The effects of colostrum consumption and feed restriction during marketing and transportation of male dairy beef calves: Impact on pre-transport nutritional status and on farm recovery

The aim of this study was to evaluate the effects of colostrum consumption and feed restriction on biomarkers of stress, nutritional and health status, gut functionality, and behavior in male dairy beef calves being marketed and transported. A total of 82 male Holstein calves (42 ± 1.2 kg of body weight and 14 ± 0.9 d of age) were used to study the amount of colostrum given at birth at the dairy farm of origin, the degree of feed restriction suffered at an assembly center simulation (d -4 to d -1), and the effects of a 19 h transportation (d -1). Treatments were as follows: control calves (CTRL; n = 16) were fed 10 L of colostrum at the dairy farm of origin, milk replacer (MR) and concentrate at the assembly center, and were not transported; calves fed high colostrum and milk replacer (HCMR; n = 17) were given 10 L of colostrum at the dairy farm of origin, MR at the assembly center, and transported; calved fed high colostrum and rehydrating solution (HCRS; n = 16) were given 10 L of colostrum at the dairy farm of origin, a rehydrating solution (RS) at the assembly center, and transported; calves fed low colostrum and milk replacer (LCMR; n = 17) were given 2 L of colostrum at the dairy farm of origin, MR at the assembly center, and transported; and calves fed low colostrum and rehydrating solution (LCRS; n = 16) were given 2 L of colostrum at the dairy farm of origin, RS at the assembly center, and transported. Transported calves mimic a 19-h transportation. After transport, all calves were fed 2.5 L of MR twice daily and had ad libitum access to concentrate, straw, and water. Calves' recovery was followed for 7 d. Concentrate intake and health records were collected daily from d -4 until d 7 and body weight (BW) and blood samples were collected on d -4, -1, 0, 1, 2, and 7 of the study. Results showed that the feeding regimen provided at the assembly center reduced BW for the HCRS and LCRS calves compared with the CTRL, HCMR, and LCMR calves. Concentrate intake peaked on d 0 in the transported calves, followed by a reduction of intake on d 1 after transportation. Concentrate intake recovery was lower for the LCRS and LCMR calves. On d -1, nonesterified fatty acids and β-hydroxybutyrate concentrations were greater for the HCRS and LCRS calves compared with the CTRL, HCMR, and HCRS calves. After transportation, serum Cr-EDTA concentration was greater for the HCRS and LCRS calves than the HCMR, LCMR, and CTRL calves. The LCRS calves had the lowest serum concentration of citrulline. Finally, health scores were greater for the LCRS calves from d 0 to 7. In summary, both the greatest degree of feed restriction during the assembly center and the low colostrum consumption at birth negatively affected the recovery of concentrate consumption and BW, gut functionality, health status, and behavior in calves after arrival at the rearing farm.

Evaluation of potential biomarkers to determine adequate colostrum provision in male dairy-beef calves upon arrival at the rearing facility beyond 14 days of age

Colostrum consumption is crucial for passive immunization and development of the newborn calf. However, the incidence on failed transfer of passive immunity in male calves destined to dairy-beef production remains high to date. In addition, the lack of an automated procedure to validate the immunization status upon arrival at rearing facilities in calves beyond 14 d of age impedes the identification of failed transfer of passive immunity, and therefore, of those calves at high risk of suffering diseases. For this study, 82 newborn male Holstein calves (43.3 ± 0.86 kg of body weight; mean ± standard error) from a commercial dairy farm were used to investigate potential serum biomarkers of colostrum provision. The potential biomarkers selected were IgG, IgG1, cholesterol, alkaline phosphatase, gamma-glutamyl transferase (GGT), and total protein (TP). Treatments were as follows: high-colostrum (HC; n = 49), in which calves received 4 L of colostrum within the first 2 h after birth and 2 L of colostrum in the next 3 feedings within the first 24 h after birth, for a total of 10 L of colostrum; and low-colostrum (LC; n = 33), in which calves received only 2 L of colostrum within the first 2 h after birth. After colostrum consumption, calves were allocated to individual hutches and fed 2 L of milk replacer twice daily at a concentration of 125 g/L as fed. Starter feed and water were offered ad libitum. At approximately 14 d of age (14.2 ± 0.81 d of age; mean ± standard error) calves were transported 2.5 h to a research unit at IRTA (Torre Marimon, Spain) simulating the arrival to a rearing facility. Blood samples were collected before feeding at birth, 48 h after birth, and at arrival to the rearing facility. Results on the serum concentrations of the potential biomarkers at arrival to the rearing facility showed that IgG, IgG1, GGT, and TP were greater for the HC calves compared with the LC calves. Serum concentrations of cholesterol and alkaline phosphatase did not show differences between treatment groups. Additionally, body weight losses from birth until arrival to the rearing facility were greater for the LC treatment compared with the HC. Because of their low cost, quickness, and ease of measurement, GGT and TP were good indicators of colostrum intake in calves arriving at rearing facilities beyond 14 d of age.

Assessment of three commercial ELISAs for the detection of antibodies against Porcine epidemic diarrhea virus at different stages of the immune response

Three commercial ELISAs -two based on spike (E1 and E3) and one on nucleocapsid protein (E2)-were used to analyze the development and persistence of antibodies against Porcine epidemic diarrhea virus (PEDV). Seventy-five four-week-old PEDV-negative piglets were inoculated orally with a European G1b PEDV (INOC) and fourteen were kept as controls (CTRL). After the inoculation, E3 detected positive animals as soon as 7 days post inoculation (dpi), while the earliest detection with E1 and E2 was at 14 dpi. All samples were positive at 21 and 28 dpi using E1 and E3, respectively, while E2 failed to detect 23.3 % of the inoculated pigs at any time point. The percentages of positive samples were different through the study: E1 and E3 > E2 from 14 to 56 dpi; and E3 > E1 > E2 from 56 to 154 dpi (P < 0.05). Five months after the inoculation, E3 still detected 92.0 % (IC95 % = 85.1-98.8 %) of pigs as positive, while E1 and E2 detected only 27.0 % (IC95 % = 16.0-37.9 %) and 0%, respectively. The sensitivity for E2 never exceeded 0.62. Specificity was 1 for all ELISAs. These different outcomes could be related to the ELISA strategies (indirect versus competition), the antigens used, the cut-off, or to other intrinsic factors of each test. The observed differences could be of importance when assessing whether older animals, such as fatteners or gilts, had previously been in contact with PEDV.

Evaluation of ultraviolet-C and spray-drying processes as two independent inactivation steps on enterotoxigenic Escherichia coli K88 and K99 strains inoculated in fresh unconcentrated porcine plasma

The objectives of this study were to assess the effectiveness of an ultraviolet (UV‐C, 254 nm) irradiation system and the spray‐drying method as two independent safety steps on inactivation of Escherichia coli K88 and K99 spiked in porcine plasma at 6·46 ± 0·04 log₁₀ ml⁻¹ and 6·78 ± 0·67 log₁₀ ml⁻¹ respectively for UV‐C method, and at 7·31 ± 0·39 log₁₀ ml⁻¹ and 7·66 ± 0·11 log₁₀ ml⁻¹, respectively for the spray‐drying method. The UV‐C method was performed at different UV light doses (from 750 to 9000 J l⁻¹) using a pilot plant UV‐C device working under turbulent flow. Spray‐drying treatment was done at inlet temperature 220 ± 1°C and two different outlet temperatures, 80 ± 1°C or 70 ± 1°C. Results indicated that UV‐C treatment induced a 4 log₁₀ viability reduction for both E. coli at 3000 J l⁻¹. Full inactivation of both E. coli strains was achieved in all spray‐dried samples dehydrated at both outlet temperatures. The special UV‐C system design for turbid liquid porcine plasma is a novel treatment that can provide an additional redundant biosafety feature that can be incorporated into the manufacturing process for spray‐dried animal plasma.

Significance and Impact of the Study

The safety of raw materials from animal origin such as spray‐dried porcine plasma (SDPP) may be a concern for the swine industry. Ultraviolet treatment at 254 nm (UV‐C) of liquid plasma has been proposed as an additional biosafety feature in the manufacturing process of SDPP. We found that UV‐C exposure in the liquid plasma at 3000 J l⁻¹ reduces about 4 log10 ml⁻¹ for E. coli K88 and K99. Full inactivation of both E. coli strains was achieved in all spray‐dried samples. The incorporation of UV‐C treatment to liquid plasma improves the robustness of the SDPP manufacturing process.

Combined effects of spray-drying conditions and postdrying storage time and temperature on Salmonella choleraesuis and Salmonella typhimurium survival when inoculated in liquid porcine plasma

The objective of this study was to determine the effectiveness of the spray-drying process on the inactivation of Salmonella choleraesuis and Salmonella typhimurium spiked in liquid porcine plasma and to test the additive effect of immediate postdrying storage. Commercial spray-dried porcine plasma was sterilized by irradiation and then reconstituted (1:9) with sterile water. Aliquots of reconstituted plasma were inoculated with either S. choleraesuis or S. typhimurium, subjected to spray-drying at an inlet temperature of 200°C and an outlet temperature of either 71 or 80°C, and each spray-drying temperature combinations were subjected to either 0, 30 or 60 s of residence time (RT) as a simulation of residence time typical of commercial dryers. Spray-dried samples were stored at either 4·0 ± 3·0°C or 23·0 ± 0·3°C for 15 days. Bacterial counts of each Salmonella spp., were completed for all samples. For both Salmonella spp., spray-drying at both outlet temperatures reduced bacterial counts about 3 logs at RT 0 s, while there was about a 5·5 log reduction at RT 60 s. Storage of all dried samples at either 4·0 ± 3·0°C or 23·0 ± 0·3°C for 15 days eliminate all detectable bacterial counts of both Salmonella spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

Safety of raw materials from animal origin like spray-dried porcine plasma (SDPP) may be a concern for the swine industry. Spray-drying process and postdrying storage are good inactivation steps to reduce the bacterial load of Salmonella choleraesuis and Salmonella typhimurium. For both Salmonella spp., spray-drying at 71°C or 80°C outlet temperatures reduced bacterial counts about 3 log at residence time (RT) 0 s, while there was about a 5.5 log reduction at RT 60 s. Storage of all dried samples at either 4.0 ± 3.0°C or 23.0 ± 0.3°C for 15 days was effective for eliminating detectable bacterial counts of both Salmonella spp.

Schmallenberg virus detection in Culicoides biting midges in Spain: First laboratory evidence for highly efficient infection of Culicoides of the Obsoletus complex and Culicoides imicola

Since Schmallenberg disease was discovered in 2011, the disease rapidly spread across Europe. Culicoides biting midges have been implicated as putative Schmallenberg vectors in Europe. The detection of Schmallenberg virus (SBV) in field collected Culicoides was evaluated through retrospective (2011-2012) collections and captures performed in 2013. This study represents the first detection of SBV in field collected Culicoides in Spain. Infectious midges were detected at the foothills of Pyrenees, Aramunt, in the summer 2012. All the specimens infected with Schmallenberg were of the species Culicoides obsoletus s.s. confirming its putative vector status in Spain. Experimental infection on field collected Culicoides provided evidence of atypical high efficiency for SBV vector infection and transmission potential in local populations of Culicoides imicola and in Culicoides of the Obsoletus complex. However, captured individuals of C. imicola were more susceptible to SBV infection than C. obsoletus s.l. (p < .001), with an infection ratio of 0.94 and 0.63, respectively. In contrast, a Culicoides nubeculosus colony appeared to be refractory to SBV infection.

Half-life of porcine antibodies absorbed from a colostrum supplement containing porcine immunoglobulins

Absorption of immunoglobulins (Ig) at birth from colostrum is essential for piglet survival. The objective was to evaluate the half-life of antibodies absorbed in the bloodstream of newborn piglets orally fed a colostrum supplement (CS) containing energy (fat and carbohydrates) and IgG from porcine plasma. Viable piglets (n = 23; 900 to 1,800 g BW) from 6 sows were colostrum deprived and blood sampled and within the next 2 h of life randomly allocated to either control group (n = 9) providing 30 mL of Ig-free milk replacer or a group (n = 14) receiving 30 mL of CS by oral gavage. Piglets were transported to a Biosafety Level 3 facility (Centre de Recerca en Sanitat Animal, Spain) and fed Ig-free milk replacer every 3 to 4 h for 15 d. Survival, weight, plasma IgG content by radial immunodiffusion (RID), and antibodies against porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), porcine reproductive and respiratory syndrome (PRRS), Mycoplasma hyopneumoniae (Mhy), and swine influenza virus (SIV) were determined by specific ELISA before treatment administration, at 24 h, and weekly for 56 d. Clinical symptoms were not observed for either group. Mortality index was lower (17 vs. 38%; P < 0.02) and BW higher (17.7 vs. 15.3 kg; P = 0.035) for pigs supplemented with CS than piglets in the control group. At 24 h postadministration, the CS group had a plasma IgG mean of 7.6 ± 0.06 vs. 0.14 ± 0.03 mg/mL for the control group. The IgG levels in the CS group decayed until day 21 when de novo synthesis of IgG was detected in 25% of piglets. Half-life of antibody concentration (HLAC) by RID was 6.2 d. In the CS group, efficiency of PCV2 and PPV antibody transfer was high. For PCV2, all animals remained positive by day 56 and the calculated HLAC was 17.7 d. For PPV, 72.7% of piglets were ELISA positive by day 35 and HLAC was 12.0 d. For PRRS, all piglets remained positive by day 14 and the calculated HLAC was 11.9 d. For Mhy and SIV the calculated HLAC were 8.4 and 3.0 d. In summary, half-life of antibodies derived from blood plasma in the bloodstream of newborn piglets varied from 3.0 to 17.7 d. The study also confirm that antibodies derived from porcine plasma were well absorbed and can be an useful tool for providing protection against several or specific pathogens and can be a good alternative to formulate CS for newborn piglets.

Comparison of different vaccination schedules for sustaining the immune response against porcine reproductive and respiratory syndrome virus

In order to better understand how immunization against porcine reproductive and respiratory syndrome virus (PRRSV) can be improved using commercial vaccines, different strategies of immunization were applied in the field using an inactivated vaccine (INV), a modified live vaccine (MLV) or a combination of the two and the responses compared. In experiment 1 (E1), 21 piglets were distributed in three groups. Group A was vaccinated with a commercial INV at 2.5, 3.5 and 6.5 months old; group B pigs received the INV at 1.5, 2.5, 5.5 and 6.5 months old, while pigs in group C were kept as unvaccinated controls. At 7.5 months of age all pigs were challenged with PRRSV and followed for 21 days. In experiment 2 (E2), 32 piglets were distributed evenly in four groups. Groups A, B and C were vaccinated with a commercial MLV at 1.5 months old, while group D pigs were kept as controls. At 4.5 months old, groups A and C received the INV while B received a second MLV, 1 month later group C pigs received a third INV. At 6.5 months old all pigs were challenged as in E1. In both experiments, total antibodies, neutralizing antibodies (NA) and cell-mediated immunity (CMI) were evaluated, and viraemia was determined after challenge. In E1, immunization with an INV induced high interferon-γ responses after the second and subsequent vaccinations. Development of NA after challenge was faster in INV vaccinated pigs compared to unvaccinated controls. In E2, re-vaccination with INV induced NA responses similar to re-vaccination with MLV; however, a significant increase in NA titres after challenge was only detected in group C pigs. The use of combined protocols (MLV+INV) was superior to the use of MLV alone in inducing cell mediated immunity. In conclusion, the highest immune responses against PRRSV after a single shot were achieved with MLV; after that, INV re-vaccination should be considered as the best strategy to induce significant boosters.

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.

Lack of transmission of porcine circovirus type 2 to weanling pigs by feeding them spray-dried porcine plasma

An experiment was conducted to determine whether spray-dried porcine plasma containing 2.47 x 10(5) dna copies of porcine circovirus type 2 (pcv-2) could infect weanling pigs when fed to them. Five specific pathogen-free (spf) weanling pigs were fed ad libitum for 45 days a control diet and six pigs were fed a test diet containing 8 kg sdpp per 100 kg feed. The two groups were housed in separate biosecurity level-3 rooms. None of the pigs in either group developed any clinical signs or became pcv-2 viraemic or seroconverted.

Effects of spray-dried porcine plasma and plant extracts on intestinal morphology and on leukocyte cell subsets of weaned pigs

We evaluated the effects of a 6% spray-dried porcine plasma (SDPP) and a plant extracts mixture (XT; 5% carvacrol, 3% cinnamaldehyde, and 2% capsicum oleoresin) on the productive performance, intestinal morphology, and leukocyte cell subsets of early-weaned pigs compared with a control group. Morphometry of the jejunum, ileum, and colon, and immune cell analysis of blood, ileocolic lymph node (LN), and ileal Peyer's patches were done in 24 weaned pigs (20 +/- 2 d) at 19 or 21 d postweaning. Although SDPP and XT treatments did not increase ADG or ADFI, SDPP improved the G:F ratio (P = 0.024) compared with the control group. Dietary SDPP reduced the percentages of blood monocytes (P = 0.006) and macrophages in ileal Peyer's patches and LN (P = 0.04), of B lymphocytes (P = 0.04) and gammadelta+ T cells in LN (P = 0.009), and of intraepithelial lymphocytes (P = 0.026) as well as the density of lamina propria cells in the colon (P < 0.01). Dietary XT reduced intraepithelial lymphocyte numbers in jejunum (P = 0.034) and the percentages of blood cytotoxic cells (P = 0.07) and B lymphocytes in LN (P = 0.03); however, XT increased blood monocytes (P = 0.038) and the density of lamina propria lymphocytes in the colon (P = 0.003). These results indicate that dietary SDPP and plant extracts can affect intestinal morphology and immune cell subsets of gut tissues and blood in weaned pigs. Furthermore, the effects of SDPP suggest lower activation of the immune system of the piglets.

Descriptive epidemiology of the outbreak of classical swine fever in Catalonia (Spain), 2001/02

Spain suffered an outbreak of classical swine fever between June 14, 2001 and May 7, 2002, which affected 49 herds; this paper describes the epidemiological characteristics of the 39 herds that were affected in Catalonia, an area of high pig density in the north east of Spain. The outbreak took place in two waves, which affected first the province of Lleida and then Barcelona. A total of 291,058 animals were slaughtered, 59,595 belonging to infected herds; 22 of the infected herds were detected on the basis of clinical suspicion on the part of the farmer or farm veterinarian, and the other 17 were detected by surveillance methods. The transmission of the virus between herds was attributed to the movement of people in 23 per cent of the cases, to animals in 13 per cent, vehicles in 10 per cent, proximity 18 per cent, the pick-up service of the rendering plant in 8 per cent and slurry in 5 per cent; in the other nine herds (23 per cent) the route of entry of the disease could not be established. The viruses isolated in the two waves of the outbreak were 100 per cent homologous and belonged to subgroup 2.3. The origin of the outbreak remains unknown.

Changes in peripheral blood leukocyte populations in pigs with naturally occurring exudative epidermitis

The objective of the study was to analyze changes in peripheral blood leukocyte subsets in cases of naturally occurring exudative epidermitis (EE) in pigs. Five of ten piglets developed the chronic clinical form of EE 2-5 days after weaning (PW). Blood samples were obtained at 7, 14 and 21 days from both normal and clinically affected piglets for routine haematology and for the determination of CD45, CD21, CD4, CD8 and gammadeltaTCR cell markers by flow cytometry. When compared with clinically normal piglets EE affected pigs showed significantly decreased values of monocytes at 14 and 21 days PW, and increased numbers of neutrophils and leukocytes at 21 days PW. The EE affected pigs also had an early significant CD4(+) and CD8(high+) T lymphocyte proliferative response at 7 days PW. However affected pigs had a significantly reduced number of B (CD21(+)) and gammadeltaTCR(+) T lymphocytes in blood at 21 days PW. Although all values remained within the normal range, the significant differences in some peripheral blood leukocyte subsets between the two groups of piglets suggest that the generalised cutaneous infection with Staphylococcus hyicus is severe enough to induce a systemic inflammatory and immune responses.

Different European-type vaccines against porcine reproductive and respiratory syndrome virus have different immunological properties and confer different protection to pigs

Immunization of piglets with two different European-type modified live vaccines against porcine reproductive and respiratory syndrome (PRRS) virus produced different outcomes. After vaccination, pigs became viremic (42 days), neutralizing antibodies did not develop, and frequencies of virus-specific gamma-interferon-secreting cells (IFN-gamma-SC) were low. Levels of interleukin-10 (IL-10) produced by peripheral blood mononuclear cells (PBMC) seemed to inversely correlate with interferon-gamma responses. After a challenge with a virulent Spanish strain, one vaccine (V3) protected piglets against viremia while the other (V1) did not. The vaccine V3 induced the highest IFN-gamma-SC frequencies. IL-2, IL-4 or transforming growth factor-beta responses were not detected at any time for neither of the vaccines. In contrast, haptoglobin rose in sera of viremic pigs after the challenge. These results indicated a strong involvement of IFN-gamma, and maybe IL-10, in the development of immunity against PRRS virus.

Efficacy of spray-drying to reduce infectivity of pseudorabies and porcine reproductive and respiratory syndrome (PRRS) viruses and seroconversion in pigs fed diets containing spray-dried animal plasma

Three experiments were conducted to evaluate viral inactivation by the spray-drying process used in the production of spray-dried animal plasma (SDAP). In Exp. 1, bovine plasma was inoculated with pseudorabies virus (PRV) grown in PK 15 cells. Three 4-L batches were spray-dried in the same manner and conditions of industrial SDAP production but with laboratory spray-drying equipment. Presence of infectivity was determined before and after spray-drying by microtiter assay in PK 15 cell cultures. Before spray-drying, all three samples contained 10(5.3) tissue culture infectious dose50 (TCID50)/mL of PRV. After four consecutive passages, no viable virus was detected in samples of spray-dried bovine plasma. In Exp. 2, bovine plasma was inoculated with porcine respiratory and reproductive syndrome (PRRS) virus propagated previously in MARC cell culture to provide approximately 10(6.3) TCID50/mL. Three 4-L batches were spray-dried in the same manner as Exp. 1. Before spray-drying, samples contained TCID50 of 10(4.0), 10(3.5), and 10(3.5)/mL, respectively. After four consecutive passages in MARC cell cultures, no viable virus was detected in spray-dried bovine plasma. In Exp. 3, 36 weaned piglets (28 d of age) were fed a common diet for 14 d and were determined to be negative for PRV, PRRS, and porcine parvovirus titer. Afterwards, pigs were allotted to six pens with six pigs per pen and fed diets containing either 0 or 8% SDAP (as-fed basis) for 63 d. The SDAP used in the feed contained antibody (titer 1:400) against porcine parvovirus. Blood samples were collected from pigs on d 0 and 63 to determine whether feeding SDAP caused seroconversion and development of antibodies against parvovirus, PRRS, or PRV. Inclusion of SDAP in the diet improved growth of pigs without seroconversion. Spray-drying conditions used in this study were effective in eliminating viable pseudorabies and PRRS viruses from bovine plasma. In this study, feeding SDAP that contained functional antibodies did not promote seroconversion in naïve animals.

Evolution of ORF5 of Spanish porcine reproductive and respiratory syndrome virus strains from 1991 to 2005

ORF5 sequences of porcine reproductive and respiratory syndrome virus (PRRSV) were analysed to determine genetic diversity, codon usage, positive and negative selection sites and potential changes in the predicted glycoprotein 5 (GP5). A hypothetical GP5 containing all selected sites was constructed to determine its characteristics. These sequences corresponded to isolates obtained 10 years apart (1991–1995, 18 strains) and a second set (n = 46) from 2000 to 2005. Similarity to Lelystad virus (LV) decreased from 95.5% in 1991–1995 to 89.5% in 2000–2005. Three highly variable regions were found in ORF5. Codon usage was different in both sets for leucine, glutamine, serine and proline. Thus, 2000–2005 sequences used codons more similar to those present in highly expressed pig genes compared to the 1991–1995 set. Twenty four sites of positive selection and 20 sites of negative selection were found in GP5, most of them in transmembrane regions. Additional glycosylation in N37 of GP5 was common in 2000–2005 but some sequences lack a glycosylation site in N46. The hypothetical GP5 was only 88.1% similar to LV and was less hydrophobic. Taking together these results suggest that PRRSV is still adapting to pig cells.

Immune responses of pigs after experimental infection with a European strain of Porcine reproductive and respiratory syndrome virus

The purpose of this experiment was to study the immune response of pigs during an experimental infection with a European strain of Porcine reproductive and respiratory syndrome virus (PRRSV). Five pigs were challenged intranasally with PRRSV strain VP21 and another five were kept as controls. Clinical course and humoral and cell-mediated responses were monitored for 70 days post-infection (p.i.). Infected pigs developed mild signs at 24 h p.i. Viraemia was detectable by nested RT-PCR until day 14 p.i. Earliest seroconversions (ELISA) were seen by day 7 p.i. (three of five animals) and, by day 14, all inoculated pigs had seroconverted (ELISA and immunoperoxidase monolayer assay). Virus-neutralizing antibodies were undetectable until day 56 p.i. and, by day 70 p.i., two inoculated pigs still were negative. Flow-cytometry assays using peripheral blood mononuclear cells (PBMC) showed an upshift in CD8+ cells (day 7 p.i.) and a downshift of CD21+ cells (days 7 and 28 p.i.). Regarding cell-mediated responses, development of PRRSV-specific gamma interferon-secreting cells (IFN-γ-SC) and interleukin 4-secreting cells (IL4-SC) in PBMC was examined by ELISPOT assay. IFN-γ-SC were not detected significantly until day 14 p.i., whereas, for IL4-SC, no differences between groups were seen. Concurrently with the onset of viraemia and the development of clinical signs, serum haptoglobin levels and interleukin 10 (IL10) in PRRSV-stimulated PBMC-culture supernatants increased significantly. These differences disappeared later on. For IL2, IL4, IL8 or transforming growth factor beta, no differences were seen among groups. These results are compatible with a model in which the immune response does not fully control the outcome of the infection.

Retrospective study on porcine circovirus type 2 infection in pigs from 1985 to 1997 in Spain

A retrospective survey was performed to detect lesions of Postweaning multisystemic wasting syndrome (PMWS) and nucleic acid of porcine circovirus type 2 (PCV2) in archived formalin-fixed, paraffin-embedded tissues from 189 pigs, and antibodies to this virus in sera of 388 pigs from the Spanish livestock between the years 1985 and 1997. PCV2 nucleic acid was detected by in situ hybridization (ISH) in tissues from 78 of 189 (41.3%) examined pigs. Variable amount of viral genome was detected in association with slight to severe microscopic lymphoid lesions consisting of lymphocyte depletion and histiocytic infiltration. The first positive case of PMWS with typical lesions and ISH positive corresponded to a pig necropsied in 1986. Two hundred and eighty-two of 388 (72.7%) sera were positive by immunoperoxidase monolayer assay. Serological and pathological data of the present study indicate that PCV2 was a enzootic infection in Spain since 1985, suggesting that the introduction of this virus in the livestock occurred previously.

Changes in peripheral blood leukocyte populations in pigs with natural postweaning multisystemic wasting syndrome (PMWS)

The objective of the present study was to analyze, by flow cytometry, changes in PBMC subsets in pigs having postweaning multisystemic wasting syndrome (PMWS), a new condition associated to porcine circovirus type 2 (PCV2) infection. Thirteen acutely PMWS affected pigs were selected from a farm seronegative to porcine reproductive and respiratory syndrome virus (PRRSV) and to Aujeszky's disease virus (ADV); 11 clinically healthy pigs were selected from a high health farm with no history of PMWS and free of the major swine pathogens, and used as a control group. All pigs were necropsied, and tissue samples were fixed in formalin; blood with EDTA anticoagulant was used to perform the flow cytometric analysis. PBMC were incubated with mAb against porcine CD3, CD4, CD8, CD25, CD45, IgM, SWC3, and SLA-Class II. Flow cytometric analysis showed substantial changes in leukocyte subsets in the peripheral blood of PMWS-affected pigs, which were characterized by an increase of monocytes, a reduction of T (mainly CD4(+)) and B-lymphocytes, and the presence of low-density immature granulocytes. Altogether, these changes would suggest an inability of acutely PMWS-affected pigs to mount an effective immune response.

Study of the persistence of Aujeszky's disease (pseudorabies) virus in peripheral blood mononuclear cells and tissues of experimentally infected pigs

The presence of Aujeszky's disease virus (ADV) in peripheral blood mononuclear cells (PBMC) and tissues of experimentally infected pigs was studied. Vaccinated and unvaccinated pigs were inoculated with different doses of Aujeszky's disease NIA-3 strain. Pigs were periodically bled and PBMC were used for virus isolation and PCR detection of virus. Tissues were obtained at the time of death (8 weeks post-inoculation) and used for ADV genome detection by PCR. ADV genome was amplified from PBMC during the acute phase of infection and, in some experimental groups, up to 38 days post-inoculation (PI). The virus was sporadically detected by virus isolation performed from PBMC. In neural tissues, ADV was constantly amplified from the trigeminal ganglia and the olfactory bulb of persistently infected pigs (euthanized 8 weeks PI). In other tissues, the viral genome was rarely detected in lymph nodes and tonsils, and occasionally, in the bone marrow. Our results indicated that PBMC are not an appropriate source for detecting ADV persistence, since inconsistent results were obtained throughout the experiments. In neural tissues, the olfactory bulb turned out to be as important a target for ADV persistence as the trigeminal ganglia. Viral genome detection in the bone marrow indicated that this tissue may play a role in the establishment of a persistent infection.

Aujeszky's disease (pseudorabies) virus detection in cerebrospinal fluid in experimentally infected pigs

The presence of Aujeszky's disease virus in cerebrospinal fluid of experimentally infected pigs was studied using the techniques of virus isolation and PCR. Pigs, some of which were previously vaccinated against Aujeszky's disease, were inoculated with different doses of the Aujeszky's disease NIA-3 strain. At the time of death or sacrifice, a sample of cerebrospinal fluid was taken and tested for the presence of virus using the mentioned techniques. Virus was isolated only from one sample, while it was detected by PCR in most of them. The higher sensitivity of the PCR technique and the possible presence of antiviral antibodies in the cerebrospinal fluid are reasons that can be argued to explain this fact. By PCR, the virus was detected more efficiently when digested cerebrospinal fluid cells were used as DNA source than when using whole cerebrospinal fluid, suggesting that the virus could be cell-associated. Aujeszky's disease virus could not be detected by PCR in pigs which survived the acute phase of the infection and were euthanased at 8 weeks post-inoculation, when they were latently infected. This indicated that the cerebrospinal fluid is not an adequate sample for the diagnosis of latency. Since Aujeszky's disease virus was detected from most of the tested samples, we believe that this could be an adequate procedure for the quick diagnosis of Aujeszky's disease.

Bilateral encephalomalacia in a pig related to latent Aujeszky's disease virus infection

A case of bilateral encephalomalacia in a pig related to latent Aujeszky's disease virus infection is reported. The pig was experimentally inoculated with the NIA-3 strain and survived the infection after showing intense central nervous system disease. Abnormal behaviour was observed up to the date of death. The pig was demonstrated to be latently infected with the virus by polymerase chain reaction (PCR). The main microscopic lesion was a bilateral encephalomalacia which involved structures related to the limbic system. A complete description of lesions observed and their relation to abnormalities shown by the pig are exposed.

Porcine epidemic abortion and respiratory syndrome (mystery swine disease). Isolation in Spain of the causative agent and experimental reproduction of the disease

In March of 1991, a disease that affected pregnant sows and caused a high mortality in unweaned piglets was detected in Spain. Based on the clinical signs observed, mystery swine disease, which had been described recently in Germany, Holland and Belgium, was suspected. From the samples obtained from the affected farm, a filtrable agent (0.22 micron) was isolated on cell culture. It produced cytopathic effects, its replication was intracytoplasmic, it was sensitive to chloroform, and cross-reacted with a Lelystad reference serum. When inoculated into pregnant sows, the agent produced inappetence for 2-4 days, without hyperthermia. One of the sows aborted at 100 days of gestation; the two others had delayed parturitions (days 115 and 116). There was a mixture of healthy piglets, mummified fetuses, stillbirths and weak piglets. Microscopic examination of the lungs of healthy piglets killed at 8 and 12 days of life revealed the presence of interstitial pneumonia. The sera from the three sows at 39 days after infection cross-reacted with the Lelystad virus (titres > or = 1/640), whereas pre-inoculation sera did not recognize it (titres < or = 1/10). This is the first report from Spain of the isolation of an agent (antigenically related to the Lelystad virus), capable of reproducing the disease previously designated as mystery swine disease.