Brachyspira in dogs: risk factors of shedding in central Germany and longitudinal study of an infected kennel

BACKGROUND

Brachyspira (B.) pilosicoli is a zoonotic pathogen, able to infect different animal species such as pigs, poultry, and rodents, causing intestinal spirochetosis. An association of gastrointestinal clinical signs, such as diarrhea, with the isolation of B. pilosicoli from fecal samples or rectal swabs has not been proven in dogs. Other Brachyspira species commonly isolated from dogs, such as "B. canis" and "B. pulli", are considered commensals. This study investigated the occurrence of different Brachyspira species in rectal swabs and fecal samples in an independent canine cohort in central Germany. These included samples from shelter dogs, hunting dogs, and dogs presenting at regional small animal practices with various clinical signs. Data about the dogs, including potential risk factors for Brachyspira isolation, were obtained using a standardized questionnaire. The study also longitudinally investigated a colony of Beagle dogs for Brachyspira over 5 years.

RESULTS

The rate of Brachyspira spp. isolation was 11% and included different Brachyspira species ("B. canis", "B. pulli", and B. pilosicoli). "B. canis" was detected in 18 dogs, whereas B. pilosicoli was only isolated from 1 dog in the independent cohort (not including the Beagle colony). Risk factors for shedding Brachyspira and "B. canis" were being less than 1 year of age and shelter origin. Gastrointestinal signs were not associated with the shedding of Brachyspira. B. pilosicoli and "B. canis" were isolated from several dogs of the same Beagle colony in 2017 and again in 2022, while Brachyspira was not isolated at multiple sampling time points in 2021.

CONCLUSIONS

Shedding of B. pilosicoli in dogs appears to be uncommon in central Germany, suggesting a low risk of zoonotic transmission from dogs. Commensal status of "B. canis" and "B. pulli" is supported by the results of this study. Findings from the longitudinal investigation of the Beagle colony agree with an asymptomatic long-term colonization of dogs with "B. canis" and B. pilosicoli and suggest that introducing new animals in a pack can trigger an increased shedding of B. pilosicoli.

Cecal Reduction of Brachyspira and Lesion Severity in Laying Hens Supplemented with Fermented Defatted ‘Alperujo’

Antimicrobial resistance demands the development of therapeutic alternatives such as prebiotics, probiotics, and nutraceuticals. The aim of this study was to assess the antimicrobial proprieties of the nutraceutical fermented defatted “alperujo”, derived from olive oil production, in a laying hen farm (n = 122,250) endemic with avian intestinal spirochetosis (Brachyspira spp.). Part of the batch (n = 1440) was divided into six groups of 240 hens each that included 80 or 108-week-old laying hens, supplemented with 0%, 2%, or 6% fermented defatted ‘alperujo’ for a month. At the end of the experiment, eight hens from each group were autopsied and cecal content was subjected to (i) Brachyspira culture and species identification by PCRs, and (ii) direct DNA extraction and Brachyspira qPCR. Furthermore, the ceca were processed for histopathology. Microbiological isolation revealed B. pilosicoli and B. hyodysenteriae co-infection in all groups. The 80-week-old hen group 2% supplemented showed a reduction in the cecal Brachyspira content (qPCR) compared with non-supplemented hens. Cecal histopathology showed a diffuse mild infiltration of lymphocytes, plasma cells, and heterophils; and hyperplasia of the gut-associated lymphoid tissue hyperplasia which decreased in severity in 80-week-old supplemented hens. The reduction in Brachyspira colonization and the severity of the lesions observed in supplemented hens highlights a potential protective function against avian intestinal spirochetosis.

Retrospective analysis of necrotizing typhlitis cases associated with Brachyspira spp. in British rheas

This paper describes a retrospective analysis of necrotizing typhlitis in common rheas (Rhea americana) diagnosed in the United Kingdom by the Animal & Plant Health Agency (APHA). From January 2008 to January 2020, seven cases of spirochaetal typhlitis associated with Brachyspira spp. were identified using the Veterinary Investigation Diagnosis Analysis database. Gross examination was combined with selective anaerobic culture, polymerase chain reaction, and histopathology to diagnose typhlitis associated with spirochaetal infection. Whole-genome sequencing was subsequently utilized on archived isolates from six of the seven submissions, overcoming issues with traditional testing methods and yielded gains in the identification of Brachyspira to species level. Brachyspira hyodysenteriae, an organism traditionally associated with typhlitis in rheas, was isolated in three sequenced submissions. One of these also demonstrated co-infection with Brachyspira intermedia. Brachyspira suanatina, Brachyspira hampsonii, and Brachyspira alvinipulli were identified by sequencing as single infections in the remaining three animals. This report demonstrates the ability of Brachyspira species other than B. hyodysenteriae to colonize the caeca of rheas presenting with typhlitis. Additionally, the B. alvinipulli isolate harboured a tva(A) gene, indicating higher potential pleuromutilin resistance, which has not previously been described in this Brachyspira species. This study discusses the epidemiology of examined cases and examines the potential role other species may play in these outbreaks.

Antimicrobial resistance in Brachyspira - An increasing problem for disease control

Across all bacterial species the continuing reduction in susceptibility to antimicrobial agents is a critical and increasing threat for disease control. This mini-review outlines the extent of this problem amongst anaerobic intestinal spirochaetes of the genus Brachyspira, of which there are currently nine officially recognised species. These include some important pathogens that may cause colitis with diarrhoea and/or dysentery in various mammalian and avian species, but most notably in pigs and in adult chickens. The most economically significant pathogen is Brachyspira hyodysenteriae, the spirochaete which causes swine dysentery in countries throughout the world. Control of infections with Brachyspira species has long relied on the prophylactic or therapeutic use of antimicrobials, but increasingly strains with reduced susceptibility and sometimes multidrug resistance to previously effective antimicrobial agents are being encountered. In this mini-review we outline these problems and explain the extent and molecular basis of the emerging resistance. Future control will rely on developing and applying standardised methods for measuring antimicrobial susceptibility; improving surveillance of resistance using traditional phenotypic as well as genomic analysis of known resistance determinants; improving understanding of the molecular basis of resistance to different drug classes; improving farmer and veterinarian education about prudent antimicrobial use so as to reduce selective pressure on the emergence of resistance; and developing alternatives to antimicrobials as a means to control these infections.

Vaccination of chickens with the 34 kDa carboxy-terminus of Bpmp72 reduces colonization with Brachyspira pilosicoli following experimental infection

The anaerobic intestinal spirochaete Brachyspira pilosicoli colonizes the large intestine of a variety of species of mammals and birds, and may result in colitis, diarrhoea and reductions in growth rate. Naturally occurring infections in chickens are largely confined to adult laying and breeding birds. In this study, the 34 kD carboxy-terminus of the prominent outer membrane protein Bmp72 of B. pilosicoli was expressed as a histidine-tagged recombinant protein and used to immunize two groups (B and C) of 15 individually housed layer chickens. Vaccination was with either 100 μg (B) or 1 mg (C) protein emulsified with Freund's incomplete adjuvant delivered into the pectoral muscles, followed three weeks later by 1 mg of protein in phosphate buffered saline delivered via crop tube. Two weeks later these and 15 non-vaccinated positive control birds (group A) housed in the same room were challenged via crop tube with B. pilosicoli avian strain CPS1. B. pilosicoli was detected in the faeces of all control birds and in 14 of the vaccinated birds in each vaccinated group at some point over the 30-day period following challenge. Colonization was delayed and the duration of excretion was significantly reduced (P = 0.0001) in both groups of vaccinated birds compared to the non-vaccinated control birds. Fewer immunized birds had abnormal caecal contents at post mortem examination compared to non-vaccinated birds, but the difference was not statistically significant. This study indicates that recombinant Bmp72 C-terminus has potential to be developed for use as a vaccine component to provide protection against B. pilosicoli infections. RESEARCH HIGHLIGHTS Laying chickens were immunized with recombinant Brachyspira pilosicoli membrane protein Bpmp72. Immunized birds had a highly significant reduction in the duration of colonization. Fewer immunized than control birds had abnormal caecal contents after infection. Bpmp72 showed potential for use as a novel vaccine component for B. pilosicoli.