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).     

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).     

Factors affecting piglet mortality in loose farrowing systems on commercial farms

Crating sows in farrowing systems greatly restricts their normal behaviour (e.g. movement, nest-building, leaving the nest site for defecation), which is usually justified by the assumption that piglet mortality is higher with loose-housed sows. Based on experiments showing that this is not the case, farrowing crates were banned in Switzerland in 1997, with a 10-year transitional period. Since then, many farms have introduced loose farrowing systems, enabling an analysis of risk factors for piglet mortality in crateless farrowing systems based on a large sample size. Data from a Swiss sow recording scheme (UFA2000) were analysed using generalised linear mixed-effects models with an underlying Poisson distribution. Average total piglet mortality for the years 2002 and 2003 on 99 farms (N = 12457 litters) with loose farrowing systems amounted to 1.36 liveborn piglets per litter. The number of crushed piglets was 0.64 piglets per litter, whereas the number of piglets that died for other reasons was 0.72 piglets per litter.Herd size, pen size, possibility of confinement of the sow, presence of piglet protection bars and year of data collection did not significantly influence total piglet losses, losses due to crushing and losses due to reasons other than crushing. With greater litter size at birth, significantly more losses occurred due to all reasons (total, crushed, others). Total piglet mortality and losses for reasons other than crushing were significantly higher in older sows. Losses were therefore mainly attributable to sow-related characteristics rather than to the design of the farrowing pen.     

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.     

Obstetric and fetal outcomes in dystocic and eutocic sows to an injection of exogenous oxytocin during farrowing

Sixty hybrid Yorkshire-Landrace penned sows, 30 with eutocic farrowing and 30 experiencing a dystocic parturition, were studied to evaluate the obstetric and neonatal outcomes to low doses of oxytocin administered at advanced stages of parturition. Animals in each group were randomly subdivided into 2 subgroups: 15 eutocic and 15 dystocic sows received oxytocin 0.083 IU/kg (equivalent to 1 IU/12 kg body weight), administered intramuscularly after the delivery of the 5th piglet; the other 15 eutocic and 15 dystocic sows received saline solution intramuscularly at the same time. Oxytocin decreased the number of intrapartum deaths by approximately 50% (P = 0.002). No piglet was born dead from the saline- and oxytocin-treated eutocic sows. The highest viability score was observed among piglets born to eutocic sows treated with oxytocin. In summary, this dose schedule would help to decrease the number of stillbirths in both eutocic and dystocic farrowing sows.     

Impacts of a freedom farrowing pen design on sow behaviours and performance

The limited space in farrowing crate imposes many challenges, such as prolonged farrowing duration and high piglet stillbirth rate. Although the features of farrowing pens compensate for the drawbacks of farrowing crates, they are associated with high piglet crushing mortality caused by the greater space afforded to sows and their rolling-over behaviour. Therefore, a freedom farrowing pen was designed to overcome the drawbacks of both farrowing crates and farrowing pens. The main features of the freedom farrowing pen are its left anti-crushing bar and detachable right anti-crushing bar on the sides of the sow lying area. It also has a 10 cm-high anti-crushing bar in the non-lying area. Eighteen healthy, multiparous Yorkshire sows (3-7 parity) were averaged and randomly assigned to farrowing crates, farrowing pens, and freedom farrowing pens to compare the effects of the farrowing systems on sow behaviour and performance. Results showed that the farrowing duration and the mean piglet birth intervals were longer for the sows in farrowing crates than for those in farrowing pens and freedom farrowing pens (P<0.05), but there was no difference between the sows in farrowing pens and those in freedom farrowing pens (P>0.05). The piglet stillbirth rate was higher for the sows in farrowing crates than for those in farrowing pens and freedom farrowing pens (P<0.001). Crushing mortality was higher among piglets in farrowing pens (P<0.001), but there was no difference between piglets in freedom farrowing pens and those in farrowing crates (P>0.05). The freedom farrowing pen and the farrowing pen allowed sows to turn around and move freely, but because of the different structures of their anti-crushing bars, the increase in sow movement did not cause higher piglet crushing mortality (P>0.05). Sows in freedom farrowing pens were found to be more protective of their piglets.     

Influence of supplementary iron in late pregnancy on the performance of sows and litters

On eight farms alternate sows and gilts within three weeks of their expected farrowing date were injected intramuscularly in the neck with 8 ml of an iron (gleptoferron) preparation containing 200 mg iron/ml, or kept as uninjected controls. Data from 513 iron-injected and 488 control animals were used in the analysis of results. Small, but not statistically significant, improvements were observed in the numbers of piglets born alive and dead/litter, the birth weights and weaning weights at three weeks, the numbers of piglets fostered on and off/litter, piglet mortality, the number weaned/litter and the weaning to service interval. The condition scores of the iron-injected sows were marginally below those of the controls at weaning, but their condition scores at farrowing had also been slightly below those of the controls. A summation of these trends would suggest an overall benefit of approximately 0.45 pigs/sow/year in favour of the iron-injected sows.     

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.     

Swine fever. Immunisation of piglets

Vaccination against Swine Fever using the CL Chinese strain can be done in 7-day-old piglets if they are born of non-immune sows. The simultaneous weaning and vaccination emphasises the safety of this strain. The excellent immunity observed confirms the immunocompetence of 7-day-old piglets. In piglets born of immune sows and also weaned at 7 days, passive protection can extend beyond the age of 2 months if the sow is vaccinated several months prior to gestation. The immune level of the piglets would seem to depend on the interval between vaccination of the sow and farrowing and can be attributed to the quality of the antibodies transmitted by the colostrum. Piglets born of sows vaccinated 10 months prior to farrowing can be vaccinated as early as 5 weeks; the protection percentage observed at the age of about 6 months is over 80%. A booster injection at this age then confers immunity to future breeders throughout their economic life, i.e. 4 years in the reported experiment.     

An evaluation in pigs of Nobi-Vac AR and an experimental atrophic rhinitis vaccine containing P multocida DNT-toxoid and B bronchiseptica

The trial involved eight large white sows obtained from a closed experimental specific pathogen free herd. Four sows (two each for an experimental vaccine and for Nobi-Vac AR) were vaccinated twice (eight weeks and two weeks before parturition) with 2 ml of vaccine administered intramuscularly. Two unvaccinated sows were used as an infected control group and two unvaccinated sows served as an uninfected control group. Forty-six piglets (28 from vaccinated sows and 18 from unvaccinated sows) were challenged by intranasal instillation of Bordetella bronchiseptica at two days of age and Pasteurella multocida type D, dermonecrotic toxin at seven days of age. Among the infected control group some piglets died and there were clinical signs of pneumonia and severe turbinate atrophy. In the vaccinated groups the results showed that immunisation of the pregnant sows had provided a good level of antibodies, which were transmitted to their offspring. There was a significant reduction in the clinical signs and no lesions were observed in the group vaccinated with the experimental vaccine and only moderate atrophy of the turbinates in the Nobi-Vac AR group. B bronchiseptica and P multocida were never recovered from the lungs of the vaccinated groups and in the nasal cavities their frequency declined with age.     

Feeding sorghum ergot (Claviceps africana) to sows before farrowing inhibits milk production

Objective To assess the impact of feeding different amounts of sorghum ergot to sows before farrowing. Design Fifty‐one pregnant sows from a continually farrowing piggery were sequentially inducted into the experiment each week in groups of four to seven, as they approached within 14 days of farrowing. Diets containing sorghum ergot sclerotia within the range of 0 (control) up to 1.5% w/w (1.5% ergot provided 7 mg alkaloids/kg, including 6 mg dihydroergosine/kg) were randomly allocated and individually fed to sows. Ergot concentrations were varied with each subsequent group until an acceptable level of tolerance was achieved. Diets with ergot were replaced with control diets after farrowing. Post‐farrowing milk production was assessed by direct palpation and observation of udders, and by piglet responses and growth. Blood samples were taken from sows on three days each week, for prolactin estimation. Results Three sows fed 1.5% ergot for 6 to 10 days preceding farrowing produced no milk, and 87% of their piglets died despite supplementary feeding of natural and artificial colostrums, milk replacer, and attempts to foster them onto normally lactating sows. Ergot inclusions of 0.6% to 1.2% caused lesser problems in milk release and neo‐natal piglet mortality. Of 23 sows fed either 0.3% or 0.6% ergot, lactation of only two first‐litter sows were affected. Ergot caused pronounced reductions in blood prolactin, and first‐litter sows had lower plasma prolactin than multiparous sows, increasing their susceptibility to ergot. Conclusion Sorghum ergot should not exceed 0.3% (1 mg alkaloid/kg) in diets of multiparous sows fed before farrowing, and should be limited to 0.1% for primiparous sows, or avoided completely.     

猪伪狂犬病基因缺失活疫苗(SA215)免疫母猪后仔猪母源抗体消长规律及首免日龄

在研究猪伪狂犬病基因缺失活疫苗 (SA 2 15 )免疫接种母猪所产仔猪母源抗体消长规律 ,并绘制其消长曲线的基础上 ,确定了仔猪首免日龄。对免疫母猪所产仔猪于不同日龄进行抗体检测结果表明 ,全部仔猪均获得了高水平母源抗体 ,7日龄高达 2 8.56 ,6 0日龄降至 2 2 .56 ;随着日龄增长 ,抗体水平呈逐渐降低趋势 ,2次大幅下降出现在 14～ 2 1日龄、30～ 6 0日龄。对免疫母猪所产仔猪分别于不同日龄免疫接种 1头份剂量疫苗 (SA2 15 ) ,7d后采血进行抗体检测 ,结果表明 ,7日龄、14日龄、2 1日龄免疫接种仔猪均未引起明显抗体水平升高 ,反而较同期仔猪略有降低 ,30日龄和 6 0日龄免疫接种仔猪则出现了抗体水平的升高 ,其中以 6 0日龄仔猪升高幅度为大。结合母源抗体消长规律 ,确定猪伪狂犬病基因缺失活疫苗 (SA2 15 )免疫母猪所产仔猪的首免日龄为 30日龄     

Rolling behaviour of sows in relation to piglet crushing on sloped versus level floor pens

The study focused on the rolling behaviour of sows and the crushing of piglets by sows' rolling behaviour. The experiment examined the influence of sloped floor in loose housed farrowing pens on the rolling behaviour of sows and crushing of piglets. The experimental unit was made up of 24 pens. There were two experimental pen designs with piglet creep in the corner of the pen and piglet creep across the end of the pen, respectively. Both of the experimental pen designs had a 10% sloped floor in the sow's resting area. The two control pen designs were identical to the experimental pen designs, but with a level floor. The behaviour of 85 sows and their litters was continuously video recorded. Behavioural observations were made from birth of the first piglet and until 3 days after birth of the first piglet. Rolling behaviour of sows caused significantly more trapped piglets under the sow than lying down from standing (P = 0.04). Rolling behaviour caused 64% of the trapped piglets and lying down from standing caused 36% of the trapped piglets. Rolling from udder to side without protection trapped significantly more piglets than rolling from udder to side near slanted wall or piglet protection rails and rolling from side to udder (P < 0.001). With a certain pen design sloped floor reduced rolling from udder to side without protection (P = 0.007) and reduced the number of trapped piglets (P = 0.01), but results concerning lying behaviour showed that sloped floor pushed sows to rest on the level part of the floor. The results indicate that rolling behaviour that crushes piglets can be reduced, and sows prefer to lie on a level floor.     

Effects of late introduction of sows to two farrowing environments on the progress of farrowing and maternal behavior

To evaluate the effect of late introduction to farrowing pens on the progress of farrowing and maternal behavior, 20 primiparous and 20 multiparous sows were allocated randomly to 1 of 2 treatments: 1) early introduction to pen (EP, n = 20) and 2) late introduction to pen (LP, n = 20). To evaluate the difference between loose-housed sows and crated sows when introduced late to the farrowing environment, a third treatment was included: late introduction to farrowing crate (LC, n = 20). Sow behavior and piglet birth intervals were recorded using video recordings from 16 h before the birth of the first piglet (BFP) until 48 h after BFP. Behavioral data were analyzed using PROC MIXED in SAS and the percentage of stillborn piglets and the response of the sow to piglet scream were analyzed using PROC GENMOD in SAS. Before farrowing (16 to 3 h before BFP), sows introduced late to pens had more postural changes per hour than sows introduced early to pens (LP = 12.7, EP = 8.9; P = 0.04), whereas there were no differences between sows introduced late to crates and sows introduced late to pens (LC = 14.2, LP = 12.7; P = 0.53). Interbirth interval (P = 0.04), variation in the interbirth interval (P = 0.01), and percentage of stillborn piglets (P = 0.003) were affected by an interaction between parity and treatment. In multiparous sows there were no differences between treatments (P > 0.18) either in the progress of farrowing or in the percentage of stillborn piglets. For primiparous sows, there were no differences (P > 0.22) between sows that were introduced late to pens and sows that were introduced early to pens. Primiparous sows that were introduced late to crates compared with pens had longer interbirth intervals (LC = 29 +/- 4.9 min, LP = 16 +/- 2.9 min; P = 0.02), a greater variation of these intervals (LC = 35 +/- 8.3 min, LP = 16 +/- 3.6 min; P = 0.006), and a greater percentage of stillborn piglets (LC = 21%; 95% confidence interval ranging 14 to 30%, LP = 5%; 95% confidence interval ranging from 2 to 12%; P = 0.004). After farrowing, neither postural changes, time spent in lateral lying, number of near-crushing situations, nor the response to piglet scream test were affected by treatment (P > 0.09). When sows and gilts were introduced late to farrowing pens, neither progress of farrowing nor maternal behavior of importance for piglet crushing was influenced. However, crating primiparous sows that were introduced late to the farrowing environment compared with pen housing had detrimental effects on the progress of farrowing and the percentage of stillborn piglets.     

Factors affecting the transfer of porcine parvovirus antibodies from sow to piglets

The aim of the study was to investigate the effects of a number of environmental, behavioural and biological factors on passive immunization of piglets as assessed by transfer of porcine parvovirus (PPV) antibodies (ab) from the colostrum of PPV vaccinated mothers to the serum of the piglets. Twenty primiparous sows were housed in pens with peat, straw and branches for nest building. Half the sows were prevented from achieving feedback from a completed farrowing nest by repeated removal of the nest from 10 to 12 h after nest building had begun, whereas the other half kept their nests. Sow serum PPV-ab titres were positively related to colostrum PPV-ab titres at birth of the first piglet (BFP) (P < 0.001). Litter average piglet PPV-ab titre was positively related to both sow serum and colostrum PPV-ab titres (both P < 0.001). In addition, in the individual piglets. PPV-ab titres were reduced as time from BFP to birth and time from birth to first sucking increased and time spent sucking decreased (all P < 0.01). There were no effects of treatment, time spent in lateral recumbency by the sow, number of times the sow stood or piglet weight on day 1 on piglet serum PPV-ab titres. Preventing prolonged farrowing, while at the same time ensuring the piglets' access to the udder, is important for transfer of maternal immunity. Measurements of specific antibodies in sow serum during the periparturient period and in piglet serum at 28 days of age may provide a practical tool for evaluating transfer of maternal immunity from sow to piglets.     

Effect of the sow vaccination regimen on the decay rate of maternally derived foot-and-mouth disease antibodies in piglets

Three pairs of sows were vaccinated against foot-and-mouth disease (FMD) at various intervals before farrowing and samples of blood were collected from their piglets periodically for 70 days after birth. When the sows were vaccinated 12 to 13 days before farrowing the predominating FMD neutralising antibody at time of parturition was IgM and the observed half lives of the maternally derived antibodies in the piglets were short (four to eight days). However, when sows were last vaccinated 30 to 32 days before farrowing, the maternally derived FMD neutralising antibodies in the piglets were predominantly IgG and the observed half lives were seven to 21 days. These observed half lives for IgG were shown to be closely related to the period over which the maternally derived antibodies could be demonstrated and to the rate of increase of the piglet's blood volume over the same period. If corrections were made for increase in blood volume the decay rate of IgM antibodies in piglets was seven to 18 days while the decay rate for IgG was greater than 408 days. This result suggested that there was little or no IgG catabolism or excretion during the first 70 days of the piglet's life.     

Protection of piglets against atrophic rhinitis by vaccinating the sow with a vaccine against Pasteurella multocida and Bordetella bronchiseptica

The efficacy of a new vaccine against atrophic rhinitis in pigs was tested in the Netherlands and Denmark. The vaccine contained protein dO (a truncated Pasteurella multocida toxin which is immunogenic and non-toxic), inactivated Bordetella bronchiseptica whole cells, and an adjuvant. The sows were either vaccinated intramuscularly with 2 ml of the vaccine at six to eight and two to four weeks before expected farrowing or left unvaccinated as controls. All the piglets were challenged intranasally with B bronchiseptica when three to seven days old and with P multocida three to four days later. Pigs born to the vaccinated sows performed significantly better than pigs born to the control sows when judged on growth, average daily weight gain and snout scores. The challenge organisms were reisolated more frequently from the control pigs than from the pigs in the vaccinated group. The vaccinated sows and their progeny developed high titres of antibodies against B bronchiseptica and P multocida toxin.     

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.     

Elimination of strains of Streptococcus suis serotype 2 from the tonsils of carrier sows by combined medication and vaccination

The effect of vaccination with a killed whole-cell vaccine of extracellular factor-positive Streptococcus suis serotype 2 (S suis 2 EF(+)) combined with medication with amoxicillin on the presence of virulent S suis 2 EF(+) strains on the tonsils of sows and their offspring was evaluated. In two herds, 14 pregnant sows that carried these virulent strains, as detected by PCR in three consecutive tonsillar brush samples, were selected and randomly assigned to be treated or left untreated as controls. The treated sows were vaccinated at six and three weeks before the expected farrowing date and medicated from one week before expected farrowing until the end of the experiment. Two weeks before parturition, the sows were housed in individual isolation farrowing rooms, and the sow and its litter were sampled by using tonsil brushes and tonsil swabs, respectively. Approximately 27 days postpartum, the sows and their piglets were euthanased and their tonsils were collected and analysed by pcr. No S suis 2 EF(+) could be detected in the tonsils of the seven treated sows, but the tonsils of the seven untreated sows remained positive. Only one of the litters of the untreated sows became infected, five days after birth, and none of the litters of the treated sows became infected.     

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 6.8 × 10⁹ 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.