, but isolates from different sources were genetically very similar. Because many canine isolates were genetically similar to the human reference strains, transmission between dogs and humans may be possible. WGS sequencing of strains from different sources is needed to further investigate the epidemiology and virulence of S. halichoeri.

Epidemiological analysis of Arcanobacterium phocae isolated from cases of mink dermatitis of a single farm

The present study was designed to identify nine Arcanobacterium phocae strains isolated from cases of mink dermatitis of a single farm in Finland and characterize the strains for epidemiological relationships. All nine strains and previously described A. phocae used for comparative purposes were identified and further characterized phenotypically, by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), by Fourier Transform Infrared Spectroscopy (FT-IR) and genotypically by detection of phocaelysin encoding gene phl with a previously developed loop-mediated isothermal amplification (LAMP) assay and by sequencing 16S rRNA gene and gene phl, the elongation factor tu encoding gene tuf and the β subunit of bacterial RNA polymerase encoding gene rpoB. Genetic relatedness among isolates was determined using whole-genome single nucleotide polymorphism (wgSNP) analysis. The wgSNP results, partly the MALDI-TOF MS and FT-IR analyses and sequencing of the genes, revealed that the nine A. phocae strains recovered from a single farm showed close sequence similarities among each other and differed from previously investigated A. phocae strains isolated from other farms and animals in Finland and from the A. phocae type strain. This indicated a close epidemiological relationship of the A. phocae strains isolated from a single farm and that the nine A. phocae strains of the present study might have developed from a common ancestor.

Streptococcus halichoeri: Comparative Genomics of an Emerging Pathogen

Streptococcus halichoeri is an emerging pathogen with a variety of host species and zoonotic potential. It has been isolated from grey seals and other marine mammals as well as from human infections. Beginning in 2010, two concurrent epidemics were identified in Finland, in fur animals and domestic dogs, respectively. The fur animals suffered from a new disease fur animal epidemic necrotic pyoderma (FENP) and the dogs presented with ear infections with poor treatment response. S. halichoeri was isolated in both studies, albeit among other pathogens, indicating a possible role in the disease etiologies. The aim was to find a possible common origin of the fur animal and dog isolates and study the virulence factors to assess pathogenic potential. Isolates from seal, human, dogs, and fur animals were obtained for comparison. The whole genomes were sequenced from 20 different strains using the Illumina MiSeq platform and annotated using an automatic annotation pipeline RAST. The core and pangenomes were formed by comparing the genomes against each other in an all-against-all comparison. A phylogenetic tree was constructed using the genes of the core genome. Virulence factors were assessed using the Virulence Factor Database (VFDB) concentrating on the previously confirmed streptococcal factors. A core genome was formed which encompassed approximately half of the genes in Streptococcus halichoeri. The resulting core was nearly saturated and would not change significantly by adding more genomes. The remaining genes formed the pangenome which was highly variable and would still evolve after additional genomes. The results highlight the great adaptability of this bacterium possibly explaining the ease at which it switches hosts and environments. Virulence factors were also analyzed and were found primarily in the core genome. They represented many classes and functions, but the largest single category was adhesins which again supports the marine origin of this species.

Identification of Arcanobacterium phocae isolated from fur animals by phenotypic properties, by MALDI-TOF MS analysis and by detection of phocaelysin encoding gene phl as probable novel target

In the present study 12 Arcanobacterium phocae strains isolated from fur animals in Finland, including foxes, minks and Finnraccoons, could successfully be identified phenotypically, by matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS) and genotypically by sequencing 16S rDNA and phocaelysin (PHL) encoding gene phl. The PHL of all 12 A. phocae strains in the present study and reference strains A. phocae DSM 10002^T and A. phocae DSM 10003 displayed, as typical members of the cholesterol dependent cytolysin-group of toxins, the variant undecapeptide sequence EATGLAWDPWW which appeared to be most closely related to arcanolysin of Arcanobacterium haemolyticum and pyolysin of Trueperella pyogenes. In addition, gene phl could be determined with a newly designed loop-mediated isothermal amplification (LAMP) assay. The detection of mass spectra by MALDI-TOF MS and the LAMP assay based on gene phl might help to reliably identify A. phocae in future and also elucidate the role this species plays in infections of fur animals.

Questionnaire survey of detrimental fur animal epidemic necrotic pyoderma in Finland

Background

In 2007, a previously unrecorded disease, fur animal epidemic necrotic pyoderma (FENP), was detected in farmed mink (Neovision vision), foxes (Vulpes lagopus) and Finnraccoons (Nyctereutes procyonoides) in Finland. Symptoms included severe pyoderma with increased mortality, causing both animal welfare problems and economic losses. In 2011, an epidemiologic questionnaire was mailed to all members of the Finnish Fur Breeders’ Association to assess the occurrence of FENP from 2009 through the first 6 months of 2011. The aim was to describe the geographical distribution and detailed clinical signs of FENP, as well as sources of infection and potential risk factors for the disease.

Results

A total of 239 farmers (25%) returned the questionnaire. Clinical signs of FENP were observed in 40% (95% CI 34–46%) of the study farms. In addition, the survey clarified the specific clinical signs for different animal species. The presence of disease was associated with the importation of mink, especially from Denmark (OR 9.3, 95% CI 2.6–33.0). The transmission route between Finnish farms was associated with fur animal purchases. Some risk factors such as the farm type were also indicated. As such, FENP was detected more commonly on farms with more than one species of fur animal in comparison to farms with, for example, only foxes (OR 4.6, 95% CI 2.4–8.6), and the incidence was higher on farms with over 750 breeder mink compared to smaller farms (OR 3.8, 95% CI 1.6–9.0). Contact between fur animals and birds and other wildlife increased the risk of FENP on farms. Responses also indicated that blocking the entry of wildlife to the animal premises protected against FENP.

Conclusions

FENP was most likely introduced to Finland by imported mink and spread further within the country via domestically purchased fur animals. Some potential risk factors, such as the type and size of the farm and contact with wildlife, contributed to the spread of FENP. Escape-proof shelter buildings block the entry of wildlife, thus protecting fur animals against FENP.

Electronic supplementary material

The online version of this article (doi:10.1186/s13028-017-0322-z) contains supplementary material, which is available to authorized users.