Efficacy of experimentally produced spray-dried plasma on infectivity of porcine circovirus type 2

Estimated quantity of swine virus genomes based on quantitative PCR analysis in spray-dried porcine plasma samples collected from multiple manufacturing plants

This survey was conducted to estimate the incidence and level of potential viral contamination in commercially collected porcine plasma. Samples of spray dried porcine plasma (SDPP) were collected over a 12- month period from eight spray drying facilities in Spain, England, Northern Ireland, Brazil, Canada, and the United States. In this survey, viral load for several porcine pathogens including SVA, TGEV, PRRSV (EU and US strains), PEDV, PCV-2, SIV, SDCoV and PPV were determined by qPCR. Regression of Ct on TCID₅₀ of serial diluted stock solution of each virus allowed the estimate of potential viral level in SDPP and unprocessed liquid plasma (using typical solids content of commercially collected porcine plasma). In this survey SVA, TGEV or SDCoV were not detected in any of the SDPP samples. Brazil SDPP samples were free of PRRSV and PEDV. Samples of SDPP from North America primarily contained the PRRSV-US strain while the European samples contained the PRRSV-EU strain (except for one sample from each region containing a relatively low estimated level of the alternative PRRSV strain). Estimated viral level tended to be in the range from <1.0 log₁₀ TCID₅₀ to <2.5 log₁₀ TCID₅₀. Estimated level of SIV was the exception with a very low incidence rate but higher estimated viral load <3.9 log₁₀ TCID₅₀. In summary, the incidence of potential viral contamination in commercially collected porcine plasma was variable and estimated virus level in samples containing viral DNA/RNA was relatively low compared with that occurring at the peak viremia during an infection for all viruses or when considering the minimal infectious dose for each of them.

The impact of porcine spray-dried plasma protein and dried egg protein harvested from hyper-immunized hens, provided in the presence or absence of subtherapeutic levels of antibiotics in the feed, on growth and indicators of intestinal function and physiology of nursery pigs

The objective of this experiment was to compare the effects of spray-dried plasma protein (SDPP) and dried egg protein (DEP), without (AB-) or with (AB+) in-feed antibiotics, on growth performance and markers of intestinal health in nursery pigs raised in commercial conditions. This 42-d experiment utilized 1,230 pigs (4.93 ± 0.04 kg body weight; approximately 15-18 d of age). Pigs were randomly assigned to one of six dietary treatments that were arranged as a 2 × 3 factorial of in-feed antibiotics (AB- vs. AB+) and a specialty protein additive (none [CON], porcine SDPP, or DEP). Diets were fed in four phases with phases 3 and 4 as a common diet across all treatments. Specialty protein additives were fed in phases 1 (0-13 d; 3% SDPP, and 0.20% DEP) and 2 (13-26 d; 2% SDPP, and 0.10% DEP). Antibiotics were fed in phases 1-3 (662 mg chlortetracycline [CTC]/kg, 28 mg carbadox/kg, and 441 mg CTC/kg, respectively). Ileal tissue and blood samples were collected from 48 pigs (8 per treatment) on d 20. Data were analyzed using PROC MIXED of SAS (9.4) with pen as the experimental unit; protein additives, antibiotics, and their interaction were fixed effects and block was a random effect. The pigs experienced naturally occurring health challenges in weeks 2 and 4. In the AB- diets, SDPP and DEP increased average daily gain (ADG; P = 0.036) and average daily feed intake (ADFI; P = 0.040) compared to CON; in the AB+ diets, neither SDPP nor DEP increased ADG or ADFI compared to CON but SDPP did increase these parameters over DEP. The SDPP and DEP diets decreased the number of individual medical treatments compared to CON (P = 0.001). The AB+ increased ileal mucosal interleukin (IL)-1 receptor antagonist (P = 0.017). Feeding DEP reduced the concentration of mucosal IL-1β compared to CON, but not SDPP (P = 0.022). There was a trend for SDPP and DEP to increase villus height:crypt depth compared to CON (P = 0.066). Neither antibiotics or protein additive affected serum malondialdehyde concentration or ileal mRNA abundance of claudin-3 or 4, occludin, or zonula occludens-1 (P > 0.10). In conclusion, SDPP and DEP improved growth performance of weaned pigs in the absence of antibiotics but neither improved growth compared to CON when feeding standard antibiotic levels. The specialty proteins had a positive effect on health; specialty proteins and antibiotics were able to modulate some markers of intestinal inflammation and morphology.

Spray dried plasma as an alternative to antibiotics in piglet feeds, mode of action and biosafety

The use of growth promoting and therapeutic antibiotics in piglet feed has been a concerning subject over the last few decades because of the risk of generating antimicrobial resistance that could be transferred to humans. As a result, many products have been proposed as potential alternatives to the use of antibiotics, and among these, spray dried plasma is considered one of the most promising. However, there have been concerns about its biosafety, particularly during periods of emergence or re-emergence of swine diseases in different regions of the world, such as the recent porcine epidemic diarrhea virus outbreak in North America. The objectives of this paper are to review recent publications about the use of spray dried plasma as an alternative to antibiotics in weaned pig diets, the possible mechanisms of action of spray dried plasma, and the existing evidence related to the biosafety of spray dried animal plasma. Particular attention is given to studies in which spray dried plasma has been directly compared to antibiotics or other alternative antimicrobial products. Several studies on the possible modes of action for spray dried plasma, such as preservation of gut barrier function or modulation of the immune response, are also reviewed. Finally, the paper focuses on the review of the existing studies on the risks of disease transmission with the use of spray dried plasma from porcine origin. Overall, spray dried plasma is a promising alternative to in-feed antimicrobials for piglets, particularly during the early stages of the post-weaning phase. Additionally, there is enough evidence to support that commercial spray dried porcine plasma is a safe product for pigs.

The spray-drying process is sufficient to inactivate infectious porcine epidemic diarrhea virus in plasma

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Porcine epidemic diarrhea virus (PEDV) is economically important to pig production.

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Spray-dried pig plasma has been implicated in PEDV transmission.

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PEDV-positive pig plasma and PEDV-spiked plasma were tested in a swine bioassay.

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The spray-drying process effectively inactivated PEDV.

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The risk of transmitting PEDV through spray-dried pig plasma is minimal.

Porcine epidemic diarrhea virus (PEDV) is considered an emergent pathogen associated with high economic losses in many pig rearing areas. Recently it has been suggested that PEDV could be transmitted to naïve pig populations through inclusion of spray-dried porcine plasma (SDPP) into the nursery diet which led to a ban of SDPP in several areas in North America and Europe. To determine the effect of spray-drying on PEDV infectivity, 3-week-old pigs were intragastrically inoculated with (1) raw porcine plasma spiked with PEDV (RAW-PEDV-CONTROL), (2) porcine plasma spiked with PEDV and then spray dried (SD-PEDV-CONTROL), (3) raw plasma from PEDV infected pigs (RAW-SICK), (4) spray-dried plasma from PEDV infected pigs (SD-SICK), or (5) spray-dried plasma from PEDV negative pigs (SD-NEG-CONTROL). For the spray-drying process, a tabletop spray-dryer with industry-like settings for inlet and outlet temperatures was used. In the RAW-PEDV-CONTROL group, PEDV RNA was present in feces at day post infection (dpi) 3 and the pigs seroconverted by dpi 14. In contrast, PEDV RNA in feces was not detected in any of the pigs in the other groups including the SD-PEDV-CONTROL group and none of the pigs had seroconverted by termination of the project at dpi 28. This work provides direct evidence that the experimental spray-drying process used in this study was effective in inactivating infectious PEDV in the plasma. Additionally, plasma collected from PEDV infected pigs at peak disease did not contain infectious PEDV. These findings suggest that the risk for PEDV transmission through commercially produced SDPP is minimal.

Porcine epidemic diarrhea virus RNA present in commercial spray-dried porcine plasma is not infectious to naïve pigs

Porcine epidemic diarrhea virus emerged in North America in April 2013 and has since been identified in 30 U.S. States, Canada and Mexico. The rapid spread of PEDV has raised concerns about the role of feed and particularly pork-by-product components such as spray-dried porcine plasma (SDPP) in PEDV transmission. The aim of this study was to determine the infectivity of PEDV RNA present in commercial SDPP. Specifically, 40 3-week-old PEDV naïve pigs were randomly assigned to one of five treatment groups. At day post inoculation (dpi) 0, NEG-CONTROL pigs were sham-inoculated, PEDV-CONTROL pigs received cell culture propagated PEDV, and SDPP-CONTROL pigs were switched to a diet with 5% SDPP containing 5.1±0.1 log10 PEDV RNA copies/g. To evaluate a potential positive effect of anti-PEDV antibodies in SDPP on PEDV challenge, four days prior to PEDV challenge the pigs in the SDPP-PEDV group were switched to and remained on a 5% SDPP diet through dpi 28. Another group, EGG-PEDV, was orally administered a commercial egg-derived liquid PEDV globulin product from dpi -4 through 6. All PEDV-CONTROL pigs began shedding PEDV in feces by dpi 3 and seroconverted between dpi 7 and 14, whereas pigs in NEG-CONTROL and SDPP-CONTROL groups remained PEDV RNA negative and did not seroconvert to PEDV for the study duration. This indicates no evidence of infectivity of the PEDV RNA in the SDPP lot utilized. Furthermore, under the study conditions SDPP or egg-derived liquid PEDV globulin addition did not significantly alter PEDV-shedding or overall disease course after experimental challenge.

Investigation into the role of potentially contaminated feed as a source of the first-detected outbreaks of porcine epidemic diarrhea in Canada

In January 2014, approximately 9 months following the initial detection of porcine epidemic diarrhea (PED) in the USA, the first case of PED was confirmed in a swine herd in south‐western Ontario. A follow‐up epidemiological investigation carried out on the initial and 10 subsequent Ontario PED cases pointed to feed as a common risk factor. As a result, several lots of feed and spray‐dried porcine plasma (SDPP) used as a feed supplement were tested for the presence of PEDV genome by real‐time RT‐PCR assay. Several of these tested positive, supporting the notion that contaminated feed may have been responsible for the introduction of PEDV into Canada. These findings led us to conduct a bioassay experiment in which three PEDV‐positive SDPP samples (from a single lot) and two PEDV‐positive feed samples supplemented with this SDPP were used to orally inoculate 3‐week‐old piglets. Although the feed‐inoculated piglets did not show any significant excretion of PEDV, the SDPP‐inoculated piglets shed PEDV at a relatively high level for ≥9 days. Despite the fact that the tested PEDV genome positive feed did not result in obvious piglet infection in our bioassay experiment, contaminated feed cannot be ruled out as a likely source of this introduction in the field where many other variables may play a contributing role.

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.

Commercially produced spray-dried porcine plasma contains increased concentrations of porcine circovirus type 2 DNA but does not transmit porcine circovirus type 2 when fed to naive pigs

The porcine circovirus type 2 (PCV2) antibody and DNA status of porcine plasma products collected during the commercial spray-drying process were evaluated. Samples evaluated included 52 pooled liquid plasma (fresh) samples collected at 14 regional abattoirs before transport to 1 of 2 spray-drying facilities, 32 pooled liquid plasma (concentrated) samples collected after arrival at the spray-drying facilities at different stages before the spray-drying process, and 32 samples in powdered form (spray-dried) collected after spray drying. All 116 samples were positive for PCV2 antibody, with PCV2 ELISA sample-to-positive ratios ranging from 9.2 to 13.6 on a DM basis. Porcine circovirus type 2 DNA (4.5 to 7.9 log(10) PCV2 copies/mL, DM basis) was present in 82.7% (43/52) of the fresh plasma samples, 71.9% (23/32) of the concentrated plasma samples and 78.1% (25/32) of the spray-dried plasma samples, with a greater prevalence of PCV2b than PCV2a. To determine the infectivity of PCV2 DNA-positive commercial spray-dried plasma, nine 10-wk-old 68-kg PCV2-naïve pigs were randomly assigned to 1 of 3 treatment groups and rooms: 1) a negative control (no plasma in the feed, not inoculated with PCV2); 2) a positive control (no plasma in the feed, inoculated with PCV2); and 3) plasma-fed pigs (4% porcine plasma in the feed for 42 d, not inoculated with PCV2). All positive control pigs became viremic by 7 d postinoculation and seroconverted by 42 d postinoculation, whereas pigs in the negative control group and in the spray-dried plasma group were PCV2 PCR negative and did not seroconvert to PCV2 for the duration of the study. The results indicate that PCV2 DNA and antibodies are commonly found in commercial spray-dried plasma. However, no evidence of infectivity of the PCV2 DNA was found in naïve pigs when commercial spray-dried plasma was included in the diet under the conditions of this study.

Spread of porcine circovirus associated disease (PCVAD) in Ontario (Canada) swine herds: Part II. Matched case-control study

Background

The emergence of porcine circovirus associated disease (PCVAD) was associated with high mortality in swine populations worldwide. Studies performed in different regions identified spatial, temporal, and spatio-temporal trends as factors contributing to patterns of the disease spread. Patterns consistent with spatial trend and spatio-temporal clustering were already identified in this dataset. On the basis of these results, we have further investigated the nature of local spread in this report. The primary objective of this study was to evaluate risk factors for incidence cases of reported PCVAD.

Results

A time-matched case-control study was used as a study design approach, and conditional logistic regression as the analytical method. The main exposure of interest was local spread, which was defined as an unidentified mechanism of PCVAD spread between premises located within 3 kilometers of the Euclidean distance. Various modifications of variables indicative of local spread were also evaluated. The dataset contained 278 swine herds from Ontario originally sampled either from diagnostic laboratory submissions or directly from the target population. A PCVAD case was defined on the basis of the producer's recall. Existence of apparent local spread over the entire study period was confirmed (OR = 2.26, 95% CI: 1.06, 4.83), and was further identified to be time-varying in nature - herds experiencing outbreaks in the later part of the epidemic were more likely than control herds to be exposed to neighboring herds experiencing recent PCVAD outbreaks. More importantly, the pattern of local spread was driven by concurrent occurrence of PCVAD on premises under the same ownership (OR_{EXACTwithin ownership} = 25.6, 95% CI: 3.4, +inf; OR_{EXACToutside ownership} = 1.3, 95% CI: 0.45, 3.3). Other significant factors included PRRSv status of a herd (OR_EXACT = 1.9, 95% CI: 1.0, 3.9), after adjusting for geographical location by including the binary effect of the easting coordinate (Easting > 600 km = 1; OR_EXACT = 1.8, 95% CI: 0.5, 5.6).

Conclusions

These results preclude any conclusion regarding the existence of a mechanism of local spread through airborne transmission or indirectly through contaminated fomites or vectors, as simultaneous emergence of PCVAD could also be a result of concurrent change in contributing factors due to other mechanisms within ownerships.