Antimicrobial Drug Consumption on Swiss Pig Farms: A Comparison of Swiss and European Defined Daily and Course Doses in the Field

Defined Daily Doses (DDD) and Defined Course Doses (DCD) have been established in both human and veterinary medicine in order to standardize the measurement of treatments in a population. In 2016 the European Medicines Agency published average defined daily dose (DDDvet) and defined course dose (DCDvet) values for antimicrobial agents used in livestock production. Similarly, national defined doses (DDDch and DCDch) for the pig sector in Switzerland have recently been determined. The aim of this study was to compare the outcome of calculating antimicrobial consumption based on either DDDvet/DCDvet or DDDch/DCDch. Data from 227 Swiss pig farms describing antimicrobial use in 2015 was collected. The numbers of treatment days and treatments were calculated using DDDvet/DCDvet and DDDch/DCDch respectively, for each farm in total and for different antimicrobial classes. Associations between calculated numbers of DDDvet/DCDvet and DDDch/DCDch on farm level were investigated. In addition, differences concerning antimicrobial use were investigated between different production types of farms (piglet-producer, finishing farm or farrow-to-finishing farm). Using DDDch/DCDch values we calculated 1,805,494 treatment days and 433,678 treatments compared to 1,456,771 treatment days (19% ratio) and 303,913 treatments (30% ratio) based on DDDvet/DCDvet. Penicillins (21.4/26.6%), polypeptides (18.6/27.6%) and fluoroquinolones (9.5/8.8%) were the most frequently used classes of antimicrobials based on calculation using both DDDch and DDDvet. Similar findings were observed for complete treatments (DCDch/vet) (penicillins: 52.8/39.6%; polypeptides: 7.8/14.2%; fluoroquinolones: 13.2/12.9%). The number of treatment days or treatments per farm was higher for piglet-producers and farrow-to-finishing farms compared to finisher farms regardless of whether Swiss or European DDD or DCD values were used for the calculation (each P < 0.001). Similar results for antimicrobial use (AMU) obtained at farm level were observed when calculated either by Swiss or European definitions. Nevertheless, marked differences could be observed in the assessment of the use of specific antimicrobial classes in the field based on DDDvet/DCDvet compared to DDDch/DCDch.

Long-Term Circulation of Atypical Porcine Pestivirus (APPV) within Switzerland

In 2015, a new pestivirus was described in pig sera in the United States. This new "atypical porcine pestivirus" (APPV) was later associated with congenital tremor (CT) in newborn piglets. The virus appears to be distributed worldwide, but the limited knowledge of virus diversity and the use of various diagnostic tests prevent direct comparisons. Therefore, we developed an APPV-specific real-time RT-PCR assay in the 5'UTR of the viral genome to investigate both retro- and prospectively the strains present in Switzerland and their prevalence in domestic pigs. Overall, 1080 sera obtained between 1986 and 2018 were analyzed, revealing a virus prevalence of approximately 13% in pigs for slaughter, whereas it was less than 1% in breeding pigs. In the prospective study, APPV was also detected in piglets displaying CT. None of the samples could detect the Linda virus, which is another new pestivirus recently reported in Austria. Sequencing and phylogenetic analysis revealed a broad diversity of APP viruses in Switzerland that are considerably distinct from sequences reported from other isolates in Europe and overseas. This study indicates that APPV has already been widely circulating in Switzerland for many years, mainly in young animals, with 1986 being the earliest report of APPV worldwide.

Phenotypic and genotypic characteristics of Escherichia coli with non-susceptibility to quinolones isolated from environmental samples on pig farms

Background

In the last decade, the growth of the pig-farming industry has led to an increase in antibiotic use, including several used in human medicine, e.g. (fluoro)quinolones. Data from several studies suggest that there is a link between the agricultural use of antibiotics and the prevalence of antibiotic-resistant bacteria in the pig farm environment, including (fluoro)quinolone resistance. This poses a threat to human and animal health. Our goal was to phenotypically and genotypically characterize 174 E. coli showing non-susceptibility to quinolones isolated from environmental samples from pig farms. Antimicrobial susceptibility testing (AST) was performed using the disk diffusion method. PCR and sequence analysis were performed to identify chromosomal mutations in the quinolone resistance-determining regions (QRDR) of gyrA and the isolates were screened for the presence of the plasmid-mediated quinolone resistance (PMQR) genes aac-(6')-Ib-cr, qepA, qnrA, qnrB, qnrC, qnrD and qnrS.

Strain relatedness was assessed by phylogenetic classification and multilocus sequence typing (MLST).

Results

Of 174 isolates, 81% (n = 141) were resistant to nalidixic acid, and 19% (n = 33) were intermediately resistant. Overall, 68.4% (n = 119) were multidrug resistant. This study revealed a prevalence of 79.9% (n = 139) for gyrA QRDR mutations, and detected 21.8% (n = 38) isolates with at least one PMQR gene. The two most frequently detected PMQR genes were qnrB and qnrS (13.8% (n = 24) and 9.8% (n = 17, respectively). E. coli belonging to phylogenetic group A (48.3%/n = 84) and group B1 (33.3% /n = 58) were the most frequent. E. coli ST10 (n = 20) and ST297 (n = 20) were the most common STs.

Conclusions

E. coli with non-susceptibility to quinolones are widespread among the environment of Swiss pig farms and are often associated with an MDR phenotype. In several cases these isolates possess at least one PMQR gene, which could spread by horizontal gene transfer. E. coli from pig farms have diverse STs, some of which are associated with human and animal disease.

Electronic supplementary material

The online version of this article (10.1186/s40813-019-0116-y) contains supplementary material, which is available to authorized users.

[Defining daily doses and total doses for the measurement of antibiotic usage in Swiss pig production]

INTRODUCTION

A significant Antibiotic-Monitoring-System is essential to analyse the use of antibiotics and to a better understanding of trends in resistance development. In human and veterinary medicine, for example, a system based on defined daily and treatment doses (Defined Daily Dose: DDD and Defined Course Dose: DCD) is applied. These definitions can be used to estimate the number of treatment days and treatments with antimicrobial agents in a population. For veterinary medicine, the European Medicines Agency (EMA) has published the European values DDDvet and DCDvet in the farm animal sector. The aim of this study was to define Swiss daily and treatment doses (DDDch and DCDch) for the treatment of pigs and to compare them with the EMA values in order to investigate the differences between individually collected national doses and average international doses. For the comparison, the quotient of Swiss and European values was calculated and the influence of the application form of an active substance and the number of active substances contained in a preparation was investigated. One hundred and three veterinary preparations with 138 active substances were assigned a DDDch and DCDch value. A comparison with EMA values was possible for 118 active substances. The comparison showed median values of 0.91 for the daily doses and 0.90 for the treatment doses, so that the daily and treatment doses in Switzerland are lower than the corresponding EMA doses. Both the form of application (injection solutions: 1.00; premixes: 0.76; P=0.02) and the number of active substances in the preparation (one active substance: 1.00; two active substances: 0.76; three active substances: 0.43; each P.

[Milk production without use of -antibiotics]

INTRODUCTION

At present, the usage of antimicrobial agents in organic dairy farming is a subject of controversial public debate because of its impact on animals, humans and the environment. This study shows how farms can be successfully managed without using antimicrobials for udder diseases. Thereby, animal welfare and targeted low bulk tank somatic cell counts should not be neglected. The operating data analysed in this study was collected during feeding and milking time on 18 swiss dairy farms that have not been treating diseased udders with antibiotics for at least 3 years. This study is a cross-sectional study. Farmers put the focus on breed characteristics such as a high life performance, low bulk tank somatic cell counts over several lactations, animals with a calm character, and small-formed cows with a deep flank. A trend towards dual-purpose breeds was observed. Few persons were involved in the milking process. Moreover, 94% of the farmers were raising their own young cattle directly on the farm. Consequently, animal transport has been minimized. Furthermore, clear management practices and work processes as well as a good animal observation influenced decisively the production success. additionally some farmers used phytotherapy, homeopathy and tried and true home remedies.

Clinical cystoisosporosis associated to porcine cytomegalovirus (PCMV, Suid herpesvirus 2) infection in fattening pigs

Cystoisospora (syn. Isospora) suis is the causative agent of neonatal porcine coccidiosis and one of the main causes of diarrhoea in suckling piglets worldwide. Infection with porcine cytomegalovirus (PCMV, Suid herpesvirus 2) causes inclusion body rhinitis in pigs. In a Swiss pig herd (n = 2 boars, 7 sows, 2 gilts, 18 finishing pigs, 30 fattening pigs, 54 suckling piglets), an outbreak of PCMV infection with high morbidity in all age categories, characterized by fever, anorexia, reduced general condition, respiratory signs and increased piglet mortality, was diagnosed by histopathology and molecular methods. Five fattening pigs (age ~ 17 weeks) additionally showed diarrhoea, not typical for PCMV infections, and one fattener had to be euthanized due to poor condition. Histopathologically, severe fibrinopurulent jejunoileitis with extensive atrophy and fusion of intestinal villi, loss of goblet cells and crypt abscesses associated to C. suis infection were present. In the liver, herpesvirus intranuclear inclusion bodies were observed and PCMV was confirmed by PCR/sequencing. No further infectious causes of diarrhoea (i.e. Rotavirus A; TGEV; PEDV; PCV-2; enterotoxigenic Escherichia coli or Lawsonia intracellularis) were detected in the euthanized fattener. Coproscopically, C. suis oocysts were identified in the faeces from further fatteners with diarrhoea. While C. suis usually produces disease only in suckling piglets, its association with severe intestinal lesions and diarrhoea in ~ 17-week-old fatteners was surprising. It is supposed that the underlying PCMV infection might have contributed to the presentation of clinical cystoisosporosis in fattening pigs. The interaction mechanisms between these two pathogens are unknown.

•

A Porcine Cytomegalovirus (PCMV) outbreak was diagnosed in a Swiss pig herd

•

Cystoisospora suis caused diarrhoea in 17 week-old fattening pigs co-infected with PCMV

•

PCMV infection may produce immunosuppression in pigs

•

PCMV may have contributed to presentation of clinical cystoisosporosis in fattening pigs

[Effect of herd health management on the prevalence of Postpartum Dysgalaktie Syndrome (PPDS) and the treatment incidence]

INTRODUCTION

The Postpartum Dysgalaktie Syndrome (PPDS) also known as metritis agalactia mastitis (MMA), is considered the most common disease of the sow after farrowing. The reasons for PPDS are multifactorial and are to be found in the areas of management and hygiene, feeding, water supply and animal specific factors such as body condition and age of the sows. In this study a veterinary herd health management was carried out in 28 pig farms with PPDS, with the aim to reduce the PPDS prevalence and animal treatment incidence (TI). In 20 of 28 problem farms the PPDS-prevalence could be decreased from 37.4% (± 21.8%) to 24.5% (± 14.1%). The TI was not significantly reduced. The most effective procedures to reduce the PPDS-prevalence were the use of a prepartal transition feed, optimizing the PPDSdiagnostic and the use of nonsteroidal antiinflammatory drugs (NSAID) and oxytocin in the PPDS-treatment.

[Influence of probiotics on the establishment of a competitive flora, as well as on antibiotic use and performance parameters in pig breeding farms]

INTRODUCTION

The aim of the present study was to investigate the effect of Probiotics in Progress (PIP) on the establishment of a competitive flora as well as on antibiotic use and losses of suckling piglets in pig breeding farms. The tested products were PIP AHC® and PIP AHS® produced by "Chrisal AG" in Lommel, Belgium. PIP`s are cleaning products containing Bacillus spores. According to the manufacturer's specifications, they are able to establish a steady non-pathogenic stable flora. In a field trial in 19 pig breeding farms, the use of PIP-products did not lead to any reduction of antibiotic use or improvement of fertility parameters, especially in relation to losses of suckling piglets. In addition, we compared the bacterial flora using PIP products with the flora under conventional management conditions in a farrowing pen by means of swab samples. The use of PIP-products did not lead to any significant effect on the pen flora. Only very few swab samples contained a majority of probiotic Bacillus spp.

Lethal Gastric Mucosal Necrosis due to Administration of Oral Ferrous Bisglycinate Chelate to Suckling Piglets

The oral application of a newly developed ferrous bisglycinate paste for suckling piglets at a dose of 180 mg/kg body weight led to increased death rates in 10% (n = 10) of Swiss test pig breeding farms (n = 100). Necropsy examination of suckling piglets (n = 12), selected randomly from the test farms with increased death rates, demonstrated severe gastric mucosal ulceration and necrosis. Due to the presence of crystalline iron surface coating within the gastric lesions, the iron was considered as the toxic principle and cause of death. To demonstrate the direct toxicity of ferrous bisglycinate, the paste was administered experimentally to a litter of suckling piglets (n = 11). Different time points (24, 48 and 72 h post partum) and doses (180 mg/kg and 360 mg/kg) were investigated. The manufacturer's recommended dose of 180 mg/kg corresponded to approximately 36 mg Fe/kg and to 6.4 % of the acute lethal dose₅₀ of oral iron in rats. In all piglets the lesions were reproduced and most severe at the earliest time point (24 h post partum) and with the highest applied dose (360 mg/kg). The lesions were in accordance with those described from oral iron intoxication in man, suggesting pigs as an ideal animal model for oral iron toxicity studies.

Experimental Toxoplasma gondii infections in pigs: Humoral immune response, estimation of specific IgG avidity and the challenges of reproducing vertical transmission in sows

Ten pregnant sows were experimentally inoculated per os with T. gondii in order to investigate vertical and galactogenic transmission of the parasite and the evolution and maturation of the specific IgG humoral response in the sows and piglets. Five seronegative sows received 10⁴T. gondii (CZ isolate clone H3) sporulated oocysts during late-pregnancy (Exp. 1), three sows received 10⁴ oocysts during mid-pregnancy (Exp. 2) and three sows from Exp. 1 (and two seronegative sows) were re-inoculated with 10⁵ oocysts during a further pregnancy (late-pregnancy) (Exp. 3). Besides, six 4.5 week-old piglets inoculated per os with 5×10³ oocysts were also included in the serological investigations. All animals seroconverted (PrioCHECK Toxoplasma Ab porcine ELISA, Prionics, Switzerland) by 2-3 weeks post inoculation (wpi) and remained seropositive for at least 38 weeks or until euthanasia. Four chronically infected sows from Exp. 1 and 2 were serologically monitored during a further pregnancy and no reactivation, but a decrease of the antibody levels was observed at farrowing (Exp. 4). In all experiments, the specific IgG-avidity was initially low, increased during the course of infection and after re-inoculations. An avidity index (AI) ≥40% could be used to rule out recent infections (<8 weeks) in most (15 of 16) animals. In some piglets (18.6% of 70) delivered by inoculated sows (Exp. 1 and 2), maternal antibodies were still detectable at 2 months (but not by 3 months) of age, with constant high avidity values, comparable to those of the dams at farrowing. In all experiments, the sows remained asymptomatic and delivered non-infected offspring at term. A total of 208 normal and 5 stillborn piglets delivered by the inoculated sows (Exp. 1-4) tested serologically negative before colostrum uptake. Placentas (n=88) from all sows and tissues (brain, liver, lung, heart, and masseter muscle) from 56 delivered piglets were analysed histopathologically and by real-time PCR for T. gondii with negative results. Colostrum and milk samples from all sows were negative by real-time PCR for T. gondii DNA. In addition, no seroconversion was observed in 16 piglets from seronegative dams that were transferred to infected dams one day after birth to detect a possible infection through colostrum or milk during the suckling period. Although vertical transmission of T. gondii was demonstrated in naturally infected pigs, many factors involved in the outcome of vertical transmission and congenital toxoplasmosis in pigs are still unknown.

Occurrence, clinical involvement and zoonotic potential of endoparasites infecting Swiss pigs

In order to estimate the diversity, clinical involvement and zoonotic potential of parasites in pigs submitted for diagnosis to the PathoPig project of the Swiss Federal Food Safety and Veterinary Office, faeces (n=125) from suckling piglets (n=39), weaners (n=60) and piglets beginning fattening (n=26) from 74 Swiss farms were examined by 3 coproscopical methods (i.e. sedimentation/zinc chloride-flotation; SAFC and Ziehl-Neelsen staining). Samples microscopically positive for Cryptosporidium were further tested by PCR/sequencing for species assessment. The most frequently detected parasite was Balantidium coli, a facultative pathogenic ciliate with zoonotic potential, in 5.1, 36.7 and 50.0% of suckling, weaners and fatteners and 43.2% of farms; however, no association with disease was observed. Isospora (syn. Cystoisospora) suis infections were detected in 13.3 and 11.1% of suckling piglets with and without diarrhoea, and in 10.0 and 13.3% of weaners and fatteners with diarrhoea, respectively, and were significant associated with emaciation. Cryptosporidium infections were detected in 10.3, 15.0 and 19.2% of sucklings, weaners and fatteners, respectively, and in 18.9% of the farms. Interestingly, two age-related species were identified: C. suis in younger piglets (2 to 6weeks) and C. scrofarum in older ones (6 to 17weeks). None of the pigs infected with C. scrofarum (n=8), but 3 of 4 piglets infected with C. suis (co-infection with I. suis in 2 cases) had diarrhoea. The zoonotic species C. parvum was not detected, nevertheless, sporadic cases of human infection with the porcine-adapted species have been reported. Ascaris suum, Trichuris suis and Strongylida were rarely detected (<4%) in all age categories.

The effect of the administration of three different antimicrobial premix formulations via the liquid feeding system on the occurrence of Enterobacteriaceae resistant to tetracycline in the liquid feed for pigs

INTRODUCTION

The oral group treatment is still a common procedure in swine production. This project studied the effect of the application of 3 different formulations of antimicrobial premixes (1. chlortetracycline, 2. chlortetracycline + sulfadimidine + tylosin, 3. sulfadimidine + sulfathiazole + trimethoprim) via the liquid feeding system on the occurrence of tetracycline-resistant Enterobacteriaceae (Ent-Tetr) in the liquid feed. 156 and 112 feed samples were collected between April and December 2015 in 13 case and 14 control farms, respectively. The 27 farms were randomly selected pig fattening farms located in different parts of Switzerland. The number of feed samples that contained Ent-Tetr as well as the number of Enterobacteriaceae resistant to tetracycline per sample was significantly higher in the case group than in the control group. The use of any of the 3 antimicrobial combinations turned out to be the main risk factor for the occurrence of Ent-Tetr in the liquid feed. Our results suggest that liquid feed containing antimicrobials is a reservoir of antimicrobial resistant bacteria in swine production.

[Evaluation of risk factors for Mastitis-Metritis-Agalactia in pig farms in Switzerland]

Mastitis-Metritis-Agalactia (MMA), also known as postpartum dysgalactia syndrome (PPDS) is the most important disease complex in sows after birth. The present study compared 30 MMA problem herds (over 12% of farrowing sows affected) with 30 control farms (less than 10% of farrowing sows affected) to identify risk factors and treatment incidence. Important risk factors identified were in gilts the integration into the herd after the first farrowing, in gestating sows firm fecal consistency as well as in lactating sows soiled troughs, a low flow rate (<2 liters per minute) in drinking nipples and a high prevalence of lameness. The treatment incidence was also significantly different between the two groups. The MMA prevalence could be reduced through optimization of husbandry, feeding and management, which could essentially diminish the use of antibiotics.

[Lung and pleural lesions before and after implementation of a national eradication program against enzootic pneumonia and actinobacillosis as well as changes of slaughter carcass organs in slaughter pigs in Switzerland]

In a representative cross-sectional study during 12 months of the years 2008/2009 in four abattoirs in Switzerland, lung and pleura lesions as well as lesions of slaughter carcasses and organs of 34 706 pigs were studied for frequency and type of macroscopic lesions. Of the 24276 examined pigs, 91.2% of the lungs, 94.4% of the heart and 95.5% of the livers showed no macroscopically visible lesions. Pigs that were produced for a label program had significantly less bronchopneumonia and pneumonia residuals, pleuritis and liver lesions due to echinococcosis. Pigs supervised by the Swiss Pig Health Service (SGD), showed significantly less bronchopneumonia and pneumonia residuals, diffuse pleuritis, pleuritis/pericarditis and milkspots compared to the non-SGD supervised farms. Thanks to the national eradication program for enzootic pneumonia (EP) and actinobacillosis, the health-status of lungs has been considerably improved and the prevalence of pleurisy decreased considerably. The results of this study indicate a good herd health in Swiss pig production.

Risk factors for oral antimicrobial consumption in Swiss fattening pig farms - a case-control study

Background

Antimicrobial consumption in veterinary medicine is of great importance. Increased awareness by the public and media has led to demands for decreased use of antimicrobials in pigs. This study aimed to identify risk factors for regular oral antimicrobial consumption in Swiss fattening pig farms, and to quantify the amount of antimicrobial active substances administered orally to pigs at the farm level.

Results

A case–control study was performed on 99 fattening farms between May 2014 and January 2015. Seventy-two case farms (with oral group treatment of antimicrobials in at least 50 % of pigs) and 27 control farms (with no regular oral group treatment) were visited once during the study. Data about potential risk factors and antimicrobial consumption were collected by questionnaire. Antimicrobial consumption was recorded and treatment incidence (TI) was calculated for all farms over a one year period. Sulphonamides and tetracyclines were the antimicrobials consumed in the greatest quantity. The median TI for oral antimicrobial use in the case group was 224.7. In the control group, the median TI was 0 for oral antimicrobial use, with values ranging from 0 to 140.1. In a multivariable regression model, seven risk factors associated with regular oral antimicrobial group treatment were identified: mixing pigs from different suppliers within the same pen, absence of a work protocol that ensures treating of healthy pigs before sick pigs, distance to next pig farm < 500 metres, external analysis of production parameters, no availability of dirty visitor boots, the farmer not working on other farms, and no application of homoeopathic agents.

Conclusions

The results of this study point out the importance of increasing farmers’ awareness of good farming practices and biosecurity. Important recommendations for decreasing oral antimicrobial consumption identified by this study include avoiding mixing pigs from different suppliers in the same pen and strictly handling sick pigs after healthy ones. Improvements in these areas could enhance the overall health of pigs and thereby reduce the consumption of antimicrobials on pig farms.

Latent porcine circovirus type 2-infected domestic pigs: A potential infection model for the effective development of vaccines against latent or chronic virus induced diseases

Until recently, knowledge of the pathogenicity of Circoviridae and Anelloviridae family members was limited. Our previous discoveries provided clues toward resolving this issue based on studies of the latent nature of porcine circovirus type 2 (PCV2) genotype group members. We developed a conventional pig infection model that indicated that weaners already harbored latent PCV2 infection in the thymus, which enabled the viruses to specifically modulate the maturation of T-helper cells. This finding raised the possibility that the thymi of normal fetuses were already infected with PCV2. The present findings further substantiate our hypothesis that PCV2 masquerades as the host by infecting fetuses before they acquire immune-competence. We provide the first demonstration that all domestic pig fetuses preferentially harbor latent PCV2-infected cells in their thymi. These PCV2-infected cells are different from thymocytes and are located in the medulla of the fetal thymus. These latent PCV2-infected cells in fetuses are found at the same location and share characteristics with the infected cells observed in adolescent pigs. Moreover, fetuses also harbor these infected cells in other lymph system organs. We provide the first demonstration that the fetal thymus virus pools are minimally affected by sow vaccination, highlighting the immune-privileged character of this organ. Furthermore, we found a striking reduction in virus-infected cells in the fetal spleen and an increase in PCV2-infected cells in the fetal intestine of anti-PCV2-vaccinated mothers. These data indicate that specific immune response interactions occur between mothers and their progeny that are not dependent on the humoral immunity of the mother and cannot be attributed to the rudimentary humoral responses of the fetuses because these pig fetuses do not have any PCV2-specific antibodies. These shifts in our understanding of the PCV2-infected cell pool will lead to different avenues in the search for effective vaccination strategies against latent and chronic pathogens.

Longitudinal study on the colonisation and transmission of methicillin-resistant Staphylococcus aureus in pig farms

Knowledge about the dynamics of methicillin-resistant Staphylococcus aureus (MRSA) in pigs lacks detail at the level of individual animal. The aim of our study was therefore to determine the colonisation status of MRSA in individual pigs from birth to slaughter in order to gain a better understanding of substantial factors involved in transmission. Two farrow-to-finish and two grow-to-finish herds were included in the study. A total of 1728 nasal swabs from 390 pigs and 592 environmental wipes were collected at 11 different time points. Intermittent colonisation throughout the entire production cycle was conspicuous in the tracking of MRSA in individual pigs. Almost all pigs from a MRSA-positive herd changed MRSA status several times, which implies that pigs are transiently rather than permanently colonised. We highly recommend the definition of MRSA status at herd level rather that at the level of the individual pig when considering prevention measures against MRSA. Therefore, to avoid the further spread of MRSA in countries with moderate prevalence, such as in Switzerland, defining farms as MRSA positive or MRSA negative and allowing the trade of pigs only within herds of the same status seems feasible. This will also be important for combating the further dissemination of livestock-associated (LA)-MRSA into healthcare facilities and the community via humans who have close contact with animals.

Prevalence of Chlamydial Infections in Fattening Pigs and Their Influencing Factors

Chlamydial infections in pigs are associated with respiratory disease, diarrhea, conjunctivitis and other pathologies. The aim of this study was to define the prevalence of Chlamydiaceae in Swiss fattening pigs by applying sensitive and specific detection methods and to correlate prior antibiotic treatment and farm related factors with differences in prevalence. Conjunctival and fecal swabs were collected from 636 pigs in 29 Swiss fattening pig farms with and without antibiotic treatment, at the beginning and the end of the fattening period. The swabs were screened by real-time PCR for Chlamydiaceae. For the chlamydial detection and species-identification, a DNA-microarray analysis was performed. All farms were positive for Chlamydiaceae with 94.3 and 92.0% prevalence in fecal swabs as well as 45.9 and 32.6% in conjunctival swabs at the first and second time points, respectively. Antibiotic treatment could not clear the infection on herd level. Potential contact with wild boars was a significant risk factor, while hygiene criteria did not influence chlamydial prevalence. A correlation of chlamydial positivity to diarrhea, but not to conjunctivitis was evident. Chlamydia suis was the predominant species. Mixed infections with C. suis and C. pecorum were common, with a substantial increase in C. pecorum positivity at the end of the fattening period, and this finding was associated with ruminant contact. C. abortus was detected in one conjunctival swab. In this study, C. suis inhabited the intestinal tract of nearly all examined pigs, implying a long-term infection. C. pecorum was also common and might be transmitted to pigs by ruminants.