Comparison of Porcine circovirus type 2 (PCV2) infection in light and heavy pigs of market age on farms with routine PCV2 vaccination

Commercial vaccines against Porcine circovirus type 2 (PCV2) are widely used on swine farms. Marked body weight variation at marketing age is a problem on conventional pig farms using all-in/all-out barn management. The aim of this study was to investigate whether PCV2 infection could be a factor influencing body weight variation. Seven conventional farms that routinely used PCV2 vaccination were selected, and 60 serum samples from light and heavy pigs at each site were tested for PCV2 antibody titers and viremia. At 3 farms the mean antibody titer, proportion of viremic pigs, and virus load differed significantly between the light and heavy groups. These preliminary results suggest that PCV2 infection may be a factor contributing to weight variation in vaccinated market-age hogs.     

Effect of vitamin supplements on some aspects of performance, vitamin status, and semen quality in boars

The aim of the present study was to determine the effects of dietary supplements of vitamins on vitamin status, libido, and semen characteristics in young boars under normal and intensive semen collection. Sixty Landrace, Yorkshire, and Duroc boars were allocated randomly from 6 to 10 mo of age to one of the following diets: 1) basal diet (industry level) for minerals and vitamins (Control, n = 15); 2) basal diet supplemented with vitamin C (ASC, n = 15); 3) basal diet supplemented with fat-soluble vitamins (FSV, n = 15); and 4) basal diet supplemented with water-soluble vitamins (WSV, n = 15). After puberty (approximately 12 mo of age), semen was collected at a regular frequency (three times every 2 wk) for 5 wk. Thereafter, all boars were intensively collected (daily during 2 wk). A recovery period (semen collection three times every 2 wk) followed and lasted for 10 wk. Sperm quality (percentage of motile cells and percentage of morphologically normal cells) and quantity (sperm concentration, semen volume, and total sperm number) were recorded as well as direct and hormone related measurements of boar libido. Blood and seminal plasma samples were taken to monitor vitamin status. High concentrations of B6 (P < 0.05) and folic acid (P < 0.05) were observed in the blood plasma of WSV boars, whereas greater concentrations of vitamin E (P < 0.01) were obtained in FSV boars. In the seminal plasma, folic acid concentrations tended to be greater in WSV boars (P < 0.08). During the intensive collection period, there was a tendency (P < 0.06) for semen production to be greater in WSV boars, the effect being less pronounced (P < 0.10) in FSV boars. During the recovery period, the percentage of motile sperm cells was greater in WSV boars (P < 0.03) and, to a lesser extent, in FSV boars (P < 0.10) compared with Control boars. Sperm morphology and libido were not affected by treatments. These results indicate that the transfer of vitamins from blood to seminal plasma is limited and the dietary supplements of water-soluble and fat-soluble vitamins may increase semen production during intensive semen collection.     

Antibody Response in Calves Following Administration of Attenuated Infectious Bovine Rhinotracheitis (IBR) Vaccines

The serum antibody response of calves vaccinated against infectious bovine rhinotracheitis by the intramuscular route was compared to calves vaccinated subcutaneously. Immunological response in the calves as determined by serum neutralization tests was highly variable; however, a significantly greater percentage (87.5%) of the calves inoculated subcutaneously responded to vaccination by producing a four-week post-vaccinal serum titer of two or higher as compared to only 47.8% of the calves that were vaccinated intramuscularly. Of those calves that were vaccinated a second time, all maintained or had produced titers of two or higher within four weeks after the second immunization. However, the existing circulating serum antibody titers resulting from the first vaccination of nine of 22 calves were lowered by repeat vaccination.     

Semen characteristics and libido in boars treated repeatedly with PGF2alpha

The objective was to determine the effects of repeated injections of PGF2alpha (Lutalyse; Pfizer) on semen and libido characteristics in terminal-line boars. Semen was collected once weekly from wk 0 to 15 and on four consecutive days during wk 16. Boars received an i.m. injection of 10 mg of PGF2alpha (n = 11) or 2 mL of vehicle (n = 11) immediately before entering the collection room. For the weekly collections, semen volume (220.3 +/- 3.2 mL; mean +/- SE), gel weight (38.7 +/- 0.7 g), total sperm cells (65.4 +/- 1.2 billion), motile sperm cells (67.4 +/- 0.6 %), and sperm velocity (125.9 +/- 1.2 microm/s), were affected by time (P < 0.01) but not by treatment (P > 0.10). Sperm concentration (0.31 +/- 0.01 billion/mL) was not affected (P > 0.10) by time or treatment. The percentage of morphologically normal sperm cells, assessed at wk 16, did not differ (P = 0.39) between groups (80.8 +/- 1.0). Libido was evaluated from wk 0 to 16. There were no effects of treatment or time (P > 0.10) on the period from injection to the start of ejaculation (225.6 +/- 9.1 s). Duration of ejaculation was affected by treatment (P < 0.01; 472.0 +/- 43.1 s and 280.4 +/- 43.1 s, for PGF2alpha-treated and control boars, respectively) and time (P < 0.01). During the intensive collection period (wk 16), semen volume (200.1 +/- 7.1 mL), gel weight (39.2 +/- 1.5 g), sperm concentration (0.19 +/- 0.01 billion/ mL), total sperm cells (39.5 +/- 3.6 billion), motile sperm cells (65.6 +/- 2.2%), and sperm velocity (117.8 +/- 3.7 microm/ s) were affected by time (P < 0.10) but not by treatment (P > 0.10). The period from injection to the start of ejaculation tended to decrease (by 44%) during the intensive collection period in PGF2alpha-treated boars, but not in controls (treatment x time, P = 0.07). Regardless, the period from injection to the start of ejaculation did not differ (P = 0.63) between groups on d 4 of the intensive collection period. Duration of ejaculation was affected by treatment (P < 0.01; 459.1 +/- 24.1 s for PGF22alpha-treated boars vs. 303.1 +/- 24.1 s for controls) but not by time (P > 0.10). Overall, there were no exceptional positive or negative effects of long-term treatment with PGF2alpha on semen characteristics and libido in boars.     

Assessing PCV2 antibodies in field pigs vaccinated with different porcine circovirus 2 vaccines using two commercial ELISA systems

Porcine circovirus type 2 (PCV2) is the primary causative agent for post-weaning, multisystemic, wasting syndrome. Consequently, serologic detection of and vaccination against PCV2 are important for the swine industry. Among several serological tests, the enzyme-linked immunosorbent assay (ELISA) is commonly used to measure anti-PCV2 antibody levels. In the present study, we used two commercial ELISA systems to comparatively evaluate anti-PCV2 antibodies in field pigs treated with three different PCV2 vaccines. Among a total of 517 serum samples, the results of the two ELISAs were fully concordant for 365 positive and 42 negative samples, indicating 78.7% agreement. In addition, the Pearson coefficient (0.636) indicated a moderate correlation between data from the two ELISAs. Results from the farms with pigs vaccinated with the three different PCV2 vaccines demonstrated that most of the vaccinated animals underwent seroconversion. However, the increase and duration of antibody titers varied depending on the vaccine, the presence of maternal antibodies, and the vaccination program. PCV2 serologic status and anti-PCV2 antibody levels of herds from this study could be utilized to determine the best timing for vaccination and assessing vaccination compliance.     

Nested polymerase chain reaction detection and duration of porcine circovirus type 2 in semen with sperm morphological analysis from naturally infected boars.

A nested polymerase chain reaction (nPCR) protocol was applied to porcine semen to demonstrate the porcine circovirus type 2 (PCV2) shedding patterns and duration in naturally infected boars. Sperm morphology analysis was performed on a subset of samples to determine if the presence of PCV2 DNA in semen was associated with reduced semen quality. Semen was collected serially from 43 boars representing 6 breeds, aged 33.9 to 149.3 weeks. Of the 903 semen samples collected, 30 samples (3.3%) were positive for PCV2 DNA by nPCR from 13 boars. Boars shedding PCV2 DNA in semen ranged between 35.9 and 71.0 weeks of age, and shedding occurred during a period of up to 27.3 weeks. A semen nPCR test was 2.6 times more likely to be positive when collected from pigs that were < or =52 weeks of age, and 3.0 times more likely to be positive when collected from pigs that were < or =26 weeks from time of entry into the stud main unit (generalized estimating equations: P = 0.02; 95% confidence interval [CI] of the odds ratio 1.2 to 5.5, and P = 0.01; 95% CI of the odds ratio 1.3 to 6.9, respectively). These results demonstrate a sporadic and long-term shedding pattern of PCV2 DNA in semen from naturally infected boars. PCV2 DNA in semen does not appear to have detrimental effects on sperm morphology; however, boar age and, possibly, breed may contribute to the persistence of PCV2-shedding in semen.     

The effect of age on serum antibody titers after rabies and influenza vaccination in healthy horses

BACKGROUND: The proportion of geriatric horses within the equine population has increased in the past decade, but there is limited information on the immune function of these animals. HYPOTHESIS: Aged horses will have a lesser increase in serum antibody response to vaccination. ANIMALS: Thirty-four aged healthy horses (> or = 20 years) and 29 younger adult horses (4-12 years) of various breeds. METHODS: All horses were vaccinated with vaccines of killed rabies and influenza virus. Horses in each age group were allocated to receive either rabies or influenza booster vaccine 4 weeks after the initial vaccination. Serum samples were taken at 0, 4, 8, and 24 weeks. Rabies serum neutralization titers and equine influenza virus specific antibody sub-isotypes (IgGa, IgGb, IgG(T), and IgA) as well as single radial hemolysis (SRH) titers were determined. RESULTS: Rabies antibody titers were similar in the 2 age groups at all sampling times. Aged horses had higher IgGa and IgGb influenza antibody titers before vaccination than younger horses but similar titers after vaccination (P= .004 and P= .0027, respectively). Younger horses had significantly greater increases in titer than aged horses at all sampling times for IgGa (P= .001) and at 8 and 24 weeks for IgGb (P= .041 and .01, respectively). There was no detectable serum IgG(T) at any time point. A significant booster vaccine effect was seen for both antirabies and anti-influenza titers. Anti-influenza titer before vaccination also had a significant effect on subsequent antibody response. CONCLUSIONS AND CLINICAL IMPORTANCE: Healthy aged horses generated a primary immune response to a killed rabies vaccine similar to that of younger adult horses. Aged horses had a significantly reduced anamnestic response to influenza vaccine.     

Effect of vaccination with live or killed Pasteurella haemolytica on resistance to experimental bovine pneumonic pasteurellosis

Using 6- to 8-month-old beef calves, 3 experiments were conducted to compare the effect of vaccination with live or killed Pasteurella haemolytica on resistance to a transthoracic challenge exposure with the organism and to correlate serum antibody response with resistance. In each experiment, calves were vaccinated twice at 1-week intervals and were challenge exposed 21 days after the first inoculation. Lung lesions were evaluated by a system, such that higher scores indicated the more severe lesions. In each experiment, calves immunized with live P haemolytica had lower lesion scores than calves vaccinated with saline solution or bacterin. In 2 of the experiments, the differences were significant (P less than 0.05). In all experiments, calves vaccinated parenterally with a commercial P haemolytica/P multocida bacterin or with a formalin-killed P haemolytica bacterin had lesion scores that were not significantly different (P greater than 0.05) than for control calves vaccinated with saline solution. Live and killed bacterial preparations induced a significant serum antibody response to P haemolytica as measured by a quantitative fluorometric immunoassay. The antibody response to vaccination was not affected by preexisting titers to P haemolytica. Serum antibody titers were not consistently as high for calves vaccinated with bacterins as for calves vaccinated with live organisms. Although high antibody titers correlated with low lesion scores when calves vaccinated with saline solution or live organisms were analyzed collectively, there was not a significant correlation between the 2 variables when calves, vaccinated with saline solution or with bacterin, were analyzed collectively. These data indicate that, although bacterins may induce a detectable serum antibody response, they do not induce protection against transthoracic challenge exposure to P haemolytica.     

Vaccination of llamas, Llama glama, with an experimental killed encephalomyocarditis virus vaccine

Encephalomyocarditis virus (EMCV) is a pandemic virus that has caused mortality in numerous captive wildlife species worldwide. An experimental killed vaccine was created from two EMCV isolates associated with zoo animal mortality in the southern United States. The vaccine was tested for safety and efficacy in eleven llamas (Llama glama). All animals received an initial vaccination and a second booster vaccination 4 wk later. Serum antibody responses were monitored at initial vaccination and at 4 wks, 8 wk, 6 mo, and 12 mo postvaccination. Eight of the 11 llamas vaccinated experienced at least a 4-fold increase in serum antibody titers to EMCV. Antibody titers of those eight animals remained elevated above prevaccination levels when measured at 12 mo. The experimental killed EMCV vaccine tested may be a useful tool to prevent EMCV infection in llamas when given in 2 doses 4 wk apart, and then revaccinated or with antibody levels monitored annually thereafter.     

Assessment of serum antibody titers against canine distemper virus, canine adenovirus type II, and canine parvovirus in Alaskan sled dogs before and after a long-distance race

OBJECTIVE: To determine serum antibody titers against canine distemper virus (CDV), canine adenovirus type II (CAV-2), and canine parvovirus (CPV) in trained sled dogs prior to and after completion of a long-distance race. DESIGN: Prospective cohort study. ANIMALS: 195 Alaskan sled dogs (from 18 kennels) that participated in the 2006 Iditarod Trail Race. PROCEDURES: All 1,323 dogs participating in the race had been vaccinated against the 3 viruses at 19 to 286 days prior to initial blood sample collection (obtained within the month preceding the race). Within 12 hours of race completion, blood samples were collected from 195 dogs (convenience sample) and matched with each dog's prerace sample. Serum antibody titers (90% confidence intervals [CIs]) were determined via serum neutralization assays. RESULTS: After racing, geometric mean titers against CDV and CPV were significantly higher (2,495 [90% CI, 321 to 16,384] and 6,323 [90% CI, 512 to 32,768], respectively) than prerace values (82 [90% CI, 11 to 362] and 166 [90% CI, 32 to 1,024], respectively). Sixty-one of 194 (31.4%) dogs had > or = 4-fold increases in anti-CPV antibody titers after racing. Prerace serum antibody titers against CDV, CPV, and CAV-2 varied significantly by sled team but were not associated with time since vaccination. CONCLUSIONS AND CLINICAL RELEVANCE: Postrace increases in serum anti-CDV and anti-CPV antibody titer might reflect exposure of dogs to these agents immediately before or during racing. Dogs had no clinical signs of CDV-, CAV-2-, or CPV-associated disease; therefore, the clinical importance of these titer changes is uncertain.     

Vaccination against the avian infectious bronchitis virus affects sperm concentration, sperm quality and blood testosterone concentrations in cockerels

1. It was previously found that cockerels vaccinated with live attenuated avian infectious bronchitis virus (AIBV) have decreased serum testosterone concentrations, epididymal stones and reduced fertility. The objectives of this study were twofold: to determine if reduced fertility following vaccination with live attenuated virus was the result of reduced sperm concentration or reduced sperm quality and to determine if vaccination with a killed strain of virus caused a similar reduction in sperm function in vivo. 2. Specific-pathogen-free Single Comb White Leghorn cockerels were divided into three treatment groups: no vaccination (NONVAC), vaccination with killed AIBV virus (KVAC) or vaccination with live attenuated AIBV virus (LVAC). Semen was collected daily from 17 to 27 weeks of age, and semen quality was assessed frequently by analysing sperm concentration, viability, motility, and ability to reach and interact with the ovum in vivo. Blood plasma was assayed for testosterone concentration. 3. Differences in sperm analysis among treatment groups were limited. Sperm viability was increased in NONVAC during week 20 which then decreased in week 22 when compared to vaccinated cockerels. Acrosome damage was increased in vaccinated cockerels in week 22, and decreased in weeks 25 and 27 when compared to controls, which correlate to the period of epididymal stone development. Plasma testosterone concentrations and sperm concentrations among treatment groups were different only at 16 and 19 weeks of age, respectively. There were no differences across treatment groups in sperm mobility through Accudenz or in numbers of sperm holes in perivitelline membranes of eggs following insemination with semen from 27-week-old cockerels. No differences were observed in viability or acrosome integrity between cockerels with and without epididymal stones within treatment groups. 4. In conclusion, pre-pubertal vaccination against AIBV and subsequent epididymal stone formation had a limited effect on sperm concentration, sperm quality and plasma testosterone concentrations. Vaccination with killed AIBV vaccine did not diminish effects on sperm function in vivo.     

Effects of dietary supplementation with an organic source of selenium on characteristics of semen quality and in vitro fertility in boars

Semen characteristics in boars fed organic or inorganic sources of Se were assessed in 3 experiments. Crossbred boars were randomly assigned at weaning to 1 of 3 dietary treatments: I) basal diets with no supplemental Se (control), II) basal diets with 0.3 mg/kg of supplemental Se from an organic source (Sel-Plex, Alltech Inc., Nicholasville, KY), and III) basal diets supplemented with 0.3 mg/kg of supplemental Se from sodium selenite (Premium Selenium 270, North American Nutrition Co. Inc., Lewisburg, OH). For Exp. 1, semen was collected from boars (n = 10/dietary treatment) on 5 consecutive days at 15 mo of age. Effects of treatment × day were detected for the proportions of progressively motile (P = 0.02) and rapidly moving (P = 0.03) spermatozoa, and measures of sperm velocity, including path velocity of the smoothed cell path (P = 0.05) and average velocity measured in a straight line from the beginning to the end of the track (P = 0.05). Negative effects of day of semen collection on sperm motility were least pronounced in boars fed Sel-Plex. Experiment 2 was conducted when boars were 17 mo of age, and semen was collected (n = 10 boars/dietary treatment), diluted in commercially available extenders, and stored at 18°C for 9 d. Effects of treatment × day were detected for percentages of motile (P = 0.01) and static (P = 0.01) spermatozoa, amplitude of lateral head displacement (P = 0.02), frequency with which the sperm track crossed the sperm path (P = 0.04), straightness (P = 0.01), and average size of all sperm heads (P = 0.03). In general, sperm cells from boars fed Sel-Plex were better able to maintain motility during liquid storage compared with boars fed sodium selenite. For Exp. 3, semen was collected from boars (n = 6/dietary treatment) at 23 mo of age, and spermatozoa were evaluated at d 1 and 8 after semen collection using in vitro fertilization procedures. There was a tendency for an effect (P = 0.11) of dietary treatment on fertilization rate with Sel-Plex-fed boars having the greatest value (70.7%). The results of this study suggest that there are positive effects of dietary supplementation with Sel-Plex on boar semen characteristics and that organic Se supplementation may help ameliorate the negative effects of semen storage on characteristics of sperm motility.     

Immune potency of lyophilized, killed vaccine for equine viral arteritis and its protection against abortion in pregnant mares

Immune potency test was conducted in horses by inoculating a killed vaccine for equine viral arteritis (EVA) which had been freeze-dried and contained aluminum hydroxide adjuvant. Serum neutralizing (SN) antibody to equine arteritis virus (EAV) was detected at maximal titers of 1:80 to 1:640, 1 to 2 weeks after 2-dose vaccination of 6 female horses. However, 6 pregnant mares inoculated with the vaccine which had been kept in storage for 1 year at 4°C produced much higher titers ranging from 1:320 to 1:1280. A maximal mean titer of 1:199.5 occurred in the 1st and 2nd week after 2-dose inoculation with the nonpreserved vaccine, whereas a maximal mean titer of 1:794.3 occurred in the 2nd week using the preserved vaccine. The horses showed no systemic or local adverse reactions clinically or hematologically after vaccination. Four of the 6 vaccinated pregnant mares were exposed to the Bucyrus strain of EAV but resisted challenge exposure, while 3 nonvaccinated control pregnant mares revealed acute EVA causing abortion and death. Isolation of EAV was positive from the body tissues of the aborted and dead fetuses and their dams, but was negative from the vaccinated mares. No significant rise of SN antibody titers was detected in the vaccinated mares following challenge exposure, suggesting that the vaccine can protect against EAV infection in pregnant mares and prevent abortion or death.     

Effects of gastrointestinal parasites on parasite burden, rectal temperature, and antibody titer responses to vaccination and infectious bovine rhinotracheitis virus challenge

Thirty-three colostrum-deprived Holstein bull calves (initial BW of 131 ± 4 kg) were used to determine the effect of timing of anthelmintic administration relative to vaccination on antibody titer response to vaccine component antigens. When calves were at least 3 mo of age, they were sorted randomly into individual pens and assigned to 1 of 3 treatment groups, treatments consisted of 1) dewormed 2 wk before vaccination (DPV), 2) dewormed at the time of vaccination (DV), or 3) control, vaccinated but not dewormed (CONT). All calves were inoculated with infective larvae of brown stomach worms (Ostertagia ostertagi) and intestinal worms (Cooperia spp.) on d 1, 7, 10, 14, and 18 for a total dose of 235,710 infective larvae per calf. Calves (DPV and DV) were dewormed on d 21 or 35 with a 10% fenbendazole suspension at 5 mg/kg of BW. On d 35, all calves were vaccinated with a modified-live virus respiratory vaccine containing IBRV (infectious bovine rhinotracheitis virus), BVDV-1 (bovine viral diarrhea virus genotype 1), BVDV-2 (BVDV genotype 2), PI-3 (parainfluenza-3), and BRSV (bovine respiratory syncytial virus). During the 103-d experiment, weekly fecal egg counts, blood, and rectal temperatures were collected and health status was recorded daily. Blood samples were obtained weekly to determine serum neutralizing (SN) antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 and cytokine levels for IL-4, IL-6, TNF-α (tumor necrosis factor-α), and IFN-γ (interferon-gamma). There was a tendency (P < 0.09) for CONT calves to have greater IL-4 concentrations. By design, control calves had greater (P < 0.01) fecal egg counts during the experiment. All calves developed antibody titers to IBRV, BVDV-1, BVDV-2, and PI-3 by d 15 postvaccination. On d 88, all calves were challenged with IBRV and blood samples were obtained on d 88, 89, 90, 93, 95, 98, 99, and 103. All calves had increased rectal temperatures during the final 7 d of the IBRV challenge. However, the CONT group had greater (P < 0.01) rectal temperatures on each sampling day except d 90 compared with the DPV and DV treatments. Therefore, deworming before or at vaccination reduced parasite burden and decreased rectal temperature increase after an IBRV challenge. Deworming strategy had no effect on antibody response to vaccination or IBRV challenge.     

Response of broiler chickens to fowl cholera vaccination at 1 to 6 weeks of age.

Broiler chickens, in groups of 10, received a single vaccination by the stick-wing route at 1, 2, 3, 4, 5, 6, or 11 weeks of age with live Clemson University strain of Pasteurella multocida. Twenty non-vaccinates kept in isolation served as controls. Cholera serum antibody titers in all chickens were determined by enzyme-linked immunosorbent assay at weekly intervals. Chickens vaccinated once at 1, 2, 3, 4, 5, and 6 weeks, respectively, attained 25.2%, 28.7%, 34.7%, 46.2%, 51.8%, and 64.6% of the titers of those vaccinated once at 11 weeks of age. Variation in antibody response was greatest in chickens vaccinated at 1 or 2 weeks of age. Additionally, chickens vaccinated at 1 or 2 weeks of age showed the longest response time (5 weeks) to reach maximum antibody titers after a single vaccination. When the original vaccinates were revaccinated at 11 weeks of age, all showed a secondary response equal to or greater than that seen in chickens vaccinated once at 11 weeks of age. Age of the chickens at the time of vaccination and antibody titer were positively correlated (r = 0.997). Overall antibody responses to vaccination were higher and much more uniform as birds increased in age.     

Vaccination of neonatal colostrum-deprived calves against Pasteurella haemolytica A1.

Colostrum-deprived Holstein calves were vaccinated at 2 and 4 wk of age with a Pasteurella haemolytica A1 culture supernatant vaccine to determine whether active immune responses and protection could be induced in this age group in the absence of maternal antibodies. All calves responded to vaccination with high titers of IgM antibodies to capsular polysaccharide within 1 wk of primary vaccination. Mean titers of IgG1 and IgG2 antibodies to this antigen increased significantly by 2 wk after secondary vaccination, but peak antibody titers were low. All of the vaccinated calves seroconverted with production of leukotoxin-neutralizing antibodies, but peak antibody titers were low. Vaccinated calves experienced considerable lung damage after experimental challenge, but survival rate, clinical scores, and percent lung involvement were significantly better than those of control (placebo-injected) calves.     

Efficacy of swine influenza A virus vaccines against an H3N2 virus variant

We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.     

A field evaluation of mortality rate and growth performance in pigs vaccinated against porcine circovirus type 2

OBJECTIVE: To evaluate, under field conditions, the effects of a commercial porcine circovirus type 2 (PCV2) vaccine on mortality rate and growth performance in a herd infected with PCV2 that had a history of porcine circovirus disease. DESIGN: Randomized controlled clinical trial. ANIMALS: 485 commercial, cross-bred, growing pigs. PROCEDURES: Prior to weaning, pigs were randomly assigned within litter to a vaccination or unvaccinated control group. Pigs in the vaccination group were given a commercial PCV2 vaccine at weaning and 3 weeks later. Mortality rate was recorded, and pigs were weighed prior to vaccination, when moved from the nursery, and prior to marketing. Infection status was assessed by serologic testing and detection of viral DNA in serum. RESULTS: Compared with control pigs, pigs vaccinated against PCV2 had a significantly lower mortality rate during the finishing phase, significantly higher average daily gain during the finishing phase, and significantly lower likelihood of being lightweight at the time of marketing. For vaccinated pigs, overall mortality rate was reduced by 50% and average daily gain during the finishing period was increased by 9.3%. At the time of marketing, vaccinated pigs weighed an average of 8.8 kg (19.4 lb) more than control pigs, without any difference in days to marketing. Serum PCV2 antibody titers increased in control pigs, and PCV2 DNA was detected, indicating active PCV2 infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that vaccination against PCV2 was effective at reducing mortality rate and improving growth performance among pigs in a herd infected with PCV2.     

Intraocular vaccination with an inactivated highly pathogenic avian influenza virus induces protective antibody responses in chickens

Because it is expected to induce cross-reactive serum and mucosal antibody responses, mucosal vaccination against highly pathogenic avian influenza (HPAI) is potentially superior to conventional parenteral vaccination. Here, we tested whether intraocular vaccination with an inactivated AI virus induced protective antibody responses in chickens. Chickens were inoculated intraocularly twice with 10⁴ hemagglutination units of an inactivated H5N1 HPAI virus. Four weeks after the second vaccination, the chickens were challenged with a lethal dose of the homologous H5N1 HPAI virus. Results showed that most of the vaccinated chickens mounted positive antibody responses. The median serum hemagglutination inhibition titer was 1:80. Addition of CpG oligodeoxynucleotide 2006 or cholera toxin to the vaccine did not enhance serum antibody titers. Cross-reactive anti-hemagglutinin IgG, but not IgA, was detected in oropharyngeal secretions. In accordance with these antibody results, most vaccinated chickens survived a lethal challenge with the H5N1 HPAI virus and did not shed the challenge virus in respiratory or digestive tract secretions. Our results show that intraocular vaccination with an inactivated AI virus induces not only systemic but also mucosal antibody responses and confers protection against HPAI in chickens.     

猪圆环病毒2型感染对猪繁殖与呼吸综合征灭活疫苗体液免疫的影响

本试验采用ELISA方法对单独接种猪繁殖与呼吸综合征病毒(PRRSV)变异株灭活苗组(HP组,n=3)和PCV2感染且出现病毒血症后接种PRRSV变异株灭活苗组(PCV2/HP组,n=3)不同时相血清中的PRRSV抗体进行检测;并对HP和PCV2/HP组血清中PCV2特异的抗体和核酸分别进行ELISA和荧光定量PCR检测。结果表明,在首免后70 d HP组血清平均抗体效价极显著高于PCV2/HP组(P<0.01);首免后56、63和77 d HP组平均抗体效价明显高于PCV2/HP组。其中在首免后56和63 d HP组抗体阳性率均达67%(2/3),PCV2/HP组在相应时相抗体阳性率为0;在首免后70和77 d HP组抗体阳性率均达100%(3/3),PCV2/HP组在相应时相抗体阳性率仅为0和33%(1/3)。结果提示PCV2感染可在一定程度上抑制PRRSV变异株(JXA1)特异性的抗体反应。