The use of different vaccination schedules for sows to protect piglets against Aujeszky's disease

Several Aujeszky's disease virus (ADV) vaccination protocols of sows were evaluated with regard to the passive protection conferred on piglets in a recently built commercial farm. Three different groups of sows were vaccinated using a Bartha K-61 strain. One group received an inactivated vaccine during pregnancy and the other two groups received attenuated vaccines, either during pregnancy (day 65) or on the seventh day of lactation. At farrowing, sows vaccinated during lactation had lower seroneutralization titres than those vaccinated during pregnancy either with inactivated or attenuated vaccines. Accordingly, their piglets were the ones with lower levels of maternally transferred neutralizing antibodies. At 4 weeks of age, five piglets born of each group of sows were challenged intranasally with a neurotropic strain of ADV. Piglets born of sows vaccinated during pregnancy with inactivated and attenuated vaccines gained 1.50 kg bodyweight and 2.50 kg bodyweight during 7 days, respectively, and did not show clinical signs, while piglets from sows vaccinated during the previous lactation lost 0.60 kg and presented moderate to severe clinical signs of ADV. Vaccination of sows during pregnancy provided more protection against ADV for piglets than sow vaccination before mating. Piglets born from sows vaccinated with attenuated or inactivated vaccines did not present remarkable differences on protection.     

Antibody response to Mycoplasma hyopneumoniae infection in vaccinated pigs with or without maternal antibodies induced by sow vaccination

Vaccination with bacterins is an important tool for the control of Mycoplasma hyopneumoniae infection of pigs. Because such vaccination often involves piglets that have suckled M. hyopneumoniae antibody-positive dams it is important to understand the effect of pre-existing (passively acquired) antibody on vaccine-induced immunity. To investigate this issue experimentally, 20 sows that were seronegative for M. hyopneumoniae were selected from a M. hyopneumoniae-infected herd and then randomly allocated to one of four treatment groups (five sows/group): Group A, vaccinated sows/vaccinated piglets; Group B, vaccinated sows/non-vaccinated piglets; Group C, non-vaccinated sows/vaccinated piglets; Group D, non-vaccinated sows/non-vaccinated piglets. Sows (Groups A and B) were vaccinated 14 days before farrowing and seroconverted within the next 14 days. Conversely, none of the non-vaccinated sows was seropositive at farrowing. Piglets (Groups A and C) were vaccinated when they were 7 days of age. Regardless of treatments none of the piglets had any evidence of an active immune response until many of those of Groups A and C and a few of those of Groups B and D seroconverted after it had been shown that at least some pigs of all groups had been naturally infected with a field strain of M. hyopneumoniae. This pattern of immune responsiveness (i.e. the collective results of Groups A, B, C and D) suggested that vaccination of pigs had primed their immune system for subsequent exposure to M. hyopneumoniae, and that passively acquired antibody had little or no effect on either a vaccine-induced priming or a subsequent anamnestic response. According to the statistical analysis sow serological status did not interfere with the antibody response in early vaccinated piglets. In conclusion, the results pointed out that early vaccination of piglets may assist M. hyopneumoniae control independently from the serological status of sows.     

Humoral immunity of neonatal swine after FMD vaccination

The possible effect on pig protection after vaccination pregnant sows and their piglets against FMD at various age was examined using the SN test. Three experiments were conducted with three sow in each (8-9 piglets each). In the first experiment sows were not vaccinated but their piglets were vaccinated on 10th, 20th and 60th day of age. In second experiment sows were vaccinated at the end of rest period and in the middle of pregnancy. Pigs from one sow were vaccinated on 10th, from second sow on 20th and from the third sow on the 60th day of age. Pigs which were vaccinated on the 10th and 20th day of age were revaccinated on the 60th day of age. In third experiment sows were vaccinated at the end of the rest period and in the middle of pregnancy. Their piglets were not vaccinated. The conclusion may be drawn that if the epidemiological situation requires, systemic vaccination of all pigs then, on large farms (where pig production is planned) all sows should be vaccinated at the end of the rest period (first vaccination) and on the 55th-60th day of pregnancy. The next vaccination should be done in the middle of the next pregnancy. A vaccination program of piglets, according to our results, should depend on the vaccination program used for their dams.     

Influence of the vaccination regime on the herd immune response for swine fever

Surveys in three areas with emergency vaccination programmes revealed that 86-94% of the pigs vaccinated in the initial mass campaign had developed an adequate antibody titre against swine fever as compared with 29-55% of the pigs involved in supplementary vaccination campaigns. The serological response of piglets born from immunised sows rose with the age of vaccination from 11% at 5-6 weeks to 42% at 7-8 weeks and 77% at 9-10 weeks. In piglets born from immunised sows, a 50% 'take' of the vaccine was not obtained before the age of 8-9 weeks. Re-vaccination of gilts born from immunised dams improved the immune status to almost the level observed after mass campaigns. To strengthen herd immunity in vaccination areas, the age of supplementary vaccination has been raised to 7-9 weeks, while breeding gilts are re-vaccinated when 6-7 months old.     

Response of young pigs to foot-and-mouth disease oil emulsion vaccination in the presence and absence of maternally derived neutralising antibodies

Serum samples and bodyweights were taken at regular intervals for six to seven months from piglets, born to foot-and-mouth disease (FMD) vaccinated or unvaccinated sows, which had been vaccinated at one, two, four or eight weeks old. Young pigs, devoid of maternally derived antibodies (MDA), were capable of responding to FMD vaccination at one week old, with no deleterious effects on their growth rate. However, their immunity to experimental infection at six to seven months old was poor (33.3 per cent). Vaccination of four or eight-week-old piglets, born to unvaccinated sows, protected 87.5 per cent from a similar challenge. In piglets, born to FMD vaccinated sows, the MDA had a suppressive effect on the early vaccination response. This suppression, which was affected by the titre of MDA present in the piglets at the time of vaccination, was complete in one-, two- and four-week-old piglets and partial in eight-week-old piglets. Furthermore, none of these piglets were immune to experimental infection at six to seven months old.     

Long-term administration of a commercial porcine reproductive and respiratory syndrome virus (PRRSV)-inactivated vaccine in PRRSV-endemically infected sows

The purpose of this study was to investigate the safety and efficacy of a commercial European porcine reproductive and respiratory syndrome virus (PRRSV)-inactivated vaccine after 18-month use in gilts/sows at a farm with high seroprevalence. In a farrow-to-finish farm with 1100 sows, all sows and gilts were systematically vaccinated with the PRRS-inactivated PROGRESSIS vaccine for a period of 18 months. Farm's reproductive and litter characteristics were longitudinally recorded for this period and historically compared with those of the year prior to vaccination. Serology, employing immunoperoxidase monolayer assay, had confirmed a high prevalence of PRRS-specific antibodies in most age groups within the farm prior to vaccination. Seroprevalence during the experiment ranged between 0% and 100% in weaners and growers, but remained at stable high levels (> 93%) in finishing pigs and gilts throughout all 2-year period of serology measurements. No local or systemic vaccine side effects were noted throughout the trial period. Vaccinations had resulted over time in a significant improvement of sow reproductive performance (e.g. reduction of premature farrowings, abortions and increase of farrowing rate) and litter characteristics (e.g. increase of the number of live born and weaned pigs and decrease of stillborn, mummified, weak and splay-legged piglets). It has also been observed that the higher the degree of immunization of a sow, the better the improvement of her reproductive parameters. Sows after vaccination have shown improved characteristics compared to homoparous sows prior to the application of vaccinations in the farm.     

Intestinal defence of the neonatal pig: interrelationship of gut and mammary function providing surface immunity against colibacillosis.

The neonatal requirements for maternal passive immunity and the lactation immunobiology with regard to sow immunisation for neonatal protection are reviewed. A vaccination protocol which combines oral and parenteral antigen administration to produce antibody activity mediated mainly by IgM is described. Its efficacy in affording protection to neonatal piglets was tested against a lethal oral infection with a virulent strain of Escherichia coli "Abbottstown". Piglets suckled on vaccinated or non-vaccinated sows were exposed to an infective challenge in the gastrointestinal tract and the relative pathology in test and control groups observed over the neonatal period. Death ensued in 76 per cent of piglets suckled on control sows and 26 per cent of piglets suckled on sows vaccinated by two intramuscular injections. Litters suckled on orally vaccinated sows were able to resist a similar infective challenge, there being only one fatality out of 42 piglets.     

Long‐term administration of a commercial porcine reproductive and respiratory syndrome virus (PRRSV)‐inactivated vaccine in PRRSV‐endemically infected sows

The purpose of this study was to investigate the safety and efficacy of a commercial European porcine reproductive and respiratory syndrome virus (PRRSV)‐inactivated vaccine after 18‐month use in gilts/sows at a farm with high seroprevalence. In a farrow‐to‐finish farm with 1100 sows, all sows and gilts were systematically vaccinated with the PRRS‐inactivated PROGRESSIS® vaccine for a period of 18 months. Farm's reproductive and litter characteristics were longitudinally recorded for this period and historically compared with those of the year prior to vaccination. Serology, employing immunoperoxidase monolayer assay, had confirmed a high prevalence of PRRS‐specific antibodies in most age groups within the farm prior to vaccination. Seroprevalence during the experiment ranged between 0% and 100% in weaners and growers, but remained at stable high levels (>93%) in finishing pigs and gilts throughout all 2‐year period of serology measurements. No local or systemic vaccine side effects were noted throughout the trial period. Vaccinations had resulted over time in a significant improvement of sow reproductive performance (e.g. reduction of premature farrowings, abortions and increase of farrowing rate) and litter characteristics (e.g. increase of the number of live born and weaned pigs and decrease of stillborn, mummified, weak and splay‐legged piglets). It has also been observed that the higher the degree of immunization of a sow, the better the improvement of her reproductive parameters. Sows after vaccination have shown improved characteristics compared to homoparous sows prior to the application of vaccinations in the farm.     

Induction of lactogenic immunity to transmissible gastroenteritis virus of swine using an attenuated coronavirus mutant able to survive in the physicochemical environment of the digestive tract.

A transmissible gastroenteritis (TGE) coronavirus mutant (188-SG), selected as attenuated and resistant to acidity and proteases of the digestive tract of adult pigs, was used as vaccine ("Nouzilly strain") in sows to protect suckling piglets against a challenge exposure carried out with a highly virulent TGEV strain. The pregnant sows were immunized once (42-49 days before farrowing) or twice (42-49 and 7-15 days before farrowing) by the oral, intramuscular or conjunctival route with the 188-SG strain. Sows exposed to virulent TGEV in the field and experimentally infected sows (two oral inoculations during pregnancy) were used as positive controls leading to high protection. The neutralizing antibody response to vaccination and/or infection was studied in serum and milk. No protection against mortality was observed in the litters of (1) the nine seronegative, susceptible sows, with piglet mortality of 65/70, (2) the seven once orally vaccinated sows, with mortality of 44/54, (3) the seven sows vaccinated twice by the conjunctival route, with mortality of 55/76. Moderate protection was observed in (1) the eight sows vaccinated intramuscularly twice with piglet mortality of 36/90, (2) the seven orally and intramuscularly vaccinated sows with piglet mortality of 31/51. In of 3 contrast, improved protection was observed in (1) the 10 sows vaccinated twice orally, with piglet mortality of 23/95, (2) the four naturally infected sows with piglet mortality of 6/41, (3) the six sows experimentally infected with virulent TGEV with piglet mortality of 1/59. No correlation was found between neutralizing antibodies titers in serum and milk and protection rate of the piglets. The results indicate that relative protective lactogenic immunity against TGEV is induced only by repeated ingestion of the attenuated 188-SG strain of TGEV.     

猪瘟病毒持续感染对母猪繁殖性能及仔猪猪瘟疫苗免疫效力的影响

利用来源于同一猪场的2头猪瘟病毒(HCV)持续感染的带毒母猪及所产35头仔猪(包括13头死胎)和6头阴性对照猪,观察母猪的胎儿发育成活状况、仔猪HCV带毒率及HCV垂直传播对仔猪猪瘟兔化弱毒疫苗(HCLV)免疫效力的干扰作用,同时进行水平传播试验和观察HCV持续感染对母猪繁殖功能的影响。结果表明：HCV持续感染对其中1头母猪的胎儿发育和成活有明显影响,而对另1头母猪的胎儿发育没有明显影响;HCV持续感染母猪可经过胎盘垂直传播病毒给仔猪,传播率达45％～86％;吃初乳和接种HCLV不能阻止带毒仔猪的死亡,9头带毒仔猪在45d内死亡4头;免疫HCLV不能使带毒仔猪产生免疫保护力。5头猪在强毒攻击后死亡4头;HCV垂直传播的带毒猪可发生水平传播,并引起3／4感染猪死亡;HCV持续感染可引起母猪生殖系统病理变化。导致繁殖障碍。     

Vaccination of pregnant sows against transmissible gastroenteritis with two attenuated virus strains and different inoculation routes

Summary Two attenuated transmissible gastro-enteritis (T. G. E.) virus strains were used for vaccination experiments in sows. Four different experiments were carried out (see Table 1). In each experiment, 9 sows were vaccinated during pregnancy and 3 sows served as controls. They were kept together in one farrowing house. The sows were due to farrow at about the same time. The sows and their litters were challenged shortly after farrowing by exposing 3 piglets of 2 control litters to virulent TGE virus. The following vaccination schedules were used (see Table 1): twice intramuscularly with TGE-vac (a commercially available TGE-vaccine), one oral administration followed by an intramuscular vaccination with an attenuated TGE Purdue (Pu) strain, twice orally with Pu strain in enteric coated capsules, and one direct intra intestinal administration followed by 2 intramuscular vaccinations or 3 intramuscular vaccinations with the Pu strain. All sows, except most of those treated with enteric coated capsules, seroconverted demonstrably (Table 2). The geometric mean seroneutralization (SN) titer log 2 varied from 4.1 to 7.5 after the first vaccination and from 7.6 to 10 after the second vaccination. None of the vaccination schedules resulted in an effective lactogenic immunity. The morbidity in the piglets was 100% within 3 to 5 days after challenge. The mortality rate varied from 44 to 80% in litters from vaccinated sows and from 71 to 100% in litters from control sows (see Table 3). Clinical signs were observed in 33,3% of the control sows and in 36% of the vaccinated sows. No correlation was found between the titer of SN antibodies in the sera of the piglets and their survival rate (Table 4). A rapid decrease in antibody concentration was observed, during the first week of lactation in milk samples collected from 4 orally and intramuscularly vaccinated sows (Table 5).     

不同年龄猪群中猪瘟抗体监测及免疫效果分析

为制订合理的猪瘟免疫程序,本研究采用正向间接血凝试验(IHA)对某规模化猪场进行猪瘟免疫监测和分析。结果表明:猪瘟母源抗体的合格率、抗体效价平均值均存在随着仔猪日龄的增长而呈逐渐下降的趋势;35 d～40 d仔猪母源抗体的合格率达78.79%、抗体平均效价为5.97 Log2;仔猪35 d～40 d实施猪瘟首免,其一免抗体合格率和抗体效价均比20 d首免有所提高;同一窝仔猪的猪瘟母源抗体,有11%窝次的猪差距在3个～8个滴度;母猪猪瘟免疫抗体的合格率,一胎母猪稍低,其它经产母猪基本接近;猪瘟抗体效价的平均值随胎龄增加而升高,并且抗体的离散度则随胎龄增加而缩小。因此,在母猪实施与仔猪同时免疫的猪场,40日龄左右是较佳的首免日期。     

Immunisation of pregnant sows with a live Salmonella cholerae suis vaccine

Sows were immunised subcutaneously with a live Salmonella cholerae suis (SCS) vaccine prior to farrowing. Serological tests demonstrated a high level of SCS colostral antibodies at parturition. Piglet sera negative for antibodies at birth contained a high level of SCS antibodies 24 h after the ingestion of vaccinated sow colostrum. Experiments were carried out to establish if these maternally derived antibodies could protect the piglets against an intranasal (IN) challenge with a field isolate of SCS. It was concluded that pregnant sows could be safely immunised with a live SCS vaccine thus providing their piglets with a passive immunity which protected them against an intranasal challenge.     

Vaccination of pregnant sows against transmissible gastroenteritis with two attenuated virus strains and different inoculation routes

Summary

Two attenuated transmissible gastro‐enteritis (T. G. E.) virus strains were used for vaccination experiments in sows.

Four different experiments were carried out (see Table 1). In each experiment, 9 sows were vaccinated during pregnancy and 3 sows served as controls. They were kept together in one farrowing house. The sows were due to farrow at about the same time. The sows and their litters were challenged shortly after farrowing by exposing 3 piglets of 2 control litters to virulent TGE virus.

The following vaccination schedules were used (see Table 1): twice intramuscularly with TGE‐vac (a commercially available TGE‐vaccine), one oral administration followed by an intramuscular vaccination with an attenuated TGE Purdue (Pu) strain, twice orally with Pu strain in enteric coated capsules, and one direct intra intestinal administration followed by 2 intramuscular vaccinations or 3 intramuscular vaccinations with the Pu strain.

All sows, except most of those treated with enteric coated capsules, seroconverted demonstrably (Table 2). The geometric mean seroneutralization (SN) titer log 2 varied from 4.1 to 7.5 after the first vaccination and from 7.6 to 10 after the second vaccination.

None of the vaccination schedules resulted in an effective lactogenic immunity. The morbidity in the piglets was 100% within 3 to 5 days after challenge. The mortality rate varied from 44 to 80% in litters from vaccinated sows and from 71 to 100% in litters from control sows (see Table 3). Clinical signs were observed in 33,3% of the control sows and in 36% of the vaccinated sows.

No correlation was found between the titer of SN antibodies in the sera of the piglets and their survival rate (Table 4).

A rapid decrease in antibody concentration was observed, during the first week of lactation in milk samples collected from 4 orally and intramuscularly vaccinated sows (Table 5).     

Influence of long-term vaccination of a breeding herd of pigs against PCV2 on reproductive parameters

The objective of the study was to evaluate an efficacy of sows vaccination protocols in the herd with serious problems affecting efficacy of reproduction. The study was performed in a large pig herd with about 1200 sows. Before vaccination against PCV2, farrowing rate in this farm was about 65%. Sows, boar and replacement gilts were immunized using Circovac vaccine (Merial, France) according to producer's recommendations. Parameters of production were analyzed since 2007 until 2010 in selected batches of sows inseminated at the same weeks of the year (17th, 18th, 19th and 20th) to eliminate seasonal variability. In total, 940 sows were subjected to the study. No significant changes in management during these years were introduced. The applied protocol of sow herd long-term vaccination proved to be very efficient. All measured production parameters: reproduction rate, number of piglets born alive, birth weight of piglets and number of piglets weaned per a litter improved after implementation of immunization program. Moreover, further improvement was observed with vaccination in the following reproduction cycles. The most spectacular effect of vaccination regarded average farrowing rate that increased from 64.76% in control group to 86.93% after basic vaccination. Two years after implementation of vaccination program this parameter reached 93.6%. Number of piglets weaned per sow per a litter improved from 10.31 to 11.74 after one year of vaccination and remained relatively stable through the following year. Simultaneously, the percentage of newborn piglets with birth weight < 1 kg decreased significantly (p < 0.05). To summarize, vaccination against PCV2 influenced positively the insemination rate, number of piglets born alive and weaned per litter as well as birth body weight and percentage of piglets weighing < 1 kg.     

Effect of sow vaccination against Mycoplasma hyopneumoniae on sow and piglet colonization and seroconversion, and pig lung lesions at slaughter

The objectives of the present study were to compare Mycoplasma hyopneumoniae (Mh) colonization and serologic status on Mh vaccinated and non-vaccinated sows and to assess the effect of sow vaccination on colonization and serologic status of their piglets at weaning as well as presence of enzootic pneumonia (EP) lung lesions at slaughter. Fifty sows (25 vaccinated and 25 unvaccinated) as well as five of their piglets were included in the study. Blood samples and nasal swabs from sows at 7 weeks pre-farrowing and 1 week post-farrowing and from piglets at 3-4 weeks of age were taken. Nasal swabs and sera were tested by a nested polymerase chain reaction (nPCR) to detect Mh DNA and by an enzyme-linked immunosorbent assay (ELISA) test to detect antibodies to the pathogen, respectively. Finally, at 23 weeks of age, pigs were sent to the slaughter where the extension of EP-compatible gross lesions was assessed. Vaccination with two doses of Mh vaccine resulted in a significantly higher (p<0.05) percentage of seropositive sows than in the non-vaccinated group at 1 week post-farrowing. On the contrary, no statistical significant differences were found in the number of nasal nPCR positive sows among different treatments (p>0.05). At 3-4 weeks of age, a significantly higher percentage (p<0.001) of seropositive piglets came from vaccinated than from non-vaccinated sows. Although the number of Mh infected piglets coming from non-vaccinated sows was higher than the one from vaccinated sows, the difference was not statistically significant (p>0.05). Overall, piglets from vaccinated sows had a significant lower (p<0.05) mean of EP-compatible lung lesions (1.83+/-2.8) than piglets from non-vaccinated sows (3.02+/-3.6). Under the conditions described in this study, sow vaccination did not affect sow or piglet colonization but increased the percentage of seropositive sows and piglets at weaning and reduced significantly the mean EP-compatible lung lesion scoring at slaughter.     

Immune response of sows and their offspring to pseudorabies virus: serum neutralization response to vaccination and field virus challenge.

One month prior to breeding, sows were vaccinated with an attenuated pseudorabies virus vaccine or challenged with a field strain of pseudorabies virus. A third group of sows were not vaccinated or challenged before breeding. Pigs from these sows were vaccinated at 3, 6, or 12 weeks of age and challenged with virulent virus three weeks later. One pig from each litter served as an unvaccinated, unchallenged control. Serum neutralization titers of these pigs were monitored from birth until 22 weeks of age. Titers of the sows were monitored through breeding, gestation and farrowing. The maximum prefarrowing anti-pseudorabies virus titer in the field virus challenged sows occurred four weeks following challenge. A significant decline in titers occurred at farrowing. Titers rose from one week postfarrowing and then declined. Titers in the field virus infected sows were consistently two to threefold greater than those of the vaccinated sows. The maximum prefarrowing anti-pseudorabies virus titer in the vaccinated sows occurred six weeks following vaccination. The geometric mean titer in these sow's then decreased and increased for two weeks after farrowing. The results in the pigs can be summarized as follows: Pigs from control sows had a greater serological response following field virus challenge than following vaccination with a modified live virus. Pigs from control sows responded serologically to vaccination at 3, 6 and 12 weeks of age. Pigs from control sows which were challenged at 6, 9 and 15 weeks of age had similar antibody responses. Pigs from vaccinated sows had no increase in titer following vaccination at three and six weeks of age. Titers increased when these pigs were vaccinated at 12 weeks of age. There was no significant increase in mean titers of pigs from challenged sows following vaccination at 3, 6 and 12 weeks of age. Vaccinated pigs from control and vaccinated sows had a secondary response following challenge three weeks after vaccination.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunogenicity of a recombinant hemagglutinin neuraminidase-Porcine rubulavirus produced by Escherichia coli of Porcine rubulavirus gives protective immunity of litter after challenge

Porcine rubulavirus (PRV) is a contagious virus that affects the Mexican swine industry. This work aimed to evaluate the immunogenicity of an recombinant hemagglutinin neuraminidase-Porcine rubulavirus (rHN-PorPV) candidate vaccine on pregnant sows, and the protective efficacy afforded to their 7-day-old suckling piglets against PRV lethal challenge. Three sows were immunized with rHN-PorPV formulated with immune-stimulating complex (ISCOMs) and two sows with rHN-PorPV protein alone as well as a mock-immunized pregnant sow (negative control). Quantitative ELISA detected a high concentration of anti-rHN-PorPV Immunoglobulin G (IgG) antibodies in sow sera after the second dose of vaccine administered on day 14 until farrowing, showing viral-neutralizing and cross-neutralization activity against different variants of PRV. Sera samples from piglets of immunized sows (with or without adjuvant), showed high concentrations of IgG antibodies. As expected, piglets from the negative control sow (n=5), exhibited severe signs of disease and 100% of mortality after PRV challenge study. Conversely, 75% and 87.5% of the piglets born from the rHN-PorPV and the rHN-PorPV-ISCOMs-immunized sows (n=8), survived, respectively, showing milder PRV clinical signs. Our data indicate that rHN-PorPV candidate vaccine produced in Escherichia coli induces efficient humoral response in pregnant sows and that the maternally derived immunity provides high protection to suckling piglets against PRV lethal challenge.     

Protection against neonatal Escherichia coli diarrhoea in pigs by vaccination of sows with a new vaccine that contains purified enterotoxic E. coli virulence factors F4ac, F4ab, F5 and F6 fimbrial antigens and heat-labile E. coli enterotoxin (LT) toxoid

The efficacy of a new vaccine against neonatal Escherichia coli diarrhoea in piglets containing purified F4ab, F4ac, F5 and F6 fimbriae and detoxified heat-labile toxin (LT) was tested in challenge experiments by the method described by the European Pharmacopoeia (3rd edn, EDQM, Council of Europe, Strasbourg, France). A group of 11 young sows from a herd without E. coli problems was vaccinated 6-8 and 2-4 weeks prior to expected farrowing and another group of nine young sows were non-vaccinated controls. Escherichia coli antibody titres were determined in serum samples taken from the sows before first vaccination and before farrowing and in colostrum samples. The newborn piglets were allowed to suckle colostrum from their mother immediately after birth. The piglets were marked with individually numbered ear tags. Approximately 12 h after birth, 118 piglets from vaccinated sows and 79 piglets from non-vaccinated control sows were challenged by oral instillation of 5 ml of a freshly prepared culture of one of the challenge strains [O8:K87:F4ab (LT+) or O149:K91:F4ac (LT+) or O9:K30:F5 or O9:K103:F6 respectively]. The challenge cultures contained as a mean 6.8x10(9) CFU/ml. After challenge the piglets were observed for 7 days and mortality and morbidity were recorded. Vaccinated sows developed significant levels of antibody titres in colostrum and serum. Control sows stayed at a low/seronegative level. The protective efficacy was excellent because 66.7-87.5% of the piglets from vaccinated sows remained without clinical signs after challenge. Only 0.0-28.0% of the piglets from non-vaccinated sows remained healthy and more than 47.1% of the piglets in this group died after challenge. It is concluded that the new vaccine is very effective in protection of piglets against neonatal E. coli diarrhoea.     

The influence of age and maternal antibodies on the postvaccinal response against swine influenza viruses in pigs

The influence of age and maternal immunity on the development and duration of postvaccinal humoral response against swine influenza viruses (SIV) were investigated under experimental conditions. Piglets born to immune and non-immune sows were vaccinated twice with bivalent inactivated vaccine. Vaccination was done according to 5 different schedules: 1+4, 1+8, 4+8, 8+10 or 8+12 weeks of age. Antibodies to the haemagglutinin type 1 and 3 were determined using the haemagglutination inhibition (HI) test. Maternally derived antibodies (MDA) against H1N1 and H3N2 in the serum of unvaccinated piglets born to immune sows were above the positive level until about 13-14 and 9-10 weeks of life, respectively. No serological responses were seen in any of the groups after the first vaccination. After the second dose of vaccine production of antibodies was observed even before the complete disappearance of maternal antibodies. MDA, however, were associated with reduced antibody response. In MDA-negative piglets, an active humoral postvaccinal response was developed in all vaccinated pigs. The age at which the vaccine was given was associated with the differences in the magnitude of antibody response to SIV. In general those pigs that were vaccinated for the first time at the age of 1 week, developed lower maximum titres after the second vaccination, and become seronegative earlier than pigs that were vaccinated for the first time at 4 or 8 weeks of age.