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The aim of the study was to test whether acidified drinking water, with two millilitres of an acid mixture per litre, was able to reduce the number of Salmonella infections in finishing pig herds. In each compartment, half of the pens were supplied with acidified water and the other pens served as negative control. In three herds the required dose was not applied to the pigs as a result of various practical problems. In another herd, all pigs remained seronegative throughout the study. Analysis of the remaining three herds showed a large and significant treatment effect in one herd (P<0.001). As a result of the small number of observations and the overall lower seroprevalence in the control groups, the other two herds only showed a statistical trend to a treatment effect (0.10

The purpose of this investigation was to study the incidence and course of Salmonella infections in finishing pig herds in order to asses the stability of a given Salmonella herd status. Five low- and 7 high-seroprevalence herds were followed for seven sampling rounds. Each round, blood and faecal samples were tested in an indirect ELISA and by bacteriological culturing, respectively. In high-seroprevalence herds a positive Salmonella status was an indication of a long-term problem and the status was relatively stable over time. The herds experiencing clinical salmonellosis were not necessarily the herds with the highest seroprevalence. It is possible to deliver sero-negative finishers to the slaughterhouse, even though these pigs were seropositive as growers. In three out of five low-prevalence herds, major infection incidents occurred, indicating that changes in the Salmonella status should be anticipated. Low-prevalence herds can remain negative over a longer period of time as a result feeding a complete liquid feed containing fermented by-products.

In the course of the 1997-1998 CSF epidemic in the Netherlands, two semen collection centres (SCC) became infected. As an eradication strategy for an acute crisis situation, it was concluded that all semen of the boars at the SCCs collected and distributed in the risk period of 28 January to 7 March 1997 was potentially contaminated (suspect semen). As a consequence, a total of 1,680 pig herds, mainly located in the southern part of the Netherlands, were officially declared CSF suspect. The purpose of this study was to investigate whether infection of farms through contaminated semen played a significant role in the CSF epidemic. A total of 123 CSFV infected herds were identified, that had received suspect semen from one or both of the infected SCCs. In 87 out of these 123 infected herds, infection by way of artificial insemination (AI) could be excluded either according to the insemination information or the infection pattern observed. In only 21 herds, infection by way of AI was regarded as possible according to the insemination information and infection pattern. Owing to missing information, no conclusion could be drawn about the possibility of infection of 15 farms by way of AI. Thus, we conclude that at most 36 farms may have been infected through AI during the CSF epidemic in the Netherlands.

Reports on the effects of mange on the production performance of pigs are conflicting. So far, studies have used experimental infections, by depositing encrusted lesions from chronically infected pigs into the ears of experimental pigs. However, this is a poor representation of what happens under natural field conditions. The purpose of our study was to quantify the effects of sarcoptic mange on production performance and pruritus in pigs that were infected by contact with S. scabiei var. suis-infected pigs. A total of 80 piglets were matched by sex and weight and randomly divided between experimental and control compartments. In the experimental compartment, each of three naturally S. scabiei var. suis-infested pigs were randomly allocated to three pens with 13 susceptible pigs each. From day 0 to 35, the growth performance of pigs in the experimental compartment was significantly (P=0.04) worse (35 g/d) than of pigs in the control compartment. From day 35 to 112, there was a statistical trend (P=0.10) that the growth performance of pigs in the experimental compartment was lower (50 g/d) than that of pigs in the control compartment. For the complete fattening period (0-112 or more days), the growth performance of pigs in the experimental compartment was significantly (P=0.05) worse (41 g/d) than that of pigs in the control compartment. Mean feed conversion ratio (kg feed per kg gain) was 2% higher in the experimental compartment compared with the control compartment. Pigs in the experimental compartment had a nine times (95% CI: 2 - 44) higher chance of showing pruritic behaviour than pigs in the control compartment.

The Aujeszky's disease virus (ADV) eradication campaign in The Netherlands is based on compulsory vaccination and certification of ADV-free herds and consists of three stages: reduction of transmission of ADV, tracing and elimination of remaining sources of ADV, and, in the last stage prohibition of vaccination. This paper summarizes the progress made in the first two stages of the eradication. Between 1994-1999, ADV seroprevalence decreased sharply in all four regions in The Netherlands, both in the sow and the finishing pig population. In the sow population, the mean ADV prevalence in the northern, eastern and western regions decreased to less than 0.5% in the first quarter of 1998, and to approximately 1% in the southern region. For the finishing pig population, the mean ADV prevalence decreased to less than 0.6% in all four regions in the first quarter of 1998. The proportion of sow herds that were certified ADV-free increased steadily from approximately 40% in the last quarter of 1996 to 96% in the first quarter of 1999. The proportion of finishing pig herds that were certified ADV-free showed the same spectacular increase as in the sow population: from approximately 14% in the last quarter of 1996 to 90% in the first quarter of 1999. It is anticipated that the last stage of the ADV eradication campaign, stopping vaccination, will be achieved very soon. Monitoring wild boars for ADV between 1994 and 1999 indicated that ADV is uncommon within the wild boar population. Therefore, it seems that ADV infection in the wild boar population is not an important reservoir in The Netherlands.

Serum samples from 102 veterinarians and 191 pig farmers from the southern part of the Netherlands were investigated for antibodies against Brucella abortus, Leptospira spp, Streptococcus suis serotype II, Hantavirus (HV), and lymphocytic choriomeningitis virus (LCMV). All samples were collected in 1993 and stored until this study was performed. The prevalence of antibodies against B.abortus in veterinarians (4.5%) was significantly higher (P = 0.01) than in pig farmers (0%). None of the veterinarians (0%) and only one pig farmer (0.5%) had antibodies against Leptospira spp. Furthermore, significantly (P = 0.015) more veterinarians (6%) than pig farmers (1%) had antibody titres against muramidase-released protein (MRP),a protein of pathogenic S. suis serotype II strains. None of the veterinarians and a total of 3 (1.6%) pig farmers had antibody titres against HV. The prevalence of antibodies against LCMV tended to be higher in pig farmers (2.6%) than in veterinarians (0%) (P = 0.10). It can be concluded that the prevalence of antibodies against the investigated zoonotic agents in veterinarians and pig farmers is low.

The results of an inventory of field cases of amyloid arthropathy in chickens and of routine post-mortem recordings over a two years period are described. Studies were also performed to evaluate the amyloidogenic potential of arthrotropic bacterial species (Staphylococcus aureus, Escherichia coli and Salmonella enteritidis) isolated from chickens as well as several Enterococcus faecalis isolates compared to the amyloidogenic E. faecalis isolate (previously isolated from amyloidotic joints). As chicken anemia virus was also isolated from amyloidotic joints of field cases, it was also screened for its amyloidogenic potential. In another experiment, Mycoplasma synoviae, inactivated E. faecalis isolate 6085.94, Freund's adjuvant and an arthrotropic reovirus field isolate were also screened for amyloidogenicity by intra-articular injection. These studies showed that the ability to elicit extensive amyloid arthropathy is reserved primarily to E. faecalis, but that this property is not common to every E. faecalis isolate. Intra-articular application of complete Freund's adjuvant led to the formation of extensive joint amyloid deposits. Of the other micro-organisms studied, S. aureus, S. enteritidis and E. coli were also able to cause joint amyloidosis, but in very small amounts. Inactivated E. faecalis, chicken anemia virus and reovirus did not cause amyloid arthropathy after intra-articular inoculation. This study is consistent with results of the analyses of previous field cases and of the induction of amyloid arthropathy in chickens, suggesting a considerable role for E. faecalis in this clinical-pathological entity. Finally, strain typing by analysis of chromosomal DNA restriction endonuclease digests by pulsed-field gel electrophoresis (PFGE) of amyloidogenic, non-amyloidogenic, amyloid-associated and other E. faecalis isolates from various origins showed that all amyloidogenic and amyloid-associated E. faecalis isolates had similar restriction digests, suggesting clonal spread.

From February to June 1995, 5-12 blood samples were collected in each Dutch pig herd and tested for antibodies against pseudorabies virus (PRV). The percentage of PRV-seropositive pig-finishing herds in three regions with more than 1,000 pigs/km2 (regions 2, 4 and 7) was 6% (region 2), 12% (region 7), and 25% (region 4). The percentage of PRV-seropositive pig-finishing herds in five regions with fewer than 1,000 pigs/km2 (regions 1, 3, 5, 6, and 8) was 3% (region 1), 9% (region 3), 6% (region 5), 0% (region 6), and 4% (region 8). The small sample size allows only the detection of major outbreaks and the percentages of PRV-seropositive herds therefore under-estimate the actual virus circulation in the regions. The fraction of PRV introductions that will result in a major outbreak depends on the herd immunity and thus on the vaccination programme of the herds. By combining for each herd the occurrence or absence of a major outbreak with the herd immunity induced by the vaccination programme, we estimated the average rate at which PRV was introduced into finishing herds in the eight regions. The average number of PRV introductions per finishing herd per finishing period (16 weeks) in the pig-dense regions was estimated at 0.20 in region 2, 0.83 in region 4, and 0.48 in region 7. In the less densely populated regions this rate was estimated at 0.08 in region 1, 0.34 in region 3, 0.17 in region 5, 0.00 in region 6, and 0.09 in region 8. The eight regions could be classified into four areas with a statistically different (P < 0.05 in Mann Whithey U test) rate of PRV introduction: i) regions 1, 6, and 8; ii) regions 2 and 5; iii) regions 3 and 7; and iv) region 4.

The prevalence of allergy, lung function disorders, and bronchial hyperreactivity was studied in 102 Dutch veterinarians, subdivided into five professional groups (predominantly working with either swine, cattle, poultry, companion animals, or as a non-practitioner). The mean age of the participants was 43 years; 6 participants were females. Twenty-two per cent of the participants were overweight, and relatively more non-practitioners than practitioners were overweight. Approximately 23% of the vets reported complaints of prolonged fatigue. The data suggest a relationship between complaints of prolonged fatigue and a more than average number of daily working hours. Only a small proportion of vets were sensitized against several allergens. There were no significant differences in prevalence of distinct lung function disorders or bronchial hyperreactivity between professional groups. It is hypothesized that the respiratory complaints (chronic coughing, chronic phlegm production, stuffed nose, sneezing) reported by the vets predominantly working in swine and/or poultry practice could be caused by irritation and/or inflammation of the first part of the trachea-bronchial tree that has no measurable and permanent consequences for changes in lung function or increased bronchial hyperreactivity. The results of a skin test against allergens and determination of allergen-specific IgE in blood indicated that the respiratory complaints were probably not related to allergy against the panel of allergens tested.

Dust and endotoxin exposure was measured in the Spring and Autumn in 96 veterinary practitioners, subdivided in four professional groups ((predominantly working with either swine, cattle, poultry, or companion animals). Furthermore, peak expiratory flow (PEF) variability was measured four times a day over a week in Spring and Autumn in order to detect occupation-related respiratory disorders. The participants kept a log book in which they recorded their activities during these periods. Practitioners working with swine, cattle, or poultry had a significantly higher exposure to dust (+/- 5 times) and endotoxin (+/- 10 times) than companion animal practitioners. PEF variability measurements gave no indications for an increased prevalence of bronchial hyperreactivity related to occupational activities. Respiratory protective devices (RPD) were used selectively. Only a small proportion of the practitioners used them at any time when entering a animal confinement building. Swine and cattle practitioners worked for approximately 3.6 hours per day in animal buildings, whereas poultry practitioners worked in the environment of poultry buildings for approximately 2.8 hours per day.

Risk indicators for Pasteurella haemolytica related summer pneumonia in lambs in The Netherlands were investigated using a mail questionnaire survey of 860 flocks. The response rate was 64% (n = 550). Multivariate risk analysis indicated that taking sheep to sheep fairs, the purchase of sheep and/or lambs, the lack of possibility for indoor housing, and an increased flock size were associated with increased risk of occurrence of summer pneumonia in lambs of the home flock.

The breeding and finishing pig populations in four Animal Health Service regions in the Netherlands were monitored with respect to pseudorabies virus (PRV) seroprevalence. Analysis of data of the seroprevalence survey of 1994 indicated that two samples per herd was sufficient to estimate the seroprevalence in both the sow and finishing pig populations. In the northern, eastern, southern, and western regions, 115, 645, 940, and 218 sow herds and 114, 1036, 954, and 323 pig finishing herds were sampled, respectively. In the breeding pig population, the PRV-seroprevalence decreased from 27% to 17% in the eastern region, from 32% to 17% in the southern region, from 18% to 12% in the western region, and from 10% to 6% in the northern region. In the finishing pig population, the PRV-seroprevalence decreased from 15% to 6% in the eastern region, from 19% to 6% in the southern region, and from 12% to 5% in the western region. There was no significant difference in PRV seroprevalence in finishing pigs in the northern region between the survey of 1994 and 1995.

The prevalence of antibiotic resistant Escherichia coli isolates from faecal samples from 110 veterinarians with different specialties (predominantly working with cattle, swine, poultry, or small animals or working as a non-practitioner, e.g. in government or industry) was investigated. In 22% and 13% of the veterinarians E. coli isolates showed a high level of resistance to oxytetracycline and ampicillin respectively. A significantly higher percentage of cattle practitioners had a high level of antibiotic resistance against ampicillin than did swine practitioners. Furthermore, a significantly higher percentage of poultry practitioners had a high level of antibiotic resistance against oxytetracycline than did swine practitioners and non-practitioners. A significantly higher percentage of practitioners recently (within last 6 months) used antibiotics for personal intake than did the group of non-practitioners. There was no evidence for a relationship between personal intake of antibiotics and the occurrence of a high level of resistance to ampicillin or oxytetracycline. The prevalence of E. coli isolates, that were resistant to several antibiotics was highest in cattle and poultry practitioners and the lowest in swine practitioners. A possible explanation for the observed differences in high level resistance to oxytetracycline and ampicillin between veterinary specialty groups is a difference in exposure to antibiotics during practice.

In a study population of 90 sow herds in the southern Netherlands, the occurrence of sows returning to oestrus more than five days after insemination (SRO) was investigated. In these herds information with regard to the herd system, herd size, and breeding management was recorded. The occurrence of SRO was recorded with the on-farm computer management system CBK-plus. The incidence of SRO was defined as the average number of gilts or sows returning to oestrus more than five days after insemination per 100 first inseminations. The average incidence of SRO in the study population was 18.3 per 100 first inseminations. Multivariate analysis resulted in a model with a significant effect of herd operation (herds with only sows had a lower incidence of SRO than herds with sows and finishing pigs), breeding strategy (herds with two or more inseminations per oestrus in a sow had a lower incidence of SRO than herds with one insemination per oestrus) and percentage of sows artificially inseminated (a higher percentage of artificial insemination was associated with a higher incidence of SRO).

In the European Union, vaccination campaigns against Pseudorabies virus (PRV) in swine have been started to eradicate PRV. Specific sampling designs are needed to monitor PRV seroprevalence at a regional level. This paper demonstrates how sampling theory can be applied to design a disease seroprevalence survey, using PRV as an example. In the spring of 1994, the four regions in the Netherlands covered by the regional Animal Health Services were monitored with respect to PRV seroprevalence. Per region, blood samples from approximately 1400 herds, with two animals per herd, were collected. The sampling design accounted for stratification by fattening pig and sow population within each region. The regional PRV seroprevalence of swine in the Southern region was the highest (24.9%), closely followed by the PRV seroprevalence of swine in the Eastern region (20.5%). These regions have the highest density of swine in the Netherlands. The PRV seroprevalence in the Western and Central region (11.7%) was about half of the seroprevalence in the Southern and Eastern regions; the lowest regional PRV seroprevalence was observed in the Northern region (3.5%). The Northern part also has the lowest pig density. The PRV seroprevalence was approximately two times higher in sows than in fattening pigs.

In 280 slaughter pigs, the oesophageal region of the stomach was examined to test the hypothesis that there is a (causal) relationship between the intensity of bile staining of oesophagogastric tissue due to bile regurgitation and the severity of oesophagogastric lesions. When the stomachs were opened, almost all stomachs contained bile and 99.6% of stomachs showed bile staining of the pars oesophagea. A total of 14.3% of the stomachs showed distinct erosions and/or ulceration. A considerable proportion of the stomachs (58.5%) had hyperkeratosis as the only lesion. Only two animals showed a completely intact epithelium. There was no evidence for an increased proportion of oesophagogastric lesions with an increased intensity of bile staining. No dark yellow to green staining was observed; a just detectable to an obvious yellow was seen. This is an indication for bile regurgitation of recent origin. Therefore, there is no evidence for the hypothesis that the regurgitation of bile into the stomach is positively linked to the occurrence of oesophagogastric lesions in fattening pigs. It is suggested that various factors associated with slaughter, such as fasting and slaughter procedure, are primarily responsible for the presence of bile and the staining of the pars oesophagea in the stomachs.

As no systematic study has been done to get an accurate estimate of the incidence of return to oestrus after first insemination in sows in the Netherlands, the objectives of this investigation were: 1) to obtain an estimate of the incidence of return to oestrus after insemination at the herd level; 2) to investigate the association between incidence of return to oestrus after first insemination and reproduction characteristics in order to get an impression of the economic importance of reproductive failure. These objectives were investigated by using the reproduction results of 240 swine breeding herds in the Southern Netherlands in 1987. This information was obtained from CBK plus computerized herd management records. The average incidence rate of return to oestrus after first insemination at a herd level was 16.9 per 100 first inseminations. The occurrence of return to oestrus after first insemination was distinctly higher in the insemination months July and August compared to the rest of the year. An increased incidence, with 10 returns per 100 first inseminations corrected for confounders in a multiple linear regression model, was associated with a decrease of approximately 0.3 live born piglets/sow/year. A prospective longitudinal study was started in 1988 and 1989 in 37 sow herds. Individual sows were monitored from weaning to first insemination, to the occurrence of return to oestrus, or not, after first insemination, and to farrowing. The investigation focused in particular on the relationship between return to oestrus after first insemination and seroconversion against porcine parvovirus (PPV) and Leptospira interrogans serovar bratislava (L. bratislava).(ABSTRACT TRUNCATED AT 250 WORDS)

The data presented here were obtained using blood samples from 159 healthy, conventionally managed sows from 37 breeding herds. Sows were sampled at weaning and at 4-5 weeks gestation. Paired blood samples were analysed from sows that had a normal pregnancy and subsequently farrowed. The mean values of serum total protein, albumin and gamma globulin concentration were lower in the blood samples obtained at weaning compared with those obtained at 4-5 weeks gestation. Leucocyte count was higher, mostly as a result of a higher segmented neutrophil count, in the blood samples obtained at weaning compared with those obtained at 4-5 weeks gestation.

The ability of pig suppliers to separate pigs with abnormalities from pigs without abnormalities at the end of the finishing period was investigated. Nineteen hundred and seventy-eight pigs, delivered by 22 pig suppliers, were involved in the experiment. The pigs were inspected on the farm by the pig supplier and, separately, by a veterinary expert. The animals were sent in 22 deliveries to one slaughterhouse. A veterinary meat inspector carried out the ante- and post-mortem inspections. The results of the inspections were compared. The measure of agreement, Cohen's Kappa (CK), indicated a poor (CK less than 0.40) to fair (0.40 less than CK less than 0.75) agreement among the results of the different inspection procedures, depending on the abnormality under investigation. There was a fair to good agreement for the abnormality 'tail lesion' among all inspections. Some findings of the live animal, such as 'straggler', were associated with a wide range of post-mortem abnormalities. It is concluded that preselection is possible and that the economic and practical feasibility of preselection should be investigated.

In a cohort study, 40 pig finishing herds were selected: twenty pig herds with a low and twenty pig herds with a high prevalence of several pathological lesions recorded at slaughter in a six-month period before the start of the study. Blood samples were taken from 20 pigs per herd at the end of the finishing period to investigate haematological and clinicochemical profiles. There was only a significant difference in serum albumin concentration between the low and high lesion prevalence groups. There were distinct differences in blood profiles between pig herds, but also between batches of pigs within a herd, housed in different compartments. Differences between castrated males and gilts were also demonstrated with respect to mean values of the blood variables haemoglobin, iron, copper, beta-globulin, eosinophils and segmented neutrophils. However, the differences were not of a biologically important magnitude. The mean values of the blood variables pepsinogen and lymphocytes differed significantly between pig herds from the two participating integration groups. Pigs with a higher albumin concentration, a lower gamma-globulin concentration, a higher copper concentration and a higher creatine kinase activity in serum showed a higher daily weight gain.

The relationship between the extent of seropositivity for Aujeszky's disease virus (ADV), Actinobacillus pleuropneumoniae (App.) serotype 2 and porcine influenza (PI) viruses serotype H1N1 and H3N2 in pigs on the one hand and the health status of the pigs and some farm and management conditions in the herds on the other hand was studied in 45 pig finishing herds, all members of one integration group. The health status was assessed by the extent of clinical signs, the use of veterinary drugs and the prevalence of pathological lesions in pigs at slaughter. There was no relationship between the extent of seropositivity on the one hand and clinical signs and use of veterinary drugs on the other hand. However, there was a positive relationship between the extent of seropositivity and the percentage of pigs with lesions of the respiratory tract at slaughter. Furthermore, the study indicates that the variation in seropositivity between pigs herds is associated with management related factors that particularly influence the possibility of the spreading of viruses. A sero-epidemiological investigation in 14 pig herds with recurrent pneumonia problems revealed a high percentage of seropositive pigs per herd. Furthermore, in a large number of herds, pigs were simultaneously seropositive for ADV and App. serotype 2, for ADV and PI serotype H1N1 or for ADV and PI serotype H3N2.

Differences in haematological and clinicochemical profiles of blood of apparently healthy slaughter pigs collected at the farm and at slaughter were investigated in relation to the severity of pathological-anatomical lesions. For this purpose blood-samples of castrated male pigs were collected once at seven different farms and from the same pigs one to three days later at the slaughterhouse. In general, as far as the investigated blood variables are concerned, there were distinct and significant differences in the mean values between farm and slaughter blood-samples. As a rule the mean values of the investigated blood variables were higher in the slaughter blood than in the farm blood. The effects are most pronounced for leucocyte concentration and for the activity of the enzymes creatine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and gamma-glutamyltransferase (gamma-GT). For the blood variables albumin, lymphocytes and magnesium there were significant, but not so strong interactions between the sites of blood-sampling and the groups, which were classified according to the severity of pathological-anatomical lesions. Despite the fact that there were significant differences in the mean values of blood profiles of the slaughter pigs between the sites of blood sampling, this effect was only manifest as a difference in the level of the values of the blood variables. This means that clinicochemical and haematological profiles from groups of pigs at slaughter reflect the herd's health status at the farm and can be used when monitoring it.(ABSTRACT TRUNCATED AT 250 WORDS)

Over a period of six months, approximately 4700 blood samples were collected from 97 pig-finishing farms in the provinces of Noord-Brabant and Gelderland and screened for antibodies with respect to Aujeszky's disease virus (ADV), porcine influenza virus (PI) and Actinobacillus (Haemophilus) pleuropneumoniae (App). There were significant differences in the percentages of seropositive pigs between the two provinces, which may be related to the difference in the density of the pig population in the two provinces. In practice, it was possible to perform a reliable sera collecting procedure at the slaughterhouse. No farms remained seronegative with respect to most of the disease agents during the sampling period. There was a high degree of variation in the percentages of seropositive pigs per farm as to most of the disease agents. Evidence was found that animals that were seropositive with respect to ADV were significantly more susceptible to becoming seropositive with respect to App. serotype 2, and vice versa. The same connection was observed for PI serotype H1N1 and PI serotype H3N2. Furthermore, evidence was found that pigs seropositive with respect to PI serotype H1Ni only, or to PI serotype H1N1 and ADV or PI serotype H3N2 show a significant decrease in average daily weight gain compared to pigs that were seronegative.