A study on the severity and relevance of porcine circovirus type 2 infections in Dutch fattening pigs with respiratory diseases.

This study was set up to get more insights in the severity and relevance of porcine circovirus type 2 (PCV2) infections in Dutch fattening farms in an endemic PCV2-situation with no clinical signs of post-weaning multisystemic wasting syndrome (PMWS). In part A of the study, in total 29 commercial fattening farms with varying percentages of pneumonia and pleurisy at slaughter were examined. Blood samples were collected at random by cross-sectional sampling; 10 in the age of 10-12 weeks, 10 at the age of 16 weeks and 10 blood samples at the end of the finishing period (20-22 weeks of age). Serum samples were examined for the presence of PCV2 IgM and IgG antibodies and for antibodies against other porcine lung pathogens. In part B, 8 "high" and 8 "low" herds were selected. The 8 "high" herds were defined as herds having high percentages of lung lesions (pneumonia) at slaughter, and the 8 "low" herds had low percentages of pneumonia at slaughter. For both the "high" and "low" herds, 3 pigs showing signs of respiratory distress were selected for necropsy (n=48). Lung tissue samples were examined post-mortem for macroscopic and histopathological lesions, and for the presence of bacteria and viruses. The results of part A showed that, pigs at 16 weeks of age with IgM antibodies against PCV2 had a lower probability of having pleuritis at slaughter (OR 0.34, P<0.000). Pigs in the age category of 20-22 weeks, and with IgM antibodies against PCV2, also had a lower probability of having pneumonia at slaughter (OR 0.29, P=0.032). In part B lobus apicalis pneumonia, PCV2 in macroscopically unaffected lungs, Pasteurella multocida, Mycoplasma hyopneumoniae, and swine influenza viruses were all found significantly more often in "high" than in "low" pigs at autopsy. High PCV2 DNA loads (>10(4) PCV2 DNA copies/mg) were found in lungs of 14 (58%) "high", and in 7 (29%) of the "low" pigs (P=0.13). In 11 of the 19 affected lungs from "high" pigs, high PCV2 DNA loads were found in combination with one or more other lung pathogens, while this was found only in 5 of the 17 affected lungs from "low" pigs (P=0.02). This study confirms the hypothesis that PCV2 plays a role in pneumonia and pleurisy in 10-24 weeks old fattening pigs, not only in herds with a high prevalence of PMWS, but also in herds with no clinical signs of PMWS.

[Effect of the Stellamune Mycoplasma vaccine on growth, energy conversion, death, and medication use in fattening pigs on a pig farm chronically infected with Mycoplasma hyopneumoniae]. / Het effect van het Stellamune Mycoplasmavaccin op groei, energiewaardeconversie, sterfte en medicijngebruik van vleesvarkens op een chronisch met Mycoplasma hyopneumoniae besmet varkensbedrijf.

The effect of Stellamune Mycoplasma vaccine, administered to piglets aged 2-15 days and then 13-15 days later, on daily weight gain, energy conversion, and use of medication was examined in fattening pigs on a chronically Mycoplasma hyopneumoniae infected pig farm. Half of the piglets were vaccinated and the other half acted as controls. In the study design, half of the pens in the fattening unit were allocated to vaccinated pigs; the other half to non-vaccinated pigs, pen was the experimental unit. In the fattening pens sows and castrated boars were separated. The study consisted of a total of 37 pens with vaccinated, and 37 pens with non-vaccinated pigs in 12 different compartments within the pig herd. In the finishing period, mean growth performance and mean energy conversion (EV/kg) of vaccinated animals was 65 grams/day higher and 0.07 EV/kg lower than in control pigs. Furthermore, the incidence of individual curative medication against respiratory problems was more than 4 times higher in control pigs than in vaccinated pigs. There was a tendency for a higher number of group medications against respiratory problems in control pigs than in vaccinated pigs. It is concluded that, in this herd, vaccination against M. hyopneumoniae was successful from an economic point of view.

[Analysis of survey data about the effect of vaccination of sows against blue pig abortion (PRRS) in the Netherlands]. / Analyse van enquêtegegevens naar het effect van abortus blauw (PRRS)-vaccinatie bij zeugen in Nederland.

Questionnaires were used to collect information on the experience of pig breeders with the vaccination of sows against PRRS. There was a 1-year interval between the two questionnaires. Sixty-two pig breeders returned the first questionnaire and 36 returned the second questionnaire. Before they started vaccination, 61% of the pig breeders sent samples to the laboratory of the Animal Health Service for investigation. At least one blood sample was positive for PRRS antibodies, but PRRS virus was not detected in any of the samples. Repeat breeding was the most important reason to vaccinate sows. On 54 farms (77%) sows were first vaccinated during the suckling period, on one farm (2%) sows were vaccinated during gestation, and on 7 farms (11%) all sows were vaccinated irrespective of their phase of reproduction. Repeat vaccinations were given during the suckling period on all farms. Mild side effects were reported on 16 farms (25%). Repeat breeding was the most important adverse reaction, followed by anoestrus. After 1 year, 58% of the pig breeders expressed satisfaction with vaccination. Twenty-eight pig breeders stopped vaccinating their sows in the first year, mainly because vaccination had no effect on the technical results. The effect of PRRS on the technical results of eight farms before and a year after vaccination was analysed. Although technical results were slightly better after vaccination, it was not clear whether this improvement was due to vaccination. From the results of this study it can be concluded that, without good diagnostic investigations, the routine vaccination of sows against PRRS is not economically viable in herds infected with PRRS virus.

Use of colostrum to detect antibodies against glycoprotein I of Aujeszky's disease virus.

Serum and colostrum samples taken from 499 sows from five herds of pigs endemically infected and vaccinated against Aujeszky's disease virus, were used to investigate whether colostrum could be used to detect antibodies against glycoprotein I (gI) of the virus. Using serum as the reference, the test applied to colostrum had a sensitivity of 97 per cent and a specificity of 88 per cent. When samples were taken from 50 sows from a gI seronegative vaccinated herd, one colostrum sample was gI-positive, giving a specificity for the test of 98 per cent. The mean gI antibody titres in colostrum were about six times higher than in serum. Samples of colostrum were also taken from 132 sows from eight unvaccinated herds free of Aujeszky's disease virus. All these samples were gI-negative, giving a specificity of 100 per cent. Colostrum samples can be stored for at least six weeks at -20 degrees C without compromising the test results, and the repeatability and reproducibility of the test applied to colostrum were good.

[The effect of parvovirus vaccination in sows through their 4th parity and the role of influenza H1N1 virus]. / Onderzoek naar het effect van een parvovaccinatie bij zeugen tot en met de vierde pariteit en de betekenis van het influenza H1N1 virus.

The effects of vaccination of a porcine parvovirus (PPV) in gilts and the first four litters were studied in a pig-breeding herd. In addition to determination of the technical results, PPV and influenza (H1N1) titres were measured. From the serological findings it was apparent that PPV and influenza (H1N1) virus circulated during the trial. The number of total-born and live-born piglets was significantly higher in the first litter when PPV-vaccinated and non-vaccinated gilts were compared. On the basis of these results, it is recommended to vaccinate sows and gilts after the first litter.

[Determination of estrone sulfate levels in the blood and urine of pigs]. / Oestronsulfaatbepaling bij het varken in bloed en urine.

The concentration of oestrone sulphate was determined in plasma as well as in urine to verify early pregnancy in pigs (within 24-29 days after mating). The threshold level in plasma was 0.70 ngr/ml. and in urine 50 ngr/ml. Accuracy was ninety-nine per cent in samples of plasma and ninety-two per cent in samples of urine respectively.

[Effects of the addition of increased nitrates to the drinking water of fattening pigs and weaned piglets]. / Verslag van een onderzoek naar de gevolgen van extra nitraattoevoeging aan drinkwater voor mestvarkens en gespeende biggen.

Three experimental studies were done on the effects of increased concentrations of nitrate in the drinking water of weaned piglets and flattening pigs throughout the weaning and fattening periods respectively on the experimental piggery in Raalte for pigs in the northern and eastern Netherlands. To begin with, prospective studies were done in three times four individually housed experimental animals which were given 100, 200 and 500 mg of nitrate per litre of drinking water respectively throughout the fattening period. The results obtained were compared with the findings in twenty controls. When the weaned piglets were studied, two groups of weaned piglets, each consisting of an odd hundred piglets, fifty per cent of which served as an experimental group, the other fifty per cent serving as a group of controls, were compared. The experimental group was given drinking water to which 220 mg of nitrate per litre were added. When the fattening pigs were studied, two groups, each consisting of seventy animals, were compared. Fifty per cent served as a control group and fifty per cent as an experimental group. The experimental groups were given drinking water to which 500 mg of nitrate per litre were added. The nitrate and nitrite levels of the drinking water supplied were measured at regular intervals. The studies in fattening pigs included the examination of blood samples for the concentrations of haemoglobin and methaemoglobin halfway and at the conclusion of the periods. The additional nitrate in the drinking water did not have any negative effect on the haemoglobin and methaemoglobin levels of the drinking water or on the results obtained in these studies. Studies on meat and organs were done in five controls and five experimental animals from the fattening pigs studied. Marked differences were not observed in any case. It is concluded that an increased concentration of nitrate in drinking water does not have any injurious effect on the health of and the results obtained in weaned piglets, provided the drinking water is of good quality in addition to having an increased nitrate level.

A field evaluation of Nobi-Vac atrophic rhinitis vaccine.

A field trial was carried out with Nobi-Vac AR vaccine in 11 swine breeding herds. One herd suffered from severe B. bronchiseptica (BB+) rhinitis in piglets, while no clinical Atrophic Rhinitis (AR) was observed. Ten herds were described as AR problem herds, because clinical AR was observed for at least 1 year in spite of the fact that medication of sows and piglets was carried out and adequate housing and management systems were available in most herds. BB+ was isolated in 9 of these 10 farms and the AR pathogenic P. multocida (PM+) in all these farms. The trial started when piglets were born of sows which had been vaccinated 3 times. All piglets between 7 and 10 weeks old were examined clinically for AR. Nasal swabs from 20 pigs on each farm were screened bacteriologically for BB+ and PM+ every other month. A severe reoccurrence of AR was found in 2 of the 10 AR problem farms. In these 2 herds the 'all in-all out' system was not applied in farrowing and weaning houses. In the 8 other AR problem herds the percentage of pigs with AR decreased significantly below the average level of 1% per year. The percentage of pigs infected with BB+ and PM+ also decreased significantly. PM+ was significantly related to the percentage of clinical AR piglets. Seasonal effects contributed to a minor extent to the percentage of AR piglets. After 2.5 years of this trial PM+ could not be isolated during the last 12 months in six of the remaining AR problems herds. The conclusion is that Nobi-Vac AR vaccination of the sow gave protection against clinical AR in piglets on those farms (80%) which provided adequate housing and management systems.

[Study of porcine parvovirus antibodies on a breeding farm]. / Onderzoek naar porcine parvovirus antilichamen op een vermeerderingsbedrijf.

Serological examination of porcine parvovirus (PPV) haemagglutinating antibodies is reported in replacement gilts after a PPV infection on a large farm. It seems that PPV is no longer active on the farm after PPV infection.