Review: Livestock disease resilience: from individual to herd level.

Infectious diseases are a major threat to the sustainable production of high-producing animals. Control efforts, such as vaccination or breeding approaches often target improvements to individual resilience to infections, i.e., they strengthen an animal's ability to cope with infection, rather than preventing infection per se. There is increasing evidence for the contribution of non-clinical carriers (animals that become infected and are infectious but do not develop clinical signs) to the overall health and production of livestock populations for a wide range of infectious diseases. Therefore, we strongly advocate a shift of focus from increasing the disease resilience of individual animals to herd disease resilience as the appropriate target for sustainable disease control in livestock. Herd disease resilience not only captures the direct effects of vaccination or host genetics on the health and production performance of individuals but also the indirect effects on the environmental pathogen load that herd members are exposed to. For diseases primarily caused by infectious pathogens shed by herd members, these indirect effects on herd resilience are mediated both by individual susceptibility to infection and by characteristics (magnitude of infectiousness, duration of infectious period) that influence pathogen shedding from infected individuals. We review what is currently known about how vaccination and selective breeding affect herd disease resilience and its underlying components, and outline the changes required for improvement. To this purpose, we also seek to clarify and harmonise the terminology used in the different animal science disciplines to facilitate future collaborative approaches to infectious disease control in livestock.

Circulation of Porcine Parvovirus Types 1 through 6 in Serum Samples Obtained from Six Commercial Polish Pig Farms.

Porcine parvoviruses are small non-enveloped DNA viruses, very resistant to inactivation, and ubiquitous in the global pig population. Porcine parvovirus type 1 (PPV1) has been known since the 1960s and is a major causative agent of reproductive failure in breeding herds. During the last decade, several new parvoviruses have been identified in pigs by molecular methods and have been consecutively designated as PPV2 through PPV6. Epidemiology data for these viruses are limited, and the impact of these newly recognized parvoviruses on pigs is largely unknown. To further generate knowledge on the distribution of PPVs in pigs, a total of 247 serum samples were collected from six commercial Polish pig farms during 2013-2015 and tested by PCR assays and ELISAs. The pigs ranged from two to 18 weeks of age at sample collection. Breeding herds supplying the investigated farms were routinely vaccinated against PPV1. While all growing pig samples were negative for PPV1 DNA, young pigs were frequently negative for PPV1 antibodies and seroconversion to PPV1 was commonly seen at 9-10 weeks of age. The PPV2 antibody detection was highest in young pigs (2-6-week-old) and decreased in older pigs indicating passively acquired antibodies. The DNA prevalence rates in the serum samples analysed were 19% for PPV2, 7.7% for PPV3, 2.4% for PPV4, 4.0% for PPV5 and 6.1% for PPV6. Most PPV DNA-positive samples were identified in 9- to 18-week-old pigs with no obvious association with disease on the farm. All recently emerging PPV genotypes were detected in Polish farms. Similar to previous reports in other pig populations, PPV2 was the most frequent PPV genotype circulating in Poland.

Prevalence of the Novel Torque Teno Sus Virus Species k2b from Pigs in the United States and Lack of Association with Post-Weaning Multisystemic Wasting Syndrome or Mulberry Heart Disease.

The family Anelloviridae includes a number of viruses infecting humans (Torque teno viruses, TTV) and other animals including swine (Torque teno sus viruses, TTSuV). Two genetically distinct TTSuV species have been identified from swine thus far (TTSuV1 and TTSuVk2), although their definitive association with disease remains debatable. In 2012, a novel TTSuV species was identified from commercial swine serum and classified in the genus Kappatorquevirus as TTSuVk2b. The other Kappatorquevirus species, TTSuVk2a, has been associated with post-weaning multisystemic wasting syndrome (PMWS) when coinfected with porcine circovirus type 2 (PCV2). Therefore, in this study, we initially amplified a portion of TTSuVk2b ORF1 and, subsequently, assessed the molecular prevalence of the virus in pigs in the United States. A total of 127 serum and 115 tissue samples were obtained from pigs with PMWS or mulberry heart disease (MHD) in six states and tested by PCR for the presence of TTSuVk2b DNA. Approximately 27.6% of the serum and 21.7% of tissue samples tested positive for TTSuVk2b DNA, and the positive products were confirmed by sequencing. However, we did not detect a correlation between TTSuVk2b infection and PMWS or MHD. The near full-length genomic sequence of US TTSuVk2b was determined, and sequence analysis revealed that the US TTSuVk2b isolates were 95% identical to the TTSuVk2b isolate from Spain, with most of the variations clustering in ORF1. We conclude that the novel TTSuVk2b species is present in pigs in the United States and its potential association with a disease warrants further investigation.

A porcine reproductive and respiratory syndrome virus candidate vaccine based on the synthetic attenuated virus engineering approach is attenuated and effective in protecting against homologous virus challenge.

Current porcine reproductive and respiratory syndrome virus (PRRSV) vaccines sometimes fail to provide adequate immunity to protect pigs from PRRSV-induced disease. This may be due to antigenic differences among PRRSV strains. Rapid production of attenuated farm-specific homologous vaccines is a feasible alternative to commercial vaccines. In this study, attenuation and efficacy of a codon-pair de-optimized candidate vaccine generated by synthetic attenuated virus engineering approach (SAVE5) were tested in a conventional growing pig model. Forty pigs were vaccinated intranasally or intramuscularly with SAVE5 at day 0 (D0). The remaining 28 pigs were sham-vaccinated with saline. At D42, 30 vaccinated and 19 sham-vaccinated pigs were challenged with the homologous PRRSV strain VR2385. The experiment was terminated at D54. The SAVE5 virus was effectively attenuated as evidenced by a low magnitude of SAVE5 viremia for 1-5 consecutive weeks in 35.9% (14/39) of the vaccinated pigs, lack of detectable nasal SAVE5 shedding and failure to transmit the vaccine virus from pig to pig. By D42, all vaccinated pigs with detectable SAVE5 viremia also had detectable anti-PRRSV IgG. Anti-IgG positive vaccinated pigs were protected from subsequent VR2385 challenge as evidenced by lack of VR2385 viremia and nasal shedding, significantly reduced macroscopic and microscopic lung lesions and significantly reduced amount of PRRSV antigen in lungs compared to the non-vaccinated VR2385-challenged positive control pigs. The nasal vaccination route appeared to be more effective in inducing protective immunity in a larger number of pigs compared to the intramuscular route. Vaccinated pigs without detectable SAVE5 viremia did not seroconvert and were fully susceptible to VR2385 challenge. Under the study conditions, the SAVE approach was successful in attenuating PRRSV strain VR2385 and protected against homologous virus challenge. Virus dosage likely needs to be adjusted to induce replication and protection in a higher percentage of vaccinated pigs.

Mixed treatment comparison meta-analysis of porcine circovirus type 2 (PCV2) vaccines used in piglets.

Porcine circovirus type 2 (PCV2) vaccination is globally one of the most commonly used intervention strategies in growing pigs since several products became commercially available in 2006. While multiple trials have described the efficacy of individual PCV2 vaccines relative to non-vaccination, few studies provide product-to-product comparisons of efficacy. Given the well-documented efficacy of PCV2 vaccines, information about the comparative efficacy of available vaccines is more relevant to producers and veterinarians than comparison to non-vaccination. The objective of this study was to provide comparative estimates of changes in average daily gain effect associated with the use of the commercially available PCV2 vaccines. PubMed, CAB Abstracts, AGRICOLA, the USA Department of Agriculture Center for Veterinary Biologics database of licenses and provisions, and the proceedings of the Annual Meeting of the American Association of Swine Veterinarians, the Allen D. Leman Swine Conference, the Iowa State University Swine Disease Conference for Swine Practitioners, and the International Pig Veterinary Society Congress were used as the sources of information. Trials of licensed PCV2 vaccines administered according to manufacturers' specifications to intensively raised piglets with a known herd porcine reproductive and respiratory syndrome virus (PRRSV) status were considered relevant to the meta-analysis. Relevant studies had to report average daily gain (ADG) from weaning to finish and PCV2 infection had to be naturally occurring.

Neutralizing antibodies against porcine circovirus type 2 in liquid pooled plasma contribute to the biosafety of commercially manufactured spray-dried porcine plasma.

Neutralizing antibodies (NA) inherently present in pooled plasma collected at commercial abattoirs may provide some protection against potential porcine circovirus type 2 (PCV2) infectivity of plasma. Moreover, these NA may also contribute to the biosafety of spray-dried porcine plasma (SDPP). The objective of the study was to characterize and quantify the PCV2 antibody neutralizing capacity in pooled liquid porcine plasma and SDPP samples collected from industrial spray-drying facilities located in the Southeast and Midwest regions of the United States and the Northeast region of Spain. In the United States, PCV2 NA was determined in 1 sample of pooled liquid plasma from commercial spray-drying plants in the Southeast and 1 from the Midwest region. Obtained results were compared with those of a plasma sample from a PCV2 vaccinated sow and 1 from a PCV2 antibody negative sow. In Spain, 15 pooled liquid porcine plasma samples and 10 SDPP samples were collected at a commercial spray-drying plant total and NA against PCV2 were determined. Results with pooled liquid porcine plasma from commercial spray-drying facilities in the United States indicated that NA titers against PCV2 in these samples (log2 8.33 ± 0.41 and 9.0 ± 0.0) were similar or greater than the plasma from the PCV2-vaccinated sow (log2 6.33 ± 0.41). The analysis of U.S. samples indicated that liquid plasma diluted to 1:256 (10(-2.41)) was able to neutralize between 100 to 200 PCV2 virus particles or about 4 logs10 median tissue culture infective dose (TCID50) per milliliter. Similarly, samples from the Spanish pooled liquid plasma and the SDPP samples indicated an increased amount of NA activity against PCV2. Specifically, a dilution of 10(-2.47 ± 0.33) of plasma was able to inactivate 100 PCV2 virus particles; therefore, the inactivation capacity of commercial liquid plasma was greater than 10(4) TCID50/mL. The calculated 90% reduction in infected cells because of NA in pooled plasma samples (log2 8.2 ± 0.38) was less (P < 0.05) than in its concentrate form of SDPP (mean, log2 10.2 ± 0.85). In conclusion, PCV2 NA contained in liquid pooled plasma from market pigs was detected at greater concentrations than that from a vaccinated sow and that after spray-drying biological neutralizing activity was conserved, which implies that the inherent NA in liquid plasma may have an important role in the biosafety of commercially produced SDPP.

Randomized blinded challenge study to assess association between Moraxella bovoculi and Infectious Bovine Keratoconjunctivitis in dairy calves.

The objective of this study was to evaluate if Moraxella bovoculi was associated with Infectious Bovine Keratoconjunctivitis (IBK) using a corneal scarification model in calves. A 3-arm single-eye block-randomized and blinded challenge study was designed as follows: corneal scarification only, corneal scarification and inoculation with M. bovoculi (ATCC strain: BAA-1259; origin: CA) and corneal scarification and inoculation with Moraxella bovis (strain Epp63-300; origin: NADC). The study was conducted in 3 replicates of 10-12 animals housed in individual pens with no nose-to-nose contact. Calves were enrolled after an ophthalmologist confirmed the absence of corneal, conjunctival, and eyelid abnormalities. Calves were scarified and inoculated in one randomly selected eye, then observed for the primary outcome of interest (corneal ulcers) until euthanized 10 days following scarification. Research group members assessing the outcome were blind to allocation status. The study was approved by the institutional animal care and use committee. Of 36 animals purchased for the study, 5 were excluded prior to enrollment due to ophthalmic abnormalities. Of the 31 enrolled calves, 9/10 (90%) of M. bovis calves, 0/10 (0%) of M. bovoculi calves and 1/11 (9%) of control calves developed corneal ulcerations consistent with IBK in the scarified eyes. The absence of corneal ulcerations in M. bovoculi BAA-1259 inoculated calves suggests it is not a causal organism for IBK in this model and the pathogenicity of this ATCC strain has not been established. Consistent corneal ulceration development in the M. bovis inoculated group demonstrates the ability of the model to induce IBK ulcers.

Current state of knowledge on porcine circovirus type 2-associated lesions.

Porcine circovirus type 2 (PCV2), a small single-stranded DNA virus, was initially discovered in 1998 and is highly prevalent in the domestic pig population. Disease manifestations associated with PCV2 include postweaning multisystemic wasting disease (PMWS), enteric disease, respiratory disease, porcine dermatitis and nephropathy syndrome (PDNS), and reproductive failure. Although these clinical manifestations involve different organ systems, there is considerable overlap in clinical expression of disease and presence of lesions between pigs and within herds. It is now widely accepted that PCV2 can be further subdivided into different types, of which PCV2a and PCV2b are present worldwide and of greatest importance. This review will focus on PCV2-associated lesions in different organ systems.

Erysipelothrix rhusiopathiae isolates recovered from fish, a harbour seal (Phoca vitulina) and the marine environment are capable of inducing characteristic cutaneous lesions in pigs.

In order to determine the diversity and pathogenicity of Erysipelothrix spp. isolates recovered from marine fish, a harbour seal (Phoca vitulina) and the marine environment, 14 isolates were characterized by genotyping, serotyping, determination of the surface protective antigen (spa) gene type and assessment of virulence in a pig bioassay. All 14 isolates were Erysipelothrix rhusiopathiae. Isolates were determined to be of serotypes 2 (n = 3), 3 (n = 1), 4 (n = 1), 12 (n = 1), 15 (n = 1) or 21 (n = 6), and one isolate cross-reacted with serotypes 5 and 21. The spa gene analysis determined that 64.3% (n = 9) were spaA and 35.7% (n = 5) were spaB1. In pigs, 10/14 isolates induced small plaques to diamond-shaped cutaneous lesions consistent with Erysipelothrix spp. infection. The results of this study indicate that the marine E. rhusiopathiae isolates have greater genetic and antigenic diversity than pig isolates and are capable of inducing classical skin lesions in pigs.

Improving ante mortem diagnosis of Erysipelothrix rhusiopathiae infection by use of oral fluids for bacterial, nucleic acid, and antibody detection.

Swine erysipelas is an economically important disease caused by Erysipelothrix rhusiopathiae. Pen-based collection of oral fluids has recently been utilized for monitoring infection dynamics in swine operations. The diagnostic performance of bacterial isolation, real-time PCR, and antibody detection by enzyme-linked immunosorbent assay (ELISA) and fluorescent microbead-based immunoassay (FMIA) methods were evaluated on pen-based oral fluid samples from pigs experimentally infected with E. rhusiopathiae (n=112) and from negative controls (n=32). While real-time PCR was a sensitive method with an overall detection rate of 100% (7/7 pens) one day post inoculation (dpi), E. rhusiopathiae was successfully isolated in only 28.6% (2/7 pens). Anti-Erysipelothrix IgM and IgG antibodies in pen-based oral fluids were detected at 4 to 5 dpi by FMIA and at 5 and 8 dpi by ELISA. The number of infected animals per pen, and in particular the timing of antimicrobial treatment administration impacted bacterial isolation and ELISA results. In oral fluid field samples, E. rhusiopathiae DNA was found in 23.3% of the samples while anti-E. rhusiopathiae IgG and IgM antibodies were found in 59.6% and 5.5% of the samples, respectively. The results suggest that an algorithm integrating oral fluids as specimen and real-time PCR and FMIA as detection methods is effective for earlier detection of an erysipelas outbreak thereby allowing for a more effective treatment outcome.

Vaccination of sows reduces the prevalence of PCV-2 viraemia in their piglets under field conditions.

The objectives of this study were to further understand vertical transmission of porcine circovirus type 2 (PCV-2) and the effect of dam vaccination on PCV-2 viraemia in newborn piglets. Randomly selected sows from each of two breeding herds were designated as non-vaccinated or vaccinated groups. A commercial inactivated PCV-2 vaccine was administered at weaning and 18 days later to half of the sows on each farm. At parturition, colostrum was collected from 70 dams on each farm and postsuckle (Farm 1) or presuckle blood (Farm 2) was collected from five randomly selected piglets per litter. Colostrum samples had an anti-PCV-2 antibody prevalence of 98.5 per cent (135/137) with significantly (P = 0.0039) higher concentrations in vaccinated dams. Among piglets, 43.9 per cent (301/685) were seropositive for PCV-2 and 11.7 per cent (80/686) were PCV-2 DNA-positive. All the PCV-2 DNA-positive samples were further characterised and 28 were PCV-2a, 28 PCV-2b, and five mixed PCV-2a and PCV-2b infection. The prevalence of PCV-2 DNA in piglets was lower (0.7-22.8 per cent) compared with previous studies (44.8-90 per cent) indicating a change in PCV-2 ecology likely due to wide use of vaccination. Under the study conditions, dam vaccination reduced PCV-2 viraemia in the offspring with colostrum access.

Development of a novel fluorescent microbead-based immunoassay and comparison with three enzyme-linked immunoassays for detection of anti-Erysipelothrix spp. IgG antibodies in pigs with known and unknown exposure.

A novel fluorescent microbead immunoassay (FMIA) using the recombinant polypeptide SpaA415 was developed for detection of anti-Erysipelothrix spp. IgG in pig sera. The diagnostic performance of the FMIA was evaluated on samples from pigs with known and unknown Erysipelothrix spp. exposure and compared to an in-house enzyme-linked immunosorbent assay (ELISA-1) based on the same capture antigen, and two commercially available ELISAs (ELISA-2 and ELISA-3). Sera from pigs experimentally infected with Erysipelothrix rhusiopathiae serotype 1a (n=60) or 19 (n=12), sera from pigs vaccinated with a commercial attenuated-live vaccine based on serotype 1a (n=12) or a commercial bacterin based on serotype 2 (n=12), and 90 field samples were utilized. The sensitivity on 22 true positive samples collected in the later stages of infection/post-vaccination was 100% for the FMIA and ELISA-1, 63.6% for ELISA-2 and 81.8% for ELISA-3. The earliest antibody response was detected 7days post inoculation with the FMIA (77.8%) and ELISA-1 (11.1%), and at 14days post-vaccination (dpv) with FMIA (50%) and ELISA-1 (50%). On field samples, a higher seroprevalence was found in pigs older than 21days with all four assays. Kappa analysis indicated that the FMIA and ELISA-1 had almost complete agreement whereas the agreement was slight with ELISA-2 and fair with ELISA-3. The sensitivity of both immunoassays based on the rSpaA415 antigen was higher compared to that of the two commercial ELISAs. The rSpaA415 FMIA has great potential as an inexpensive ELISA alternative for detection of antibodies against E. rhusiopathiae in the future.

Development and evaluation of an enzyme-linked immunosorbent assay based on a recombinant SpaA protein (rSpaA415) for detection of anti-Erysipelothrix spp. IgG antibodies in pigs.

The aim of this study was to develop an enzyme-linked immunosorbent assay (ELISA) for detection of anti-Erysipelothrix spp. IgG in pig sera by utilizing recombinant polypeptide SpaA415 (rSpaA415) based on surface protective antigen (Spa) A (SpaA) of Erysipelothrix spp. The sensitivity of the rSpaA415 ELISA was evaluated on sera from pigs experimentally infected with E. rhusiopathiae serotype 1a (n=72), serotype 19 (n=12), or experimentally vaccinated with a commercial attenuated-live vaccine based on serotype 1a (n=12), a commercial bacterin based on serotype 2 (n=12), or an experimental bacterin based on serotype 2 (n=300). Specificity was tested using 221 negative control samples. The earliest antibody response was detected at 7 days post-inoculation (dpi) and 14 days post-vaccination (dpv). At the cutoff of 0.9 sample optical density, the sensitivity was 96.5% and the specificity was 100%. In experimentally infected pigs, the sensitivity of the rSpaA415 ELISA ranged from 5.5 to 100% which improved as dpi increased. Antimicrobial treatment, administered prior to appearance of clinical signs, decreased assay sensitivity. In vaccinated pigs, the rSpaA415 ELISA had a sensitivity of 48.3-100%. Serum samples from rabbits each hyperimmunized with one of the 28 Erysipelothrix spp. serotypes were used to determine cross-reactivity with strains expressing SpaB, SpaC or no currently recognized Spa protein and antibodies against E. tonsillarum were not detected. These data suggest that the novel rSpaA415 ELISA test is a useful tool to detect anti-IgG antibodies against different serotypes of E. rhusiopathiae in infected or vaccinated pigs without cross-reacting with the economically less important E. tonsillarum strains.

Vaccination with inactivated or live-attenuated chimeric PCV1-2 results in decreased viremia in challenge-exposed pigs and may reduce transmission of PCV2.

The objectives were to determine transmissibility of PCV2 to naïve contact pigs 140 days after infection of resident pigs and the benefit of vaccination with live-attenuated or inactivated chimeric PCV2 vaccines on chronic PCV2 infection. Twelve 6-week old PCV2 naïve pigs were randomly divided into four groups of three pigs: negative controls, positive controls, and pigs vaccinated with either a live-attenuated or inactivated chimeric PCV1-2 vaccine. All animals were bled weekly and tested for anti-PCV2 antibodies and PCV2 and PCV1-2 DNA and all groups except negative controls were challenged at 10 weeks. Two pigs vaccinated with the live PCV2 vaccine were PCV1-2 viremic at a single observation point. Both vaccine regimens induced an anti-PCV2 antibody response which was detected sooner and reached a higher level with the commercial inactivated vaccine. Both vaccines significantly decreased the concentration and duration of PCV2 viremia compared to the positive controls. PCV2 DNA was detected in lymphoid tissues of 1/3 pigs in the live-attenuated vaccine group and 3/3 positive control pigs. Three, 2-week old, PCV2 naïve contact pigs were comingled with each group at 168 days post-vaccination or 140 days post-challenge. After seven days of co-housing, the resident pigs were removed and the contact pigs remained for six weeks. Evidence of chimeric PCV1-2 vaccine or PCV2 challenge virus transmission to naïve contact pigs was lacking in all groups. The results of this study suggest that 140-day closure of a small pig population in a controlled environment may result in stabilization and elimination of PCV2.

Descriptive epidemiology of Moraxella bovis, Moraxella bovoculi and Moraxella ovis in beef calves with naturally occurring infectious bovine keratoconjunctivitis (Pinkeye).

PROBLEM ADDRESSED: Infectious bovine keratoconjunctivitis (IBK) is an ocular disease that causes substantial weight loss in beef calves. OBJECTIVE: The objective of this study was to evaluate the association between Moraxella bovoculi, Moraxella bovis and Moraxella ovis and IBK incidence. METHODS AND APPROACH: A cohort design was used. From 239 calves and 478 eyes, 77 randomly chosen eyes were monitored for M. bovoculi, M. bovis, M. ovis and IBK incidence over 4 months. One hypothesis tested was that IBK hazard in eyes was not associated with detection of M. bovoculi, M. bovis and M. ovis. A secondary hypothesis tested that IBK cases were not associated with increased prevalence of M. bovoculi, M. bovis and M. ovis. RESULTS: 23% of 77 eyes developed IBK. M. ovis was identified in one IBK-negative eye. The adjusted hazard ratio (HR) for IBK incidence from eyes where M. bovoculi or M. bovis were recovered prior to disease occurrence were not statistically significant (M. bovoculi HR=1.38, 95% CI: 0.54-3.53, p=0.49, M. bovis HR=1.60, 95% CI: 0.48-5.53, p=0.44). The adjusted hazard ratio for M. bovoculi in IBK lesions was 6.45 (95% CI: 3.35-12.44, p<0.001). The adjusted hazard ratio for M. bovis in IBK lesions was 2.33 (95% CI: 1.22-4.45, p=0.01). CONCLUSION: A temporal association between prior exposure to M. bovoculi or M. bovis and subsequent IBK incidence was not demonstrated. However, M. bovoculi and M. bovis are more frequently recovered from eyes with IBK lesions than unaffected eyes and this provides weak evidence for a causal role.

Outbreak of mortality in psittacine birds in a mixed-species aviary associated with Erysipelothrix rhusiopathiae infection.

Erysipelothrix rhusiopathiae septicemia, associated with an increased mortality of captive psittacines in a mixed-species aviary, was diagnosed by histopathology, Gram staining, bacterial culture and sequencing, immunohistochemistry, and real-time polymerase chain reaction (PCR). Over a period of 23 days with no premonitory signs, 2 rainbow lorikeets and an eclectus parrot died. Of these birds, one lorikeet and the eclectus were submitted for necropsy. The main pathologic findings were thrombosis (2/2), bacterial embolism/thromboembolism (2/2), necrotizing hepatitis (2/2), necrohemorrhagic myocarditis (1/2), fibrinohemorrhagic and heterophilic visceral coelomitis (1/2), submandibular necrosuppurative dermatitis with necrotizing vasculitis and bacterial and fungal thromboembolism (1/2), and locally extensive rhabdomyonecrosis with bacterial embolism (1/2). Intralesional bacteria were positive by Gram staining and immunohistochemistry in both cases. E. rhusiopathiae was isolated by routine bacterial culture from the liver of the lorikeet, which was also positive by real-time PCR. This report is one of the rare descriptions of erysipelas in psittacines, and to the authors' knowledge, it appears to be the first in the described species using immunohistochemistry and real-time PCR on avian paraffin-embedded tissues for the diagnosis.

Polymicrobial respiratory disease in pigs.

Respiratory disease in pigs is common in modern pork production worldwide and is often referred to as porcine respiratory disease complex (PRDC). PRDC is polymicrobial in nature, and results from infection with various combinations of primary and secondary respiratory pathogens. As a true multifactorial disease, environmental conditions, population size, management strategies and pig-specific factors such as age and genetics also play critical roles in the outcome of PRDC. While non-infectious factors are important in the initiation and outcome of cases of PRDC, the focus of this review is on infectious factors only. There are a variety of viral and bacterial pathogens commonly associated with PRDC including porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), porcine circovirus type 2 (PCV2), Mycoplasma hyopneumoniae (MHYO) and Pasteurella multocida (PMULT). The pathogenesis of viral respiratory disease is typically associated with destruction of the mucocilliary apparatus and with interference and decrease of the function of pulmonary alveolar and intravascular macrophages. Bacterial pathogens often contribute to PRDC by activation of inflammation via enhanced cytokine responses. With recent advancements in pathogen detection methods, the importance of polymicrobial disease has become more evident, and identification of interactions of pathogens and their mechanisms of disease potentiation has become a topic of great interest. For example, combined infection of pigs with typically low pathogenic organisms like PCV2 and MHYO results in severe respiratory disease. Although the body of knowledge has advanced substantially in the last 15 years, much more needs to be learned about the pathogenesis and best practices for control of swine respiratory disease outbreaks caused by concurrent infection of two or more pathogens. This review discusses the latest findings on polymicrobial respiratory disease in pigs.

Studies on porcine circovirus type 2 vaccination of 5-day-old piglets.

Porcine circovirus type 2 (PCV2) vaccines have become widely used since they became available in 2006. It is not uncommon for producers to use PCV2 vaccines in pigs younger than what is approved by manufacturers. The objective of this study was to determine the efficacy of a chimeric and a subunit PCV2 vaccine administered at 5 or 21 days of age. Forty-eight PCV2-naïve piglets were randomly divided into six groups of eight pigs each. Vaccination was done at day 5 or day 21, followed by triple challenge with PCV2, porcine parvovirus (PPV), and porcine reproductive and respiratory syndrome virus (PRRSV) at day 49. Vaccinated pigs seroconverted to PCV2 approximately 14 days postvaccination and had a detectable neutralizing antibody response by 21 days postvaccination regardless of age at vaccination. At day 49, the pigs vaccinated with the chimeric vaccine had significantly higher levels of neutralizing antibodies than the pigs vaccinated with the subunit vaccine. After challenge, vaccinated pigs had significantly decreased levels of PCV2 viremia and a decreased prevalence and severity of microscopic lesions compared to the positive-control group, which had severe lymphoid lesions associated with abundant PCV2 antigen, compatible with PCV-associated disease. The results of this study indicate that, under the conditions of this study, vaccination of PCV2-naïve pigs at day 5 or day 21 resulted in development of a detectable humoral immune response and provided reduction or complete protection against PCV2 viremia and PCV2-associated lesions after triple challenge with PCV2, PPV, and PRRSV.

Development and evaluation of a multiplex real-time PCR assay for the detection and differentiation of Moraxella bovis, Moraxella bovoculi and Moraxella ovis in pure culture isolates and lacrimal swabs collected from conventionally raised cattle.

AIM: To develop a multiplex real-time PCR assay for the detection and differentiation of Moraxella bovis (M. bovis), M. bovoculi and M. ovis. METHODS AND RESULTS: The multiplex real-time PCR assay was validated on three reference strains, 57 pure culture isolates and 45 lacrimal swab samples. All reference strains were identified correctly with no cross-reactions between species. Sequencing of 53 of the 57 culture isolates confirmed the results obtained with the multiplex real-time PCR, and the assay had 96·5% (55/57) concordance with a Moraxella spp. multiplex conventional PCR assay on the isolates. Among the lacrimal swab samples, the concordance between the multiplex real-time PCR and culture was 86·7% (39/45) for M. bovoculi and 75·6% (34/45) for M. bovis. CONCLUSIONS: The multiplex real-time PCR assay is specific and sensitive and can be used directly on lacrimal swab samples. SIGNIFICANCE AND IMPACT OF STUDY: The lack of a rapid, specific and sensitive detection method is a barrier for determining the roles of M. bovis, M. bovoculi and M. ovis in infectious bovine keratoconjunctivitis cases, and the developed PCR assay will contribute to improved understanding of the epidemiology and pathogenesis of these three Moraxella species.