Dermatitis/nephropathy syndrome of pigs

Revisiting Porcine Circovirus Disease Diagnostic Criteria in the Current Porcine Circovirus 2 Epidemiological Context

Current knowledge on porcine circovirus diseases (PCVD) caused by Porcine circovirus 2 (PCV-2) includes the subclinical infection (PCV-2-SI), systemic (PCV-2-SD) and reproductive (PCV-2-RD) diseases, and porcine dermatitis and nephropathy syndrome (PDNS). Criteria to establish the diagnosis of these conditions have not changed over the years; thus, the triad composed by clinical signs, lesions and viral detection in lesions are still the hallmark for PCV-2-SD and PCV-2-RD. In contrast, PCV-2-SI diagnosis is not usually performed since this condition is perceived to be controlled by default through vaccination. PDNS is diagnosed by gross and histopathological findings, and PCV-2 detection is not recognized as a diagnostic criterion. Molecular biology methods as a proxy for PCVD diagnoses have been extensively used in the last decade, although these techniques should be mainly considered as monitoring tools rather than diagnostic ones. What has changed over the years is the epidemiological picture of PCV-2 through the massive use of vaccination, which allowed the decrease in infectious pressure paralleled with a decrease in overall herd immunity. Consequently, the need for establishing the diagnosis of PCVD has increased lately, especially in cases with a PCV-2-SD-like condition despite vaccination. Therefore, the objective of the present review is to update the current knowledge on diagnostic criteria for PCVDs and to contextualize the interest of using molecular biology methods in the overall picture of these diseases within variable epidemiological scenarios of PCV-2 infection.

Induction of Porcine Dermatitis and Nephropathy Syndrome in Piglets by Infection with Porcine Circovirus Type 3

Porcine circovirus type 3 (PCV3) is an emerging porcine circovirus that has been associated with porcine dermatitis and nephropathy syndrome (PDNS)-like clinical signs, reproductive failure, cardiac pathologies, and multisystemic inflammation in piglets and sows. Many aspects of PCV3 infection biology and pathogenesis, however, remain unknown. Here, we used a PCV3 virus stock from the rescue of an infectious PCV3 DNA clone to intranasally inoculate 4- and 8-week-old specific-pathogen-free piglets for evaluation of PCV3 pathogenesis. For 4-week-old piglets, typical clinical signs resembling those of PDNS-like disease were observed when piglets were inoculated with PCV3 alone or PCV3 combined with immunostimulation by keyhole limpet hemocyanin, with a mortality of 40% (2/5) for both types of inoculated piglets during a 28-day observation period postinoculation. Both types of inoculated piglets showed similar progressive increases in viral loads in the sera and had seroconverted to PCV3 capsid antibody after inoculation. Pathological lesions and PCV3-specific antigen were detected in various tissues and organs, including the lung, heart, kidney, lymph nodes, spleen, liver, and small intestine, in both types of inoculated piglets. The levels of proinflammatory cytokines and chemokines, including interleukin 1 beta (IL-1β), IL-6, IL-23α, gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and chemokine ligand 5 (CCL5), were significantly upregulated in both groups of inoculated piglets. Eight-week-old piglets also exhibited a similar PDNS-like disease but without death after PCV3 inoculation, as evidenced by pathological lesions and PCV3 antigen in various tissues and organs. These results show for the first time successful reproduction of PDNS-like disease by PCV3 infection and further provide significant information regarding the pathogenesis of PCV3 in piglets.IMPORTANCE Porcine circovirus type 3 (PCV3), an emerging porcine circovirus, is considered the cause of porcine dermatitis and nephropathy syndrome (PDNS)-like clinical signs and other systemic diseases in piglets and sows. To evaluate the pathogenesis of PCV3 infection in vivo, we used a PCV3 virus stock from the rescue of an infectious PCV3 DNA clone to intranasally inoculate 4- and 8-week-old specific-pathogen-free piglets and demonstrated successful reproduction of PDNS-like disease in animals that were inoculated with PCV3 alone or PCV3 combined with immunostimulation by keyhole limpet hemocyanin. Both 4- and 8-week-old PCV3-inoculated piglets showed similar increases in viral loads in the sera and had seroconverted to PCV3 capsid antibody. Pathological lesions and PCV3-specific antigen were detected in various tissues and organs, while numerous proinflammatory cytokines and chemokines in the sera were significantly upregulated after PCV3 inoculation. These results will provide significant information regarding the pathogenesis of PCV3 in piglets.

PCV2 infection aggravates ochratoxin A-induced nephrotoxicity via autophagy involving p38 signaling pathway in vivo and in vitro

Ochratoxin A (OTA) is reported to induce nephrotoxicity in animals and humans. Porcine circovirus type 2 (PCV2) could induce porcine dermatitis and nephropathy syndrome. To date, little is known whether virus infection aggravates mycotoxin-induced toxicity. This work aimed to study the effects of PCV2 infection on OTA-induced nephrotoxicity and its mechanism in vivo and vitro. The results in vivo showed that PCV2 infection aggravated OTA-induced poor growth performance, nephrotoxicity, p38 phosphorylation and autophagy as demonstrated by Atg5, LC3 II and p62 protein expressions in kidney of pigs. The results in vitro indicated that PCV2 infection significantly aggravated OTA-induced nephrotoxicity as demonstrated by cell viabilities, annexin V/PI binding and caspase 3 activities, and induced p38 phosphorylation and autophagy in PK15 cells. p38 inhibitor decreased Atg5 and LC3 protein expression induced by PCV2 infection and OTA combined treatment. Adding autophagy inhibitor 3-MA or CQ alleviated the aggravating effects of PCV2 infection on OTA-induced nephrotoxicity. Atg5-specific siRNA eliminated the aggravating effects of PCV2 infection on OTA-induced nephrotoxicity. Taken together, these data indicate that in vivo and in vitro PCV2 infection aggravated OTA-induced nephrotoxicity via p38-mediated autophagy.

A Novel Porcine Circovirus Distantly Related to Known Circoviruses Is Associated with Porcine Dermatitis and Nephropathy Syndrome and Reproductive Failure

Porcine circovirus-associated disease (PCVAD) is clinically manifested by postweaning multisystemic wasting syndrome (PMWS), respiratory and enteric disease, reproductive failure, and porcine dermatitis and nephropathy syndrome (PDNS). Porcine circovirus 2 (PCV2) is an essential component of PCVAD, although an etiologic role in PDNS is not well established. Here, a novel circovirus, designated porcine circovirus 3 (PCV3), was identified in sows that died acutely with PDNS-like clinical signs. The capsid and replicase proteins of PCV3 are only 37% and 55% identical to PCV2 and bat circoviruses, respectively. Aborted fetuses from sows with PDNS contained high levels of PCV3 (7.57 × 10⁷ genome copies/ml), and no other viruses were detected by PCR and metagenomic sequencing. Immunohistochemistry (IHC) analysis of sow tissue samples identified PCV3 antigen in skin, kidney, lung, and lymph node samples localized in typical PDNS lesions, including necrotizing vasculitis, glomerulonephritis, granulomatous lymphadenitis, and bronchointerstitial pneumonia. Further study of archived PDNS tissue samples that were negative for PCV2 by IHC analysis identified 45 of 48 that were PCV3 positive by quantitative PCR (qPCR), with 60% of a subset also testing positive for PCV3 by IHC analysis. Analysis by qPCR of 271 porcine respiratory disease diagnostic submission samples identified 34 PCV3-positive cases (12.5%), and enzyme-linked immunosorbent assay detection of anti-PCV3 capsid antibodies in serum samples found that 46 (55%) of 83 samples tested were positive. These results suggest that PCV3 commonly circulates within U.S. swine and may play an etiologic role in reproductive failure and PDNS. Because of the high economic impact of PCV2, this novel circovirus warrants further studies to elucidate its significance and role in PCVAD.

IMPORTANCE

While porcine circovirus 2 (PCV2) was first identified in sporadic cases of postweaning multisystemic wasting syndrome in Canada in the early 1990s, an epidemic of severe systemic disease due to PCV2 spread worldwide in the ensuing decade. Despite being effectively controlled by commercial vaccines, PCV2 remains one of the most economically significant viruses of swine. Here, a novel porcine circovirus (PCV3) that is distantly related to known circoviruses was identified in sows with porcine dermatitis and nephropathy syndrome (PDNS) and reproductive failure. PCV2, which has previously been associated with these clinical presentations, was not identified. High levels of PCV3 nucleic acid were observed in aborted fetuses by quantitative PCR, and PCV3 antigen was localized in histologic lesions typical of PDNS in sows by immunohistochemistry (IHC) analysis. PCV3 was also identified in archival PDNS diagnostic samples that previously tested negative for PCV2 by IHC analysis. The emergence of PCV3 warrants further investigation.

Complete Genomic Sequence of a Novel Porcine Circovirus 2 Strain, CC12

The genome sequence of a novel porcine circovirus 2 strain (CC12) is composed of 1,767 nucleotides, with two major open reading frames (ORFs). ORF1 encodes two replication-associated proteins (Rep and Rep′) with the unique mutation N186S, and ORF2 encodes a viral capsid protein (Cap) with two rare mutations, R59K and A190T.

Porcine circovirus type 2 (PCV2): genetic variation and newly emerging genotypes in China

Background

Porcine circovirus type 2 (PCV2), the causative agent of postweaning multisystemic wasting syndrome (PMWS), is a serious economic problem for the swine industry in China. In this study, we investigated the genetic variation of PCV2 in China using strains isolated from 2004-2008. Viruses were isolated from samples collected from pigs with multi-systemic lesions and clinical signs of PMWS from different regions of China, and the genomes of these viruses were sequenced. The assembled sequences were used to define the genotypes of these strains; PCR-RFLP methodology was used to distinguish isolates and capture ELISA was used to demonstrate the antigenic changes resulted from ORF2 gene mutation of the isolates.

Results

We identified 19 PCV2 isolates, including four newly emerging PCV2 mutant strains. The 19 isolates were designated into three genotypes (PCV2a, PCV2b and PCV2d). PCV2d represented a novel genotype and a shift from PCV2a to PCV2b as the predominant genotype in China was identified. This is the first report of 1766 nt PCV2 harboring a base deletion at other new different positions. Amino acid sequence analysis identified two novel ORF2 mutations (resulting in ORF2 sequences 705 and 708 nt in length) in three deletion strains (1766 nt) and one strain with a genome 1767 nt in length. Finding of two amino acids elongation of the ORF2-encoded Cap protein is firstly observed among PCV2 strains all over the world. The isolates were distinguished into different genotypes by PCR-RFLP methodology and antigenic changes were present in Cap protein of mutation isolates by capture ELISA.

Conclusions

The results of this study provide evidence that PCV2 is undergoing constant genetic variation and that the predominant strain in China as well as the antigenic situation has changed in recent years. Furthermore, the PCR-RFLP method presented here may be useful for the differential identification of PCV2 strains in future studies.

Multiply-primed rolling-circle amplification (MPRCA) of PCV2 genomes: applications on detection, sequencing and virus isolation

Multiply-primed rolling-circle amplification (MPRCA) was used to amplify porcine circovirus type 2 (PCV2) genomes isolated from tissues of pigs with signs of post-weaning multisystemic wasting syndrome (PMWS). Two of the amplified PCV2 genomes were cloned in prokaryotic plasmids and sequenced. Both were nearly identical (1767 nt) except for one silent substitution in the region coding for the capsid protein (ORF2). In addition, they showed high nucleotide sequence similarity with PCV2 isolates from others countries (93-99%). To investigate whether the MPRCA amplified PCV2 genomes could be used to produce infectious virus, the cloned genomes were isolated from the plasmids, recircularized and used for transfection in PK-15 cells. This procedure led to the production of infectious virus to titres up to 10(5.55) TCID(50)/mL. It was concluded that MPRCA is a useful tool to amplify PCV2 genomes aiming at sequencing and virus isolation strategies, where particularly useful is the fact that it allows straightforward construction of PCV2 infectious clones from amplified genomes. However, it was less sensitive than PCR for diagnostic purposes.

Porcine circovirus type 2 and porcine circovirus-associated disease

Porcine circovirus type 2 (PCV2) belongs to the viral family Circoviridae and to the genus Circovirus. Circoviruses are small, single-stranded nonenveloped DNA viruses that have an unsegmented circular genome. PCV2 is the primary causative agent of several syndromes collectively known as porcine circovirus-associated disease (PCVAD). Many of the syndromes associated with PCVAD are a result of coinfection with PCV2 virus and other agents such as Mycoplasma and porcine reproductive and respiratory syndrome virus. PCV2 infection is present in every major swine-producing country in the world, and the number of identified cases of PCVAD is rapidly increasing. In the United States, the disease has cost producers an average of 3-4 dollars per pig with peak losses ranging up to 20 dollars per pig. The importance of this disease has stimulated investigations aimed at identifying risk factors associated with infection and minimizing these risks through modified management practices and development of vaccination strategies. This paper provides an overview of current knowledge relating to PCV2 and PCVAD with an emphasis on information relevant to the swine veterinarian.

Influence of husbandry and control measures on porcine circovirus type 2 (PCV-2) dynamics within a farrow-to-finish pig farm: a modelling approach

We assessed, using a modelling approach, the influence of several management practices within a farrow-to-finish farm on the age of PCV-2 infection. The impact of PCV-2 vaccination with different vaccination schemes on infection dynamics, was also tested. A stochastic individual-based model describing the population dynamics in a typical French farrow-to-finish pig farm was built and coupled with an epidemiological model of PCV-2 infection. The parameters of the infectious model were mainly obtained from previous transmission experiments. Results were subjected to a survival analysis of time-to-infection. For each comparison, the reference situation was no vaccination followed by random mixing of piglets after birth and after weaning. The risk of early infection was significantly reduced when mixing of piglets was reduced at different stages (avoiding cross-fostering and grouping piglets by litters in small pens after weaning, hazard ratio (HR)=0.52 [0.46; 0.59]). Sow-targeted vaccination delayed the infectious process until the waning of passive immunity and piglet-targeted vaccination considerably decreased the force of infection leading to a dramatic decrease of the total number of infections (HR=0.44 [0.37; 0.54]). The effect was even more pronounced when strict management measures were applied (HR=0.24 [0.19; 0.31]). Changing from a low (3%) prevalence of PCV-2-infected semen to a higher one (18%) significantly increased the risk of early infections (HR=1.36 [1.2; 1.53]), whereas reducing replacement rate or changing sow housing from individual crates to group housing had a limited impact on PCV-2 dynamics.

Porcine circovirus diseases

Porcine circovirus type 2 (PCV2) is a member of the familyCircoviridae, a recently established virus family composed of small, non-enveloped viruses, with a circular, single-stranded DNA genome. PCV2, which is found all over the world in the domestic pig and probably the wild boar, has been recently associated with a number of disease syndromes, which have been collectively named porcine circovirus diseases (PCVD). Postweaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS) and reproductive disorders are the most relevant ones. Among them, only PMWS is considered to have a severe impact on domestic swine production. PMWS mainly affects nursery and/or fattening pigs; wasting is considered the most representative clinical sign in this disease. Diagnosis of this disease is confirmed by histopathological examination of lymphoid tissues and detection of a moderate to high amount of PCV2 in damaged tissues. Since PMWS is considered a multifactorial disease in which other factors in addition to PCV2 are needed in most cases to trigger the clinical disease, effective control measures have focused on the understanding of the co-factors involved in individual farms and the control or elimination of these triggers. PDNS, an immuno-complex disease characterized by fibrino-necrotizing glomerulonephritis and systemic necrotizing vasculitis, has been linked to PCV2, but a definitive proof of this association is still lacking. PCV2-associated reproductive disease seems to occur very sporadically under field conditions, but it has been characterized by late-term abortions and stillbirths, extensive fibrosing and/or necrotizing myocarditis in fetuses and the presence of moderate to high amounts of PCV2 in these lesions. Taking into account that scientific information on PCV2 and its associated diseases has been markedly expanded in the last 8 years, the objective of this review is to summarize the current state of knowledge of the most relevant aspects of PCV2 biology and PCVD.

Postweaning Multisystemic Wasting Syndrome (PMWS) in pigs with particular emphasis on the causative agent, the mode of transmission, the diagnostic tools and the control measures. A review

Postweaning multisystemic wasting syndrome (PMWS) is a worldwide emerging disease of weaned piglets. The objective of this review is to summarize the current knowledge regarding PMWS, its causative agent, mode of transmission, diagnostic techniques to detect PCV-2, the possible control measures, and the association of PMWS and PCV-2 with porcine dermatitis and nephropathy syndrome (PDNS). The causative agent of PMWS is porcine circovirus type 2 (PCV-2), however, not all pigs infected with PCV-2 develop the syndrome. PCV-2 is consistently associated with PMWS and PMWS is considered not to occur without it. Both the syndrome and the virus are not regarded as new. Co-factors that could activate PCV-2 to cause PMWS are considered. This enigmatic nature of both the syndrome and the virus is triggering a concern towards uncertainties of the viral transmission, its introduction in to the herd, effective tools of diagnosis, and control strategies.

A review of porcine circovirus 2-associated syndromes and diseases

Clinical expression of porcine circovirus 2 (PCV2) infection in swine may result in several distinct syndromes and diseases including post-weaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure, porcine respiratory disease complex, granulomatous enteritis, necrotizing lymphadenitis, and possibly exudative epidermitis. Association of PCV2 with congenital tremor in piglets is still controversial. The extent of the involvement of PCV2 in swine disease other than PMWS is currently poorly understood. This review concentrates on PCV-2-associated syndromes and diseases other than PMWS.

Surto de Circovirose (Síndrome Definhante Multissistêmica de Suínos Desmamados) no estado do Rio de Janeiro

Descreve-se o primeiro surto de Síndrome Definhante Multissistêmica de Suínos Desmamados (SDMSD) na Região Sudeste do Brasil, no estado do Rio de Janeiro. A enfermidade que afetou principalmente suínos desmamados com idade em torno de 4 meses, levou a morte pelo menos 14 animais. A granja onde o surto ocorreu, tinha péssimas condições sanitárias e de manejo. Clinicamente, a doença caracterizou-se por má condição corporal, pouco desenvolvimento, tosse, taquipnéia, dispnéia, diarréia, ataxia, tremores após estímulo, decúbito e convulsões, com evolução aguda a subaguda. À necropsia, os achados mais importantes foram um aumento de volume de linfonodos e pulmões não-colapsados, com áreas consolidadas, principalmente nos lobos craniais e porção anterior dos lobos médios. O exame histológico revelou, com maior freqüência, infiltração linfo-histiocítica com células sinciciais em linfonodos, baço, placas de Peyer, rim, pulmão e fígado, depleção ou hiperplasia linfóide, bem como pneumonia bronco-intersticial linfo-histiocitária e áreas de broncopneumonia secundária. O diagnóstico firmou-se pela observação dos sintomas e das lesões histológicas típicas e foi confirmado por exame imunohistoquímico e PCR. O estudo teve por objetivo caracterizar os aspectos epidemiológico e clínico-patológico desse surto, já que a mesma tem causado grandes perdas econômicas, diretas ou indiretas, à suinocultura mundial.

Diffuse global granulomatous glomerulonephritis in a pig

Diffuse global granulomatous glomerulonephritis with unique morphological characters was detected in a pig. The structure of the basement membrane of glomerular tufts was destroyed in almost all glomeruli. Various inflammatory cells consisted mainly of macrophages infiltrated severely into the glomerular tuft and the Bowman's space of and extended to the periglomerular interstitium. Periarteritis with fibrinoid necrosis was occasionally seen in the arterioles and small arteries running through the renal parenchyma and pelvis. In the present case, the results of either the immunohistochemical reactions to the antigens against PRRSV or PCV-2 or Ziel-Neelsen staining for acid-fast bacilli were negative and no pathogenic bacteria were cultured.

Characterisation of Hungarian porcine circovirus 2 genomes associated with PMWS and PDNS cases

The authors report the data of the first survey on the incidence of post-weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) in Hungary. A PCR method specific for the detection of porcine circovirus 2 (PCV-2) was developed, which proved to be suitable for diagnostic purposes. PCR screening of organ samples from pigs suspected to be affected with PMWS or PDNS revealed the presence of PCV-2 in 80% of the cases. Six PCV-2 genomes from Hungarian isolates were completely sequenced. Phylogenetic comparison with all the available PCV-2 sequences showed that porcine circoviruses circulating in Hungary are more variable than in several other European countries. Two Hungarian strains clustered together with the Spanish strains forming a distinct group; two others fell in a common group with the French, UK, and Dutch strains, whereas another two strains showed the closest relationship to two of the three known German PCV-2 sequences.

Porcine dermatitis and nephropathy syndrome. clinical and pathological features of cases in the United Kingdom (1993-1998)

This paper documents the salient clinical and pathological features of porcine dermatitis and nephropathy syndrome (PDNS) in 96 pigs submitted from 55 units in the UK from 1993 to 1998. This series of cases pre-dated the emergence of post-weaning multisystemic wasting syndrome (PMWS) in the UK. The morbidity during outbreaks was 1% or less. Affected pigs ranged from 14 to 70 kg in weight and most died after a short clinical illness. Fifty-five pigs had multifocal or coalescing erythematous skin lesions, some progressing to dermal necrosis. Biochemistry showed raised serum urea, creatinine and gamma globulin levels accompanied by proteinuria. All cases showed bilateral renal enlargement with petechiae throughout the cortices. Microscopically these renal lesions ranged in chronology from acute necrotizing glomerulitis and vasculitis with multiple hyaline casts in renal tubules to chronic glomerular sclerosis with interstitial inflammation and fibrosis. Haemorrhagic dermatitis when present was associated with necrotizing vasculitis in the dermal vessels. Vasculitis was sometimes detected in other tissues including subcutis, lymph nodes, spleen, liver, joint synovial membrane, gastric and intestinal submucosa or serosa and meninges but its frequency and distribution varied considerably in individual pigs. Immunostaining showed deposits of IgG and IgM in damaged glomeruli, renal casts and skin lesions. The aetiology and pathogenesis of the condition remain unknown but the histopathological and immunological findings suggest a systemic immune-complex disorder resulting in vasculitis with particular predilection for kidney and skin.

Occurrence of porcine dermatitis and nephropathy syndrome in Hungary

In the past few years a characteristics, often fatal disease associated with cutaneous lesions and nephropathy has been observed in several large pig herds and household pig stocks of Hungary. In addition to general symptoms and slight fever in several cases, the disease was characterised by cutaneous lesions occurring mostly on the ventral part of the thorax and abdomen, on the extremities and ear pinnae, and in the nasal and perianal region. In the acute phase, circumscribed hyperaemic, confluent, crust-covered areas were seen. Histological examination revealed necrosis of the epithelial layer and lympho-histiocytic vasculitis in the corium, here and there accompanied by thrombosis and fibrinoid degeneration. The kidneys were pale brown and harder to tear, with cortical petechiae in most cases. By histopathological examination, intra- and extracapillary glomerulonephritis accompanied by fibrinoid exudation was seen. Some of the renal tubules were dilated, others were atrophied, and in advanced cases proliferation of the intertubular connective tissue and inflammatory cell infiltration also occurred. Necrotic vasculitis was also observed in some cases. By immunohistochemical examination IgA, IgG and IgM, and in a single case C3 belonging to the complement system were observed in the pathologically changed skin areas and kidneys. By polymerase chain reaction (PCR), porcine circovirus type 2 (PCV-2) was detected. Bacteriological and serological examinations did not reveal infections of aetiological importance.

First report of post-weaning multisystemic wasting syndrome and porcine dermatitis and nephropathy syndrome in pigs in Greece

Post-weaning multisystemic wasting syndrome (PMWS) and porcine dermatitis and nephropathy syndrome (PDNS) are two recently described conditions of pigs at the late nursery and fattening stages. The aim of this short communication was to describe the first reported occurrence of these conditions and of porcine circovirus type 2 (PCV2) infection in Greece. The clinical signs, gross post-mortem changes and histopathological changes observed in affected pigs, were similar to those previously described for both PDNS and PMWS. As in previous reports, the lesions were associated with PCV2 infection, which was demonstrated by immunohistochemical and in situ hybridization methods.

Typing of Pasteurella multocida isolated from pigs with and without porcine dermatitis and nephropathy syndrome

Porcine dermatitis and nephropathy syndrome (PDNS) is a sporadic, usually fatal disease of growing and finishing pigs that has been recognized in many pig-producing countries. Pasteurella multocida strains isolated from 15 pigs with PDNS and 51 pigs without PDNS were characterized by capsule and somatic antigen typing, random amplified polymorphic DNA (RAP-D) typing, and restriction analysis of genomic DNA using pulsed-field gel electrophoresis (PFGE). While capsular, somatic, and RAP-D typing did not discriminate PDNS isolates from non-PDNS isolates, all of the isolates from PDNS cases showed an identical ApaI PFGE restriction pattern. This pattern was also found in a high proportion (36%) of P. multocida strains isolated from non-PDNS cases. Isolation of a single variant of P. multocida from tissues of pigs with PDNS warrants further investigation into the possible role of these bacteria in the etiology of the disease.

Detection of Pasteurella multocida in pigs with porcine dermatitis and nephropathy syndrome

Comprehensive bacterial cultures were made on samples from 20 pigs that had died of porcine dermatitis and nephropathy syndrome after a short clinical illness. Eleven species of porcine bacterial pathogens and a range of commensal organisms were isolated. Pasteurella multocida was isolated from 16 of the 20 cases but the other pathogens occurred much less commonly. P. multocida was isolated from between one and five sites per case and from the tonsils, retropharyngeal lymph node or lungs in 14 of the 16 cases. Immunohistochemical investigations of kidneys from 30 cases of the syndrome (including the 20 cases in the bacteriological study) revealed P. multocida-specific staining in 26 of the cases, primarily in the renal tubular epithelial cells of the proximal convoluted tubules, but also in the glomeruli, in lesions of renal vasculitis and in the cytoplasm of interstitial mononuclear cells.

Colocalization of porcine reproductive and respiratory syndrome virus and porcine circovirus 2 in porcine dermatitis and nephrology syndrome by double-labeling technique

Simultaneous detection of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus 2 (PCV2) was achieved by a double-labeling technique using a combination of immunohistochemistry and in situ hybridization in five pigs with naturally occurring porcine dermatitis and nephropathy syndrome (PDNS). Both PRRSV and PCV2 were isolated from a homogenate of pooled skin and kidney from three pigs. PRRSV RNA was demonstrated by reverse transcription polymerase chain reaction (PCR) in skin, kidney, lymph node, and tonsil homogenates from all pigs. PCV2 DNA was demonstrated by PCR in kidney, lymph node, tonsil, liver, and lung homogenates from all pigs. For double-labeling studies, the tissue samples were processed sequentially, first by immunohistochemistry and then by in situ hybridization. The most consistent and intense staining for PRRSV and PCV2 was in the kidney, lymph node, and tonsil. PRRSV antigen and PCV2 DNA were also detected in the skin. This morphologic study is the first to confirm the presence of both PRRSV and PCV2 in the same tissues in pigs with naturally occurring PDNS.

Identification of porcine circovirus in tissues of pigs with porcine dermatitis and nephropathy syndrome

Thirty-three pigs affected by porcine dermatitis and nephropathy syndrome, 30 from Spain and three from the USA, were investigated in order to detect porcine circovirus (PCV) in their tissues. A standard in situ hybridisation technique using a specific DNA 317-bp probe based on a well-conserved sequence of PCV (which recognises both PCV-1 and PCV-2) was applied to formalin-fixed, paraffin-embedded tissues. Twenty-eight of the 30 Spanish pigs and all three American pigs had PCV in at least one tissue. Viral nucleic acid was detected mainly in lymphoid organs, and especially the lymph nodes. The viral genome was also found, in order of decreasing quantity, in Peyer's patches, tonsil, lung, spleen, kidney, liver, and skin. Viral nucleic acid was located mainly within the cytoplasm of monocyte/macrophage lineage cells, including follicular dendritic cells, macrophages, histiocytes and Kupffer cells. No viral nucleic acid was found in damaged glomeruli or arteriolar walls. In frozen samples available from three Spanish pigs, the virus was identified as type 2 by using the polymerase chain reaction and restriction fragment length polymorphism. Most of the pigs from which serum was available were seropositive against porcine respiratory and reproductive syndrome virus (PRRSV), and PRRSV antigen was detected in the lung of two of the Spanish pigs. These results suggested that PCV is present in tissues of almost all pigs affected by PDNS, and PCV has to be considered as a possible agent involved in the pathogenesis of the syndrome.

Porcine dermatitis and nephropathy syndrome in Spain

In August 1995, the first case of porcine dermatitis and nephropathy syndrome was diagnosed in the north-eastern part of Spain; the pig showed characteristic dermal and renal lesions. Between then and January 1996, nine further animals from five different herds were diagnosed; they showed signs of anorexia, depression and, sometimes, pyrexia. Diarrhoea, Glässer's disease, conjunctivitis and gastric ulcers also occurred on the farms where the diagnoses were made. The affected pigs died of renal failure with diffuse fibrinous glomerulonephritis and a systemic necrotising vasculitis. Chronic interstitial nephritis, glomerulosclerosis and scar-like marks on the skin were observed in chronic cases. Other common findings in both acute and chronic cases were a diffuse depletion of lymph node lymphocytes with infiltration by syncytial cells (50 per cent of cases) and interstitial pneumonia. All the animals tested positive for porcine reproductive and respiratory syndrome virus (PRRSV) by serological tests and virus isolation. Serum urea and creatinine concentrations were above normal in the acutely affected animals. The pathogenesis of the condition is unknown but the lesions and immunopathological observations by other authors suggest that a type III hypersensitivity is a possible aetiology. The occurrence of PRRSV in these pigs suggests that the virus might be implicated in the pathogenesis of porcine dermatitis and nephropathy syndrome.

Cutaneous and systemic necrotizing vasculitis in swine

A systemic vasculitis involving particularly the skin and kidneys has been recently described in swine under the name dermatitis/nephropathy syndrome. Twelve pigs with gross cutaneous lesions typical of this condition were necropsied, and morphologic, immunohistochemical, microbiologic, and epidemiologic characteristics were studied. The pigs were divided into three groups comprising eight pigs with acute lesions, two with chronic lesions, and two with acute lesions kept for sequential skin biopsies. Acute skin lesions consisted of round to irregular, red to purple macules and papules that often coalesced to form large, irregular patches and plaques. With time, the lesions became covered by crusts and faded gradually, sometimes leaving scars. Characteristic distribution included the perineal area of the hindquarters, limbs, dependent parts of the abdomen and thorax, and margins of the ears. In the acute phase of the disease, necrotizing and leucocytoclastic vasculitis of small-caliber blood vessels were observed within the dermis and panniculus and in various extracutaneous locations such as the renal pelvis and synovial membranes. All pigs had macroscopic evidence of pneumonia and generalized lymphadenopathy. Microscopically, they had interstitial pneumonia and perivascular cuffing of mononuclear cells in various tissues including skin. The presence of immunoglobulins and complement was demonstrated by immunofluorescence in and around necrotic vessels of the skin in the early stages. Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) antigens were detected by immunohistochemistry in macrophages located around vessels of the tissues examined (skin and kidneys) in acute and chronic cases. PRRSV RNA was demonstrated by reverse transcription-polymerase chain reaction in lung and spleen homogenates from all pigs. The PRRSV was isolated in cell culture from 11 of the pigs. These findings suggest that PRRSV infection may play a role in the pathogenesis of this systemic vascular disease of swine.

Spontaneous glomerulonephritis in swine

In this investigation, 32 cases of naturally occurring glomerulonephritis in swine were studied retrospectively (1973-1993). Almost all affected pigs were crossbred and more than half were growing pigs. Nearly two thirds of the pigs showed gross renal lesions characterized by bilateral kidney enlargement, palor, edema, and/or cortical petechiation. The most commonly encountered extrarenal lesions were serous bodily effusions and gastric ulcers. The renal disease was considered the primary cause of death in 11 pigs. Histologically, the renal lesions in all pigs were characterized by a generalized and global proliferative glomerulonephritis. Mesangioproliferative glomerulonephritis was diagnosed in 2 pigs, whereas the glomerular lesions found in the other pigs (30/32) were characterized by a proliferative and exudative glomerulonephritis frequently associated with crescent formation. In all pigs, there was histologic evidence of proteinuria. A focal necrotizing vasculitis was found in the kidneys of 7 pigs. Although probably of immune origin, the precise etiopathogenesis of the porcine glomerulonephritis described herein after remains unknown.