Isolation and Characterization ofCampylobacter hepaticusfrom Layer Chickens with Spotty Liver Disease in the United States

Developing a selective culturing approach for Campylobacter hepaticus

Campylobacter hepaticus, the causative agent of Spotty Liver Disease (SLD) is an important disease in cage-free egg producing chickens causing mortality and production drops. C. hepaticus is a slow growing Campylobacter easily overgrown by fecal bacteria. It is currently only reliably isolatable from bile samples. A selective media for isolation from feces or environment would assist diagnosis and impact assessment. Growth of five Australian C. hepaticus isolates was studied using Horse blood agar (HBA), sheep blood agar (SBA), Bolton, Preston and Brain Heart Infusion (BHI) base media. Blood and/or bile were added to Bolton, Preston and BHI medias. C. jejuni was used as a positive control. Plates were incubated in duplicate under microaerophilic conditions at 42°C for 10 days and examined at days 3-5 and 7-10 of incubation. Each isolate was examined for sensitivity to 14 antimicrobials using HBA sensitivity plates. Growth was inhibited by BHI and by added bile, while blood improved growth. Further replicates using SBA, HBA, Bolton and Preston media showed best growth on Bolton agar with blood. All five C. hepaticus isolates were resistant to trimethoprim and vancomycin, while four were also resistant to rifampicin and bacitracin. Media based upon Bolton plus blood supplemented with vancomycin and trimethoprim might be used as the most appropriate media for selective growth of C. hepaticus. The addition of bile to media for C. hepaticus isolation and growth will inhibit growth and is not advised.

Scratch area as an epidemiological risk factor for Spotty Liver Disease in cage-free layers in Australia

Spotty Liver Disease (SLD) is a serious problem in laying hens farmed in cage-free systems. The causative organism, Campylobacter hepaticus, is regarded as having a fecal-oral method of transmission and hence may build up and spread readily in housing systems which allow ease of direct contact of hens with the flock's fecal material. The epidemiology of SLD has not been thoroughly investigated. An initial cross-sectional analytical epidemiological survey of SLD in free range and barn layer systems was conducted in Australia over 2019 to 2021.The survey involved rearing flocks (n = 32) which were then followed through into laying flocks (n = 24) up to 40 wk of age. Cloacal swabs were collected during rearing and lay for C. hepaticus detection by PCR. Flocks were classified as "Cases" (n = 18) where clinical SLD according to the case definition was observed or "Controls" (n = 6) which were clinically unaffected. No C. hepaticus was detected in cloacal swabs from rearing houses whereas the organism was detected in 18 Case flocks in lay and from 2 Control flocks in lay. All layer houses that incorporated a scratch area (n = 13) were categorized as Cases. Thus, having a scratch area is a key determinant for SLD and no analyses of further contributory factors from these flocks were able to be made. Of the remaining 11 flocks which had floors fully covered by slats, 5 were Cases (45%). Further risk factor analysis was compromised by this small sample size and identification of other significant associations was not possible. A larger survey investigating flocks laying in houses with fully slatted floors was undertaken to further the understanding of SLD epidemiology and is reported in a companion paper.

Detection, characterization, and persistence of Campylobacter hepaticus, the cause of spotty liver disease in layer hens

A Campylobacter species was first described as the etiological agent of Spotty Liver Disease (SLD) in 2015 and subsequently named as Campylobacter hepaticus in 2016. The bacterium predominantly affects barn and/or free-range hens at peak lay, is fastidious and difficult to isolate, which has impeded elucidation of its sources, means of persistence and transmission. Ten farms from South-Eastern Australia, of which 7 were free range entities participated in the study. A total of 1,404 specimens from layers and 201 from environmental sources, were examined for the presence of C. hepaticus. In this study, our principal findings included the continuing detection of C. hepaticus infection in a flock following an outbreak, indicating a possible transition of infected hens to asymptomatic carriers, that was also characterized by no further occurrence of SLD in the flock. We also report that the first outbreaks of SLD on newly commissioned free-range farms affected layers ranging from 23 to 74 wk of age, while subsequent outbreaks in replacement flocks on these farms occurred during the more conventional peak lay period (23-32 wk of age). Finally, we report that in the on-farm environment, C. hepaticus DNA was detected in layer feces, inert elements such as stormwater, mud, soil, as well as in fauna such as flies, red mites, Darkling beetles, and rats. While in off-farm locations, the bacterium was detected in feces from a variety of wild birds and a canine.

Comparative genomic analysis of Campylobacter hepaticus genomes associated with spotty liver disease, Georgia, United States

Campylobacter hepaticus has re-emerged as an important cause of disease in egg laying birds worldwide, resulting in morbidity, mortality, and significant losses in eggs for the breeding and table egg laying industries. Although birds may appear asymptomatic, the disease is characterized by spots on the liver of birds and histopathological analysis reveals multifocal fibrogranulocytic necrotizing hepatitis microscopically. The re-emergence of C. hepaticus may be linked with housing practices as the disease appears more prevalent in pasture raised birds with outside exposure. Here we describe, the whole genome sequences and comparative analysis of four C. hepaticus genomes associated with an outbreak on pasture raised breeders from a farm in Georgia, United States. All four genomes were relatively similar in size and virulence genes harbored. Using these genomes, comparison with current C. hepaticus genomes available in NCBI and other databases and other members of the Campylobacter species was carried out. Using current tools available, virulence gene factor content was compared, and it was found that different tools lead to different numbers of factors identified. The four genomes from this study were relatively similar to C. hepaticus HV10 the type strain from Australia but differed from the other sequenced US strains from Iowa and Florida. C. hepaticus was found to have an overall lower gene content for genes associated with virulence and iron acquisition compared to other Campylobacter genomes and appears to cluster differently than UK genomes on phylogenetic analysis, suggesting the emergence of two lineages of C. hepaticus. This analysis provides valuable insight into the emerging pathogen C. hepaticus, its virulence factors and traits associated with disease in poultry production in the US, potentially providing insight into targets for its control and treatment for laying birds. Our analysis also confirms genes associated with iron acquisition are limited and the presence of the multidrug efflux pump CmeABC in C. hepaticus which may promote survival and persistence in the host niche - the chicken liver/bile. One unique aspect of this study was the finding of a close genetic relationship between C. hepaticus and Campylobacter fetus species and evidence of genome reduction in relation to host niche specificity.

Investigation of Spotty Liver Disease and Campylobacter hepaticus in Layer Flocks-A Field Study

Campylobacter hepaticus (C. hepaticus) was recently discovered as the causative agent of Spotty Liver Disease (SLD). SLD affects laying hens and causes significant economic losses in egg production in several countries throughout the world. Field observations reveal that cases of SLD appear with a high risk of reoccurrence, specifically in free-range and organic brown-feathered layer lines. Possible factors contributing to the development of SLD still have to be elucidated. In this field study, one free range (Flock 1) and one organic flock (Flock 2) of brown laying hens kept on farms with a history of clinical SLD were monitored for C. hepaticus colonization, clinical signs, and egg production from 16 to 79 wk of age on the first farm and from 17 to 83 wk of age on the other. The flocks showed a significant drop in egg production at 32 to 39 or 56 wk of age, respectively, which was associated with macroscopically visible liver lesions typical for SLD. Interestingly, in both cases observed clinical disease was linked to a stressful event: heat stress for Flock 1 and respiratory symptoms for Flock 2. C. hepaticus was detected by PCR during the acute phase of the disease in Flock 1. At 50 wk after the initial clinical outbreak had waned, C. hepaticus was still able to be isolated by culture in this flock. This clearly demonstrates that C. hepaticus persists either in the birds or their environment. We speculate that this long persistence may favor chronic SLD in affected flocks and the reoccurrence of SLD in subsequent flocks. Clinically less severe SLD outbreaks may be observed after re-exposure of clinically recovered flocks.

First Report of Campylobacter hepaticus Isolation in Laying Hens and Broiler Breeders with Spotty Liver Disease in Costa Rica

Poultry producers in Costa Rica have informally reported a spotty liver disease-like syndrome for more than 20 yr. However, despite many attempts, the infectious agent responsible for this syndrome had not been identified. Therefore, following current knowledge of spotty liver disease diagnosis, we invited veterinarians and poultry producers to submit samples to the diagnostic laboratories of the Veterinary Medicine School, Universidad Nacional, to identify the infectious agent of this syndrome. Veterinarians and poultry producers were instructed to collect gallbladders and livers aseptically and send them for pathology examinations and bacterial cultures in less than 24 hr after collection. Samples were processed for standard histopathologic studies and cultured under aerophilic, anaerobic, and microaerophilic conditions. Campylobacter-like colonies were isolated and identified by biochemical and PCR tests. Here we report for the first time the isolation, biochemical characterization, and molecular confirmation of Campylobacter hepaticus in laying hens and broiler breeders with spotty liver disease in Costa Rica.

Campylobacter hepaticus in the Production Environment and Stagnant Water as a Potential Source of C. hepaticus Causing Spotty Liver Disease in Free-Range Laying Hens in Georgia, United States

Spotty liver disease (SLD) has emerged as an important cause of disease in egg-producing flocks in countries such as the United Kingdom and Australia and has emerged in the United States. The organisms implicated in SLD include Campylobacter hepaticus and, more recently, Campylobacter bilis. These organisms have been found to cause focal lesions on the livers of infected birds. Campylobacter hepaticus infection results in reduced egg production, decreased feed consumption resulting in reduced egg size, and increased mortality of highly valuable hens. In the fall of 2021, birds from two flocks (A and B) of organic pasture-raised laying hens were submitted to the Poultry Diagnostic Research Center at the University of Georgia with a history suspicious of SLD. Postmortem examination of Flock A found 5/6 hens had small multifocal lesions on the liver and were PCR positive for C. hepaticus from pooled swab analysis of samples of the liver and gall bladder. Necropsy of Flock B found 6/7 submitted birds had spotty liver lesions. In pooled bile swabs, 2/7 hens from Flock B were also PCR positive for C. hepaticus. A follow-up visit to Flock A was scheduled 5 days later, as well as a visit to a flock where SLD has not been reported (Flock C), which was used as a comparative control. Samples of the liver, spleen, cecal tonsil, ceca, blood, and gall bladder were collected from six hens per house. Additionally, feed, water nipples, and environmental water (stagnant water outside the house) were collected from the affected farm and the control farm. To detect the organism, all samples collected were subjected to direct plating on blood agar and enrichment in Preston broth with incubation under microaerophilic conditions. After multiple phases of bacterial culture purification from all samples, single bacterial cultures displaying characteristics of C. hepaticus were tested by PCR to confirm identity. From Flock A, liver, ceca, cecal tonsils, gall bladder, and environmental water were PCR positive for C. hepaticus. No positive samples were detected in Flock C. After another follow-up visit, 10 wk later, Flock A was PCR positive for C. hepaticus from gall bladder bile and feces and one environmental water sample displayed a weak positive reaction for C. hepaticus. Flock C was PCR negative for C. hepaticus. To gain more knowledge about C. hepaticus prevalence, a survey of 6 layer hens from 12 different layer hen flocks between the ages of 7 to 80 wk, raised in different housing systems, were tested for C. hepaticus. The 12 layer hen flocks were culture and PCR negative for C. hepaticus. Currently, there are no approved treatments for C. hepaticus and no vaccine is available. The results of this study suggest that C. hepaticus may be endemic in some areas of the United States, and free-range laying hens may be exposed from the environment/stagnant water in areas where they range.

Characterisation of N-linked protein glycosylation in the bacterial pathogen Campylobacter hepaticus

Campylobacter hepaticus is an important pathogen which causes Spotty Liver Disease (SLD) in layer chickens. SLD results in an increase in mortality and a significant decrease in egg production and therefore is an important economic concern of the global poultry industry. The human pathogen Campylobacter jejuni encodes an N-linked glycosylation system that plays fundamental roles in host colonization and pathogenicity. While N-linked glycosylation has been extensively studied in C. jejuni and is now known to occur in a range of Campylobacter species, little is known about C. hepaticus glycosylation. In this study glycoproteomic analysis was used to confirm the functionality of the C. hepaticus N-glycosylation system. It was shown that C. hepaticus HV10T modifies > 35 proteins with an N-linked heptasaccharide glycan. C. hepaticus shares highly conserved glycoproteins with C. jejuni that are involved in host colonisation and also possesses unique glycoproteins which may contribute to its ability to survive in challenging host environments. C. hepaticus N-glycosylation may function as an important virulence factor, providing an opportunity to investigate and develop a better understanding the system's role in poultry infection.

Campylobacter bilis, the second novel Campylobacter species isolated from chickens with Spotty Liver Disease, can cause the disease

Spotty Liver Disease (SLD) is a significant disease of commercial layer hens. It can cause up to 10 % flock mortalities and reduce egg production by 25 %. Campylobacter hepaticus has been identified as the main cause of the disease, although it also appears that predisposing factors, such as some form of stress, may increase the likelihood of clinical disease occurring. Recently, a newly identified species, Campylobacter bilis, was isolated from bile samples of clinical SLD affected chickens. To investigate the pathogenic potential of C. bilis two independent isolates were used in infection trials of layer hens. Within 6 days of oral challenge birds developed typical SLD liver lesions, demonstrating that both strains induced SLD. C. bilis could be recovered from all the challenged birds that developed SLD. Thus, each of the steps in Koch's postulates have been fulfilled, confirming that C. bilis is an additional cause of SLD. A PCR method was developed which can specifically detect C. bilis from samples with complex microbiota. The identification of this newly discovered Campylobacter species as a second cause of SLD and the provision of a rapid method to detect the SLD causing bacterium will help with SLD vaccine development and epidemiology, thus assisting in the control of this important disease of poultry.

Prevalence of Campylobacter hepaticus specific antibodies among commercial free-range layers in Australia

Spotty liver disease (SLD) caused by Campylobacter hepaticus affects the health and productivity of layer hens and is a disease of concern in poultry. In this study, blood and cloacal swab samples were collected from 709 birds across 11 free-range layer farms from different regions of Australia. The prevalence of C. hepaticus specific antibodies and DNA was assessed using a C. hepaticus specific ELISA and PCR and its correlation with mortalities and changes in egg production was analyzed to better understand the seroprevalence of C. hepaticus in Australian free-range layer farms. C. hepaticus specific antibodies were detected from birds in four of the five farms that had no history of SLD with seroprevalence as high as 41% in one of the farms. Seroprevalence of anti-C. hepaticus antibodies among flocks that had an active or previous SLD outbreak varied between 2 and 64%. C. hepaticus DNA was detected from birds in three farms with no known SLD history and five farms with confirmed SLD outbreaks. A good correlation was observed between the ELISA and PCR results with a Pearson correlation coefficient value of 0.85 (p-value = 0.001). No correlation was observed between the flock size or flock age and ELISA or PCR outcomes, and no significant difference between the seroprevalence of anti-C. hepaticus antibodies among flocks with or without a known history of SLD was established (p = 0.143). This study demonstrates the usefulness of C. hepaticus specific ELISA and PCR in identifying the occurrence of mild or sub-clinical SLD and provides a broader and more complete understanding of SLD epidemiology that will inform future research aimed at the development of methods to control SLD, such as appropriate biosecurity measures, vaccines, and feed additives.

Prevalence and Antimicrobial Resistance of Campylobacter jejuni and Campylobacter coli from Laying Hens Housed in Different Rearing Systems

Campylobacter (C.) jejuni and C. coli are responsible for food poisoning in humans. Laying hens may host the bacteria usually without developing symptoms. The aims of this paper were to evaluate the incidence of C. jejuni and C. coli infection in laying hen flocks housed in different rearing systems, the plasma levels of two welfare indicators (corticosterone and interleukin 6, IL-6) and the antimicrobial resistance of the detected Campylobacter strains. Two different flocks (1 and 2) from cage (A), barn (B) and aviary (C) farms were investigated. The highest (p < 0.05) levels of IL-6 were detected in laying hens housed in aviaries. A similar trend emerged in corticosterone level, although differences were found between C1 and C2. C. jejuni and C. coli were identified in 43.5% and 38.9% of birds, respectively. In total, 14 out of 177 (7.9%) hens simultaneously hosted C. jejuni and C. coli.C. jejuni was prevalently detected in hens housed in barns (B1: 53.3%; B2: 46.7%) and aviaries (C1: 34.6%; C2: 86.7%). Conversely, laying hens housed in cages were significantly exposed to infection of C. coli (A1: 41.9%; A2: 80%) while, regarding barns and aviaries, a significant prevalence emerged only in flocks B2 (40%) and C1 (54.8%). Simultaneous infection was statistically significant in barn B1 (36.7%). Antibiotic resistance was mainly detected among C. coli strains, and it was most frequent for fluoroquinolones and tetracycline. Multidrug resistance was also found in C. jejuni (19.7%) and C. coli (17.5%) strains. Based on the results of this study, we recommend increasing biosecurity and hygienic measures to manage hen flocks.

Alterations in Faecal Metagenomics and Serum Metabolomics Indicate Management Strategies for Patients With Budd-Chiari Syndrome

We investigated the effects of gut microbiota and serum metabolite levels in patients with Budd-Chiari syndrome (B-CS) and their importance for guiding clinical management strategies. In total, 214 B-CS patients (93 untreated and 121 treated) and 41 healthy controls were enrolled. Gut microbiota and serum metabolome were analysed using shotgun metagenomics and liquid chromatography-mass spectrometry. The gut microbiota of the patients showed abundance of Campylobacter and low levels of Saccharomyces, Deinococcus, and Thiomonas (P < 0.05). Thirty metabolites, including taurocholate and (R)-3-hydroxybutyric acid, were identified in the patients (VIP > 1, P < 0.05 and FC > 1.2 or FC < 0.83). Random forest (RF) models showed that serum metabolome could effectively identify B-CS from healthy controls and RF-metabolomics exhibited perfect discrimination (AUC = 100%, 95% CI: 100% – 100%), which was significantly higher than that achieved by RF-metagenomics (AUC = 58.48%, 95% CI: 38.46% – 78.5%). Campylobacter concisus and taurocholate showed significant positive correlation in patients with clinical manifestations (P < 0.05). Actinobacteria levels were significantly higher in untreated patients than in treated patients (P < 0.05). Campylobacter and Veillonella levels were significantly higher in treated patients than in healthy controls (P < 0.05). We identified major alterations in the gut microbiota and serum metabolome of patients with B-CS. Faecal metagenomics- and serum metabolomics-guided management strategies are required for patients with B-CS.

Enhancement of Campylobacter hepaticus culturing to facilitate downstream applications

Campylobacter hepaticus causes Spotty Liver Disease (SLD) in chickens. C. hepaticus is fastidious and slow-growing, presenting difficulties when growing this bacterium for the preparation of bacterin vaccines and experimental disease challenge trials. This study applied genomic analysis and in vitro experiments to develop an enhanced C. hepaticus liquid culture method. In silico analysis of the anabolic pathways encoded by C. hepaticus revealed that the bacterium is unable to biosynthesise L-cysteine, L-lysine and L-arginine. It was found that L-cysteine added to Brucella broth, significantly enhanced the growth of C. hepaticus, but L-lysine or L-arginine addition did not enhance growth. Brucella broth supplemented with L-cysteine (0.4 mM), L-glutamine (4 mM), and sodium pyruvate (10 mM) gave high-density growth of C. hepaticus and resulted in an almost tenfold increase in culture density compared to the growth in Brucella broth alone (log10 = 9.3 vs 8.4 CFU/mL). The type of culture flask used also significantly affected C. hepaticus culture density. An SLD challenge trial demonstrated that C. hepaticus grown in the enhanced culture conditions retained full virulence. The enhanced liquid culture method developed in this study enables the efficient production of bacterial biomass and therefore facilitates further studies of SLD biology and vaccine development.

Isoquinoline alkaloids induce partial protection of laying hens from the impact of Campylobacter hepaticus (spotty liver disease) challenge

Spotty liver disease (SLD) is a serious condition affecting extensively housed laying hens. The causative bacterium was described in 2015 and characterized in 2016 and named Campylobacter hepaticus. Antibiotics are the only tool currently available to combat SLD. However, antimicrobial resistance has already been detected, so finding therapeutic alternatives is imperative. Isoquinoline alkaloids (IQA), such as sanguinarine and chelerythrine, have been shown to have immunomodulatory effects. It has been hypothesized that IQA could ameliorate some of the deleterious effects of SLD. This study aimed to address that hypothesis in an experimental disease induction model. Birds were fed with diets containing 2 different doses of an IQA containing product, 100 mg of product/kg of feed (0.5 ppm of sanguinarine) and 200 mg of product/kg of feed (1.0 ppm of sanguinarine). Two additional groups remained untreated (a challenged positive control and an unchallenged negative control). After 4 wk of treatment, birds from all groups except the negative control group were exposed to C. hepaticus strain HV10. The IQA treated groups showed a reduction in the number of miliary lesions on the liver surface and reduced lesion scores compared with untreated hens. A significant reduction of egg mass was detected 6 d after exposure to C. hepaticus in the untreated group (P = 0.02). However, there was not a significant drop in egg-mass in the IQA groups, especially those fed with a high dose of IQA (P = 0.93). IQA supplementation did not produce significant changes in intestinal villus height and crypt depth but did result in a significant reduction in the proinflammatory cytokine, interleukin-8, in the blood (P < 0.01). Microbiota analysis showed that IQA treatment did not alter the alpha diversity of the cecal microbiota but did produce changes in the phylogenetic structure, with the higher dose of IQA increasing the Firmicutes/Bacteroidetes ratio.

Other minor changes in production indicators included an increase in feed consumption (P < 0.01) and an increase in body weight of the treated hens (P < 0.0001). The present study has demonstrated that IQA confers some protection of chickens from the impact of SLD.

Complete Genome Sequence of Campylobacter hepaticus Strain UF2019SK1, Isolated from a Commercial Layer Flock in the United States

The thermophilic Campylobacter species Campylobacter hepaticus is the causative agent of spotty liver disease (SLD) in chickens. This announcement describes the complete genome sequence of C. hepaticus strain UF2019SK1, isolated from the liver of a commercial layer chicken with SLD in the United States.

The thermophilic Campylobacter species Campylobacter hepaticus is the causative agent of spotty liver disease (SLD) in chickens. This announcement describes the complete genome sequence of C. hepaticus strain UF2019SK1, isolated from the liver of a commercial layer chicken with SLD in the United States.

Complete Genome Sequence of Campylobacter hepaticus USA52, Associated with Chicken Spotty Liver Disease

Campylobacter hepaticus was recently identified as the etiological agent of chicken spotty liver disease. Here, we report the complete genome sequence of C. hepaticus strain USA52 from the United States. The genome comprises a chromosome of 1,509,100 bp with an average GC content of 28.02%.

Development of an enzyme-linked immunosorbent assay for detecting Campylobacter hepaticus specific antibodies in chicken sera - a key tool in Spotty Liver Disease screening and vaccine development

Spotty Liver Disease (SLD) is an emerging disease of serious concern in the egg production industry, as it causes significant egg loss and mortality in layer hens. The causative agent is a newly identified Gram-negative bacterium, Campylobacter hepaticus, and knowledge about C. hepaticus pathogenesis and the potential for vaccine development is still in its infancy. Current detection methods for SLD, such as PCR and culturing, only detect an active infection and will not give any indication of a past infection from which the bacteria have been cleared. An immunological assay, on the other hand, can provide information on previous infections and therefore is crucial in vaccine development against SLD. In the present study, we have developed the first immunoassay capable of detecting C. hepaticus-specific antibodies present in the sera of infected birds. The assay uses C. hepaticus total protein extract (TPE) as the antigen coating on enzyme-linked immunosorbent assay (ELISA) plates. The cross reactivity of C. hepaticus antibodies with closely related C. jejuni and C. coli antigens was successfully overcome by pre-absorbing the sera using C. jejuni cell extracts. The assay was validated using sera samples from both naturally- and experimentally-infected birds, birds vaccinated with formalin-killed bacteria, and serum samples from SLD-negative birds (control group). The optimized ELISA assay had 95.5% specificity and 97.6% sensitivity. The immunoassay provides a useful tool for monitoring the exposure of poultry flocks to C. hepaticus infection and can be used to direct and support vaccine development. HIGHLIGHTS The first immunoassay developed for Spotty Liver Disease (SLD). A useful method for detecting C. hepaticus-specific antibodies in birds. Highly specific (95.5%) and sensitive (97.6%) assay. A key tool for use in epidemiological studies and vaccine development.

Isolation of Campylobacter hepaticus from free-range poultry with spotty liver disease in New Zealand

Case history: In October 2019, a free-range egg laying flock suffering an outbreak of spotty liver disease was investigated. Eight 32-week-old hens were examined post-mortem. Clinical and pathological findings: Five of the eight hens had sparse, focal, gross hepatic lesions typical of spotty liver disease. Histopathology of the liver showed random, focal hepatic necrosis, lymphoplasmacytic cholangitis/pericholangitis and, in one hen, severe lymphoplasmacytic cholecystitis. Campylobacter-like organisms were grown from all eight bile samples which were confirmed by PCR as Campylobacter hepaticus. The genome of C. hepaticus isolates from the outbreak were sequenced and compared to those of isolates from Australia and the United Kingdom. Phylogenetic analysis based on single nucleotide polymorphisms showed that the C. hepaticus isolates from this outbreak were most closely related to isolates from Australia. Diagnosis: Campylobacter hepaticus focal hepatic necrosis. Clinical relevance: This is the first report of an outbreak of spotty liver disease confirmed to be caused by C. hepaticus in poultry in New Zealand. Therefore infection with C. hepaticus should be considered as a differential diagnosis for mortality in laying hens around peak lay in New Zealand.

Species distribution, genetic diversity and antimicrobial susceptibility of Campylobacter isolates recovered from the preputial cavity of healthy rams in Turkey

AIMS

Campylobacter sp. are important causes of reproductive disease in ruminants worldwide. Although healthy bulls are well-known carriers for infection of cows, the role of rams as a potential source for infecting ewes is unclear. This study aimed to determine prevalence, species distribution, genetic diversity and antimicrobial susceptibility profiles of Campylobacter sp. isolated from the preputial cavity of healthy rams.

METHODS AND RESULTS

The material of this prospective study comprised 191 swab samples taken from the preputial cavity of healthy rams. Enrichment and membrane filtration were employed for the isolation of Campylobacter. Presumptive isolates were confirmed as Campylobacter by phenotypic and molecular tests. 16S rRNA gene sequence analysis was used for the definitive identification of the isolates at species level, and genotyping was performed using pulsed-field gel electrophoresis (PFGE). The susceptibility of the Campylobacter sp. isolates to various antibiotics was determined by the disk diffusion test. In all, 27 of the 191 (14·13%) swab samples were found to be positive for Campylobacter sp. (28 isolates were recovered in total). Per phenotypic and genotypic analyses, one isolate was identified as Campylobacter mucosalis and the remaining 27 isolates were identified as Campylobacter sputorum bv. faecalis. The PFGE analysis of the C. sputorum biovar faecalis isolates produced 17 clusters and 24 different pulsotypes, indicating high genetic heterogeneity. All 28 isolates were found to be susceptible to all of the antibiotics tested.

CONCLUSIONS

Healthy rams may be an important reservoir of different Campylobacter species in the preputium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated for the first time that healthy rams can carry different Campylobacter sp. including genetically diverse C. sputorum bv. faecalis and C. mucosalis in the preputial cavity. Further investigation on the potential implication of this finding on sheep reproductive health (e.g. infectious infertility, and abortion) and overall epidemiology of Campylobacter may be warranted.

Campylobacter hepaticus, the Cause of Spotty Liver Disease in Chickens: Transmission and Routes of Infection

The epidemiology of Spotty Liver Disease (SLD) was investigated by assaying 1,840 samples collected from layer chickens and the environment in poultry farms across Australia for the presence of Campylobacter hepaticus, the agent responsible SLD in chickens. A C. hepaticus specific PCR and bacterial culture were used. Results showed that birds could be infected with C. hepaticus up to 8 weeks before clinical SLD was manifested. In addition, birds could be infected long before laying starts, as young as 12 weeks old, but the peak period for SLD outbreaks was when the birds were 26-27 weeks old. Campylobacter hepaticus DNA was detected in motile organisms such as wild birds and rats and so these organisms may be vectors for C. hepaticus dissemination. Moreover, water, soil, mites, flies, and dust samples from SLD infected farms were also found to be PCR-positive for C. hepaticus DNA. However, it still remains to be determined whether these environmental sources carry any viable C. hepaticus. The indications from this study are that environmental sources are a likely transmission source of C. hepaticus. Therefore, biosecurity practices need to be strictly followed to prevent the spread of SLD amongst and between flocks. Also, a rapid, molecular detection method such as PCR should be used as to monitor for C. hepaticus presence in flocks before clinical disease is apparent, and therefore inform the use of biosecurity and therapeutic measures to help prevent SLD outbreaks.

Pathogenomics of Emerging Campylobacter Species

Campylobacter is among the four main causes of gastroenteritis worldwide and has increased in both developed and developing countries over the last 10 years. The vast majority of reported Campylobacter infections are caused by Campylobacter jejuni and, to a lesser extent, C. coli; however, the increasing recognition of other emerging Campylobacter pathogens is urgently demanding a better understanding of how these underestimated species cause disease, transmit, and evolve. In parallel to the enhanced clinical awareness of campylobacteriosis due to improved diagnostic protocols, the application of high-throughput sequencing has increased the number of whole-genome sequences available to dozens of strains of many emerging campylobacters. This has allowed for comprehensive comparative pathogenomic analyses for several species, such as C. fetus and C. concisus These studies have started to reveal the evolutionary forces shaping their genomes and have brought to light many genomic features related to pathogenicity in these neglected species, promoting the development of new tools and approaches relevant for clinical microbiology. Despite the need for additional characterization of genomic diversity in emerging campylobacters, the increasing body of literature describing pathogenomic studies on these species deserves to be discussed from an integrative perspective. This review compiles the current knowledge and highlights future work toward deepening our understanding about genome dynamics and the mechanisms governing the evolution of pathogenicity in emerging Campylobacter species, which is urgently needed to develop strategies to prevent or control the spread of these pathogens.

A review of the novel thermophilic Campylobacter, Campylobacter hepaticus, a pathogen of poultry

In 2015, a novel thermophilic Campylobacter was isolated from cases of spotty liver disease in laying hens in the UK. In 2016, it was isolated from laying hens in Australia where it was formally named Campylobacter hepaticus and confirmed as the cause of spotty liver disease. It has also been isolated from laying hens in America. It is fastidious, grows slowly on first isolation and does not grow on media used to routinely isolate Campylobacter. Spotty liver disease is an acute, randomly distributed, focal, necrotic hepatitis causing mortality in up to 10% of a flock and a 10%-15% fall in egg production. It occurs mainly in free-range hens or hens reared on the ground at around the time of peak lay. The incidence of the disease has increased in countries where there is an increase in keeping free-range laying hens. It is similar to the condition avian vibrionic hepatitis which was reported in America, Europe and Australasia in the 1950s to 1970s and the agent isolated from cases of avian vibrionic hepatitis and C. hepaticus appear to be very similar. It is not known if C. hepaticus is zoonotic but whole genome sequencing shows that it is most closely related to the known zoonotic campylobacters Campylobacter jejuni and Campylobacter coli. Human exposure to C. hepaticus is likely through similar exposure routes. Analysis of the whole genome showed a reduction in the genes for iron metabolism compared to C. jejuni. A requirement for iron was confirmed as it showed reduced growth in an iron depletion assay and this may explain its tissue tropism. With a move towards free-range egg production in many countries, the incidence of C. hepaticus hepatitis is likely to increase, but the identification of the causal agent will provide opportunities for the development of control methods.

Spotlight on avian pathology: Campylobacter hepaticus, the cause of Spotty Liver Disease in layers

Campylobacter hepaticus was recently identified as the aetiological agent of Spotty Liver Disease (SLD). SLD causes significant health and productivity losses in the Australian egg industry and the disease is present in other countries. Following the isolation and characterization of C. hepaticus, molecular tools and refined culturing methods have been developed to identify the pathogen. It is suspected that the application of these tools will lead to identification of the pathogen in many poultry production systems throughout the world. As C. hepaticus has only recently been identified, little is known about the mechanisms of pathogenesis and, hence, new research needs to be directed towards understanding SLD epidemiology and C. hepaticus virulence mechanisms to inform efforts to develop intervention strategies.

Spotty Liver Disease: A review of an ongoing challenge in commercial free-range egg production

Spotty Liver Disease is an acute infectious disease of layer chickens that was likely first described in the USA and Canada in the 1950s and 1960's. The disease occurs almost exclusively in barn and free-range production systems. Outbreaks usually, but not exclusively occur in young layers (≅25 weeks) at peak of lay. Indicators of SLD include an acute drop in egg production of up to 35%, together with increased mortality of up to 15%. A presumptive diagnosis at post mortem is made with the detection of characteristic small yellow-white necrotic hepatic lesions, together with a fibrinous peri-hepatitis, excess pericardial and peritoneal fluid, and usually enteritis with diarrhoea. Histopathology reveals a multifocal acute hepatocellular necrosis with fibrin and occasional haemorrhage. Control measures trialled include use of antibiotics, improved biosecurity and hygiene, as well as management practices directed at reducing stress in flocks. However, none other than treatment with antibiotics has been consistently effective which suggested a bacterial aetiology. In 2015, a novel fastidious thermophilic, microaerobic campylobacter was isolated from symptomatic SLD flocks in the UK. Subsequently, an Australian group isolated and further characterised a genetically similar bacterium and named it Campylobacter hepaticus. The bacterium can be cultured from the liver and bile of infected birds, although recovery from non-sterile organs such as the caecum and duodenum remains elusive. Consequently, the route of transmission remains unconfirmed, although molecular detection by PCR of C. hepaticus DNA in the gastrointestinal tract and faeces of SLD infected birds is highly suggestive of a faecal-oral route.