首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Paratuberculosis or Johne's Disease, caused by Mycobacterium avium subspecies paratuberculosis (MAP), is a notifiable disease in Germany which produces enormous economical losses in dairy farms. At present,there is no confirmed data about the actual number of infected livestock herds in Germany. A countrywide monitoring program to evaluate the prevalence in dairy herds would only be economically feasible on the basis of bulk milk testing. In this study, we evaluated two ELISA test kits (SVANOVIR Ptb-ELISA, IDEXX-M.pt. Milk test kit) for the detection of antibodies against MAP in bulk milk. First, the Paratuberculosis-status of the herd derived from the history of the farm was used as a gold standard. Paratuberculosis-negative farms were tested negative with each test, but paratuberculosis-positive or Paratuberculosis-serologically-positive farms were detected only in one case (Svanovir) or three cases (IDEXX), respectively. Even if inconclusive results are counted as positive, 82.9 % (Svanovir) or 80 % (IDEXX) of the paratuberculosis-positive or serologically paratuberculosis positive farms were not detected. Nevertheless, a re-validation of both ELISAs by means of ROC and TG-ROC analyses was attempted by searching for ideal cut-offs, optimised for bulk milk. If a high specificity was selected, no acceptable sensitivity could be reached.The best results were obtained using a sensitivity of 32.3 % at a specificity of 100 % (Svanovir). With a small change of the cut-off value, the sensitivity increased to still 57 %, but this reduced the specificity to 67 %. Similar results were obtained with the IDEXX-ELISA. We then evaluated the Svanovir-ELISA for the detection of bulk milk samples on the basis of the current paratuberculosis prevalence within 69 dairy herds from Rhineland-Palatinate using individual milk samples.When the bulk milk samples were tested in two different laboratories using the same ELISA, considerable differences in the results became evident. Nearly all samples were tested with a higher relative test result in one laboratory, which often led to differences in the classification of the prevalence levels.The estimated within-herd seroprevalences ranged between 0 % and 37 %.There was little agreement between the historical paratuberculosis herd status and the within-herd prevalence in milk serum, as reflected in a kappa-index of 0.146.To determine the sensitivity and specificity of the bulk milk ELISA by ROC and TG-ROC analysis, 116 bulk milk samples were used that had been obtained from the 69 dairy herds participating in the study. The optimal ratio of sensitivity (81 %) and specificity (77 %) relative to a "gold standard" was obtained when the cut-off was set at the 10 % level. These values for sensitivity and specificity were better than those obtained in an evaluation of the same ELISA in which the historical Paratuberculosis herd-status was used as a "gold standard." The results of this study question the suitability of the available ELISAs for bulk milk testing.Taking into account that the Svanovir-ELISA for individual milk samples has a sensitivity of 60 96% relative to the blood serum variant of the test, and that the latter has also a limited sensitivity due to the pathogenesis of paratuberculosis, the available test systems examined in this Study do not seem to be suitable for herd diagnosis by using bulk milk samples.  相似文献   

2.
Risk management of paratuberculosis (Johne's disease) in a dairy herd requires an assessment of the likelihood of paratuberculosis occurring in the herd, the economic impact of paratuberculosis on the herd and an evaluation of measures that can be taken to reduce this likelihood and impact.The likelihood of paratuberculosis occurring in the herd is related to the regional herd-level prevalence of paratuberculosis and the herd management (e.g., introducing animals from other herds). The economic impact of paratuberculosis includes production losses due to subclinical and clinical cases, losses due to increased replacement of animals and costs of control measures. Furthermore, a reduction of the price of milk from infected herds might result from consumer concerns about the zoonotic potential of paratuberculosis.Measures that reduce the likelihood of paratuberculosis occurring in a herd and its impact include preventive management measures (e.g., closed herd management and an effective separation of susceptible young stock from adult cattle), test-and-cull schemes for known infected herds and quality assurance schemes for test-negative herds. Quality assurance schemes for test-negative herds, such as schemes for 'low-Map bulk milk' and 'Map-free' herds, aim at safeguarding or increasing the profitability of these herds.Keys to success of risk management of paratuberculosis include realistic expectations of the results of paratuberculosis control, quality assurance and control programmes that are appreciated by farmers and incentives for farmers to participate in such programmes.  相似文献   

3.
Milk samples from 340 individual goats in 34 dairy herds throughout Norway were examined for Mycobacterium avium subsp. paratuberculosis (M.a. paratuberculosis) by culture and immunomagnetic separation combined with PCR (IMS-PCR). The samples included three categories; (A) vaccinated dairy goats in herds with paratuberculosis; (B) vaccinated dairy goats in herds with no history of paratuberculosis; (C) unvaccinated goats in herds with no history of paratuberculosis.Viable M.a. paratuberculosis were not detected by culture in any sample, but 24 samples (7.1%) tested positive by IMS-PCR when the PCR products were visualised by dot blot hybridisation. PCR products from five milk samples originating from five different herds were sequenced; all showed 99% homology with the IS900 sequence from M.a. paratuberculosis.M.a. paratuberculosis were detected in all sampled categories. The percentage of IMS-PCR positive samples from herds where paratuberculosis had previously been reported was significantly lower than from herds where the infection had never been diagnosed (3.3 and 9.1%, respectively, P=0.048). Similar proportions of milk samples from vaccinated and non-vaccinated goats tested positive for the presence of M.a. paratuberculosis. Vaccinated goats older than 4 years tested positive more often than vaccinated animals less than 2 years old. Samples collected in May tested significantly more often positive than milk sampled during February-March (13.8 and 2.9%, respectively, P=0.001). This study showed that raw goats' milk in Norway might be contaminated with M.a. paratuberculosis.  相似文献   

4.
Epidemiologic investigations of Salmonella infections in dairy cattle often rely on testing fecal samples from individual animals or samples from other farm sources to determine herd infection status. The objectives of this project were to evaluate the effect of sampling frequency on Salmonella isolation and to compare Salmonella isolation and serogroup classification among sample sources on 12 US dairy farms sampled weekly for 7-8 weeks. Three herds per state were enrolled from Michigan, Minnesota, New York and Wisconsin based upon predefined herd-size criteria. Weekly samples were obtained from cattle, bulk tank milk, milk filters, water and feed sources and environmental sites. Samples were submitted to a central laboratory for isolation of Salmonella using standard laboratory procedures. The herd average number of cattle fecal samples collected ranged from 26 to 58 per week. Salmonella was isolated from 9.3% of 4049 fecal samples collected from cattle and 12.9% of 811 samples from other sources. Serogroup C1 was found in more than half of the samples and multiple serogroups were identified among isolates from the same samples and farms. The percentage of herd visits with at least one Salmonella isolate from cattle fecal samples increased with overall herd prevalence of fecal shedding. Only the three herds with an average fecal shedding prevalence of more than 15% had over 85% of weekly visits with at least one positive fecal sample. The prevalence of fecal shedding from different groups of cattle varied widely among herds showing that herds with infected cattle may be classified incorrectly if only one age group is tested. Testing environmental sample sources was more efficient for identifying infected premises than using individual cattle fecal samples.  相似文献   

5.
The Danish government and cattle industry instituted a Salmonella surveillance program in October 2002 to help reduce Salmonella enterica subsp. enterica serotype Dublin (S. Dublin) infections. All dairy herds are tested by measuring antibodies in bulk tank milk at 3-month intervals. The program is based on a well-established ELISA, but the overall test program accuracy and misclassification was not previously investigated. We developed a model to simulate repeated bulk tank milk antibody measurements for dairy herds conditional on true infection status. The distributions of bulk tank milk antibody measurements for infected and noninfected herds were determined from field study data. Herd infection was defined as having either >or=1 Salmonella culture-positive fecal sample or >or=5% within-herd prevalence based on antibody measurements in serum or milk from individual animals. No distinction was made between Dublin and other Salmonella serotypes which cross-react in the ELISA. The simulation model was used to estimate the accuracy of herd classification for true herd-level prevalence values ranging from 0.02 to 0.5. Test program sensitivity was 0.95 across the range of prevalence values evaluated. Specificity was inversely related to prevalence and ranged from 0.83 to 0.98. For a true herd-level infection prevalence of 15%, the estimate for specificity (Sp) was 0.96. Also at the 15% herd-level prevalence, approximately 99% of herds classified as negative in the program would be truly noninfected and 80% of herds classified as positive would be infected. The predictive values were consistent with the primary goal of the surveillance program which was to have confidence that herds classified negative would be free of Salmonella infection.  相似文献   

6.
A 6-year study was conducted in 4 dairy herds in Iowa in which Johne's disease was diagnosed previously. Fecal specimens were collected at 6-month intervals from animals 2 years of age and over for mycobacteriologic examination. Serum samples were obtained at 3-month intervals and tested by enzyme-linked immunosorbent assay (ELISA). The antigen used in the ELISA was a potassium chloride extract of a field strain of Mycobacterium paratuberculosis. The ELISA reactions were observed in 87% of the cows from which M. paratuberculosis was isolated. Dairy producers that participated in the Johne's control program reported reduced economic losses. Increased income was attributed to improved milk production, increased value of vaccinated animals sold as replacements to other dairy herds in which Johne's disease had been diagnosed, and the increased market value of slaughter animals removed from the herd.  相似文献   

7.
The objective of this study was to investigate the impact of paratuberculosis sero-status on milk yield, fat, protein, somatic cell count and calving interval in Irish dairy herds. Serum from all animals over 12 months of age (n = 2,602) in 34 dairy herds was tested for antibodies to Mycobacterium avium subsp. paratuberculosis using an ELISA. Herds were categorised by sero-status into positive, non-negative and negative, where a positive herd contained two or more positive cows, a non-negative herd contained only one positive cow and a negative herd contained no positive cows. Data at animal, parity and herd-level were analysed by multiple regression using general linear models. Positive herds (mean herd size = 129 cows) and non-negative herds (81 cows) were larger than negative herds (72 cows) (P < 0.01). Negative herds had the highest economic breeding index (EBI), while positive herds had the highest estimated breeding value (EBV) for milk yield. There was no significant effect of paratuberculosis sero-status at animal, parity or herd-level on milk yield, milk fat or protein production, somatic cell count score (SCCS) or calving interval. Negative herds tended to have a lower SCCS than positive and nonnegative herds (P = 0.087). This study only examined the effects of paratuberculosis sero-status but did not examine the clinical effects of Johne's disease at the farm or dairy industry levels.  相似文献   

8.
A bulk milk quality assurance programme for Mycobacterium avium subsp. paratuberculosis (Map) in dairy herds was simulated with a stochastic simulation model (JohneSSim). The aim of this study was to evaluate the epidemiological and economic effects of preventive management measures and various test schemes in a simulated population of closed Dutch dairy herds over a 20-year period. Herds were certified as ;low-Map bulk milk' if, with a certain probability, the concentration of Map in bulk milk did not exceed a maximum acceptable concentration of 10(3) Map organisms per litre (based on pasteurisation studies). The programme started with an initial assessment; test-negative herds entered a surveillance procedure and test-positive herds a control procedure. The simulations showed that herd examinations by ELISA for the initial assessment, surveillance and control procedures effectively ensure the quality of ;low-Map bulk milk': > 75% of simulated herds were certified and > 96% of certified herds produced bulk milk with < 10(3) Map/L if the initial herd-level prevalence was 30%. Preventive management measures only had a minor effect on bulk milk quality of certified herds. Culling based on biennial faecal culture was more effective than culling based on annual ELISA. Average total discounted costs for 20-year participation in a programme consisting of initial assessment by ELISA, surveillance by biennial ELISA and control by biennial faecal culture were 16 Euro x 10(3) per herd. In conclusion, this study shows that a bulk milk quality assurance programme for closed Dutch dairy herds is feasible and provides information on the cost-effectiveness of different programmes. The concepts of this study equally apply to other countries because mechanisms of paratuberculosis infection, disease, and testing are comparable in other dairy cattle populations.  相似文献   

9.
Whole blood samples were obtained from multiple dairy herds in Pennsylvannia and in Wisconsin which were previously determined to be infected with Mycobacterium paratuberculosis (MpS) (Johne's disease) by fecal culture. Blood samples were shipped overnight to the National Animal Disease Center (NADC) in Ames, IA for processing and interferon-gamma (IFN-gamma) analysis. Blood samples were incubated alone (non-stimulated) or with concanavalin A (ConA), a T-cell mitogen used as a positive control in the assay, for 18h. In addition, samples were incubated with M. avium purified protein derivative (AvPPD), M. bovis purified protein derivative (BoPPD), or a whole cell sonicate of M. paratuberculosis for 18h to elicit antigen-specific IFN-gamma production. After incubation, plasma was harvested and analyzed for IFN-gamma by ELISA. Values for IFN-gamma for non-stimulated blood samples (background) were consistently low for animals in all herds evaluated. In contrast, ConA stimulation of blood samples evoked a significant secretion of IFN-gamma regardless of infection status or fecal culture results for individual cows, indicating that immune cells were still viable after overnight shipment and capable of responding to stimulation. Antigen-specific IFN-gamma results were positively correlated with infection status as determined by previous fecal shedding and/or current fecal shedding of M. paratuberculosis. Accuracy of the IFN-gamma assay for correctly predicting infection status of individual cows in the herds with low levels of infection ranged from 50 to 75% when used as a single test. Combined use of the IFN-gamma test and a commercial ELISA antibody test accurately predicted infection status of 73% of cows from a dairy herd with a high level of M. paratuberculosis infection and 90% from a well-characterized group of dairy cows at the NADC. These results indicate that the antigen-specific IFN-gamma assay is a very sensitive diagnostic tool for detection of subclinical paratuberculosis in cattle and may be useful on an individual animal basis to remove infected animals from the herd.  相似文献   

10.
Levels of antibodies to the O antigens (O:1,9,12) of Salmonella dublin were tested in 1355 serum, 1143 cow milk and 160 bulk milk samples from dairy herds using an enzyme-linked immunosorbent assay (ELISA). In order to define the background reaction, milk samples from all lactating cows and serum samples from 9 animals were collected in each of 20 salmonellosis-free herds located on the island of Bornholm, where cattle salmonellosis has not been reported. Similar samples were collected from all stalled animals in 10 herds with recent (< 6 months) outbreaks of salmonellosis located in Jutland, where salmonella infection is enzootic. Using herd history of salmonellosis, herd location and clinical status of the herds as criteria, the optimal cutoff in the milk ELISA was determined as being at least 5% of the samples having optical density > 0.5, resulting in herd sensitivity of 1.0 and herd specificity of 0.95. While none of the sera in the herds from Bornholm was ELISA positive, 2 herds had a few reactors in the milk ELISA. Using the same cutoff, all but 1 bulk milk sample from 150 herds on Bornholm was ELISA-negative, and all 10 salmonellosis-positive herds from Jutland were ELISA-positive. A significant correlation was found between ELISA reactions in milk and in serum of cows (34% and 32% respectively, rs = 0.69, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

11.
A simple random survey was conducted in Ireland during 2005 to estimate the ELISA-prevalence of paratuberculosis, commonly called Johne's disease (JD), in the cattle population. Serum samples were collected from all 20,322 females/breeding bulls over 12 months-of-age in 639 herds. All samples were tested using a commercially available absorbed ELISA. The overall prevalence of infected herds, based on the presence of at least one ELISA-positive animal, was 21.4% (95% CI 18.4%-24.9%). Herd prevalence levels amongst dairy herds (mean 31.5%; 95% CI: 24.6%, 39.3%) was higher than among beef herds (mean 17.9%; 95% CI: 14.6%-21.8%). However, the animal level prevalence was similar. The true prevalence among all animals tested, was calculated to be 2.86% (95%CI: 2.76, 2.97) and for animals >= 2 yrs, it was 3.30% (95%CI: 3.17, 3.43). For animals in beef herds, true prevalence was 3.09% (95%CI: 2.93, 3.24), and for those in dairy herds, 2.74% (95%CI: 2.59, 2.90). The majority of herds had only one ELISA-positive infected animal. Only 6.4% (95% CI 4.7%-8.7%) of all herds had more than one ELISA-positive infected animal; 13.3% (CI 8.7%-19.7%) of dairy herds ranging from two to eight ELISA-positive infected animals; and, 3.9% beef herds (CI 2.4%-6.2%) ranging from two to five ELISA-positive infected animals. The true prevalence of herds infected and shedding Mycobacterium avium subspecies paratuberculosis is estimated to be 9.5% for all herd types; 20.6% for dairy herds; and 7.6% for beef herds. If ELISA positive animals <2-years-of-age are excluded, the true herd prevalene reduces to: 9.3% for all herd types; 19.6% for dairy herds; and 6.3% for beef herds based on a test specificity (Sp) of 99.8% and test sensitivity (Se) (i.e., ability to detect culture-positive, infected animals shedding at any level) of 27.8-28.9%.  相似文献   

12.
The aim of this study was to examine whether it is possible to predict the presence of persistently infected (PI) animals with bovine viral diarrhoea virus on dairy farms in The Netherlands, based on a few blood samples of the herd, possibly in combination with a bulk milk test for antibodies. In 25 herds with, and 24 herds without, PI animal(s) the probabilities of obtaining at least x antibody positive animals out of a sample of n animals were calculated, with n varying from 3 to 7 and values for x that were considered were n, n - 1 to n - x. This probability, among animals 9-24 months old, ranged from 0.70 to 0.96 for herds with PI animals and from 0.13 to 0.37 for herds without. Using the result of bulk milk testing in addition did not add to the prediction. It was concluded that, due to the high percentage and large variation of antibody positive animals in herds without PI animals, it is not possible to predict the presence of PI animal(s) in dairy herds in The Netherlands using these methods.  相似文献   

13.
Fecal samples from 733 cows in 11 dairy herds with a low prevalence of paratuberculosis were cultured for the presence of Mycobacterium avium subsp. paratuberculosis both individually and after combining (pooling) in groups of 5. The culture procedure was the modified Jorgensen method, which uses NaOH and oxalic acid for decontamination and modified Lowenstein-Jensen agar slants for cultivation. Pooling was performed by mixing fecal samples from 5 animals ordered by age, herein referred to as strategic pooling. Culture of individual fecal samples detected M. a. paratuberculosis infections in 43 of the 733 cows and 7 of 11 infected herds (herd sensitivity = 64%). Culture of pooled fecal samples detected M. a. paratuberculosis in 28 of 151 pooled samples representing 8 of the infected 11 herds (herd sensitivity = 73%). Feces of the 43 culture-positive cows was included in 32 pools: of these 32 pools, 26 were culture positive and 6 were culture negative. In addition to the 26 positive pools containing feces from cows that were found culture positive on individual fecal samples, another 2 pools were culture positive, although comprised of feces from cows with negative results after culture of individual fecal samples. From the total of 45 infected cows that were found (43 by individual fecal culture and an additional 2 by pooled fecal culture), individual fecal culture detected 43 of these 45 (96%), while pooled fecal culture detected 39 (87%). Culture of strategically pooled fecal samples using the modified Jorgensen method was equivalent in herd sensitivity to the culture of individual fecal samples and is significantly less expensive.  相似文献   

14.
The objective of the study was to determine the diagnostic performance of the Pourquier ELISA for detection of antibodies against Mycobacterium avium subsp. paratuberculosis (Map) in individual milk samples and in bulk milk samples. For individual milk samples the specificity of the Pourquier ELISA was estimated by testing a panel of individual milk samples from certified Map-free herds. The relative sensitivity of the assay in individual milk samples and agreement of the results with those of serum samples was estimated by testing panels of paired serum-milk samples from seropositive cattle, whole-herd investigations, and moderate or heavy shedders. The specificity of the ELISA for individual milk samples was still 99.8% at a cut-off of 20% sample to positive (S/P) value, clearly lower than the cut-off defined by the manufacturer (30% S/P). The relative sensitivity for individual milk samples as compared with positive serum samples was 87% for a cut-off of 20% S/P, and 80% for a cut-off of 30% S/P. The sensitivity of this ELISA for detection of high shedders was >90% both for individual milk and serum samples, also agreement was very good (kappa=0.91 for all paired samples). The specificity of the Pourquier ELISA in bulk milk samples was investigated by testing bulk milk samples from certified Map-free herds. Feasibility of bulk milk testing was investigated by titrating ELISA positive individual milk samples in negative milk. In addition, 383 bulk milk samples from herds with a known within-herd seroprevalence were tested. The specificity of the ELISA for bulk milk samples was 100% at a cut-off of 12.5% S/P. At the cut-off recommended by the manufacturer (30% S/P) performance of the bulk milk ELISA related to herd status (> or =2 seropositive cows) was rather poor, corresponding with a sensitivity of 24% and a specificity of 99% relative to serology. However, at the revised cut-off for bulk milk of 12.5% S/P and a within-herd seroprevalence of > or =3%, sensitivity and specificity relative to serology were 85% and 96%, respectively. Given the current herd-level seroprevalence in The Netherlands, these test characteristics corresponded with positive and negative predictive values for bulk milk of 67% and 94%, respectively. In conclusion, the diagnostic performance of the Pourquier ELISA for individual milk samples creates opportunities for a cheaper and more feasible testing scheme, while the diagnostic performance for bulk milk samples warrants further consideration.  相似文献   

15.
A case-control study was undertaken during the summer of 1989 in central Alberta dairy herds to identify independent predictors of nocardial mastitis. Thirty-seven herds with nocardial mastitis were matched with control herds based on herd size, milk production, and enrolment in Alberta Dairy Herd Improvement Services. Control herds were considered free of nocardial mastitis based on negative cultures of four weekly bulk tank milk samples and one composite milk sample collected during the same period from each lactating cow in the herd. A detailed questionnaire on herd management was completed during farm visits. The use of blanket dry cow therapy was not found to be a risk factor for nocardial mastitis. Dry cow therapy with intramammary products containing neomycin and the use of multidose vials of dry cow medications were the only predisposing factors identified as being significantly associated with nocardial mastitis in central Alberta dairy herds. Use of neomycin as a dry cow therapy increased the odds of nocardial mastitis occurring in these dairy herds by 169 times.  相似文献   

16.
OBJECTIVE: To evaluate sensitivities at the herd level of test strategies used in the Voluntary Johne's Disease Herd Status Program (VJDHSP) and alternative test strategies for detecting dairy cattle herds infected with Mycobacterium paratuberculosis. DESIGN: Nonrandom cross-sectional study. SAMPLE POPULATION: 64 dairy herds from Pennsylvania, Minnesota, Colorado, Ohio, and Wisconsin. Fifty-six herds had at least 1 cow shedding M. paratuberculosis in feces; the other 8 herds were free from paratuberculosis. PROCEDURE: For all adult cows in each herd, serum samples were tested for antibodies to M. paratuberculosis with an ELISA, and fecal samples were submitted for bacterial culture for M. paratuberculosis. Sensitivities at the herd level (probability of detecting infected herd) of various testing strategies were then evaluated. RESULTS: Sensitivity at the herd level of the testing strategy used in level 1 of the VJDHSP (use of the ELISA to test samples from 30 cows followed by confirmatory bacterial culture of feces from cows with positive ELISA result) ranged from 33 to 84% for infected herds, depending on percentage of cows in the herd with positive bacterial culture results. If follow-up bacterial culture was not used to confirm positive ELISA results, sensitivity ranged from 70 to 93%, but probability of identifying uninfected herds as infected was 89%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the testing strategy used in the VJDHSP will fail to identify as infected most dairy herds with a low prevalence of paratuberculosis. A higher percentage of infected herds was detected if follow-up bacterial culture was not used, but this test strategy was associated with a high probability of misclassifying uninfected herds.  相似文献   

17.
Fifty dairy herds in Alberta were tested for the presence of Mycobacterium paratuberculosis by fecal culture and serum enzyme linked immunosorbent assay (ELISA). Individual sera (1500) were tested for antibodies to M. paratuberculosis by ELISA. Fecal samples were combined in pools of 3 (10 pools/herd) for a total of 500 pools that were cultured for M. paratuberculosis. Thirty cultures, including all 10 pools from 1 herd, were not readable due to fungal contamination. The remaining 470 cultures, representing 49 herds, yielded 16 positive pools (3.4% +/- 2.1%) from 10 herds (20.4% +/- 11.3%). The ELISA of each of the 1500 sera detected 105 (7.0% +/- 2.4%) positive sera and 20 (40.0% +/- 13.6%) positive herds, based on 2 or more individual positive sera in the herd. The true herd-level prevalence, as determined by ELISA, was 26.8% +/- 9.6%. The true herd-level prevalence, as determined by M. paratuberculosis fecal culture, ranged from 27.6% +/- 6.5% to 57.1% +/- 8.3%, depending on whether 1, 2, or all 3 individual fecal samples in the positive fecal pool were culture positive.  相似文献   

18.
Data from an epidemiological study in Ontario, involving 304 dairy herds, were used to identify associations between selected production indices and lipoarabinomannan antigen serological test results for paratuberculosis (LAM-ELISA). Analyses were conducted at both the herd and individual cow levels of organization. After analytically controlling for management and cow factors in the respective regression models, positive serological paratuberculosis status (as defined by the LAM-ELISA test), was associated with higher milk somatic cell counts at both the herd average (p less than 0.01), and individual cow levels of organization (p less than 0.0001). In contrast, LAM-ELISA test results were consistently not associated with calving intervals in either the herd average or individual cow level analyses. Associations between LAM-ELISA results and milk production were inconsistent. No associations were found at the herd level of organization, and LAM-ELISA results were not associated with a change in breed class average (BCA) for milk, between the previous and the most recent lactations of individual cattle. However, at the individual cow level, LAM-ELISA results were positively associated with higher milk production as measured by the current BCA (p less than 0.05), and individual cow average kg of milk produced per year of life since two years of age (p less than 0.0001).  相似文献   

19.
In each of 42 Danish dairy herds, ten young stock aged 8–18 months were tested for antibodies against bovine virus diarrhoea virus (BVDV). At the same time a bulk milk sample from each herd was examined for antibodies against BVDV.

The herds could be divided into two distinct groups: (1) Group A (24 herds) had three or less antibody carriers among the ten young stock sampled from each herd and were considered ‘slightly infected’; (2) Group B (18 herds) had eight or more antibody carriers in the ‘spot’ sample and were therefore considered ‘heavily infected’. Persistently infected animals were not found in two Group A herds studied by a subsequent total herd blood test but were detected in five Group B herds in which all animals in the herds were subsequently tested.

Bulk milk titers were generally higher in Group B than in Group A herds. However, there was considerable variation, and in most cases it was not possible to distinguish the two herd categories from one another by means of bulk milk titers.  相似文献   


20.
The Ostertagia-specific antibody levels in milk were monitored in 2 dairy herds to investigate seasonal variations and the relationship between individual and bulk tank milk antibody levels. Bulk tank and individual milk samples from all lactating animals were collected over a 1-year period at weekly and monthly intervals, respectively. The Ostertagia-specific antibody levels were measured with an indirect ELISA and the test results were expressed as optical density ratios (ODR). A clear seasonal pattern that followed the expected intake of infectious larvae was observed in the individual and bulk tank milk antibody levels of both herds. Within each herd, there was a large variation in the individual ODRs. This variation remained large when the distribution of individual ODRs was plotted according to high and low bulk tank milk ODR categories. The results suggest that the effect of seasonal variations on cut-off levels that predict production responses after anthelmintic control, needs to be assessed.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号