Specific Pathogen-free Herds Research Articles

Comparative Efficacy of Chimeric Porcine Circovirus (PCV) Vaccines against Experimental Heterologous PCV2d Challenges

The objective of this study was to evaluate the efficacy of two multivalent commercial porcine circovirus (PCV) vaccines against heterologous PCV2d challenges. A total of 24 crossbred male pigs aged 26 days selected from a specific pathogen-free herd were randomly divided into four groups (six pigs per group) and assigned as follows: negative control (unvaccinated/sham-challenge), vaccinated with chimeric PCV1-2a vaccine (PCV1-2a/PCV2d-challenge), vaccinated with chimeric PCV1-2a-2b vaccine (PCV1-2a-2b/PCV2d-challenge) and positive control (unvaccinated/PCV2d-challenge). At 21 days after vaccination, the pigs were intranasally and intramuscularly inoculated with either sham or field isolates of PCV2d (PCV2d/149/TH/2020). After being challenged, blood samples were obtained weekly and analyzed for levels of PCV2d viremia, neutralizing antibodies, and IgG against PCV2. At 30 days post-challenge (DPC), the pigs were euthanized and then subjected to pathological evaluations and molecular analysis. The results indicated that pigs in the PCV1-2a-2b/PCV2d-challenge and the PCV1-2a/PCV2d-challenge groups possessed significantly greater levels of PCV2d-neutralizing antibody titer when compared with the positive control group. Moreover, pigs in the PCV1-2a-2b/PCV2d-challenge group exhibited a lower degree of severity in terms of gross lesion scores and lower levels of PCV2 viremia when compared with the positive control group. This study demonstrated that vaccinating pigs with either the PCV1-2a or PCV1-2a-2b chimeric vaccines elicits a potent immune response against PCV2d infection and reduces viremia after PCV2d inoculation in pigs.

Effects of feeding naturally contaminated deoxynivalenol diets to sows during late gestation and lactation in a high-yield specific pathogen-free herd

BackgroundThe most prevalent Fusarium mycotoxin in grains is deoxynivalenol (DON). Contamination of swine feed with DON can result in reduced consumption and poor growth performance. Gestating and lactating sows need sufficient feed intake for fetus development during late gestation and milk production and body maintenance during lactation. Therefore, there is considerable concern in modern piglet production about the effects of DON contamination in sow feed. Most previous studies in sows have been done under experimental conditions, with DON levels ≥2.8 mg/kg feed. The aim of the current field trial was to investigate the effects of feeding grains that are naturally contaminated with more realistic levels of DON on sows during late gestation and lactation.MethodsIn a commercial, high-yield specific pathogen-free piglet production unit, 45 Norwegian Landrace × Yorkshire sows were fed three diets from 93 ± 1 days of gestation until weaning of the piglets, and average daily feed intake (ADFI), body weight (BW), production and reproduction performance, as well as sow blood parameters were recorded. Diets were made from naturally contaminated oats, with three concentration levels: 1) control (DON < 0.2 mg/kg), 2) DON level 1 (1.4 mg DON/kg), and 3) DON level 2 (1.7 mg DON/kg).ResultsSows that were fed DON level 1 and 2 diets showed a 4–10% reduction in feed consumption during lactation, compared with sows in the control group. However, the DON-contaminated diets did not significantly affect sow BW or backfat thickness. Similarly, there were neither effects on production or reproduction performance, nor on blood parameters in the sows. The effects on skin temperature were variable.ConclusionNaturally contaminated diets with realistic, moderately increased DON levels, fed during late gestation and lactation in a modern high-yield piglet production farm, had limited effects on sow health and production.

Porcine circovirus type 2 associated reproductive failure in a specific pathogen free (SPF) piglet producing herd in Norway: a case report

BackgroundSince 1999, scientists have published evidence of transplacental infection by porcine circovirus type 2 (PCV2) and reproductive failure in pigs. Affected herds have frequently been start-up herds, either naïve or with a high proportion of PCV2 susceptible gilts. Here, delayed farrowing in non-vaccinated gilts was observed in a commercial specific pathogen free (SPF) herd. Mummified fetuses and stillborn piglets recovered from these gilts were PCV2 positive.Case presentationThe case herd was a self-recruiting, piglet producing unit of 240 sows. After detecting livestock associated methicillin resistant Staphylococcus aureus (LA-MRSA, CC398), stamping out was imposed by the authorities. An SPF herd was re-established and all dams were vaccinated against PCV2 until the farmer decided to exclude this vaccine. The first non-vaccinated batch consisted of 76% gilts. Here, one gilt showed signs of impending farrowing. This gilt was slaughtered three to four weeks after the expected farrowing date without having expelled any uterine contents. In the subsequent batch consisting of 79% gilts, three gilts showed similar clinical signs. Delayed farrowing was observed in two of these gilts and the uterine contents from the third gilt were recovered at the abattoir. Mummified fetuses and stillborn piglets were recovered from all three gilts. High levels of PCV2 DNA (>107 viral genomic copies/ 500 ng tissue) were found in myocardial samples by real-time PCR analysis. One myocardial sample submitted for immunohistochemical (IHC) analysis showed moderate amounts of PCV2 antigen. In the subsequent batch consisting of 77% gilts, several weak-born piglets were seen across different litters.ConclusionsThis case report describes an apparent link between in utero PCV2 infection, pre partum nest-building behaviour, mammary development and delayed farrowing. To date, no reports have described imminent signs of farrowing and delayed farrowing as clinical signs in conjunction with transplacental PCV2 infection in Norway. Reinitiation of PCV2 vaccination was strongly advised in this herd due to recent depopulation and repopulation and the high proportion of gilts. Vaccination was effective because no further cases have occurred since.

Antimicrobial usage in 60 Swedish farrow-to-finish pig herds

The aim of this study was to quantify antimicrobial consumption in Swedish farrow-to-finish pig herds. Sixty herds with 100 sows or more producing more than 500 fatteners per year participated in a study where data on antimicrobial consumption over a period of one year were collected. Data on antimicrobial use were collected by substance, administration route and per age category. Antimicrobial use was measured as defined daily doses and expressed as treatment incidence (TI) per 1000 pig-days at risk. The TIs for growing pigs varied between herds, from 1.6 to 116.0 with a median of 14.3. The highest TI was recorded for suckling piglets with a median of 54.7 (range; 1.6–367.9), while the median TIs for weaners, fatteners and adults were 6.2, 2.8 and 8.4, respectively (range; 0.0–260.5; 0.0–64.9; 0.0–45.0, respectively). The within herd TIs for the different age categories were not correlated. Individual treatment, mainly consisting of injectables, was the most common form of application except for weaners for which a majority (54.8%) of the treatments were group treatments. Benzylpenicillin was the most commonly applied substance except for weaners for which oral formulations of tylosin were most common. For fatteners, group treatments constituted 8.4% of the total TI. Group treatments with oral colistin were applied to suckling piglets in five herds. Group treatments were not applied to adult pigs. The TI for weaners was significantly lower for specific pathogen-free herds. The results show that the overall antimicrobial use in Swedish farrow-to-finish pig herds varied to a great extent, and the between-herd variation indicates that there is room for improvement of pig health. Targeting suckling piglets may be most beneficial, but further studies are required to identify specific focus areas which may reduce the need for antimicrobials in this particular age group.

Specific pathogen-free pig herds also free from Campylobacter?

As Specific Pathogen-Free (SPF) pig herds are designed and managed to prevent specific pig diseases, it might be feasible to expand the list of micro-organisms also including zoonotic pathogens such as Campylobacter coli as this agent has its origin in pigs. In a previous survey, 15 of 16 of SPF herds were found free from human pathogenic Yersinia enterocolitica. Accordingly, three nucleus and seven multiplying herds were surveyed for Campylobacter to investigate whether the Norwegian SPF pig pyramid also might be free from this agent. In conclusion, the intervention of Campylobacter at the herd level might be possible as four of 10 SPF herds tested negative in two sets of samples from both autumn 2008 and summer/early autumn 2010. The four negative herds were all located in remote areas several kilometres away from conventional pig farming while the positive SPF farms were all situated in neighbourhoods with conventional pig production. It seems more difficult to control Campylobacter than some specific animal disease agents and another significant zoonotic agent, Y. enterocolitica, in pig herds.

Isolation, characterization and microincapsulation of neonatal porcine Sertoli cells obtained from a specific pathogen free (SPF) herd

Porcine Sertoli cells (pSC) have been successfully employed as cell therapy in pre-clinical studies of several immune-based and chronic degenerative diseases. In order to prevent any transmission of infectious adventitious agents to the cells graft recipients, we have set up, according to our previously described method (Luca et al., 2007) pSC monolayers obtained from specific pathogen free (SPF) certified neonatal pigs, born in the unique SPF colony in Italy. pSC were assessed and characterized as far as viability, by ethidium bromide and fluorescein diacetate (EB/FD), Mullerian inhibiting substance (AMH), and insulin-like 3 (INSL3), alpha-smooth muscle actin (ASMI) both by immunofluorescence (IF) and cytofluorimetric analysis (CA) were concerned. pSC were encapsulated in alginate microcapsules (MCpSC), with MCp- SC functional competence and biocompatibility being determined both in vitro, by AMH, inhibin B, TGF-beta, IGF-I secretion and in vivo in experimental animal models, respectively. Results demonstrated the high purity of our pSC monolayers (95% of AMH+cells), with negligible contamination by Leydig (2%) and peritubular cells (3%). Microencapsulation did not alter pSC viability and even after 4 months postimplantation, all the retrieved microcapsules retained morphology and function. In conclusion, we have uniquely obtained, from a SPF herd, highly purified, viable and functional pSC that might poten-tially apply to humans.

Prevalence of clinical signs of disease in Danish finisher pigs

Between December 1999 and February 2001, two visits, eight weeks apart, were made to 90 herds of Danish finisher pigs. The prevalence of clinical signs was recorded by three veterinary...

Pig Herds Free from Human PathogenicYersinia enterocolitica1

Pork products are a substantial source of human yersiniosis, a foodborne disease caused by Yersinia enterocolitica. Thus, the ability to eliminate this agent from pig herds would be an important step in producing human pathogen-free pork. Pig herds free from Y. enterocolitica O:3/biovar 4 have been established and maintained. According to serologic and cultural testing results, 15 of 16 specific pathogen-free herds were free from Y. enterocolitica O:3/biovar 4; this closed breeding pyramid has remained free from this organism since 1996. Pig herds free from human pathogenic Y. enterocolitica suggest that human pathogen-free herds could be attained to provide pork free from zoonotic agents.

The pig‐to‐primate immune response: relevance for xenotransplantation

The allotransplantation of some solid organs can be associated with a graft-vs.-host (GVH) response from the activity of donor B or T cells. We have investigated whether there is a risk of a GVH response following pig-to-primate organ xenotransplantation. The responses of 16 pigs (six farm-housed wild-type and five wild-type housed under high herd health conditions [all designated WT], and 5 alpha1,3-galactosyltransferase gene-knockout [GT-KO] housed under high herd health conditions) to human (n = 6) and baboon (n = 6) peripheral blood mononuclear cells (PBMC) were determined. Assays included flow cytometry, complement-dependent cytotoxicity, and mixed lymphocyte reaction. Anti-primate cytotoxic IgM antibodies were detected in the sera of all pigs, but anti-primate IgG antibodies were minimal. All pigs demonstrated a cellular proliferative response to primate PBMC that was equivalent to, or greater than, the allo response. The strength of the pig-to-primate GVH responses was proportional to the health status of the pigs, those from a high health status herd, particularly from a specific pathogen-free herd maintained under clean husbandry conditions, where colonization of the gastrointestinal tract may be reduced, having lower responses. After pig organ transplantation in a primate, if the organ is from an early-weaned, early-segregated GT-KO pig, the strength of a GVH response is likely to be relatively weak. Although not investigated here, any GVH response is likely to be suppressed by the immunosuppressive therapy administered to the recipient to suppress the anti-donor immune response.

Infectious and rearing-system related risk factors for chronic pleuritis in slaughter pigs

Chronic pleuritis (CP) in Danish pigs for slaughter is by far the most frequent finding at the routine post-mortem meat inspection. An initial investigation published in 1990 demonstrated infectious and management-related risk factors. Serological testing for additional infectious agents, as well as the need to consider the effect of disease clustering at the herd level, required a re-analysis of the data. Our re-analysis used a representative sample of 4800 pigs originating from 623 Danish herds. Each pig was examined for the presence of CP and progressive atrophic rhinitis (PAR). The gender of the pig, the weight of the carcass, and the herd of origin were also recorded. Individual blood samples were examined for seropositivity for Actinobacillus pleuropneumoniae (AP) serotypes 2, 6, 7, 12, Haemophilus parasuis, Mycoplasma hyopneumoniae (MYC) and swine influenza (SI). Herd-level information retrieved through a questionnaire included health status, production type, herd size (i.e. pigs per year) and vaccination procedures. Associations between CP and infectious, individual and herd-related factors were investigated by logistic regression with random effects. Among pigs from herds with conventional health status, seropositivity for AP serotypes 2 and 6, and MYC had odds ratios (ORs) of CP of 9.0, 1.6 and 1.8, respectively. Neither seropositivity for AP serotype 7 nor SI were associated with CP by themselves, but interacted: OR of CP of 5.3 (1.8) when present at the same time among pigs exhibiting (not exhibiting) PAR. An association of PAR with CP was found, and PAR interacted with AP serotype 7: OR=10.0 (4.3) when both factors were present among pigs exposed (non-exposed) to SI. The OR (0.97) for an increase of carcass weight by 1 kg was negligible. In pigs from specific pathogen-free (SPF) herds, seropositivity for MYC and herd size were associated with CP. Moreover, for a herd size of 1000 pigs, CP was associated with exposure to MYC by an OR of 3.3 (decreasing to 1.9 when the herd size was increased by 1000). Farrow-to-finish as opposed to finishing herd had an OR of CP of 3.2. In conventional herds, seropositivity for AP serotype 2 and MYC were associated with 51% and 29% of the occurrence of CP. In SPF herds, farrow-to-finish as opposed to finishing herds was associated with 47% of the occurrence of CP. Seropositivity for MYC was associated with 33% (39%) of the occurrence of CP in herds with a size > (≤) 1500 pigs.

Detectability and prevalence of Brachyspira species in herds rearing health class feeder pigs in Finland

Faeces samples were taken three times at two-week intervals, from the farrowing units of four herds of known Brachyspira (formerly Serpulina) status and one of unknown Brachyspira status. Brachyspira hyodysenteriae,...

Evaluation of Mycoplasma hyopneumoniae inactivated vaccine in pigs under field conditions.

An inactivated vaccine prepared from broth culture supernatant of Mycoplasma hyopneumoniae with an aluminum adjuvant was evaluated in three herds (herd A: specific pathogen-free herd, herd B: high health status herd with no clinical signs of respiratory infection, herd C: low health status herd with serious epidemiological and economical problems). A total of 212 pigs from the three herds were divided into two groups. One group was injected twice with the vaccine at 4-week intervals and the other was a control group. No adverse reactions were noted following the vaccinations either systematically or locally in any of the vaccinated pigs from any of the herds. In herd A, the vaccination provided antibody response within 4 weeks after the second vaccination and antibody responses continued for more than 12 weeks. In herds B and C, the number of pigs with lung lesions, mean percentage of lung lesions, and the numbers of M. hyopneumoniae recovered from pigs at slaughter in the vaccinated group were significantly (P < 0.05) reduced compared to the control group. Furthermore, vaccination resulted in improved average daily weight gain (ADG), improved feed conversion ratio (FCR), and improved days to market weight in herd C, whereas no difference in growth performance was shown in herd B. It is suggested that the inactivated vaccine prepared from broth culture supernatant of M. hyopneumoniae is effective in reducing clinical signs and lung lesions. Also, vaccination resulted in improved growth performance in herds where clinical signs and economic losses were significant.

Evaluation and application of ribotyping for epidemiological studies of Actinobacillus pleuropneumoniae in Denmark

The aim of the present study was to evaluate ribotyping as an epidemiological tool for Actinobacillus pleuropneumoniae and apply the method in studies of A. pleuropneumoniae infections in Danish pig herds. The evaluation of ribotyping was based on the 13 international reference strains and 106 epidemiologically unrelated Danish field strains representing the nine serotypes of biotype 1 (1, 2, 5A/B, 6, 7, 8, 10, 12, and K2:O7) and one serotype 14 of biotype 2. Enzymes CfoI and HindIII were chosen for generation of ribotype patterns. Ribotyping of the reference strains resulted in 10 CfoI types and 11 HindIII types. Ribotyping of the Danish strains resulted in 17 different CfoI ribotypes and 24 different HindIII ribotypes. Combining HindIII- and CfoI-ribotyping divided the Danish strains into 26 different types. The stability, reproducibility and typability of ribotype patterns were good, and the discriminatory power was between 0.85–0.89. The relatively low discriminatory power was caused by four predominant types, containing 61% of the isolates. The typing system was applied in studies of routes of infection of specific pathogen-free (SPF) pig herds and included 112 strains of A. pleuropneumoniae. Airborne transmission from neighboring conventional pig farms was investigated in 12 cases of infected SPF herds. Transmission via vehicles transporting pigs between SPF herds was investigated in nine cases while transmission by trading of pigs between SPF herds was investigated in two cases. Serotype 2 was isolated from all SPF herds included in this study, except one, emphasizing the high prevalence of this serotype in Denmark. By ribotyping, airborne transmission was indicated in five of 12 cases, transmission via pig transporting vehicle was indicated in six of nine cases, and transmission via trading was indicated in one of two cases. In many cases findings of predominant ribotypes made interpretations of suspected routes of transmission difficult. The relationship of strains based on ribotypes was calculated using Dices coefficient and clustered by UPGMA. HindIII ribotypes of serotype 2 strains were closely related, though only showing 43% similarity to HindIII ribotypes of remaining serotypes.

Detection of Lawsonia intracellularis, Serpulina hyodysenteriae, weakly beta-haemolytic intestinal spirochaetes, Salmonella enterica, and haemolytic Escherichia coli from swine herds with and without diarrhoea among growing pigs

A polymerase chain reaction (PCR) was optimized to detect Lawsonia intracellularis in faeces from naturally infected pigs. By combining a boiling procedure to extract DNA and a nested PCR procedure, a detection limit at 2×10 2 bacterial cells per gram of faeces was achieved. The optimized PCR was used together with conventional culture techniques to detect Serpulina hyodysenteriae, weakly beta-haemolytic intestinal spirochaetes (WBHIS), Salmonella enterica, and haemolytic Escherichia coli, in a case control study to examine selected risk factors for the development of diarrhoea in growing pigs. Herds with diarrhoea were selected as cases and randomly chosen herds without diarrhoea were chosen as controls. Infection with L. intracellularis significantly enhanced the chance of diarrhoea. S. hyodysenteriae, WBHIS group IV ( Serpulina pilosicoli), and S. enterica were isolated only from case herds which indicate that these species may influence the development of diarrhoea. In addition, herd-type had a significant impact, that is specific pathogen-free herds showed an odds ratio at 0.2 relative to conventional herds for the development of diarrhoea.

Villus height and crypt depth in weaned and unweaned pigs, reared under various circumstances in the Netherlands

The height of the villi and depth of the crypts in the small intestine were studied after weaning in pigs reared under various circumstances in the Netherlands. Pigs taken from herds with a long history of postweaning diarrhoea had in general significantly shorter villi and deeper crypts than their counterparts from a specific pathogen-free herd. Weaning was associated with villus shortening, crypt deepening and subsequent villus lengthening in pigs from the specific pathogen-free herd. Giving supplementary feed during the sucking period was beneficial in preventing shortening of the villi and this villus shortening was less severe when the crypts were deep at weaning, a condition that perhaps lessens the severity of postweaning diarrhoea.

Further evidence of long distance airborne transmission of Aujeszky's disease (pseudorabies) virus

In spite of the eradication of Aujeszky's disease in Denmark a single outbreak was recorded in December 1988 and another severe epizootic took place during the winter and spring of 1989/90. The epizootic occurred in nearly the same areas as the preceding epizootic during the winter of 1987/88. Identification of the strains of virus involved eliminated the possibility that the latest epizootic was due to the persistence of virus in the pig population. Furthermore, as during the preceding epizootic, initial recordings of the new strains were found to coincide with periods with southerly winds. It was concluded from circumstantial evidence that the concurrent introductions of virus to several farms played a major role during the epizootic.

A longitudinal study of rotavirus antibody titers in swine in a closed specific pathogen-free herd

In a newly established closed specific pathogen-free (SPF) swine herd, gilt/sow suckling and weaned pig rotavirus specific antibody titers were followed for three lactations by enzyme-linked immunosorbent assay (ELISA) to gain insight into the dynamics of herd titers to group A rotavirus. Among gilts/sows, serum antirotavirus IgG titers increased during each lactation with a subsequent drop in titer between farrowings. Serum antirotavirus IgM titers declined during each lactation and with subsequently parity. Serum antirotavirus IgA titers remained constant during lactations and among parities. In colostrum and milk, antirotavirus IgA antibody was abundant. Differences in titer were not noticed between gilts and second litter sows had significantly higher titers than the first two groups. Antirotavirus IgG was high in colostrum but nearly nonexistent in milk. This titer did not vary significantly within or among parities. There was a linear regression in the titers of baby pig serum antirotavirus IgG from the post colostral sample through to seven weeks old, after which titer began to increase. No difference in baby pig serum antirotavirus IgG was noted among the three litters. Serum antirotavirus IgA and IgM were undetectable in baby pig sera after 2–3 weeks of age. Coproantibody to rotavirus was sporadically present in pig feces for 2–3 weeks after birth with highest titers in the IgA fraction. We conclude that although it is probable that age resistance of pigs to rotavirus diarrhea occurs, humoral immunity as measured by ELISA rotavirus antibody titers may not be intimately involved in virus clearance since in our studies baby pigs passively received large amounts of antibody but still excreted pathogenic virus. The finding of increasing levels of serum antirotavirus IgG in gilt/sow serum suggests that exposure to antigen of dams occurs without significant increases in antirotavirus IgG titers in either colostrum, milk, or baby pig serum.

Prevalence of Streptococcus suis types 1 and 2 in domestic pigs in Australia and New Zealand.

Using an indirect fluorescent antibody test, 54 per cent of 734 palatine tonsils of conventional pigs slaughtered in Australia and New Zealand were found to be infected with Streptococcus suis type 1 and 73 per cent of 959 were infected with S suis type 2. Variations in the prevalence of infection in pigs from different herds were thought to be due to differences in the sample sizes rather than to real differences in the prevalence between herds. The prevalence of infection with S suis was similar in pigs of either sex and in different age groups. Streptococcus suis type 2 was detected in the blood of 3 per cent of apparently normal pigs slaughtered at a meat processing plant. The presence of this organism in edible tissue may pose a health risk to consumers and meat-workers. Both S suis types 1 and 2 were detected in the vaginas and uteri of slaughtered pigs and the female reproductive tract could be another site for the carriage of infection. Piglets from sows with vaginas infected with S suis type 2 became infected earlier than piglets from sows with uninfected vaginas. No infected male reproductive tracts were detected and venereal transmission of S suis therefore appears unlikely. Three specific pathogen free herds were found to be free from infection with both S suis types 1 and 2. It is concluded that hysterectomy derived piglets are delivered free from infection, whereas some piglets born to sows with uterine and vaginal infections are either born infected or become infected at, or soon after, birth.

A comparative study of the complement fixation test for mycoplasma hyopneumoniae in SPF and non-SPF herds of swine in Illinois

Serum samples from 458 swine from eight specific pathogen-free (SPF) herds swine were compared to samples from 178 swine from eight non-SPF herds in Illinois using the complement fixation (CF) test for Mycoplasma hyopneumoniae antibodies. In SPF herds, 9.4% of the samples gave positive test results, compared to 51.7% of the samples from non-SPF herds. The range of reactor rates in SPF herds was 0–26.9% and in non-SPF herds 3.4–100%. Used on herd basis with some modification, the CF test should be useful in monitoring state and nationally accredited SPF swine herds.