Comparison of PCR and a Swine Bioassay to Detect Hepatitis E Virus in Pig Tissues and Feces

Swine hepatitis E virus (HEV) was detected by a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in liver tissue and feces but not in skeletal muscle, pancreas, or heart from pigs experimentally infected intravenously with swine hepatitis E virus (swine HEV). Homogenates of liver tissue and suspensions of feces prepared from swine HEV-infected pigs were inoculated intravenously into naïve pigs and induced infection. There was no evidence of transmission of swine HEV to pigs by intravenous route of inoculation with heart or pancreas, or oral route with skeletal muscle homogenates or fecal suspensions prepared from HEV-infected pigs. Results indicate that there is potential for transmission of swine HEV to naïve pigs, and potentially to humans, via pig liver or liver cell xenotransplantation. Failure to detect HEV by RT-PCR in muscle tissue and failure to transmit swine HEV via oral inoculation of muscle tissue suggests that the risk of transmission of HEV in pork meat products is minimal. The route of natural transmission of HEV is thought to be fecal-oral so the failure to transmit HEV via feces suggests that a very high infectious dose is necessary, or there are other routes of transmission. The semiquantitative RT-PCR assay correlates well with that of in vitro swine bioassay

Experimental Reproduction of Severe Disease in CD/CD Pigs Coinfected with PRRSV and Type 2 Porcine Circovirus

Postweaning multisystemic wasting syndrome (PMWS) has been recognized worldwide and is characterized clinically by wasting, dyspnea, and occasionally by icterus in nursery and grow-finish pigs. Type 2 porcine circovirus (PCV2) is consistently demonstrated in PMWS lesions. At the Iowa State University Veterinary Diagnostic Laboratory, both porcine reproductive and respiratory syndrome virus (PRRSV) and PCV2 are detected in tissues from most cases of PMWS. Since PRRSV-PCV2 coinfection has also been associated with “atypical PRRS” hepatitis, 3 week old cesarean-derived, colostrum-deprived (CD/CD) pigs were inoculated with PRRSV, PCV2, both PRRSV and PCV2, or uninfected cell culture media in order to compare the independent and combined effects of these agents. PRRSV-inoculated pigs developed respiratory distress and interstitial pneumonia typical of that previously reported for this agent. None of the pigs in the PRRSV or control groups became moribund or developed hepatitis. PCV2-inoculated pigs developed lymphoid depletion and sporadic hepatitis associated with 40% mortality. Pigs in the PRRSV/PCV2 group developed severe and persistent pyrexia and dyspnea; mortality between 10 and 20 days was \u3e90% and was associated with severe interstitial pneumonia and/or hepatitis. We conclude that 1) PCV2 alone can induce clinical disease and lesions of PMWS in CD/CD pigs, 2) PCV2 alone does not induce significant respiratory disease in CD/CD pigs, 3) PCV2/PRRSV coinfection induces more severe clinical disease and lesions of PMWS than PCV2 alone, including severe interstitial pneumonia, and 4) PCV2 coinfection is responsible for the hepatitis associated with cases of “atypical PRRS.” Simultaneous coinfection of PRRSV and PCV2 has the potential to significantly exacerbate morbidity and mortality. The timing of exposure and decay of maternal antibody to PCV2 and other pathogens may play a critical role in determining whether PCV2 infection induces PMWS or remains subclinical

Infection of Pigs with Avian Hepatitis E Virus (HEV)

It is now known that HEV can cross-species barriers. In the present study, we used a pig model to determine if HEV from chickens (avian HEV) or rats (rat HEV) was infectious to pigs. Thirty six, SPF pigs were randomly separated into 4 groups of 9 pigs each. Group 1 served as the sham-inoculated group. Group 2 was inoculated with rat HEV. Group 3 was inoculated with avian HEV. In the rat and avian HEV groups, 6 pigs were inoculated with the corresponding virus and 3 pigs remained uninoculated and served as contact controls. Group 4 was inoculated with the prototype swine HEV. Necropsy of 3 pigs from each group was performed on 7, 21, and 35 days postinoculation (dpi). In the rat and avian HEV groups, 2 inoculated and 1 contact control pigs were necropsied at each time point. Liver and bile from sham-inoculated pigs were negative for HEV throughout the study. Pigs in the sham and rat HEV group remained noninfected. Pigs inoculated with avian HEV and those inoculated with the swine HEV became viremic and shed HEV in feces. Both the avian and swine HEV infected pigs had mild-tomoderate lymphoplasmacytic hepatitis. The findings indicate that avian HEV is transmissible to pigs. This may open new areas of study in the epidemiology of HEV. Pigs may be an excellent model for comparative molecular and pathogenetic studies of different HEV strains

Attenuation of porcine reproductive and respiratory syndrome virus by molecular breeding of virus envelope genes from genetically divergent strains

Molecular breeding via DNA shuffling can direct the evolution of viruses with desired traits. By using a positive-strand RNA virus, porcine reproductive and respiratory syndrome virus (PRRSV), as a model, rapid attenuation of the virus was achieved in this study by DNA shuffling of the viral envelope genes from multiple strains. The GP5 envelope genes of 7 genetically divergent PRRSV strains and the GP5-M genes of 6 different PRRSV strains were molecularly bred by DNA shuffling and iteration of the process, and the shuffled genes were cloned into the backbone of a DNA-launched PRRSV infectious clone. Two representative chimeric viruses, DS722 with shuffled GP5 genes and DS5M3 with shuffled GP5-M genes, were rescued and shown to replicate at a lower level and to form smaller plaques in vitro than their parental virus. An in vivo pathogenicity study revealed that pigs infected with the two chimeric viruses had significant reductions in viral-RNA loads in sera and lungs and in gross and microscopic lung lesions, indicating attenuation of the chimeric viruses. Furthermore, pigs vaccinated with the chimeric virus DS722, but not pigs vaccinated with DS5M3, still acquired protection against PRRSV challenge at a level similar to that of the parental virus. Therefore, this study reveals a unique approach through DNA shuffling of viral envelope genes to attenuate a positive-strand RNA virus. The results have important implications for future vaccine development and will generate broad general interest in the scientific community in rapidly attenuating other important human and veterinary viruses

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

Probing genetic control of swine responses to PRRSV infection: current progress of the PRRS host genetics consortium

<p>Abstract</p> <p>Background</p> <p>Understanding the role of host genetics in resistance to porcine reproductive and respiratory syndrome virus (PRRSV) infection, and the effects of PRRS on pig health and related growth, are goals of the PRRS Host Genetics Consortium (PHGC).</p> <p>Methods</p> <p>The project uses a nursery pig model to assess pig resistance/susceptibility to primary PRRSV infection. To date, 6 groups of 200 crossbred pigs from high health farms were donated by commercial sources. After acclimation, the pigs were infected with PRRSV in a biosecure facility and followed for 42 days post infection (dpi). Blood samples were collected at 0, 4, 7, 10, 14, 21, 28, 35 and 42 dpi for serum and whole blood RNA gene expression analyses; weekly weights were recorded for growth traits. All data have been entered into the PHGC relational database. Genomic DNAs from all PHGC1-6 pigs were prepared and genotyped with the Porcine SNP60 SNPchip.</p> <p>Results</p> <p>Results have affirmed that all challenged pigs become PRRSV infected with peak viremia being observed between 4-21 dpi. Multivariate statistical analyses of viral load and weight data have identified PHGC pigs in different virus/weight categories. Sera are now being compared for factors involved in recovery from infection, including speed of response and levels of immune cytokines. Genome-wide association studies (GWAS) are underway to identify genes and chromosomal locations that identify PRRS resistant/susceptible pigs and pigs able to maintain growth while infected with PRRSV.</p> <p>Conclusions</p> <p>Overall, the PHGC project will enable researchers to discover and verify important genotypes and phenotypes that predict resistance/susceptibility to PRRSV infection. The availability of PHGC samples provides a unique opportunity to continue to develop deeper phenotypes on every PRRSV infected pig.</p

SNAPSHOT USA 2019: a coordinated national camera trap survey of the United States

With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August-24 November of 2019). We sampled wildlife at 1,509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the United States. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as will future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication

SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe