A retrospective study into characteristics associated with the seroprevalence of pseudorabies virus-infected breeding pigs in vaccinated herds in the southern Netherlands

Vaccination programs to eradicate pseudorabies virus (PRV) are being considered in several countries. Knowledge of factors that influence PRV transmission within vaccinated breeding herds may contribute to the success of these programs. A multivariate analysis of variance of the PRV-seroprevalence in sows in 209 herds (average seroprevalence 67.0% per herd) in the southern Netherlands revealed the following risk indicators: (1) presence of finishing pigs; (2) production type (producers of finishing piglets had a higher seroprevalence than producers of breeding stock); (3) vaccination of the sows during nursing (in comparison with vaccinating all sows simultaneously at 5 month intervals, or vaccination during the second half of gestation); (4) pig density in the municipality where the herd was located (seroprevalence increased with higher pig density); (5) herd size less than 100 sows; (6) average within-herd parity (seroprevalence increased with higher withinherd parity); (7) replacement pigs raised on the premises; (8) vaccine strain administered to the sows. Purchase policy (breeding pigs purchased between 10 weeks and 7 months of age, or use of home-bred gilts only) did not significantly contribute to the multivariate model.     

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.     

Vaccination of sows against Mycoplasma hyopneumoniae with Hyoresp

The aim of the study was to investigate the serological reactions of pregnant sows to vaccination with Hyoresp. Further investigations were performed in the offspring of these sows to follow the dynamics of maternal antibodies and the reaction to vaccination at different points in time. The study was conducted in three farrow-to-finish herds endemically infected with M. hyopneumoniae. A total of 30 gilts and 31 sows were vaccinated 8 and 4 weeks ante partum with Hyoresp (Merial GmbH) or given phys. saline solution as a placebo. The offspring was divided into three groups receiving Hyoresp at 1 and 4 or at 4 and 8 weeks of age. The control group was treated with phys. saline solution at 1 and 4 weeks of age. Before vaccination, antibodies against M. hyopneumoniae were detected in 85% of the gilts and 68% of the sows, confirming the endemic infection of the herds. Vaccination of the sows induced a significant increase in the antibody concentration in serum within four weeks and enhanced the concentration of antibodies in the colostrum. As expected, significantly enhanced levels of antibodies were also detected during the first four weeks of life of the offspring of vaccinated sows. The piglets' serological reaction to vaccination at 1 and 4 weeks of age showed marked interferences with maternal antibodies, so that a reaction could be demonstrated only at 8 weeks of age. The serological reaction of piglets vaccinated at 4 and 8 weeks of age was much stronger than that of piglets vaccinated earlier. Surprisingly, the vaccination status of the sow had no effect on the serological response of the piglets in either vaccination scheme. Maternal antibodies are known to reduce the risk of M. hyopneumoniae infections in piglets. Vaccinating the sows against M. hyopneumoniae may thus be an option for farrowing-to-finish herds with an enhanced risk for infections due to ineffective separation of different age groups, poor gilt acclimatisation or high gilt replacement rates.     

Effect of vaccinating sows and their piglets on the development of Glässer's disease induced by a virulent strain of Haemophilus parasuis serovar 5

Ten pregnant gilts were divided into two groups of five and one group was vaccinated at 80 and 95 days of pregnancy with a commercial bacterin containing Haemophilus parasuis serovars 2, 3 and 5. Half the piglets born to each group of gilts were vaccinated at seven and 21 days of age with the same bacterin, and one week after they were weaned at five weeks, all the piglets were inoculated intratracheally with 10(6) colony-forming units of Hparasuis serovar 5. At slaughter, a significantly smaller percentage of the lungs of the pigs born to the vaccinated gilts was affected by pneumonic lesions, and significantly fewer of them had arthritic joint changes. The average daily liveweight gain of the pigs born to the vaccinated gilts was significantly greater than that of those born to the unvaccinated gilts, but the vaccination of the piglets had no effect. There was no significant difference between the feed conversion ratios of the four groups of piglets, and none between the average times they took to reach slaughter weight. The pigs born to the vaccinated gilts had higher ELISA titres to Hparasuis than those born to the unvaccinated gilts.     

Four-year study of lameness in piglets at a research station

Lameness in piglets up to nine weeks old was studied in a research station herd for four years; 9411 piglets were born alive, of which 9.8 per cent were treated for lameness. In litters born to gilts, 9.9 per cent of the piglets were treated for lameness, in litters born to sows of parity 3, 11.4 per cent of the piglets were treated, but in litters born to sows of parity 4 to 7 the proportion of piglets treated for lameness decreased to about 8 per cent. Around 75 per cent of all cases were observed in piglets less than three weeks old; the incidence risk of lameness decreased from 2.7 per cent during the first week of life to 0.3 per cent after weaning. The average weight of affected piglets was reduced by approximately 8 per cent at nine weeks of age. There was no overall association between lameness and sex or birth weight within sex. The mortality among lame gilts was higher at all ages than among healthy gilts, but among barrows a higher mortality was observed only during the late suckling period. Litters with 12 or more piglets had a higher incidence of lameness. Clinical signs of disease in the sow and whether the piglets were given an intramuscular injection of 200 mg of iron on their second, third or fourth day of life had no effect on the incidence of lameness.     

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.     

A reduction in litter size on an ontario Swine farm

In a 200 sow herd, the litter size fell from an average of 10.5 pigs born alive per litter from January to June, to an average of 9.2 for the remainder of the year. Management changes during the first part of the year resulted in half the sows weaning litters at three weeks of age and half the sows weaning at four weeks of age instead of at six weeks as was previously done. The subsequent litter size was 9.3 pigs born alive per litter for three-week weaned sows compared to 10.0 for four-week weaning. The management of gilt breeding was also altered by the necessity to breed groups of 12 gilts in one-week periods of time and therefore a higher proportion of gilts may have been mated on their first estrus instead of their second or third estrus as had been the case. The difference in litter size of first parity sows between the first six months and the second six months was 1.1 pigs. Parvovirus infection may have been a factor contributing to the reduction in litter size amongst first parity sows; two groups of first parity sows experienced an increase in mummified piglets, a reduced far rowing rate, and smaller litter size. However, no attempt was made at diagnosing an infectious agent. Parity distribution remained relatively unchanged during the year and was not associated with the drop in litter size.     

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.     

The pattern of endemic parvovirus infection in four pig herds

Serological surveys were conducted on the gilts and adult sows in 4 herds endemically infected with porcine parvovirus. The study assessed the influence of the type of management of breeders on the spread of virus infection and the influence of endemic parvovirus infection on reproductive parameters of the herd. The practice of holding gilts and sows in groups did not reliably promote infection or maintain a 100% level of active immunity amongst adult sows in 2 of 3 group husbandry herds. In the 4 herds, the prevalence of adult sows (greater than 12 months) with active immune haemagglutination inhibition titres (greater than or equal to 256) ranged between 44% and 100%, while between 0% and 100% of gilts (6 to 12 months of age) had active immune titres. Fully susceptible gilts older than 9 months of age held in groups, failed to become infected by 12 months of age on farms endemically infected with PPV. In 2 herds a continued low infection rate of gilts resulted in increasing the potential of breeding animals becoming susceptible to parvovirus infection as infected sows were replaced by noninfected gilts. In both herds, epidemics of parvovirus infection followed, which were characterised by an increase in reproductive failure. Parvovirus infection during the first 70 days of pregnancy reduced the average number of piglets born alive per litter by 1.6 piglets (p less than 0.05). This was due to the combined effect of more piglets being born dead per litter and an overall reduction in litter size.     

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.     

Safety and efficacy of a classical swine fever subunit vaccine in pregnant sows and their offspring

In the study three groups with five pregnant sows each were used. The animals were vaccinated twice, 2 weeks apart, in different stages of gestation, i.e. +/-4, +/-8 and +/-12 weeks after insemination and then 14 days later, respectively. From each group of sows three litters were randomly selected and vaccinated twice, 4 weeks apart, at 5 and 9, 7 and 11, and 9 and 13 weeks of life, respectively. Blood for serological investigations by virus neutralisation test and ELISA tests (for E(rns) antibodies and for E2 antibodies, separately) was taken before immunisation, at each vaccination and 2 weeks thereafter. Clinical observations shown that no local nor systemic reactions as well as no adverse effect on gestation occurred after vaccinations in any of the sows. Serological tests detected a low level of antibodies after the first vaccination and a typical booster effect after the second one. In piglets no adverse effect of the vaccination on the body weight gain was found. The presence of maternally derived antibodies (MDA) in non-vaccinated control piglets was observed up to the age of 5-13 weeks of life. The most evident immunological reaction was obtained in piglets vaccinated at the age of 5 or 7 weeks of life and revaccinated 4 weeks later. The CSFV-E2 subunit marker vaccine tested proved to be safe for pregnant sows and immunogenic for MDA positive 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.     

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.     

Reproductive performance in gilts through their first two parities

Fertility data were collected for 766 gilts from 12 breeding and commercial herds. The age at first breeding was 244.5 days and at first farrowing 363.2 days. The litter size was 9.91 piglets born (9.16 live). The farrowing rate at the first service was 87.8%. The total farrowing rate was 95.5% of the mated gilts and 88.4% of all the gilts. 9.8% were repeat breeders. 2.6% of the once mated gilts never returned to oestrus and still did not farrow. The culling rate was 11.6%. The major reason for culling was delayed puberty/anoestrus (7.7%). Of the 565 gilts having a first litter 85.3% were mated after weaning. The age at second farrowing was 541.7 days. The litter size was 10.9 piglets born (10.3 live). The farrowing rate after first service was 83.0%. The total farrowing rate of the 482 sows was 92.9% and of the 565 weaned sows 79.3%. 12.2% were repeat breeders. 4.8% of the sows once mated never returned to oestrus and still did not farrow. The culling rate was 20.7%. Culling because of anoestrus was 4.4%. The month of birth significantly influenced the number of gilts culled because of anoestrus, the age at first breeding and at first and second farrowing. The season also influenced the interval from weaning to service, the percentage of sows served within 7 days of weaning and culled because of anoestrus. No correlation between a high ultrasonic index and lowered fertility was found. The age at first breeding was 1.12 days younger per unit higher ultra-sonic index.     

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.     

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 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.     

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)     

The effect of colostral immunity on the active formation of antibodies in pigs after the administration of inactivated vaccine against Aujeszky's disease

In a large herd of pigs where a trial was performed to cure the animals from Aujeszky's disease (AD) by applying to all animals an inactivated vaccine, a post-vaccination antibody response was studied in piglets coming from the sows that were vaccinated several times. When the piglets were vaccinated at the age of eight weeks (the average virus-neutralizing titer (VNT) of colostral antibodies was 1:11.4) and revaccinated at the age of 11 weeks, 73% of the forty-five animals (examined at the age of 17 weeks) did not have any virus-neutralizing (VN) antibodies in the blood serum. After the third vaccination dose (at the age of 17 weeks), 11% of piglets did not have any VN antibodies if they were examined at the age of 22 weeks (the average antibody VNT was 1:15.3). Applying the ELISA procedure, the antibodies were demonstrated in the sera of all piglets after three vaccination doses. Shifting the time intervals of vaccination (at the age of 8, 13 and 19 weeks), the VN antibodies were found out after three vaccination doses in the sera of all piglets examined at the age of 23 weeks (the average VNT was 1:56.4). After three vaccination doses at the age of 12, 17 and 23 weeks, the VN antibodies were also demonstrated in all piglets at the age of 27 weeks (the average VNT was 1:208).     

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.