Infectious agents identified in pigs with multifocal interstitial nephritis at slaughter

Absence of serological or molecular evidence of Leptospira infection in farmed swine in the Hong Kong Special Administrative Region

Leptospirosis is an important zoonotic disease with several maintenance host species including swine. A cross sectional survey was undertaken between January to October 2020 to investigate the prevalence of leptospirosis in farmed swine in the Hong Kong Special Administrative Region (HKSAR) of China. Serum samples were collected from swine on seven farms (15 swine per farm; ten multiparous sows and five twelve-week-old weaners), while kidney samples were collected from 64 swine submitted for routine post-mortem (26 farms; average 2.4 swine per farm, range 1-6). Microscopic agglutination tests (MAT) to a panel of 24 Leptospira antigens did not reveal any evidence of seroconversion at a titre of 1:100. Polymerase chain reaction (PCR) testing of the kidney samples for Leptospira DNA did not detect any evidence of infection. Bayesian methods were used to compute the probability that the leptospirosis prevalence in farmed swine in the HKSAR was <3%, given none of the 105 swine sampled were positive on the MAT. The results of this study demonstrate no serological or molecular evidence of leptospirosis in farmed swine in the HKSAR. Subsequent statistical analysis supports the conclusion that the prevalence of leptospirosis in farmed swine in the HKSAR is negligible at present.

Ferulic acid isolated from propolis inhibits porcine parvovirus replication potentially through Bid-mediate apoptosis

Propolis from honeybee hives, which is a traditional Chinese medicine, is widely used in veterinary clinics. Many compounds have been identified and isolated from propolis. Ferulic acid (FA), one of the propolis components, previous studies have proven that it has antiviral effects. To study the mechanism of FA antiviral effects, experiments such as immunofluorescence, quantitative real-time PCR and immunoblotting were introduced. In porcine kidney (PK-15) cells, PPV infection induced the expression of the proapoptotic genes Bid, Bad, Bim and Bak, disrupted mitochondrial membrane potential, promoted mitochondria-mediated, caspase-dependent apoptotic signaling and induced apoptosis. Furthermore, the infected PK-15 cells had increased intracellular reactive oxygen species (ROS) generation. FA treatment, however, reversed these effects and increased cell viability. FA treatment also significantly decreased the PPV-induced expression of Bid, Cyt-c and Apaf-1, suggesting that ROS were involved in the activation of the mitochondria-mediated apoptosis pathway. This in vitro study showed that the antiviral activity of FA was probably associated with inhibiting the replication of PPV by blocking proapoptotic factors such as Bid, Bcl-2 and Mcl-1, and attenuating the mitochondria-mediated response by inhibiting the activation of the Bid-related signaling pathway. Pharmacological inhibitors inhibited PPV-induced apoptosis by blocking Bid, and also suppressed the expression of Caspase family proteins in ppv-induced apoptosis. Taken together, our results suggested that PPV induced PK-15 cell apoptosis via activation of Bid and Bid-related signaling pathways and that the mitochondria act as the mediators of these pathways. FA effectively and extensively attenuated this PPV action, and thus is a potential antiviral agent against PPV.

Prevalence and economic impact of cystic echinococcosis and liver fluke infections in slaughtered sheep and goat in north-central Iran, 2008-2018

Cystic echinococcosis (CE) and liver fluke infections as important zoonotic infections impose a large socioeconomic impact on societies. As an endemic region for these infections, slaughterhouse inspections should be more considered in Iran. This study aimed to analyze the 11-year record of offal condemnation due to CE, fascioliasis, dicrocoeliasis infections in sheep and goat and its economic impact at Alborz slaughterhouse, north-central Iran. The prevalence rate was calculated as the infected organs (as nominator) divided by the slaughtered cases (as the denominator) in each year and month. The annual percent changes was used to determine trends of parasitic diseases over time. The relationship between metrological indexes and the prevalence of parasitic diseases was determined by the linear regression model. Statistical analyses were done using STATA software 14. For an estimate, the economic impact, the total numbers of offal condemnation were calculated. The overall prevalence rate of fascioliasis, dicrocoeliasis, and CE was 0.95%, 2.17%, and 12.74%, respectively. There was a declining trend in the prevalence of fascioliasis and dicrocoeliasis, whereas, the prevalence of CE increased from 7.57% in 2008 to 9.53% in 2018, representing an annual change of + 0.02%. The direct economic impact was estimated at US$ 1,670,977 and US$ 25,148 for liver and lung, respectively. The number of condemned organs due to these infections is noticeable in Alborz Province, north-central, Iran. The high economic impact of these infections showed the necessity of implementing a continuously infected animal's trace-back and disease control in the site of infection.

Increasing diversity of swine parvoviruses and their epidemiology in African pigs

Detection of infectious viral agents has been on the increase globally with the advent and usage of more sensitive and selective novel molecular techniques in the epidemiological study of viral diseases of economic importance to the swine industry. The observation is not different for the pig-infecting member of the subfamily Parvovirinae in the family Parvoviridae as the application of novel molecular methods like metagenomics has brought about the detection of many other novel members of the group. Surprisingly, the list keeps increasing day by day with some of them possessing zoonotic potentials. In the last one decade, not less than ten novel swine-infecting viruses have been added to the subfamily, and ceaseless efforts have been in top gear to determine the occurrence and prevalence of the old and new swine parvoviruses in herds of pig-producing countries worldwide. The story, however, is on the contrary on the African continent as there is presently a dearth of information on surveillance initiatives of the viruses among swine herds of pig-producing countries in the region. Timely detection and characterization of the viral pathogens is highly imperative for the implementation of effective control and prevention of its spread. This review therefore presents a concise overview on the epidemiology of novel porcine parvoviruses globally and also provides up-to-date highlights on the reported cases of the viral agents in the African sub-region.

[Interstitial nephritis in pigs]

OBJECTIVE

Interstitial nephritis as a form of renal diseases can be found frequently among pigs. Nevertheless, prevalence and aetiology need to be investigated in more detail as reports about detailed analysis are lacking.

MATERIAL AND METHODS

In the present study, a total of 169 kidneys of conventionally and organically raised pigs were randomly chosen at slaughter and classified according to the degree of inflammation and the participating inflammatory cells. Moreover, PCV2 as an infectious agent was analysed by immunohistochemistry and in-situ hybridisation.

RESULTS

All of the investigated kidneys displayed mild interstitial lesions. Inflammatory cells included lymphocytes, macrophages, plasma cells, eosinophilic and neutrophilic granulocytes. Significant (p ≤ 0.0001) differences concerning the grade of inflammation and inflammatory cell occurrence could be observed between kidneys of conventionally and organically raised pigs. In comparison to conventionally raised pigs organically raised pigs showed significant (p ≤ 0.0001) more frequently a mild form of nephritis as well as a significant (p ≤ 0.0001) more frequent occurrence of lymphocytes and macrophages. In contrast to that, conventionally raised pigs had a significant (p ≤ 0.0001) higher occurrence rate of a mild to moderate form of nephritis as well as a significant (p ≤ 0.0001) higher level in occurrence of lymphocytes, macrophages, plasma cells, and neutrophilic granulocytes when compared to organically raised pigs. PCV2 DNA was detected in the kidney of only one animal.

CONCLUSION

Interstitial nephritis was found in conventionally and organically raised pigs and PCV2 was ruled out as a major pathogen for interstitial nephritis in slaughter pigs.

CLINICAL RELEVANCE

Because of the high prevalence and unknown cause further investigations are necessary to delineate the clinic relevance of this alteration and its pathogenesis.

Porcine parvovirus induces activation of NF-κB signaling pathways in PK-15 cells mediated by toll-like receptors

Porcine parvovirus (PPV) is a pathogenic factor that primarily induces severe reproductive failure of pregnant swine, which results in extensive losses to the swine industry worldwide. In this study, a potential mechanism of PPV-induced activation of the nuclear transcription factor-kappaB (NF-κB) by infection in porcine kidney cells (PK-15) was elucidated for the first time. The subcellular localization of p65 analyzed by immunofluorescence assay (IFA) showed that PPV infection induced p65 translocation from the cytoplasm to the nucleus. p65 phosphorylation was detected in PK-15 cells with progression of PPV infection. NF-κB-regulated gene expression was enhanced in a viral dose-dependent manner using the NF-κB luciferase reporter assay system. Furthermore, PPV-induced NF-κB activation was closely related to the inhibitory kappa B alpha (IκBα) degradation. Treatment with a NF-κB-specific inhibitor demonstrated that the production of PPV progeny viruses was enhanced to some extent. In addition, these results demonstrated that the adapter molecule TIR domain-containing adapter inducing IFN-β (TRIF) and myeloid differentiation primary-response protein 88 (MyD88)-dependent signaling pathways were involved in PPV-induced NF-κB activation. Together, these results provide evidence that the toll-like receptor (TLR) pathway participates in recognition of PPV and induction of NF-κB activation, and add to understanding of the molecular mechanisms underlying PPV infection.

The anti-porcine parvovirus activity of nanometer propolis flavone and propolis flavone in vitro and in vivo

Objectives. The present study was conducted to evaluate the activity of nanometer propolis flavone (NPF) on inhibiting porcine parvovirus (PPV) in vitro and in vivo. Methods. In vitro, the effect of NPF on cellular infectivity of PPV was carried out before and after adding drug and simultaneous adding and PPV after being mixed. In vivo, the anti-PPV effect of NPF in guinea pigs was performed. Results. The results showed that NPF could significantly inhibit PPV infecting porcine kidney- (PK-) 15 cells compared with propolis flavone (PF), and the activity of NPF was the best in preadding drug pattern. NPF at high and medium doses was able to observably restrain PPV copying in lung, gonad, blood, and spleen, decrease the impact of PPV on weight of guinea pigs, and improve hemagglutination inhibition (HI) of PPV in serum. In addition, it could also increase the contents of IL-2 and IL-6 in serum after PPV challenge. Conclusion. These results indicated that NPF could significantly improve the anti-PPV activity of PF, and its high concentration possessed the best efficacy. Therefore, NPF would be expected to be exploited into a new-style antiviral drug.

Development and evaluation of the rVP-ELISA for detection of antibodies against porcine parvovirus

The gene encoding the VP2 protein of porcine parvovirus (PPV) was expressed in an insect-baculovirus system. The recombinant (r) VP2 was similar antigenically/functionally to the native capsid protein as demonstrated by hemagglutination (HA), Western blotting using PPV positive sera. The purified rVP2 proteins were used as coating antigen to establish a rVP-ELISA method for detection of PPV positive and negative sera from pigs. The optimal operating conditions of the rVP-ELISA were: the concentration of rVP2 proteins coated on the wells was 2 μg/mL; the diluted concentration of serum was 1: 150 and that of the enzyme-labeled antibody was 1: 6000. A total of 596 sera were detected by this assay, and the average positive rate was 87%. Compared with France LSI kit, the result showed that the coincidence rate was 96.7%. In conclusion, the rVP2-ELISA is a sensitive and specific method for detecting antibodies against PPV.

First complete genomic characterization of a porcine parvovirus 5 isolate from China

To investigate porcine parvovirus 5 (PPV5) infections in swine herds in China, clinical specimens of piglet lungs were examined for the presence of PPV5 using a polymerase chain reaction method. A strain of PPV5 was detected, and its genome was sequenced and analyzed. In the sequence alignment and phylogenetic analysis, the Chinese PPV5 strain clustered into a distinct clade with the reference PPV5 strains. These results provide direct evidence that PPV5 is present in pigs in China. Extensive epidemiological studies are warranted to determine the geographic distribution of PPV5 in China.

Interrelação entre frequência de anticorpos anti-Leptospira spp. e exames histopatológicos (hematoxilina-eosina e Warthin-Starry) em suínos abatidos no Semiárido Paraibano

Este trabalho foi realizado em suínos abatidos no Município de Patos, Estado da Paraíba, Brasil, com o objetivo de determinar a frequência de anticorpos anti-Leptospira spp., comparando os achados sorológicos com exames histopatológicos de rim, fígado, ovário e útero. A soroaglutinação microscópica foi realizada em 126 animais. Os exames histopatológicos realizados em cortes de fígado, rim, ovário e útero, corados pela hematoxilina-eosina (HE), foram realizados em 20 animais escolhidos aleatoriamente, sendo 10 do grupo com títulos > 100 e 10 do grupo com títulos < 100. Paralelamente, foi realizada pesquisa direta de leptospiras pela técnica de Warthin-Starry em amostras de rim de todos os animais soropositivos e nos 10 animais soronegativos submetidos à HE. Dos 126 animais examinados, 18 (14,6%) foram soropositivos, com predominância de reações para o sorovar Autumnalis (11 animais; 8,73%). Quatro animais soropositivos e dois animais soronegativos apresentaram infiltrado inflamatório e necrose de graus variados em um dos rins e no fígado. Os ovários e úteros examinados não apresentaram lesões. A pesquisa direta de leptospiras pela técnica de Warthin-Starry não revelou animais positivos em nenhuma amostra testada. Em face da soropositividade encontrada (14,6%), sugere-se a importância da conscientização por parte dos produtores acerca da implantação de medidas de prevenção adequadas com o objetivo de impedir, ou pelo menos diminuir, a disseminação das leptospiras em suínos e, consequentemente, bloquear a possível transmissão do agente para os seres humanos.

Interstitial nephritis of slaughtered pigs in the State of Mato Grosso, Brazil

This study evaluated histological lesions in kidney samples from pigs with nephritis in two slaughterhouses in the State of Mato Grosso, Brazil. Four hundred samples were subjected to histology, anti-porcine circovirus type 2 (PCV2) immunohistochemistry (IHC), anti-Leptospira sp. immunofluorescence (IF), and polymerase chain reaction (PCR) for PCV2, porcine parvovirus (PPV), and Torque teno virus type 1 and 2 (TTV1, TTV2) detection. Histological lesions were found in 81% of the samples, and mononuclear interstitial nephritis was the most frequent lesion (77.50%). A follicular pattern was observed in 40.97% of the interstitial nephritis lesions. PCV2, PPV, TTV1, and TTV2 were identified in the kidneys by PCR in 27.25%, 28.50%, 94%, and 87.5% of the samples, respectively. Leptospira sp. was not detected through IF. Infection by PCV2 (PCR) and the presence of histological lesions (P=0.008) and giant cells (P=0.0016) were significantly associated. An association was observed between the TTV2-TTV1 co-infection (P<0.0001) and the risk for pathogenesis. These findings indicated that PCV2, PPV, TTV1, and TTV2 were widely distributed among pigs in the local farms and that the presence of these agents should be considered in the differential diagnosis of kidneys with interstitial nephritis in pigs.

Development of tertiary lymphoid structures in the kidneys of pigs with chronic leptospiral nephritis

Tertiary lymphoid organs (TLOs) are structures that are morphologically and functionally similar to secondary lymphoid organs. TLOs usually arise in a background of chronic inflammation. Several histological patterns of interstitial nephritis have been documented in porcine leptospirosis. Among them the lympho-follicular pattern is characterized by infiltrates of mononuclear cells organized in lymphoid follicle-like structures. Immunohistological analysis of 5 cases of porcine lympho-follicular nephritis associated with Leptospira Pomona infection demonstrated the presence of inflammatory cell populations, including B cells, T cells, macrophages and follicular dendritic cells (FDCs), which were compartmentalized as in TLOs. Immunohistochemistry for Leptospira Pomona revealed an intimate association between leptospiral antigen and FDCs. Overexpression of MHCII in different populations of both professional and non-professional antigen presenting cells was also demonstrated. FDCs play role during TLOs induction for their ability to retain non-self antigens in the form of immune complexes, thus causing persistent T cell activation, generation of a complex cytokine network and stimulation of humoral immunity. Sustained bacterial antigen presentation in the context of chronic leptospiral nephritis, may also lead to autoimmune mechanisms involved in the generation of TLOs. Whether lymphoid neogenesis and TLOs play a protective role in porcine leptospiral nephritis is still unclear.

The epitope of the VP1 protein of porcine parvovirus

Porcine parvovirus (PPV) is the major causative agent in a syndrome of reproductive failure in swine. Much has been learned about the structure and function of PPV in recent years, but nothing is known about the epitopes of the structural protein VP1, which is an important antigen of PPV. In this study, the monoclonal antibody C4 against VP1 of PPV was prepared and was used to biopan a 12-mer phage peptide library three times. The selected phage clones were identified by ELISA and then sequencing. The amino acid sequences detected by phage display were analyzed, and a mimic immuno-dominant epitope was identified. The epitope of VP1 is located in the N-terminal and contains the role amino acid sequence R-K-R. Immunization of mice indicated that the phage-displayed peptide induces antibodies against PPV. This study shows that peptide mimotopes have potential as alternatives to the complex antigens currently used for diagnosis of PPV infection or for development of vaccines.

Real-time PCR to detect and analyze virulent PPV loads in artificially challenged sows and their fetuses

To establish a real-time polymerase chain reaction with SYBR Green for detection and quantification of porcine parvovirus (PPV) in porcine tissues, two primers specific for the non-structural protein 1 gene were designed. The detection limit of this assay was 3-23 gene copies/reaction, equivalent to 0.001 TCID(50)/ml. The assay was linear over a 10(6) dilution range of template concentrations. Other porcine pathogens involved in reproductive disorders (porcine circovirus 2, porcine reproductive and respiratory virus, pseudorabies virus, classical swine fever virus) were negative by this assay. This assay could detect PPV titres at least 10(5) smaller than the hemagglutination assay. To better understand the pathogenesis of PPV, the levels of viral DNA in various tissues of artificially challenged sows and their fetuses were quantified with this method. The virus was found mainly in the heart, lung, spleen, kidney, and endometrium of sows, and mainly in the heart, spleen, lung, and testis of fetuses. This study provides a new tool for the study of PPV infection and distribution in sows and their fetuses.

Expression of Major Histocompatibility Complex Class II Antigens in Porcine Leptospiral Nephritis

Class II major histocompatibility complex (MHCII) is required for the presentation of antigens to CD4 helper T cells. During nephritis, not only primary antigen presenting cells such as histiocytes and lymphocytes, but also cytokine-stimulated tubular epithelial cells express MHCII. Leptospirosis in fattening pigs is characterized by several degrees of nephritis, from absence of lesions to severe multifocal tubulo-interstitial inflammation. Renal tissue from 20 8-month-old pigs with spontaneous nephritis and 6 control pigs without renal lesions were investigated for leptospirosis by indirect immunohistochemistry (IHC) and polymerase chain reaction (PCR). IHC for MHCII also was performed on renal samples. Serum samples were tested for different serovars of Leptospira interrogans. Control pigs were free of interstitial nephritis and negative for leptospirosis by all tests. In pigs with nephritis, serology was positive for serovar Pomona in 19/20 pigs. In 16 of these 19 pigs, leptospiral renal infection was confirmed by PCR and/or indirect IHC. Nephritic lesions were classified histologically into perivascular lymphocytic (4 pigs), lymphofollicular (6 pigs), lymphohistiocytic (8 pigs), and neutrophilic (2 pigs) pattern. MHCII expression by histiocytes and lymphocytes was observed in all lesions. Prominent MHCII expression in regenerating tubular epithelium was observed in lymphofollicular and lymphohistiocytic nephritis. No tubular colocalization between leptospiral and MHCII antigen was observed. Results suggest that during leptospiral nephritis, MHCII contributes to the intensity of the inflammatory response. Furthermore de novo MHCII expression in regenerating tubules may play a role in the defence mechanism against leptospiral tubular colonization.

Detection of porcine parvovirus by loop-mediated isothermal amplification

Loop-mediated isothermal amplification is a novel method for rapid amplification of DNA. It has been adopted widely for the detection of virus because of its simplicity, rapidity, and specificity. A loop-mediated isothermal amplification assay was developed for the detection of porcine parvovirus. Four primers specific for six regions of PPV non-structural protein 1 gene were designed with an online software. After amplifying at a constant temperature of 59-65 degrees C by Bst enzyme, a clear result was visible after 2.5% agarose gel electrophoresis. The sensitivity and specificity of this assay were evaluated by comparison with the polymerase chain reaction. The detection limit of the assay was shown to be equivalent to 5 PPV copies/reaction. Due to its specificity and simplicity, the assay should be a useful diagnostic tool for epidemiologic studies of PPV.

Characterization of interstitial nephritis in pigs with naturally occurring postweaning multisystemic wasting syndrome

Kidney samples with interstitial nephritis from 26 pigs affected by postweaning multisystemic wasting syndrome (PMWS) were selected. A histologic evaluation was carried out to describe the type of inflammation and its relationship with viral load, as assessed by in situ hybridization (ISH). Of 26 cases, 10 revealed a tubulointerstitial, lymphoplasmacytic nephritis, 11 an interstitial granulomatous nephritis, and 5 both types of inflammation (mixed type). In 4 cases of granulomatous inflammation, the pattern was not classically nodular, and a population of macrophages and lymphocytes was present (interstitial lymphohistiocytic nephritis). ISH confirmed the presence of porcine circovirus type 2 (PCV2) nucleic acid in all cases. The epithelium of the renal tubules was the most constantly ISH-positive structure. In tubulointerstitial nephritis, the higher the number of positive inflammatory cells, the more severe the inflammation. The ISH reaction was more heterogeneous and unpredictable in granulomatous nephritis, with some epithelioid and giant cells positive by ISH. To quantify macrophages distributed in the three patterns of nephritis, immunohistochemical methods using anti-major histocompatibility complex II (anti-MHC-II) and anti-lysozyme antibodies were undertaken, and semiquantitative evaluation was carried out. MHC-II was mainly expressed by lymphocytes in tubulointerstitial nephritis, but did not always stain macrophages in cases of granulomatous (including lymphohistiocytic) nephritis; the anti-lysozyme antibody revealed macrophages when present in tissues. The amount of PCV2 nucleic acid was not apparently associated with the pattern of inflammation (tubulointerstitial or granulomatous). PCV2 load seems to reflect the severity of the lymphoplasmacytic inflammation but not that of granulomatous and lympho histiocytic types.

Pathological and aetiological studies of multifocal interstitial nephritis in wasted pigs at slaughter

Multifocal interstitial nephritis in pigs has been associated with several infectious agents. The objective of the present study was to investigate several different potential infectious agents associated with "white-spotted" kidneys in pigs suffering from wasting at slaughter (aged 6-8 months). Twenty-nine case kidneys (with a "white-spotted" gross appearance) classified into 3 macroscopic lesional grades, and 15 control kidneys (lacking gross lesions), were obtained from a pig abattoir. Laboratory analyses to detect potential associations with the aforementioned pathological condition with Leptospira spp., porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome virus (PRRSV), and bacteria, were carried out. Microscopically, interstitial nephritis with a lymphofollicular inflammatory pattern (follicular nephritis) was observed in both case and control kidneys, with a higher frequency seen in the former ones. No leptospires were identified, although antibodies to the Pomona and Bratislava serovars were detected. Some pyogenic bacteria were also isolated from both case and control kidneys. PCV2 nucleic acid was only detected in 1 case kidney. PRRSV antigen was not found in any tested sample. Some pigs were tested positive for PPV by serology. Apparently, none of the studied agents were specifically associated as being the potential cause of the renal lesions in the studied wasted pigs. The fact that these chronic lesions may have been the consequence of a previous infection with one of these studied microorganisms, or more, and eventually with other non-tested infectious agents during the growing-finishing period, cannot be ruled out.