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1.
In this paper, we describe the transmission of Classical Swine Fever virus (CSF virus) within herds during the 1997–1998 epidemic in the Netherlands. In seven herds where the infection started among individually housed breeding stock, all breeding pigs had been tested for antibodies to CSF virus shortly before depopulation. Based upon these data, the transmission of CSF virus between pigs was described as exponential growth in time with a parameter r, that was estimated at 0.108 (95% confidence interval (95% CI) 0.060–0.156). The accompanying per-generation transmission (expressed as the basic reproduction ratio, R0) was estimated at 2.9. Based upon this characterisation, a calculation method was derived with which serological findings at depopulation can be used to calculate the period in which the virus was with a certain probability introduced into that breeding stock. This model was used to estimate the period when the virus had been introduced into 34 herds where the infection started in the breeding section. Of these herds, only a single contact with a herd previously infected had been traced. However, in contrast with the seven previously mentioned herds, only a sample of the breeding pigs had been tested before depopulation (as was the common procedure during the epidemic). The observed number of days between the single contact with an infected herd and the day of sampling of these 34 herds fitted well in the model. Thus, we concluded that the model and transmission parameter was in agreement with the transmission between breeding pigs in these herds.

Because of the limited sample size and because it was usually unknown in which specific pen the infection started, we were unable to estimate transmission parameters for weaned piglets and finishing pigs from the data collected during the epidemic. However, from the results of controlled experiments in which R0 was estimated as 81 between weaned piglets and 14 between heavy finishing pigs (Laevens et al., 1998a. Vet. Quart. 20, 41–45; Laevens et al., 1999. Ph.D. Thesis), we constructed a simple model to describe the transmission of CSF virus in compartments (rooms) housing finishing pigs and weaned piglets. From the number of pens per compartment, the number of pigs per pen, the numbers of pigs tested for antibodies to CSF virus and the distribution of the seropositive pigs in the compartment, this model gives again a period in which the virus most probably entered the herd. Using the findings in 41 herds where the infection started in the section of the finishers or weaned piglets of the age of 8 weeks or older, and of which only a single contact with a herd previously infected was known, there was no reason to reject the model. Thus, we concluded that the transmission between weaned piglets and finishing pigs during the epidemic was not significantly different from the transmission observed in the experiments.  相似文献   


2.
This paper describes the epidemiological characteristics of the 1997 Classical Swine Fever (CSF) outbreak that occurred in the Limburg Province of Belgium, where there is a policy of non-vaccination, intensive surveillance and eradication. Between 30 June and 17 July 1997, eight herds, located in three different areas, were confirmed to be CSF-positive. CSF virus was transmitted from the primary infected herd of one area to another five herds in the same area and to one herd in a different area. The mode of virus introduction for this primary infected herd and for the one herd that was not infected by this primary herd could not be determined. Clinical, serological, and virological findings indicated that the CSF-infected herds were detected in an early stage of the infection. The early detection of the infection together with a preventive stamping out procedure resulted in a rapid elimination of the CSF virus. A total of 46,561 pigs were slaughtered to control the spread of the infection. Another 27,579 pigs were slaughtered in the framework of the market support. The total direct costs of the episode were estimated at [symbol: see text] 10,893,337.  相似文献   

3.
The herd sensitivity (HSe) and herd specificity (Hsp) of clinical diagnosis of an infection with classical swine fever (CSF) virus during veterinary inspection of breeding sows in a herd was evaluated. Data gathered from visits to herds during the CSF outbreak in 1997-1998 in The Netherlands were used for the analysis. Herds were visited one or more times by the same or by different veterinarians. On the basis of the veterinarians' reports, each visit was coded as 0 (negative clinical diagnosis) or 1 (positive clinical diagnosis). The HSe for clinical diagnosis of CSF was modelled as a function of days elapsed since introduction of the virus. The moment of introduction of the CSF virus in the CSF-positive herds was unknown, so for each herd, a probability distribution for the unknown number of days since introduction was derived from serum samples collected at depopulation. The information from the reports of the veterinarians and from the test results of the serum samples at depopulation was combined in a Bayesian analysis. Data from CSF-negative herds were analysed to estimate HSp of clinical diagnosis of CSF. The HSe of clinical diagnosis was 0.5 at 37 days after virus introduction (95% CI: 31, 45) and reached 0.9 at 47 days after virus introduction (95% CI: 41, 54). The estimated herd specificity was 0.72 (95% CI: 0.64, 0.79). Dependence of HSe and HSp on characteristics of the veterinarians and the herds also was studied. Specialisation of the veterinarian significantly, although not markedly, affected the HSe.  相似文献   

4.
During recent years neutralizing antibodies against Border Disease Virus (BDV) were found repeatedly in German pig herds. Consequently there was a demand for a differential diagnostic system. A permanent sheep cell line and BDV reference strain Moredun were chosen and were applied in a could be used case study. A pestivirus could be isolated from piglets on a mixed farm and was characterised as 'non-Classical Swine Fever' (CSF) by using monoclonal antibodies. Due to a CSF suspicion the pig herd was destroyed immediately. Serum samples of sheep from the same farm were used for further characterisation of the new virus isolate. A neutralization test of the sheep sera was performed against different pestiviruses and the new isolate. Neutralizing antibody titres against the new virus pig isolate were significantly higher than against all other pestiviruses. BDV strain Moredun recognised the antibodies clearly, whereas CSF viral strain Alfort 187 and several isolates of bovine viral diarrhoea virus (BVDV) strains scored the lowest cross reaction.  相似文献   

5.
The National Reference Laboratory for classical swine fever (CSF) virus in the Netherlands examined more than two million samples for CSF virus or serum antibody during the CSF epizootic of 1997–1998. The immense amount of samples and the prevalence of border disease (BD) virus and bovine viral diarrhoea (BVD) virus infections in Dutch pig herds necessitated the diagnostic efforts of the laboratory to be focused on generating CSF specific test results throughout the eradication campaign.

Detection of 82% of the 429 outbreaks was achieved through the combined use of a direct immunofluorescence and peroxidase assay (FAT/IPA) with samples (tonsils) collected from clinically-suspected pigs. This suggests that in the majority of the outbreaks, the pigs had clinical signs that were recognised by the farmer and/or veterinarians, indicating the presence of CSF virus in a pig herd. A positive diagnosis of 74% of all the tissue samples (tonsils) collected at infected pig holdings was established by FAT. More than 140,000 heparinised blood samples were examined by virus isolation, resulting in the detection of 4.5% of the infected herds. CSF virus was isolated in approximately 29% of all the blood samples collected from pigs at infected or suspected farms.

Several serological surveys — each done within a different framework — led to the detection of 13.5% of the total number of outbreaks. The detection of CSF virus antibody in serum was carried out by semi-automated blocking ELISA. Approximately 28.5% of the sera which reacted in the ELISA were classified as CSF virus-neutralising antibody positive and 26.5% as positive for other pestiviruses following the virus neutralisation test (VNT).

We concluded that two of the CSF laboratory diagnostic methods described were determinative in the eradication campaign: first, the FAT for the screening of diseased pigs; and second, the ELISA and VNT when millions of predominantly healthy pigs needed to be screened for the presence of CSF serum antibody. Decision-making on the basis of results generated by either method can, however, be seriously hindered when samples are examined from pig herds with a high prevalence of non-CSF pestiviruses.  相似文献   


6.
To reduce the cost of whole herd screening for bovine viral diarrhea virus persistently infected animals, the sensitivity and specificity of an antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) and a microtiter virus isolation ELISA using saline from ear notch samples or pooled serum was determined. Pooled saline from ear notch samples, assayed by AC-ELISA, gave a sensitivity and specificity of 98% and 94%, respectively, for pools containing 2 samples and 72% and 100%, respectively, for pools of 5. The sensitivity of pooled ear notch or serum samples for bovine viral diarrhea virus detection by microtiter virus isolation (sensitivity < 5%) or serum samples for detection by AC-ELISA (sensitivity < 15%) is too low to be used for whole herd screening. Pooling saline from ear notch samples from 2 animals tested by AC-ELISA, however, could provide a less expensive, reliable method for whole herd screening for bovine viral diarrhea virus.  相似文献   

7.
ABSTRACT: Disease modelling is one approach for providing new insights into wildlife disease epidemiology. This paper describes a spatio-temporal, stochastic, susceptible- exposed-infected-recovered process model that simulates the potential spread of classical swine fever through a documented, large and free living wild pig population following a simulated incursion. The study area (300 000 km2) was in northern Australia. Published data on wild pig ecology from Australia, and international Classical Swine Fever data was used to parameterise the model. Sensitivity analyses revealed that herd density (best estimate 1-3 pigs km-2), daily herd movement distances (best estimate approximately 1 km), probability of infection transmission between herds (best estimate 0.75) and disease related herd mortality (best estimate 42%) were highly influential on epidemic size but that extraordinary movements of pigs and the yearly home range size of a pig herd were not. CSF generally established (98% of simulations) following a single point introduction. CSF spread at approximately 9 km2 per day with low incidence rates (< 2 herds per day) in an epidemic wave along contiguous habitat for several years, before dying out (when the epidemic arrived at the end of a contiguous sub-population or at a low density wild pig area). The low incidence rate indicates that surveillance for wildlife disease epidemics caused by short lived infections will be most efficient when surveillance is based on detection and investigation of clinical events, although this may not always be practical. Epidemics could be contained and eradicated with culling (aerial shooting) or vaccination when these were adequately implemented. It was apparent that the spatial structure, ecology and behaviour of wild populations must be accounted for during disease management in wildlife. An important finding was that it may only be necessary to cull or vaccinate relatively small proportions of a population to successfully contain and eradicate some wildlife disease epidemics.  相似文献   

8.
Pseudorabies virus will be eradicated from the Netherlands if a typical infectious pig (Rind) infects, on average, less than one other pig. In this review, we used a stochastic SIR model to estimate Rind using data from the field and from experiments. Rind in sow herds was estimated to be significantly less than 1 and in rearing and finishing pigs Rind was higher than 1. However, if Rind is higher than 1, PRV can still be eradicated if one infectious herd infects less than one other herd during the period that the herd is infectious(Rherd <1). Some future developments in Dutch pig husbandry (e.g. group-housing of sows) and possible risks after halting vaccination are also quantitatively evaluated.  相似文献   

9.
Vaccination programs to control Aujeszky's-disease virus (ADV) using gE-deleted vaccines are being considered in several European countries. Knowledge of factors influencing ADV-seropositivity for vaccinated herds might contribute to the success of these programs. A multivariable analysis of ADV-seropositivity in 1248 swine herds (332 farrow-to-finish, 260 farrow-to-feeder and 656 finishing herds) in the Emilia-Romagna region of Italy revealed that (1) high pig density (number of pigs in a 6-km radius), (2) gilt purchasing, and (3) increased number of fattening pigs were risk factors for farrow-to-finish herds. In farrow-to-feeder herds, ADV-seropositivity was related to (1) increased number of breeders, (2) heavy-gilt purchasing, and (3) increased pig density. In finishing herds, (1) increased herd size was related to ADV-seropositivity, whereas (2) periodic rearing suspension was protective.  相似文献   

10.
The 1997-1998 epidemic of classical swine fever in the Netherlands   总被引：9，自引：0，他引：9  
In 1997, the pig husbandry in the Netherlands was struck by a severe epidemic of classical swine fever (CSF). During this epidemic 429 CSF-infected herds were depopulated and approximately 1300 herds were slaughtered pre-emptively. In addition millions of pigs of herds not CSF-infected were killed for welfare reasons (over crowding or overweight). In this paper, we describe the course of the epidemic and the measures that were taken to control it.The first outbreak was detected on 4 February 1997 in the pig dense south-eastern part of the Netherlands. We estimate that CSF virus (CSFV) had already been present in the country by that time for 5-7 weeks and that the virus had been introduced into approximately 39 herds before the eradication campaign started. This campaign consisted of stamping-out infected herds, movement restrictions and efforts to diagnose infected herds as soon as possible. However, despite these measures the rate at which new outbreaks were detected continued to rise. The epidemic faded out only upon the implementation of additional measures such as rapid pre-emptive slaughter of herds in contact with or located near infected herds, increased hygienic measures, biweekly screening of all herds by veterinary practitioners, and reduction of the transportation movements for welfare reasons. The last infected herd was depopulated on 6 March 1998.  相似文献   

11.
Data were collected from 104 Minnesota swine farms quarantined for pseudorabies virus (PRV) infection. Each herd was serologically evaluated for the presence of antibodies to PRV in finishing pigs. Herd management practices, swine housing design, and disease profiles were described for each farm. Multiple logistic regression analysis was used to determine which factors were associated with circulation of PRV in the finishing pigs of farrow-to-finish farms. Sixty-seven (64%) of the herds had no serologic evidence of PRV circulation in the finishing section, whereas 37 herds (36%) contained at least one PRV seropositive finishing pig. The odds of a given finishing herd being seropositive for PRV were 2.85 times higher if the finishing pigs were housed in confinement (P = 0.01), 2 times higher if Actinobacillus (Haemophilus) pleuropneumoniae was a clinical problem in the herd (P = 0.03), 1.36 times less for each year that passed since the herd quarantine was issued (P = 0.01), 1.74 times higher if clinical signs of PRV were reported (P = 0.04), and 1.52 times higher if animal protein was included in at least one of the rations (P = 0.08).  相似文献   

12.
Data were collected from 39 Minnesota swine farms quarantined for pseudorabies virus (PRV) infection. Each herd was serologically evaluated for antibodies to PRV in the sows, boars, and finishing pigs. To identify PRV-seropositive swine herds, the Kappa statistic was used to estimate the effectiveness of evaluating the PRV serostatus of boars or of finishing pigs. Using the serostatus of all herd boars, the sensitivity (with 95% confidence interval) of identifying PRV-infected herds was 58 +/- 22%, and the specificity was 100 +/- 0%; Kappa statistic was 0.55. Using the serostatus of a representative sample of finishing pigs, the sensitivity of identifying PRV-infected herds (with 95% confidence interval) was 63 +/- 22%, and specificity was 87 +/- 23%; Kappa statistic was 0.40. The PRV serostatus of herd boars or of a representative sample of finishing pigs did not accurately reflect the PRV serostatus of the herd.  相似文献   

13.
The objective of this paper is to describe the severe epidemic of classical swine fever (CSF) in The Netherlands in 1997–1998 under a policy of non-vaccination, intensive surveillance, pre-emptive slaughter and stamping out in an area which has one of the highest pig and herd densities in Europe.

The primary outbreak was detected on 4 February 1997 on a mixed sow and finishing pig herd. A total of 429 outbreaks was observed during the epidemic, and approximately 700 000 pigs from these herds were slaughtered. Among these outbreaks were two artificial insemination centres, which resulted in a CSF-suspect declaration of 1680 pig herds (mainly located in the southern part of The Netherlands). The time between introduction of CSF virus (CSFV) into the country and diagnosis of CSF in the primary outbreak was estimated to be approximately 6 weeks. It is presumed that CSFV was spread from The Netherlands to Italy and Spain via shipment of infected piglets in the beginning of February 1997, before the establishment of a total stand-still of transportation. In June 1997, CSFV is presumed to be introduced into Belgium from The Netherlands.

Pre-emptive slaughter of herds that had been in contact with infected herds or were located in close vicinity of infected herds, was carried out around the first two outbreaks. However, this policy was not further exercised till mid-April 1997, when pre-emptive slaughter became a standard operational procedure for the rest of the epidemic. In total, 1286 pig herds were pre-emptively slaughtered. (approximately 1.1 million pigs). A total of 44 outbreaks (10%) was detected via pre-emptive slaughter.

When there were clinical signs, the observed symptoms in infected herds were mainly atypical: fever, apathy, ataxia or a combination of these signs. In 322 out of 429 outbreaks (75%), detection was bases on clinical signs observed: 32% was detected by the farmer, 25% by the veterinary practitioner, 10% of the outbreaks by tracing teams and 8% by screening teams of the veterinary authorities. In 76% of the outbreaks detected by clinical signs, the farmer reported to have seen clinical symptoms for less than 1 week before diagnosis, in 22% for 1–4 weeks before diagnosis, and in 4 herds (1%) the farmer reported to have seen clinical symptoms for more than 4 weeks before diagnosis.

Transportation lorries played a major role in the transmission of CSFV before the primary outbreak was diagnosed. It is estimated that approximately 39 herds were already infected before the first measures of the eradication campaign came into force.

After the first measures to stop the spread of CSFV had been implemented, the distribution of the most likely routes of transmission markedly changed. In most outbreaks, a neighbourhood infection was indicated.

Basically, there were two reasons for this catastrophe. Firstly, there was the extent of the period between introduction of the virus in the region and detection of the first outbreak. As a result, CSFV had opportunities to spread from one herd to another during this period. Secondly, the measures initially taken did not prove sufficient in the swine- and herd-dense region involved.  相似文献   


14.
The present study investigated risk factors for mortality in grow‐finishing pigs of 137 pig herds belonging to one integration company during a period of 2.5 years. Mortality data, expressed as the number of dead pigs divided by the number of pigs placed in the fattening unit were investigated retrospectively. The following potential risk factors were evaluated: type of pig herd, season and year of placement in the fattening unit, pig density in the municipality, management practices (density of the pigs in the barn, origin of the pigs), housing conditions and feeding practices. The overall average mortality percentage was 4.70%. Three variables in a multivariable regression model were significantly associated with mortality: season of placement in the fattening unit, origin of the piglets and duration of the fattening period. Pigs placed in October, November and December, were at higher risk than pigs placed in other months. Herds that purchased pigs from a merchant, used pigs from other herds with an excess of piglets for filling their fattening units or herds that purchased pigs from more than five origin herds also suffered higher mortality. The mortality also increased in case of longer duration of the fattening period. This study documented for the first time that in addition to seasonal effects and a longer duration of the fattening period, purchasing feeder pigs from one or a limited number of herds is of crucial importance to achieve low mortality in the grow‐finishing pigs.  相似文献   

15.
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.  相似文献   

16.
In this paper we describe a study of the use of the white blood cell count (wbcc) as a parameter for detecting outbreaks of Classical Swine Fever (CSF). Meta-analysis of the results of challenge experiments revealed that oronasal infection of SPF-pigs with the virulent CSF virus (CSFV) strains Brescia or NL9201 resulted in a significant decrease in the average white blood cell count during the first week after inoculation of the virus. Challenge of conventional finishing pigs and sows with the moderately virulent strain Paderborn also resulted in a significant decrease in the average wbcc. However, this decrease was not observed after inoculation of SPF pigs with the mildly virulent CSFV strains Henken, Zoelen, or Bergen. The usefulness of clinical inspection in combination with wbcc to detect CSF outbreaks in the field was examined using the results of 214 EDTA blood specimens collected from 22 infected herds and 7250 EDTA blood specimens collected from 1450 non-infected herds. Half of the infected herds had been infected with the moderately virulent CSFV strain Venhorst (closely related to strain Paderborn) during the 1997-98 epidemic in the Netherlands. The other half had been infected with the moderately virulent CSFV strain Loraine. Using these data as a starting point, 1000 samples of one to ten specimens were generated by Monte Carlo simulation. These simulated samples and the samples of the non-infected herds were analysed by use of Receiver Operating Characteristic curves. On the basis of that analysis, the optimal number of animals whose wbcc needed to be determined to detect a CSF outbreak was five. With this number of animals, in conjunction with the threshold of 8000 white blood cells per mm3 (meaning that a herd is designated as CSF suspect if one or more of the five specimens has a white blood cell count of 8000 leukocytes/mm3 or less), the test procedure had a herd sensitivity (HSE) of 94.5% and a herd specificity (HSP) of 97.2%). The HSE is defined as the percentage of samples of infected herds with a positive result of the test procedure; HSP is defined as the percentage of uninfected herds with a negative result of the test procedure. We conclude that the wbcc can help the veterinary practitioner to detect outbreaks of CSF caused by (moderately) virulent CSFV strains. However, for the detection of outbreaks caused by mildly virulent CSFV strains, the contribution of the wbcc is doubtful. Development of additional tools that can improve the clinical diagnosis of the veterinary practitioner remains desirable.  相似文献   

17.
Preweaning mortality risks, recorded death reasons and related factors for preweaning mortality were studied in 105 breeding herds. Preweaning mortality risk at the herd level was calculated as the difference between the number of pigs born alive in farrowed litters and the number of weaned pigs divided by the number of pigs born alive in litters that farrowed and weaned. The mean of annual preweaning mortality risk was 10.7%. In regression analysis, higher mortality risks were associated with higher parity at farrowing, greater numbers of pigs born alive, and longer lactation length. The period from July to September had a higher mortality risk than that from April to June. The means of cause-specific proportional mortality ratios (PMR) in trauma with low viability and scours were 80.4 and 6.2%, respectively. Sows with pig age 0-1 day during lactation had the highest daily PMR. Sows with pig age 0 to 7 days had higher PMR due to trauma and low variability than those with pig age 8 days older. Sows with pig age over 7 days had higher PMR due to scours than those with pig age 0-7 days. Careful management at farrowing and in early lactation on high parity sows with large litters should be considered to prevent piglets from death due to trauma and low viability, and appropriate herd health programs should be implemented for reducing preweaning mortality due to scours during late lactation.  相似文献   

18.
In this study, the rate of S. scabiei var. suis transmission among finishing pigs was quantified in a contact transmission experiment. Forty piglets originating from a mange free farrow-to-finish herd were randomly allocated to three groups and one S. scabiei var. suis infested finishing pig was subsequently added to each of these groups. After 35 days, the three seeder pigs were removed from the groups and the remaining 40 pigs were re-allocated to five pens. Ear scrapings, to be examined for mites, were collected from each pig on days 1, 14, 28, 42, 56, and 84 of the experiment. Blood samples, to be tested for antibodies against S. scabiei, were collected from each pig on days 0, 14, 28, 42, 56, 70, 84 and 112 after the introduction of the seeder pigs.From the results of the ear scrapings and the blood samples the number of susceptible (not infested) and infested pigs was derived at the time of each sample collection and the number of new infestations in the intervals between the sample collections. From these data the infestation rate parameter beta (average number of new infestations per infested pig per day) was estimated by use of a Generalised Linear Model (GLM) and accordingly, beta was estimated at 0.056 (95% CI: 0.037-0.085) infestations per infested pig per day.Next, by use of beta, the transmission of S. scabiei was simulated in a population of 100 finishing pigs for 100 days after the introduction of a single infested pig. For this purpose, 500 simulations were done. The 90% confidence interval of the number of infested pigs at day 100 ranged from 12 to 88 (median: 63). It was concluded that transmission of S. scabiei among finishing pigs is slow. Due to the presumed lower contact rate between sows as compared to finishing pigs, it is anticipated that transmission of S. scabiei among sows will even be slower than among finishers These findings are of particular interest for the development of surveillance programmes for S. scabiei free herds.  相似文献   

19.
Three commercial swine herds were selected for study, because pigs at slaughter consistently had lung lesions typical of bronchopneumonia and snout lesions consistent with atrophic rhinitis. Pigs were reared in the conventional system for each herd except that they were identified at birth and weighted at various intervals. At slaughter, individual pig lungs and snout were examined for lesions of pneumonia and atrophic rhinitis, respectively. Lesions were scored and correlated with growth indicators for each pig. Included in the growth indicators were: average daily gain (growing phase), average daily gain (finishing phase), average daily gain (total), and days to reach 104.5-kg body weight. Additionally, for each pig, scores for lung lesions were correlated to grades for snout lesions. Three correlation coefficients for measurements of pigs within herd B were significant and included days to 104.5-kg body weight and grades for snout lesions, -0.15 (P less than 0.02); average daily gain (finishing) and grades for snout lesions, 0.17 (P less than 0.01); and average daily gain (total) and grades for snout lesions, 0.16 (P less than 0.01). Contrary to findings in other investigations, pigs that attained market weight at the youngest age did not have the lowest score for lung lesions, the lowest grade for snout lesions, or the least extensive or severe lesions. Combining data from all 3 herds, the mean scores for lung lesions and mean grades for snout lesions decreased significantly (P less than 0.05) as the age of pigs at slaughter increased. All other statistical correlations were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

20.
In Denmark, a serological Salmonella surveillance programme in finishing pig herds has been in place since 1995. The programme was founded on data from experimental studies, which demonstrated a strong association between Salmonella serology and the prevalence of these bacteria. The current study was carried out in three Danish abattoirs to evaluate the correlation under field conditions. A total of 160 Danish finishing pig herds were included. Seven out of these were examined twice, yielding a total of 167 observations. The herds were selected according to their herd serology based on data from the national surveillance. From each herd, samples were taken from 10 finishers at slaughter. The prevalence of Salmonella bacteria was measured at four sites: (1) caecal-content; (2) carcass surface; (3) pharynx; and (4) caecal lymph nodes. A logistic regression model was constructed for each sampling site. Abattoir, sanitary slaughter and herd seroprevalence were used as explanatory variables. The results demonstrated that there was a strong association between herd serology and the prevalence of Salmonella bacteria measured at three of the sampling sites: caecal-content, pharynx, and carcass surface. For these sites, the odds for being culture-positive for Salmonella varied from 1.3 to 1.5 for each increase of 10% in herd serology (P < 0.0001). For caecal lymph nodes, however, no linear association was found.  相似文献   

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