Dr. Fernando Leite, a PhD student under the supervision of Dr. Richard Isaacson, won the Lynn Jones Memorial Award for the best oral presentation at the 97th Conference of Research Workers in Animal Diseases (CRWAD). His talk entitled “Lawsonia intracellularis vaccination decreases Salmonella enterica serovar Typhimurium shedding in co-infected pigs” presented the results of the work he did in collaboration with Drs. Gebhart, Singer, and Isaacson at the University of Minnesota.
Please join us in congratulating Fernando for his award!
Abstract: Salmonella enterica serovar Typhimurium and Lawsonia intracellularis are two of the most prevalent intestinal pathogens of swine. S. Typhimurium causes diarrhea but also results in subclinical persistent colonization of pigs and can lead to food borne illnesses. S. enterica is responsible for over 1 million cases of food borne illness per year in the United States. L. intracellularis infection has been found as a risk factor for increased S. Typhimurium shedding in swine. The objective of this study was to investigate if vaccination against L. intracellularis could lead to decreased S. Typhimurium shedding. To test this hypothesis, groups of nine pigs were either challenged with S. Typhimurium, S. Typhimurium and L. intracellularis, S. Typhimurium and vaccinated against L. intracellularis, or S. Typhimurium L. intracellularis and vaccinated against L. intracellularis. A non-infected control group served as a negative control. Fecal shedding of S. Typhimurium was monitored using an enrichment most probable number method two days after infection and weekly thereafter until animals reached the age of 14 weeks. The co-challenged vaccinated group had a tendency of shedding the least S. Typhimurium and at one-week post infection is when the greatest differences among groups was observed and the vaccinated co-challenged group shed significantly less Salmonella (p>0.05) than the group co-infected without vaccination and the group challenged with Salmonella alone. These differences were of 1.63 and 2.12 Log10 organisms per gram of feces, respectively. The instestinal microbiome of these animals is being investigated to understand how it may have impacted Salmonella shedding levels in the different treatments. These results indicate that vaccination against L. intracellularis may aid in the control of S. Typhimurium in herds co-infected with L. intracellularis.
Models are primordial to develop the best control and eradication measures as well as to decrease response time in the event of a Foot and Mouth Disease (FMD) incursion on US soil. However, to be as representative of real-life situation as possible, these models need the most accurate information on disease biology. This scientific article, written by a U of M team of epidemiologists: Drs. Kinsley, Patterson, VanderWaal, Craft, and Perez, is a meta-analysis of the peer-reviewed literature defining what the exact values for the duration of various disease periods such as: latency, incubation and sub-clinical phases are. The total duration of infection is also examined.
Abstract: In the event of a foot-and-mouth disease (FMD) incursion, response strategies are required to control, contain, and eradicate the pathogen as efficiently as possible. Infectious disease simulation models are widely used tools that mimic disease dispersion in a population and that can be useful in the design and support of prevention and mitigation activities. However, there are often gaps in evidence-based research to supply models with quantities that are necessary to accurately reflect the system of interest. The objective of this study was to quantify values associated with the duration of the stages of FMD infection (latent period, subclinical period, incubation period, and duration of infection), probability of transmission (within-herd and between-herd via spatial spread), and diagnosis of a vesicular disease within a herd using a meta-analysis of the peer-reviewed literature and expert opinion. The latent period ranged from 1 to 7 days and incubation period ranged from 1 to 9 days; both were influenced by strain. In contrast, the subclinical period ranged from 0 to 6 days and was influenced by sampling method only. The duration of infection ranged from 1 to 10 days. The probability of spatial spread between an infected and fully susceptible swine farm was estimated as greatest within 5 km of the infected farm, highlighting the importance of possible long-range transmission through the movement of infected animals. Finally, while most swine practitioners are confident in their ability to detect a vesicular disease in an average sized swine herd, a small proportion expect that up to half of the herd would need to show clinical signs before detection via passive surveillance would occur. The results of this study will be useful in within- and between-herd simulation models to develop efficient response strategies in the event an FMD in swine populations of disease-free countries or regions.
This past Friday, the Virology journal published a short report confirming the detection of a new porcine circovirus named PCV3. The virus was identified by a team of diagnosticians and researchers from the Veterinary Diagnostic Laboratory at the U of M in collaboration with the Blood Systems Research Institute and the Department of Laboratory Medicine in San Fransisco.
The pigs, gathered from three different cases, which expressed cardiac pathology and lesions of systemic inflammation tested negative for PCV2 by PCR. The article also reports the complete genetic sequences of the viruses and illustrates how different their proteins are from PCV2 and PCV1 ones in a phylogenetic tree.
Porcine circovirus 2 causes different clinical syndromes resulting in a significant economic loss in the pork industry. Three pigs with unexplained cardiac and multi-organ inflammation that tested negative for PCV2 and other known porcine pathogens were further analyzed. Methods
Histology was used to identify microscopic lesions in multiple tissues. Metagenomics was used to detect viral sequences in tissue homogenates. In situ hybridization was used to detect viral RNA expression in cardiac tissue. Results
In all three cases we characterized the genome of a new circovirus we called PCV3 with a replicase and capsid proteins showing 55 and 35 % identities to the genetically-closest proteins from a bat-feces associated circovirus and were even more distant to those of porcine circovirus 1 and 2. Common microscopic lesions included non-suppurative myocarditis and/or cardiac arteriolitis. Viral mRNA was detected intralesionally in cardiac cells. Deep sequencing in tissues also revealed the presence of porcine astrovirus 4 in all three animals as well as rotavirus A, porcine cytomegalovirus and porcine hemagglutinating encephalomyelitis virus in individual cases. Conclusion
The pathogenicity and molecular epidemiology of this new circovirus, alone or in the context of co-infections, warrants further investigations.
This is the question that Drs. Carmen Alonso, Sagar Goyal, Peter Davies, and Montse Torremorell from the College of Veterinary Medicine studied in collaboration with Drs. Bernard Olson and Peter Raynor from the College of Science and Engineering and the School of Public Health respectively, in the following paper published in Aerosol Science and Technology this past month.
In this study, the team form the University of Minnesota compared the capacity of two different air samplers to detect PRRSv and SIV in an experimental setting. The challenge to detect viral aerosol is to find a technique capable of capturing small amount of virus in a large amount of air. This experiment found that the particle size, the media used for collection as well as the extraction technique (passive or active) all had a significant effect on the detection of the viruses.
Abstract: Detection and quantification of dilute viral aerosols, as encountered outside animal housing facilities, requires methods that are able to detect small numbers of viruses in large volumes of air. This study compared the performance of two size-differentiating cascade impactors; an Andersen 8-stage (ACI; 28.3 L/min) and a high volume Tisch (TCI; 1,133 L/min) to assess sampling efficiency for detecting porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV). Samples of particles sorted by aerodynamic diameter were analyzed by quantitative polymerase chain reaction (qPCR) and collection efficiency was assessed by particle size. Collection media (minimum essential medium [MEM] and beef extract [BE]), elution technique (active versus passive), and sampling times (10, 20, and 30 min) were variables assessed for the TCI sampler. Extraction efficiency was 35% higher with BE as compared to that of MEM (p = 0.0007); active extraction technique was 19% more efficient than the passive technique (p = 0.03); time of sampling did not significantly affect the amount of virus recovered. The ACI sampler was more efficient in detecting both viruses from small and medium sized airborne particles (≤3 μm) as compared to the TCI sampler (p < 0.001). The latter sampler, however, was more efficient at IAV detection from large airborne particles (>3 μm) (p = 0.0025) indicating the potential of this sampler in detecting the presence of small amounts of viruses in aerosols under field conditions.
This past week-end, a dozen of veterinary students chose to meet with Drs. Maria Pieters and Perle Boyer at the University of Minnesota Southern research and outreach center in Waseca, MN to practice their pregnancy diagnostic skills over enjoying the unusually warm weather.
For over 3 hours, the first to third-year veterinary students each got the chance to perform an ultrasound examination on sows at various stages of gestation as well as on a sow that was not pregnant to appreciate the difference. Various tools were presented to them to compare and to get familiar with.
By the end of the lab, we are glad to say that all students were able to successfully tell if a sow was pregnant or not!