The challenges of pig farming in Hong Kong: a study of farmers' perceptions and attitudes towards a pig health and production management service.

BACKGROUND: Pig farming in Hong Kong differs markedly from other places in the world, with a highly urbanised population, the majority of pigs being imported for slaughter, and limited on-farm veterinary support. Little is known about the barriers and attitudes of pig farmers in Hong Kong and their expectations of a new pig health and production management service provided by veterinarians. We collected qualitative and quantitative data to 1) describe pig farms, 2) identify barriers to pig farming in Hong Kong and 3) describe the perceptions of the new service. Thematic analysis was conducted to identify barriers and attitudes. RESULTS: Eight and nine out of 38 pig farmers agreed to participate in the qualitative and quantitative components, respectively. All farms were farrow-to-finish farms with a median of 2800 (range 950 to 7000) pigs per farm. Three themes were identified during the interview analysis and could be ranked based on their importance to the farmers: the regulatory environment (Theme 1), veterinary support structures (Theme 2), and the sustainability of the pig industry (Theme 3). Farmers expressed dissatisfaction with the regulation of the industry and veterinary services on offer within Hong Kong. However, farmers did note that the provision of a new pig health and production management service was as a positive development. The public perception of pig farming, market forces, and competition from mainland pig farmers have resulted in sustainability challenges for the industry. CONCLUSIONS: Farmers identified very specific local systems and challenges unique to pig farming in Hong Kong. The lack of veterinary support was one of these challenges and although a certain level of scepticism towards the new pig health and production service was expressed, farmers indicated their interest and listed areas where they would benefit from improved veterinary support. Prior experiences of veterinary services clouded farmers perceptions of the usefulness of a new service. To be successful in this environment, clear communication about the goals, role and limitations of the new on farm service is crucial, as is the alignment with the needs of farmers. Despite the small sample size, the qualitative methodology used allows us to assume that these themes give a general idea of what Hong Kong farmers' concerns and attitudes are.

Factors driving pig owners' motivation and satisfaction to perform eradications from Swine dysentery.

Brachyspira hyodysenteriae is one of the agents of swine dysentery (SD) and its eradication is an effective, but costly control measure. Being a voluntary measure, knowledge about drivers of motivation and satisfaction regarding the eradication of SD would help to convince farmers to eradicate. We aimed to describe eradications performed in Switzerland and to analyse factors influencing the pig owners' perception (motivation and satisfaction) of SD eradications to provide a basis to formulate recommendations and guidelines. Pig farmers (n = 68) having conducted an SD eradication and being interested in the study were interviewed using a standardised digital questionnaire. We assessed their motivation as moderately or highly motivated. Based on the farmers' evaluation of nine aspects of the eradication, satisfaction was considered to be moderate (<7/9 aspects positively evaluated) or high (≥7/9). Farms with fattening pigs and farms with breeding stock were analysed separately in subsets. First, multivariable factor analysis for mixed data (FAMD) were performed to describe the main patterns of variation. Then, risk factors for motivation and satisfaction were quantified by means of logistic regression models. Mainly total depopulations (73.5%) had been performed. Of the 36 farmers with breeding pigs, 24 were highly motivated, and 20 highly satisfied. Of the 61 farmers with fattening pigs, 45 were highly motivated and 42 highly satisfied. The FAMD revealed that the two main components explained only 17.0% and 11.0% (breeding stock) and 13.0% and 11.0% (fattening pigs) of the total variation, respectively. For farmers with breeding stock no significant factors for motivation were detected, but they were more satisfied (OR 25.0) when they had a batch farrowing of 3 weeks. Farmers with fattening pigs were more likely to be more motivated when providing access to outdoor areas (OR 3.3) and when it was their own initiative (OR 5.5). Farmers were more likely to be satisfied when they had only fattening pigs (OR 5.7), when the eradication was their own initiative (OR 5.5) and when they did not disinfect the barns during the eradication (OR 15.6). Farmers deciding themselves to eradicate are presumably more likely convinced of the benefits of the eradication. Satisfaction associated with a 3-weeks batch farrowing might be related to an easier to organise eradication and no disinfection to reduced labour and costs. In summary, the majority of the farmers were satisfied with the eradication. Education could promote self-motivation of farmers, and subsidies might support the implementation of SD eradications.

Whole-genome analyses reveal a novel prophage and cgSNPs-derived sublineages of Brachyspira hyodysenteriae ST196.

BACKGROUND: Brachyspira (B.) hyodysenteriae is a fastidious anaerobe spirochete that can cause swine dysentery, a severe mucohaemorragic colitis that affects pig production and animal welfare worldwide. In Switzerland, the population of B. hyodysenteriae is characterized by the predominance of macrolide-lincosamide-resistant B. hyodysenteriae isolates of sequence type (ST) ST196, prompting us to obtain deeper insights into the genomic structure and variability of ST196 using pangenome and whole genome variant analyses. RESULTS: The draft genome of 14 B. hyodysenteriae isolates of ST196, sampled during a 7-year period from geographically distant pig herds, was obtained by whole-genome sequencing (WGS) and compared to the complete genome of the B. hyodysenteriae isolate Bh743-7 of ST196 used as reference. Variability results revealed the existence of 30 to 52 single nucleotide polymorphisms (SNPs), resulting in eight sublineages of ST196. The pangenome analysis led to the identification of a novel prophage, pphBhCH20, of the Siphoviridae family in a single isolate of ST196, which suggests that horizontal gene transfer events may drive changes in genomic structure. CONCLUSIONS: This study contributes to the catalogue of publicly available genomes and provides relevant bioinformatic tools and information for further comparative genomic analyses for B. hyodysenteriae. It reveals that Swiss B. hyodysenteriae isolates of the same ST may have evolved independently over time by point mutations and acquisition of larger genetic elements. In line with this, the third type of mobile genetic element described so far in B. hyodysenteriae, the novel prophage pphBhCH20, has been identified in a single isolate of B. hyodysenteriae of ST196.

Complete Circular Genome Sequences of Brachyspira hyodysenteriae Isolates of the Four Different Sequence Types Causing Swine Dysentery in Switzerland.

The complete genomes of four Brachyspira hyodysenteriae isolates of the four different sequence types (STs) (ST6, ST66, ST196, and ST197) causing swine dysentery in Switzerland were generated by whole-genome sequencing and de novo hybrid assembly of reads obtained from second (Illumina) and third (Oxford Nanopore Technologies and Pacific Biosciences) generation high-throughput sequencing.

Seroprevalence of atypical porcine pestivirus in a closed pig herd with subclinical infection.

Atypical porcine pestivirus (APPV) has recently been reported to be associated with congenital tremor in newborn piglets. Only limited information is available about the prevalence at herd level in endemically infected herds. Therefore, the aim of this study was to determine the within-herd prevalence of APPV in a sub-clinically infected sow herd in Switzerland and to analyse associations between the serological status as well as the age and sex of the pigs, litter number and days after the last insemination. In a census sampling, blood was collected from 125 sows, aged 180 days or older, and six boars. Sera were examined applying an indirect APPV-specific ELISA to individual sera and an APPV RT-PCR targeting the NS3 encoding regions of APPV to pools of five. The APPV antibody status was classified into low (S/P value ≤ 0.5), intermediate (S/P value = 0.5-1) and high reactivity (S/P value > 1.0). None of the pooled serum samples was positive for specific genome fragments of APPV. Of the 131 samples, 53.4% were highly reactive, 39.7% showed an intermediate reactivity, and 6.9% showed a low reactivity in the indirect ELISA, that is, were serologically negative. Significant associations between the S/P values and the age of the pigs (p < .001), the litter number (p < .001) and the numbers of days after the last insemination (p = .0188) were observed. The results indicate that this sow herd was previously infected with APPV, while viremia was not detected in any of the adult pigs. This might explain the absence of clinical signs in the suckling pigs. Potential reinfection and circulation of APPV in this sow herd might be due to semen from commercial boar studs or APPV-positive animals in the absence of specific clinical signs.

Risk factors for the infection with Brachyspira hyodysenteriae in pig herds.

Swine dysentery (SD), caused by infection with Brachyspira hyodysenteriae, is a serious disease in pig production worldwide. Quantitative risk factors triggering the occurrence of infection are unknown. The present case-control study aimed at identifying major risk factors related to presence of B. hyodysenteriae in pig herds. Twenty case herds and 60 randomly selected control herds with a minimum herd size of '10 sows/ 80 fattening pigs' were examined by means of a questionnaire-based interview and a herd examination. Herds with previous eradication of SD were excluded. Logistic regression models revealed that the 'positive/suspicious SD status of source herds', the regular application of treatment, purchasing more than 4 batches/ year, contact to foxes, diagnostics performed during last 12 months, liquid feeding systems, rats on farm, and >250 fatting places were associated with higher chances of a herd to be infected. On the contrary, having different sources of grower pigs within one batch, the presence of raptor birds and the presence of martens in the region were associated with fewer chances of being infected. The final multivariable logistic regression model identified purchasing more than 4 batches/ year (OR = 7.5, 95 % CI 1.8-54.3) and contact to foxes (OR = 5.9; 97.5 % CI 1.2-34.6) as the two main risk factors in our study. 'More than 4 batches/ year' implies continuous herd management supporting persistence of B. hyodysenteriae in an infected herd, but also increased number of purchases each increasing the risk of B. hyodysenteriae introduction by carrier pigs or transport vehicles. Foxes might be infected with B. hyodysenteriae by feeding on positive piglets and rodents. Besides, 'contact to foxes' might represent a lack in biosecurity. In conclusion, the risk factors detected underline the importance of biosecurity in SD prevention and control.

First identification and characterisation of Brachyspira hyodysenteriae in pigs in Hong Kong.

Swine dysentery (SD) is an important endemic disease of pigs throughout the world. The most common aetiological agent is the anaerobic intestinal spirochaete Brachyspira hyodysenteriae. The related spirochaete Brachyspira pilosicoli causes a milder form of colitis. We report the first isolation of B. hyodysenteriae and B. pilosicoli from a pig farm in Hong Kong. Faecal samples containing mucus or fresh blood were collected from the ground where finisher pigs had just been loaded into a truck for transport to the abattoir. The samples were subjected to selective anaerobic culture and PCR for B. hyodysenteriae and B. pilosicoli, and two isolates of both species were obtained. The B. hyodysenteriae isolates showed clinical resistance to tylosin and lincomycin, whilst the B. pilosicoli isolates were resistant to tylosin and showed intermediate susceptibility to lincomycin. The B. hyodysenteriae isolates were subjected to multilocus sequence typing and a single previously undescribed sequence type (ST250) was identified. Disease was not recorded in other pigs on the farm, but it may have been masked by the use of antimicrobials. Further work is required to examine the distribution of these two pathogens in this and other farms in Hong Kong and in adjoining mainland China.

Predominance of a macrolide-lincosamide-resistant Brachyspira hyodysenteriae of sequence type 196 in Swiss pig herds.

Worldwide emergence of antimicrobial-resistant Brachyspira (B.) hyodysenteriae led us question whether specific clones are present in Switzerland. Fifty-one B. hyodysenteriae isolates originating from 27 different Swiss pig herds sampled between 2010 and 2017 were characterised. Multilocus sequence typing revealed the presence of four different sequence types (STs) ST6, ST66, ST196 and ST197 with ST196 being predominant. Antimicrobial susceptibility to six different antimicrobial agents was determined by measurement of the minimal inhibitory concentration by broth dilution. Isolates were examined for the presence of point mutations and genes known to be associated with antimicrobial resistance in B. hyodysenteriae by PCR and sequence analysis. Forty-one isolates belonging to ST6 (n = 1), ST66 (n = 4) and ST196 (n = 36) exhibited decreased susceptibility to macrolides and lincomycin associated with an A2058 T/G mutation in the 23S rRNA gene. One isolate of ST66 and five isolates of ST196 exhibited decreased susceptibility to doxycycline associated with a G1058C mutation in the 16S rRNA gene. The Swiss B. hyodysenteriae population is characterised by a low genetic diversity, with macrolide-lincosamide-resistant isolates of ST196 being predominant.

Transposon-associated lincosamide resistance lnu(C) gene identified in Brachyspira hyodysenteriae ST83.

Treatment of Swine Dysentery (SD) caused by Brachyspira hyodysenteriae (B. hyodysenteriae) is carried out using antimicrobials such as macrolides, lincosamides and pleuromutilins leading to the selection of resistant strains. Whole genome sequencing of a multidrug-resistant B. hyodysenteriae strain called BH718 belonging to sequence type (ST) 83 revealed the presence of the lincosamide resistance gene lnu(C) on the small 1724-bp transposon MTnSag1. The strain also contains an A to T substitution at position 2058 (A2058T) in the 23S rRNA gene which is known to be associated with macrolide and lincosamide resistance in B. hyodysenteriae. Testing of additional strains showed that those containing lnu(C) exhibited a higher minimal inhibitory concentration (MIC) of lincomycin (MIC ≥ 64 mg/L) compared to strains lacking lnu(C), even if they also harbor the A2058T mutation. Resistance to pleuromutilins could not be explained by the presence of already reported mutations in the 23S rRNA gene and in the ribosomal protein L3. This study shows that B. hyodysenteriae has the ability to acquire mobile genetic elements conferring resistance to antibiotics.

Brachyspira hyodysenteriae detection in the large intestine of slaughtered pigs.

Detection of subclinical Brachyspira hyodysenteriae infection in pig herds using feces is challenging. However, the ability to detect the pathogen in intestinal samples of slaughtered pigs has not been investigated, to our knowledge. Therefore, we determined the detection of B. hyodysenteriae in the colon, cecum, and rectum from slaughtered pigs. We analyzed the correlation between detection rates and intestinal lesions, ingesta or fecal consistency, and time from sample collection until processing. A total of 400 ingesta-mucosal (colon, cecum) and 200 fecal (rectum) samples from 200 pigs originating from 20 different herds were bacteriologically examined using selective culture followed by Brachyspira spp. identification by PCR and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Ingesta or fecal consistency and intestinal lesions were scored. Brachyspira hyodysenteriae was detected in 23 samples from 16 intestines originating from 7 herds. Brachyspira spp. were detected in 96 samples. More intestinal (16) than fecal (7) samples tested positive for B. hyodysenteriae. For Brachyspira spp., this difference was significant (69 vs. 27; p < 0.01). In particular, colon samples tested positive ( n = 42, p = 0.06). Most (91%) of the intestines showed no lesions typical for clinical B. hyodysenteriae infection, and median ingesta or fecal consistency was "soft and formed," indicating subclinical infection, colonization, or absence of infection. Ingesta from slaughtered pigs, in particular from the colon and sites with lesions, is useful material for detection of B. hyodysenteriae.

A review of methods used for studying the molecular epidemiology of Brachyspira hyodysenteriae.

Brachyspira (B.) spp. are intestinal spirochaetes isolated from pigs, other mammals, birds and humans. In pigs, seven Brachyspira spp. have been described, i.e. B. hyodysenteriae, B. pilosicoli, B. intermedia, B. murdochii, B. innocens, B. suanatina and B. hampsonii. Brachyspira hyodysenteriae is especially relevant in pigs as it causes swine dysentery and hence considerable economic losses to the pig industry. Furthermore, reduced susceptibility of B. hyodysenteriae to antimicrobials is of increasing concern. The epidemiology of B. hyodysenteriae infections is only partially understood, but different methods for detection, identification and typing have supported recent improvements in knowledge and understanding. In the last years, molecular methods have been increasingly used. Molecular epidemiology links molecular biology with epidemiology, offering unique opportunities to advance the study of diseases. This review is based on papers published in the field of epidemiology and molecular epidemiology of B. hyodysenteriae in pigs. Electronic databases were screened for potentially relevant papers using title and abstract and finally, Barcellos et al. papers were systemically selected and assessed. The review summarises briefly the current knowledge on B. hyodysenteriae epidemiology and elaborates on molecular typing techniques available. Results of the studies are compared and gaps in the knowledge are addressed. Finally, potential areas for future research are proposed.

Chronological clinical and pathological documentation of porcine ulcerative dermatitis.

BACKGROUND: Porcine ulcerative dermatitis syndrome (PUDS) is a rare disease of breeding sows with an unknown pathogenesis. OBJECTIVE: To describe the evolution of clinical and histopathological lesions over the course of the disease and to elucidate the pathogenesis. ANIMAL: A 24-month-old, pluriparous, large white sow presented during gestation with ulcerations around the teats compatible with PUDS. METHODS AND RESULTS: Clinical and histopathological lesions were monitored over the course of the disease (i.e. during and after the subsequent pregnancy). A clear gestation-dependent flare of the lesions was observed with partial resolution occurring postpartum. The histological pattern presented as a lymphocytic interface dermatitis. CONCLUSIONS AND CLINICAL IMPORTANCE: The findings in this case report link gestation with the development of clinical signs and histological changes. Multiparity appears to enhance severity and may finally result in a self-perpetuating disease. Therefore, it seems advisable to cull breeding sows after they have developed PUDS.

Effect of soy on faecal dry matter content and excretion of Brachyspira hyodysenteriae in pigs.

The aim of this study was to investigate the effect of a soy diet on the excretion of Brachyspira hyodysenteriae in five farms with subclinically infected pigs. The effects on general health, faecal consistency and dry matter were analysed. In total, 200 pigs of different ages (group 1 <100 days of age (n=120) and group 2 ≥100 days (n=80)) were randomly assigned to the control (C) and the treatment (T) groups. Group C received the farm's standard diet. In group T half of the daily feed ration was replaced by pure soy on two consecutive days. Faecal scores were used to determine faecal consistency and a microwave method to assess faecal dry matter content (FDMC). In age group 1, soy feeding resulted in a statistically significant decrease of the FDMC of 2.5 per cent compared with group C and in age group 2 in a significant increase of 2.2 per cent compared with group C at day 2. Overall seven (T: 5, C: 2) out of 597 faecal samples tested positive for B hyodysenteriae by PCR. In conclusion, a high soy diet applied over two days influenced the faecal consistency and the FDMC in growers, finishers and sows under field conditions. Further investigations with more sensitive diagnostic methods are needed to prove a potential influence of a high soy diet on the detection rate of B hyodysenteriae in subclinically infected herds.

Rapid cytopathic effects of Clostridium perfringens beta-toxin on porcine endothelial cells.

Clostridium perfringens type C isolates cause fatal, segmental necro-hemorrhagic enteritis in animals and humans. Typically, acute intestinal lesions result from extensive mucosal necrosis and hemorrhage in the proximal jejunum. These lesions are frequently accompanied by microvascular thrombosis in affected intestinal segments. In previous studies we demonstrated that there is endothelial localization of C. perfringens type C beta-toxin (CPB) in acute lesions of necrotizing enteritis. This led us to hypothesize that CPB contributes to vascular necrosis by directly damaging endothelial cells. By performing additional immunohistochemical studies using spontaneously diseased piglets, we confirmed that CPB binds to the endothelial lining of vessels showing early signs of thrombosis. To investigate whether CPB can disrupt the endothelium, we exposed primary porcine aortic endothelial cells to C. perfringens type C culture supernatants and recombinant CPB. Both treatments rapidly induced disruption of the actin cytoskeleton, cell border retraction, and cell shrinkage, leading to destruction of the endothelial monolayer in vitro. These effects were followed by cell death. Cytopathic and cytotoxic effects were inhibited by neutralization of CPB. Taken together, our results suggest that CPB-induced disruption of endothelial cells may contribute to the pathogenesis of C. perfringens type C enteritis.

Diversity of Mycoplasma hyopneumoniae in pig farms revealed by direct molecular typing of clinical material.

Mycoplasma hyopneumoniae is the etiological agent of enzootic pneumonia in swine. Various reports indicate that different strains are circulating in the swine population. We investigated the variety of M. hyopneumoniae strains by a newly developed genetic typing method based on the polyserine repeat motif of the LppS homolog P146. PCR amplification using M. hyopneumoniae specific, conserved primers flanking the region encoding the repeat motif, followed by sequencing and cluster analysis was carried out. The study included strains isolated from different geographic regions as well as lysates from lung swabs from a series of pig farms in Switzerland. High diversity of M. hyopneumoniae was observed but farms being in close geographic or operative contact generally seemed to be affected by the same strains. Moreover, analysis of multiple samples from single pig farms indicated that these harbored the same, farm-specific strain. The results indicate that multiple strains of M. hyopneumoniae are found in the swine population but that specific strains or clones are responsible for local outbreaks. The method presented is a highly reproducible epidemiologic tool allowing direct typing of M. hyopneumoniae from clinical material without prior isolation and cultivation of strains.