Prevalence of Mycobacterium paratuberculosis in ileocecal lymph nodes of cattle culled in the United States

During 1983 and 1984, ileocecal lymph node specimens were obtained from clinically normal cattle at 76 US Department of Agriculture-inspected cull cattle slaughterhouses in 32 states and Puerto Rico. Mycobacterium paratuberculosis was isolated from the lymph nodes of 119 of 7,540 cattle. The prevalence of bovine paratuberculosis was 1.6% overall, with 2.9% in dairy culls and 0.8% in beef culls. The prevalence for females and males did not appear to differ significantly.     

Transitions in diagnostic tests used for detection of Mycobacterium avium subsp. paratuberculosis infections in cattle

Diagnosis of infections with Mycobacterium avium subsp. paratuberculosis (MAP) is difficult due to a long incubation period and lack of tests which can accurately predict the future status of animals. Early detection of infectious animals is necessary to reduce transmission of MAP. The objective of this study was to determine the time from first detection of MAP-antibodies in milk ELISA to start of MAP shedding, for animals with various shedding patterns. An observational longitudinal study was carried out over 3 years. A total of 24,076 milk and 10,074 faecal samples were obtained from 1906 cows and tested using ELISA and FC, respectively. Cows were classified into 5 shedding groups based on their repeated FC: non-shedders (NS; n=1512 cows, 79.3% of total), transient (TS; n=36, 1.9%), intermittent (IS; n=137, 7.2%), low (LS; n=143, 7.5%), and high shedders (HS; n=78, 4.1%). Results showed that 5% of TS, 30% of IS, 60% of LS and 70% of HS were ELISA-positive at the date of first positive FC, and many HS (28%) and LS (14%) were positive >or=1 year prior to first detection of shedding. FC confirmed shedding within the first year after the positive ELISA in 10% of 328 cows with fluctuating ELISA compared with 35% of 445 cows with the last 2 or more ELISAs positive. To conclude, MAP-antibodies were generally detected prior to start of bacterial shedding, with difference between the various patterns of shedding, and a positive ELISA was useful for predicting that an animal would subsequently become infectious.     

Spread and detection of psoroptic scabies of cattle in the United States

Psoroptic scabies of cattle causes substantial economic losses. An eradication program begun in 1905 virtually eradicated the disease by 1950. Complacency was followed by a resurgence of the disease, particularly in the 1970s, when more than 1,000 outbreaks were reported. Program effectiveness was reduced when the disease was often not detected or reported for several months after herds became infested. Further spread was enhanced by infested cattle moving undetected through market channels.     

Survey of antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States

OBJECTIVE: To describe antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States and evaluate the feasibility of collating this information for the purpose of monitoring antimicrobial resistance in bacterial isolates from animals. DESIGN: Cross-sectional study. PROCEDURES: A questionnaire was mailed to veterinary diagnostic laboratories throughout the United States to identify those laboratories that conduct susceptibility testing. Nonrespondent laboratories were followed up through telephone contact and additional mailings. Data were gathered regarding methods of susceptibility testing, standardization of methods, data management, and types of isolates tested. RESULTS: Eighty-six of 113 (76%) laboratories responded to the survey, and 64 of the 86 (74%) routinely performed susceptibility testing on bacterial isolates from animals. Thirty-four of the 36 (94%) laboratories accredited by the American Association of Veterinary Laboratory Diagnosticians responded to the survey. Laboratories reported testing > 160,000 bacterial isolates/y. Fifty-one (88%) laboratories reported using the Kirby-Bauer disk diffusion test to evaluate antimicrobial susceptibility; this accounted for 65% of the isolates tested. Most (87%) laboratories used the NCCLS (National Committee for Clinical Laboratory Standards) documents for test interpretation. Seventy-five percent of the laboratories performed susceptibility testing on bacterial isolates only when they were potential pathogens. CONCLUSIONS: The veterinary diagnostic laboratories represent a comprehensive source of data that is not easily accessible in the United States. Variability in testing methods and data storage would present challenges for data aggregation, summary, and interpretation.     

Economic consequences of control programs for paratuberculosis in midsize dairy farms in the United States

OBJECTIVE: To evaluate the epidemiologic efficacy and economic efficiency of current and potential future control programs for paratuberculosis (Johne's disease) on midsize dairy herds in the United States. DESIGN: Stochastic dynamic computer simulation model. SAMPLE POPULATION: Data on prices and other input variables collected from various sources were used to represent a population of midsize US dairy herds infected with paratuberculosis. PROCEDURE: The simulation model was modified to reflect management and production characteristics of midsize dairy herds in the United States. The model was validated by use of field data and expert opinion. Various control strategies then were simulated and compared on an epidemiologic basis and on the basis of economic efficiency. RESULTS: Test-and-cull strategies and vaccination against paratuberculosis were not able to decrease the mean prevalence of disease in the United States. Typically, only vaccination was economically attractive. Improved management strategies decreased the prevalence of paratuberculosis considerably and had high economic benefits. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of results of this study suggests that test-and-cull strategies alone do not reduce the prevalence of paratuberculosis in cattle and are costly for producers to pursue. Vaccination did not reduce the prevalence but was economically attractive. Finally, improved calf-hygiene strategies were found to be critically important in every paratuberculosis control program and most were economically attractive programs for midsize US dairy farms with the disease.     

National genetic improvement programs for dairy cattle in the United States

Rate of genetic improvement for milk yield has been increasing in recent years. Cows born in 1986 were about 135 kg superior in breeding value for milk yield to those born in 1985. Over 2.2 million cows contribute new data to genetic evaluations for production traits annually. These evaluations are computed with an animal model that provides best linear unbiased predictions of transmitting abilities for milk, fat, and protein yields and fat and protein percentages. The model includes effects of management group, permanent environment, herd-sire interaction, and animal genetic merit. Unknown-parent groups represent the genetic merit of base populations defined by birth year and sex. Type appraisal data are collected by breed associations and are evaluated with a sire model. Holstein cow evaluations are computed using scores from all appraisals and a multitrait model; evaluations for other breeds are computed using all appraisal scores, a repeatability model, and a single-trait system. Dystocia data are collected by individual AI organizations and dairy records processing centers; they are analyzed by a categorical-trait sire model at Iowa State University with support from the National Association of Animal Breeders. The AI organizations have been extremely important in increasing rate of genetic progress by increasing numbers of young bulls sampled, increasing selection intensity of bull dams through multiple ovulation and embryo transfer, and shortening generation interval through the use of younger cows and some virgin heifers as bull dams. (ABSTRACT TRUNCATED AT 250 WORDS)     

Radiometric pooled faecal culture for the detection of Mycobacterium avium subsp paratuberculosis in low-shedder cattle

OBJECTIVE: To identify the optimum pooling rate for pooled faecal culture (PFC) as a diagnostic tool in bovine Johne's disease control, for detection of cattle shedding low concentrations of Mycobacterium avium subsp paratuberculosis (Map). METHOD: Thirteen target animals were selected by delayed growth of Map from initial individual radiometric faecal cultures (first growth index at 5 weeks or later). A procedure based on radiometric culture and IS900 polymerase chain reaction and restriction endonuclease analysis confirmation was then used for PFC. RESULTS: Eight samples (stored for up to 17 months at -80 degrees C) yielded Map on subsequent culture, either from undiluted faeces or those mixed with normal cattle faeces at dilution rates from 1 in 5 to 1 in 50. From a regression equation, culture-positive animals were considered to be shedding relatively low levels of Map (< 6 x 10(4)/g of faeces). Pooling dilutions of more than 1 in 5 reduced PFC sensitivity. A minimum incubation period of 10 weeks at a dilution of 1 in 5 is recommended to detect such infected cattle. This pooling rate in radiometric culture is probably capable of detecting cattle shedding < or = 5 x 10(3) Map organisms/g of faeces, representing an estimated inoculum per culture vial of fewer than 20 viable organisms. CONCLUSION: Map was detected in more than 50% of the stored faecal samples from cattle shedding low concentrations of the organism. A pooling rate of 5 samples per pool is required to reliably detect infected low-shedder cattle using PFC based on radiometric culture.     

Sensitivity and specificity of the agar-gel-immunodiffusion test, ELISA and the skin test for detection of paratuberculosis in United States Midwest sheep populations

Our objective was to estimate the sensitivity and specificity of the agar-gel-immunodiffusion test (AGID), the ELISA, and the skin test for the detection of Mycobacterium avium subspecies paratuberculosis (MAP) in sheep using Bayesian methods without a gold standard. Fourteen flocks (2 465 sheep) were used. Five flocks (450 sheep) were considered MAP non-infected and 9 flocks (2 015 sheep) had sheep infected with MAP. Sheep were skin tested and blood was collected for AGID and ELISA testing. Results were analyzed using a Bayesian 3-test in 1-population model fitted in WinBUGS. The model allowed for dependence (correlation) between the two serologic tests, but these two tests were assumed to be conditionally independent of the skin test. The estimated specificity was 99.5% (95% PI of 98.9-99.9%) for the AGID; 99.3% (98.4-99.8%) for the ELISA using an optical density measured cutoff of 0.20; 99.2% (98.1-99.8%) using a cutoff of 0.15; 97.5% (95.8-98.7%) using a cutoff of 0.10; and 98.7% (97.3-99.5%) for the skin test. The estimated sensitivities were 8.3% (6.2-10.7%) for the AGID; 8.0% (6.0-10.4%), 10.6% (8.3-13.1%), and 16.3% (13.5-19.4%) for the ELISA using the cutoffs 0.20, 0.15, and 0.10 respectively; and 73.3% (62.3-85.8%) for the skin test. The skin test was specific in non-infected populations and sensitive in infected populations, although in some cases a positive skin test might represent MAP exposure rather than infection. The AGID and ELISA were specific but lacked sensitivity. The AGID and ELISA consistently identified two different populations of infected sheep with only moderate overlap between positive test results.     

Bluetongue in cattle: a serologic survey of slaughter cattle in the United States

Serologic tests for bluetongue virus (BTV) were done on 19,758 blood serum samples systematically collected at brucellosis laboratories throughout the United States from Nov 28, 1977 to Feb 20, 1978. Prevalence of BTV antibody varied from 0 to 79% of the samples collected in various states, with a national prevalence of 18.2%. The prevalence was generally low in the northern states and high in the southwestern states. The highest prevalence rates were found in Puerto Rico and the Virgin Islands.     

Potentially hazardous sulfur conditions on beef cattle ranches in the United States

OBJECTIVE: To analyze the sulfur content of water and forage samples from a geographically diverse sample of beef cow-calf operations in the United States and to estimate frequency and distribution of premises where forage and water resources could result in consumption of hazardous amounts of sulfur by cattle. DESIGN: Cross-sectional study. SAMPLE POPULATION: 709 forage samples from 678 beef cow-calf operations and individual water samples from 498 operations in 23 states. PROCEDURE: Sulfur content of forage samples and sulfate concentration of water samples were measured. Total sulfur intake was estimated for pairs of forage and water samples. RESULTS: Total sulfur intake was estimated for 454 pairs of forage and water samples. In general, highest forage sulfur contents did not coincide with highest water sulfate concentrations. Overall, 52 of the 454 (11.5%) sample pairs were estimated to yield total sulfur intake (as a percentage of dry matter) > or = 0.4%, assuming water intake during conditions of high ambient temperature. Most of these premises were in north-central (n = 19) or western (19) states. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that on numerous beef cow-calf operations throughout the United States, consumption of forage and water could result in excessively high sulfur intake. All water sources and dietary components should be evaluated when assessing total sulfur intake. Knowledge of total sulfur intake may be useful in reducing the risk of sulfur-associated health and performance problems in beef cattle.     

The availability of state-level data on interstate cattle movements in the United States

Knowledge about the patterns of animal movement – particularly feeder-cattle movement – within the USA is necessary in order to anticipate how diseases might be spread geographically. This study was conducted to explore the availability of interstate-level movement data which might be used to develop a more coherent national picture of interstate feeder-cattle movement. State Statistical Offices of the National Agricultural Statistics Service, 1996 (NASS) and Departments of Agriculture in all 50 states were contacted to determine the type of information collected regarding the import and export of feeder cattle. Eighteen of the 50 states contacted recorded updated import and export information by using certificates of veterinary inspection and (occasionally) entry permits for verification. The 18 states were: Alabama, Colorado, Florida, Hawaii, Idaho, Illinois, Indiana, Iowa, Kansas, Maryland, Massachusetts, Minnesota, New Jersey, Pennsylvania, Texas, West Virginia, Wisconsin, and Wyoming. Profiles of import and export data from Kansas, Texas, Colorado and Iowa (the primary receivers of 51% of total 1995 imports) were developed. These four states received at least 50% of their cattle imports from <9 different states. As a result, approximately half of the nation's import movement can be explained by a total of 13 states and Mexico (excluding duplicates). Also, >50% of the exports from Kansas, Texas, Colorado, and Iowa go to ≤3 states. This import and export information confirms conclusions of others that cattle tend to move toward the center of the USA. However, if more states kept comprehensive, up-to-date records of movement information, knowledge about cattle-movement patterns in the USA would be importantly increased. The lack of specific notations on certificates of veterinary inspection can lead only to perceived trends; the present records have limited value in tracking animal movement.     

An overview of beef cattle improvement programs in the United States

A periodic review of beef improvement programs is useful as a benchmark and as an opportunity to reevaluate industry direction. The history of improvement programs is reviewed with particular emphasis on recording organizations, program financing, and technological progress. The various breed associations have become the primary suppliers of performance programs, which are largely funded through registration income. Current practices are described from the aspects of traits recorded and delivery systems to collect, analyze, and distribute the data. The unique or innovative features of several breed made of the organization, technical, and educational challenges facing beef improvement. Although increased participation in genetic improvement programs is expected, substantial efforts are needed to serve adequately the needs of a changing beef cattle industry.     

Comparison of three diagnostic detection methods for tuberculosis in French cattle

Three additional techniques (Ziehl-Neelsen, auramine O/rhodamine and immunostaining using polyclonal anti-Mycobacterium bovis) to hematoxylin-eosin histopathology were evaluated for bovine tuberculosis diagnosis on 39 samples from several slaughterhouses. The immunohistochemichal technique was more sensitive and could detect a greater number of positive cattle. It has about the same sensibility as the bacteriology but it was faster.     

Regional risk of exporting cattle seropositive for bluetongue virus from the United States

OBJECTIVE: To create a stochastic model to quantify the risk that shipments of cattle from regions within the United States would contain animals seropositive for bluetongue virus and to determine shipment-level accuracy of serologic testing by use of a competitive ELISA (c-ELISA). SAMPLE POPULATION: 19,216 shipments containing 528,918 cattle and calves. PROCEDURE: Data were obtained on number of animals and state of origin of cattle in export shipments originating within the United States between January 1994 and March 2002. Probability distributions for size of export shipments were determined for all states within the United States, and distributions for agar gel immunodiffusion and c-ELISA accuracy (sensitivity and specificity) were determined from expert opinion and review of the literature. The model simulated selection of a shipment and then determined the probability that a threshold number or percentage of cattle within that shipment would have a positive c-ELISA result. Shipment-level sensitivity, specificity, positive-predictive value, and negative-predictive value were calculated. RESULTS: Substantial differences were evident in the regional probability of a shipment being declared positive, with shipments from northeastern states having the lowest probability and shipments from southwestern states having the highest probability. The c-ELISA had variable predictive values at the shipment level, depending on the threshold used and the prevalence of antibody-positive cattle within the region. CONCLUSIONS AND CLINICAL RELEVANCE: Results from this study will aid importers in making scientifically based decisions regarding risk of importing antibody-positive cattle.