Evaluation of progress made by dairy and beef herds enrolled in the Minnesota Johne's Disease Control Program

Scott J. Wells Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108

Search for other papers by Scott J. Wells in
Current site
Google Scholar
PubMed
Close
 DVM, PhD, DACVPM
,
William L. Hartmann Minnesota Board of Animal Health, Orville L. Freeman Bldg, 625 Robert St N, Saint Paul, MN 55155

Search for other papers by William L. Hartmann in
Current site
Google Scholar
PubMed
Close
 DVM, MS
, and
Paul L. Anderson Minnesota Board of Animal Health, Orville L. Freeman Bldg, 625 Robert St N, Saint Paul, MN 55155

Search for other papers by Paul L. Anderson in
Current site
Google Scholar
PubMed
Close
 DVM, MS

Abstract

Objective—To evaluate progress made by cattle herds in the control of paratuberculosis (Johne's disease) through participation in the Minnesota Johne's Disease Control Program (MNJDCP).

Design—Retrospective records analysis.

Sample Population—Data for dairy and beef herds participating in the MNJDCP.

Procedures—Data for the MNJDCP were collected for analyses. Outcome measures included changes in numbers of participating cattle producers, risk assessment scores, and within-herd seroprevalence of Johne's disease by year of program participation.

Results—Results revealed steady increases in program participation by cattle producers in Minnesota over time, with > 30% of dairy producers and 2% of beef producers in the state participating by the end of 2006. Despite risk of introduction of Johne's disease to cattle herds through continued introduction of cattle from other herds, dairy and beef herds in the Management Program of the MNJDCP reduced their on-farm risk assessment scores during the program. Dairy herds in the Management Program reduced their mean within-herd seroprevalence 1.1% during the first year, 2.6% during the first 2 years, and 4.0% during the first 3 years of program participation. Significant within-herd seroprevalence reduction was also detected for beef herds that participated in the Management Program for at least 3 years.

Conclusions and Clinical Relevance—This study revealed a reduction in the risk of withinherd transmission of Johne's disease and seroprevalence over time in dairy and beef herds in the Management Program of the MNJDCP. This is consistent with a positive effect of the program for the control of Johne's disease in cattle.

Abstract

Objective—To evaluate progress made by cattle herds in the control of paratuberculosis (Johne's disease) through participation in the Minnesota Johne's Disease Control Program (MNJDCP).

Design—Retrospective records analysis.

Sample Population—Data for dairy and beef herds participating in the MNJDCP.

Procedures—Data for the MNJDCP were collected for analyses. Outcome measures included changes in numbers of participating cattle producers, risk assessment scores, and within-herd seroprevalence of Johne's disease by year of program participation.

Results—Results revealed steady increases in program participation by cattle producers in Minnesota over time, with > 30% of dairy producers and 2% of beef producers in the state participating by the end of 2006. Despite risk of introduction of Johne's disease to cattle herds through continued introduction of cattle from other herds, dairy and beef herds in the Management Program of the MNJDCP reduced their on-farm risk assessment scores during the program. Dairy herds in the Management Program reduced their mean within-herd seroprevalence 1.1% during the first year, 2.6% during the first 2 years, and 4.0% during the first 3 years of program participation. Significant within-herd seroprevalence reduction was also detected for beef herds that participated in the Management Program for at least 3 years.

Conclusions and Clinical Relevance—This study revealed a reduction in the risk of withinherd transmission of Johne's disease and seroprevalence over time in dairy and beef herds in the Management Program of the MNJDCP. This is consistent with a positive effect of the program for the control of Johne's disease in cattle.

Paratuberculosis (Johne's disease) was recognized as an important animal health issue for the US dairy cattle industry in the mid 1990s. It was estimated in the NAHMS Dairy 2007 study1 that at least 68% of US dairy herds are infected with the causative bacterium, Mycobacterium avium subsp paratuberculosis. In 1996, the estimated cost of Johne's disease to heavily infected US dairy herds was > $200/cow in inventory/y, with an estimated national cost for the United States of > $200 million/y.2 A lower herd prevalence for US beef cow-calf operations was reported in the 1997 NAHMS beef study.3 An additional concern is the potential public health risk from M avium subsp paratuberculosis. Although the link has not been definitively proven, evidence persists that this pathogen may be one of the causes of Crohn's disease in humans.4

Because of these animal and potential public health concerns, the Johne's Committee of the USAHA created a subcommittee (ie, the National Johne's Working Group) to develop the outline for a national control program. Through this process, the USAHA, in concert with the USDA, APHIS, VS, developed what is currently known as the VBJDCP. The control program was adopted by interested states (including Minnesota) starting in the late 1990s, which used available state funding. Beginning in 2003, $21 million in federal funding was made available to the USDA, APHIS, VS for implementation of the VBJDCP. In fiscal year 2004, $18.9 million was provided, whereas $18.6 million was provided in fiscal year 2005, $13.2 million was provided in fiscal year 2006, and $12 million was provided in fiscal year 2007.

Although a general understanding of the epidemiologic aspects and control of Johne's disease was available at the start of the program,5,6 validated successful interventions in US herds were not available. Simulation models7,8 revealed the potential benefit of implementation of management-based control programs, but these have not been validated by analyses from field data. Longitudinal field reports9,10 from Australia were supportive of the effectiveness of management control of Johne's disease, but there was much debate about the efficacy of the proposed herd control program in the United States. Incomplete information was available regarding cattle producers' interest in participation, the time needed to achieve disease control in a herd, and costs and benefits of the program. Despite these concerns, a consensus was achieved through the USAHA process to move forward with development of a national control program. Federal funding was provided for several components of the program, including building of infrastructure (including obtaining funding for APHIS, VS policy staff, field personnel in various states, laboratory personnel, and database specialists and analysts), purchase of laboratory equipment and test kits for testing, and creation of cooperative agreements with states to facilitate implementation of the program, which included funding to support visits of private practitioners to cattle herds to perform risk assessments and develop herd plans.

Because the VBJDCP is a voluntary program, it remains a lower priority than other national mandatory disease control programs in the United States. This lower priority threatens future funding, especially at a time when available federal funding for animal health programs is limited. Questions have arisen about the value of the VBJDCP and its effectiveness in terms of producer participation, change in herd management, and reduction in disease transmission and infection rates.

Nationally, dairy producers are more likely to participate in the VBJDCP than beef producers, with 6,662 dairy herds in the program at the end of 2006, compared with 2,012 beef herds.11,a Minnesota has a viable cattle industry (ranked 6th in number of milk cows and 26th in number of beef cows nationally11) and an active Johne's disease control program. At the end of 2006, 1,663 of 5,400 (30.8%) Minnesota dairy herds participated in the MNJDCP, which was the highest rate of herd participation for any state; 320 of 15,000 (2.1%) Minnesota beef herds participated in the program.

The objective of the study reported here was to evaluate progress made by Minnesota cattle herds in the control of Johne's disease since inception of the MNJDCP in 1998. Expected outcome measures included funding expended and annual changes in numbers of participating cattle producers, risk assessment scores, and within-herd seroprevalence by year of program participation.

Materials and Methods

Sample population—Data were extracted for the period from 1998 through 2006 from the Minnesota Board of Animal Health generic database through the assistance of Board of Animal Health staff members. For numbers of participating cattle herds in the program, data were summarized at the end of each year. The MNJDCP herds were categorized on the basis of cattle type (dairy or beef) and category of program participation (Management Program or Test-Negative Program). Herds participating in the Management Program included cattle herds making efforts to control Johne's disease, with or without testing of the herd and without herd classification, and herds participating in the Test-Negative Program included herds at levels 1, 2, 3, or 4 of the Voluntary US Johne's Disease Test-Negative Program.

Data analysis—Herd participation in the program was calculated as the proportion of Minnesota dairy or beef cattle herds participating in the Minnesota Management or Test-Negative Program; the denominators were the estimated number of cattle herds (dairy or beef) in the state by type with at least 1 adult cow, as reported by the USDA National Agricultural Statistics Service.12 Funding information regarding expenditures for testing, including veterinary fees for collection of biological samples as well as fees for veterinarian completion of risk assessments, was provided by the Minnesota Board of Animal Health.

Data on management practices and herd size were determined annually from Johne's disease risk assessments completed by certified veterinarians.13 Herd size was recorded as the number of adult cows in the herd from the Johne's disease risk assessment. When information on herd size changed during the years a herd participated in the program, data from the most recent (up to 2006) Johne's disease risk assessment were used because these data were not maintained in the database from earlier years. Some herds did not have annual risk assessments and therefore were not included in certain analyses when data were unavailable (eg, rates of participation on the basis of herd size). Thus, the numbers of herds for each analysis were reported. A comparison of herd participation on the basis of herd size was performed by use of the χ2 test of association.

Management changes were assessed in herds that were initially participating in the Johne's Disease Management Program because these herds were considered infected with the agent that causes Johne's disease and implemented a control program. Risk scores from the Johne's disease risk assessment are considered a measure of risk of transmission of Johne's disease. For dairy herds, scores are assigned on a scale of 0 to 80 for calving area risks (with a higher score indicating a higher risk of transmission), 0 to 50 for preweaned calves, 0 to 30 for weaned calves, 0 to 24 for bred heifers, and 0 to 16 for adult cattle for a total of 200 maximum points for the on-farm score. Beef cattle herds have a maximum score of 180. An additional score from 0 to 60 is given for replacement cattle risks for an overall total of 260 for dairy herds (240 for beef herds). For year-to-year comparison of scores, the on-farm score (a summary of scores for the calving area, preweaned calves, weaned calves, bred heifers, and adult cattle but excluding replacement cattle) was considered the best summary score for evaluating management changes during the program because the on-farm score is a measure of within-herd Johne's disease transmission risk. Total score was modified by the addition of the risk score for replacement cattle starting in 2002, but this change did not affect on-farm scores. For comparisons among years, the median risk score for each year was calculated from available risk assessments. Within-herd reduction in risk scores was calculated as the change in the risk assessment score between the first year the herd participated in the Management Program and a subsequent year. For evaluation of differences from the starting risk scores (reduction in risk scores), 95% confidence intervals of the mean differences were estimated.

Estimates of Johne's disease herd testing results were calculated from available herd test information from the Minnesota Board of Animal Health. Because Johne's disease is a reportable disease to the Minnesota Board of Animal Health, all Johne's disease test results were required to be submitted to the agency. These test results were predominantly from the Minnesota Veterinary Diagnostic Laboratory, which was the official laboratory of the Minnesota Board of Animal Health and therefore performed most of the tests in the state, although other laboratories also reported test data. Annual within-herd apparent seroprevalence for Johne's disease for each herd was estimated by use of data from nonvaccinated cattle herds that tested at least 20 cows (these herds were initially categorized as Johne's Disease Management Program herds). Within-herd apparent seroprevalence estimates were calculated by use of the number of cows with positive results for an ELISA divided by the number of cows tested by use of an ELISA at any point within a calendar year. No adjustments were made for cows tested more than once throughout the year because this information was not available. Data were reported as median withinherd seroprevalences for each year. Within-herd reduction in seroprevalence by year in the program reflected the difference between ELISA-determined within-herd seroprevalence from the first year the herd participated in the Johne's Disease Management Program and any subsequent year. For evaluation of significance of mean differences of seroprevalence by year in the program, 95% confidence intervals of mean differences by year in the program were estimated. Values of P < 0.05 were considered significant.

Results

Herd participation—Several states participated in the VBJDCP in 2006, but Minnesota had the highest number of cattle herds participating in the program11,a (Table 1). Results from analyses of MNJDCP data revealed steady increases in program participation by dairy producers such that 1,663 (30.8%) Minnesota dairy producers participated in the Johne's Disease Management Program or Test-Negative Program in 2006 (Table 2). Much of the program growth has been since 2002. Herd participation in the Johne's Disease Management Program was related to herd size, with larger herds being significantly (P < 0.001) more likely to participate than smaller herds (Table 3). In 2005 through 2006, 52.9% of Minnesota dairy herds with 500 or more cows participated in the Management Program, compared with only 9.9% of herds with < 50 cows. Participation by herds in the Test-Negative Program increased over time, with 513 (9.5%) Minnesota dairy herds participating in 2006. Participation by beef producers also increased over time but at a lower rate, compared with that for dairy herds, with 320 (2.1%) beef producers participating in the program in 2006. In 2006, only 0.8% of Minnesota beef herds participated in the Test-Negative Program.

Table 1—

Participation of dairy herds in the VBJDCP in 2006, by state.

StateNo. of dairy herds in stateNo. of herds in Management ProgramNo. of herds in Test-Negative ProgramTotal No. of herds in the VBJDCPParticipating herds (%)
Minnesota5,4001,1505131,66331
Oregon720162817024
Maine46056288418
South Carolina2002733015
Pennsylvania8,7001,0142431,25714
New York6,4007273476112
Wisconsin14,9001,598181,61611
Hawaii3021310
Ohio4,4003864443010
New Jersey15067139
Georgia580430437
North Dakota500314357
Virginia1,3004836846
Vermont1,2003336696
Kentucky2,000914955
West Virginia470810184
North Carolina590129214
Florida460140143
Utah560170173
Michigan2,700713743
Indiana2,1003421553
Mississippi3302572
Missouri2,600373402
Other states18,39054963<1
Total75,1405,6231,0396,6629

Data reported here were from sources updated in December 2006, except for data for Oregon, which were updated in September 2006.11,a

Table 2—

Dairy and beef herds participating in the MNJDCP Management Program or Test-Negative Program, by year.

MNJDCP programYearDairy herdsBeef herds
No.%*No.%*
Management Program1997830.84<0.1
19981701.8100.1
19992022.2140.1
20002222.6200.1
20013484.5330.2
20025207.2450.3
20036099.2550.4
200482813.6960.6
20051,09518.91120.8
20061,15021.32011.3
Test-Negative Program19972<0.100
1998180.23<0.1
1999330.480.1
2000450.5140.1
2001490.6150.1
2002570.8170.1
2003921.4290.2
20042464.0570.4
20054738.2950.6
20065139.51190.8

Represents the percentage of dairy or beef herds, respectively, in Minnesota; a herd was defined as 1 or more cows as reported by the USDA National Agricultural Statistics Service.

Table 3—

Dairy and beef herds participating in the MNJDCP Management Program or Test-Negative Program in 2005 through 2006, by herd size.

MNJDCP programHerd size (No. of cows)Dairy herdsBeef herds No. %*
No.%*No.%*
Management Program1–492279.9820.7
50–9937116.9432.8
100–49931137.5263.3
≥ 5003752.915
Test-Negative Program1–491145.0370.3
50–991667.5151.0
100–499637.6111.4
≥ 50011.400

Percentages were calculated on the basis of the number of dairy or beef herds in Minnesota, respectively, for each size category; a herd was defined as 1 or more cows as reported by the USDA National Agricultural Statistics Service.

The MNJDCP started with state funding in 1998, with nearly $158,000 expended by the Minnesota Board of Animal Health for testing of herds (Figure 1). Since that time, state and federal funding for support of laboratory testing, veterinary fees for sample collection, and veterinarian completion of herd risk assessments increased to a peak of $571,000 in 2005, then decreased slightly to $556,000 in 2006. The surge of funding from the federal government for the cooperative State-Federal Control Program began in 2003; since that time, an increasing proportion of MNJDCP funds have been spent on completion of risk assessments and development of herd management plans by veterinarians. Overall, increased herd participation was directly correlated (r = 0.97; P < 0.001) with the increase in funds spent for these program activities. These data do not include funds spent on other aspects of the MNJDCP, such as expenses for time and travel costs of federal and state veterinarians in support of the program, nor funds spent by cattle producers on testing.

Figure 1—
Figure 1—

Funding for the MNJDCP for testing and risk assessments by certified herd veterinarians (triangles) and number of cattle herds in the MNJDCP (squares) since its inception in 1998.

Citation: Journal of the American Veterinary Medical Association 233, 12; 10.2460/javma.233.12.1920

Herd management changes subsequent to participation in the Management Program—Estimates of transmission risks for Johne's disease, which were available from analyses of risk assessments, revealed that many Minnesota cattle herds introduced cattle to their operations from other herds. In 2004, 36.3% of the 510 dairy herds in the Management Program and 43.3% of the 60 beef herds in the Management Program indicated that they had introduced cattle during the preceding year. Little change was evident for 2005, with 42.4% of 663 dairy herds and 45.6% of 68 beef herds, or 2006, with 33.8% of 672 dairy herds and 41.7% of 96 beef herds. Overall, Johne's Disease Management Program on-farm risk assessment scores for dairy herds decreased only marginally over time, although total scores remained relatively constant as a result of the addition of risk score from introduction of replacement cattle starting in late 2002 (Table 4). Although the median replacement cattle risk score for dairy and beef herds since 2003 was zero, which reflected the fact that fewer than half of the herds introduced cattle during any specific year, the mean replacement cattle score for dairy herds was 14.0, 11.1, 11.8, and 11.2 for years 2003, 2004, 2005, and 2006, respectively; the score for beef herds was 2.0, 10.7, 15.2, and 11.6 for the same years, respectively.

Table 4—

Median (25th to 75th percentile) herd risk assessment score for dairy and beef herds participating in the MNJDCP Management Program, by year.

Herd typeYearNo. of herdsOn-farm scoreTotal score*
Dairy200116956 (41–70)56 (41–70)
200240948 (36–66)49 (36–68)
200348046 (32–62)58 (38–80)
200451144 (31–60)54 (37–76)
200566348 (30–67)60 (37–84)
200667241 (23–59)51 (27–80)
Beef20011242 (34–48)42 (33–48)
20024541 (30–53)41 (31–53)
20034537 (28–46)37 (29–47)
20046042 (32–64)54 (40–82)
20056838 (24–64)60 (32–81)
20069642 (25–64)52 (31–78)

Total scores are assigned on a scale of 0 to 260 for dairy herds and 0 to 240 for beef herds, with a higher score indicating a higher risk of transmission.

Total score changed beginning late in 2002 to also include replacement cattle risk assessment score; thus, for 2002 and subsequent years, the total score = on-farm risk assessment score + replacement cattle risk assessment score.

However, dairy herds in the Johne's Disease Management Program had reduced on-farm risk assessment scores (mean of 10.5 for the first year of participation in the control program and 18.1 for the first 2 years of participation in the control program; Table 5). These reductions were maintained during subsequent years of program participation. Similarly, beef herds in the Johne's Disease Management Program had substantial reductions in on-farm risk assessment scores.

Table 5—

Mean (95% CD reduction in risk assessment scores between the first year and subsequent years for dairy and beef herds participating in the MNJDCP Management Program.

Herd typeYears comparedNo. of herdsOn-farm scoreTotal score*
Dairy1 and 262610.5 (9.0 to 12.0)8.8 (6.8 to 10.9)
1 and 348318.1 (15.6 to 20.6)13.9 (10.5 to 17.3) 
1 and 440415.3 (12.7 to 17.9)9.2 (5.7 to 12.8) 
1 and 528819.6 (16.4 to 22.8)9.7 (5.5 to 13.9) 
1 and 610624.1 (18.9 to 29.3)15.1 (8.7 to 21.6) 
Beef1 and 2735.1 (0.9 to 9.4)4.2 (-2.2 to 10.5)
1 and 35311.5 (2.8 to 20.2)10.2 (0.0 to 20.5) 
1 and 43812.7 (5.2 to 20.2)-2.4 (-13.2 to 8.4) 
1 and 53117.1 (6.9 to 27.3)9.4 (-1.8 to 20.6) 

See Table 4 for key.

Changes in within-herd seroprevalence subsequent to participation—Among dairy cattle herds in the Johne's Disease Management Program that tested at least 20 cows by use of a serum ELISA in a given year that were included in this assessment, the median number of cows tested per year was 95 cows (25th to 75th percentiles, 49 to 183 cows) in 2001, 78 cows (25th to 75th percentiles, 45 to 135 cows) in 2002, 68 cows (25th to 75th percentiles, 41 to 116 cows) in 2003, 54 cows (25th to 75th percentiles, 30 to 104 cows) in 2004, 30 cows (25th to 75th percentiles, 30 to 57 cows) in 2005, and 30 cows (25th to 75th percentiles, 30 to 70 cows) in 2006. Among this group of dairy herds, the median seroprevalence decreased from 9.9% in 2002 to 3.4% in 2006 (Table 6). The mean reduction in seroprevalence (as determined by results of an ELISA) was 1.1% from year 1 to year 2 in the program, 2.6% from year 1 to year 3 in the program, 4.0% from year 1 to year 4 in the program, and 4.9% from year 1 to year 5 in the program (Table 7). Lower participation rates of beef herds, compared with the participation rates of dairy herds, limited interpretation of study results, but a substantial reduction in within-herd seroprevalence was detected for beef herds that participated in the Johne's Disease Management Program for at least 3 years. In addition, 103 dairy herds and 52 beef herds initially in the Management Program with at least 20 cows tested by use of a serum ELISA within a specific year qualified for and entered the Test-Negative Program by 2006.

Table 6—

Median (95% CD within-herd seroprevalence of Johne's disease determined by use of a serum ELISA for dairy and beef herds participating in the MNJDCP Management Program, by year.

YearNo. of dairy herdsPositive results (%)No. of beef herdsPositive results (%)
20011468.5 (4.5–13.0)114.5 (2.5–10.0)
20022919.9 (5.6–14.8)293.3 (1.6–6.4)
20032788.3 (4.3–13.2)313.3 (2.2–6.3)
20043066.5 (3.0–11.2)293.4 (0–5.0)
20053464.3 (1.9–9.1)390.6 (0–3.3)
20063803.4 (0–7.3)520.3 (0–3.3)
Table 7—

Mean (95% CD reduction in seroprevalence of Johne's disease between the first year and subsequent years for dairy and beef herds participating in the MNJDCP Management Program.

Years comparedDairy herdsBeef herds
 No. of herdsReduction (%)No. of herdsReduction (%)
1 and 23221.1 (0.2 to 1.9)390.5 (-0.8 to 1.9)
1 and 32552.6 (1.5 to 3.8)260.8 (-1.3 to 2.8)
1 and 41924.0 (2.8 to 5.2)273.6 (1.8 to 5.4)
1 and 51234.9 (3.3 to 6.5)193.2 (1.4 to 5.1)
1 and 6603.0 (0.9 to 5.1)93.9 (0.7 to 7.1)

Discussion

The evaluation reported here was conducted with data for testing of herds and risk assessments collected longitudinally by the Minnesota Board of Animal Health. This study was designed to describe herd management and Johne's disease in cattle herds participating in the MNJDCP. The retrospective design of this assessment resulted in lack of control for selection of herds and missing information on risk assessments and seroprevalence from some herds during certain years. As such, this study was not designed to evaluate cause and effect of the control program, as could be done in a controlled clinical trial. Instead, the objective of this study was to measure change in specific Johne's disease outcomes and their correlation with duration of participation in the control program. One important result from this study was the steadily increasing number of Minnesota cattle herds that participated in the program, especially after federal funding was initiated in 2003.

Another study limitation was the use of available data on serologic testing for estimation of seroprevalence. Few herds used bacterial culture of fecal samples from individual cows for diagnostic testing because of higher costs, and therefore, results of bacterial culture of fecal samples were not used in this study. For estimation of within-herd seroprevalence, we used data from herds that tested at least 20 samples during each year in the program. Although 20 samples/herd provides only a crude estimation of apparent seroprevalence, most herds had substantially more samples tested each year, and we used all available ELISA results for this estimation. Another limitation was the reliance on risk scoring by veterinarians for the assessment of change in management practices because of the possibility that some veterinarians may have wanted to provide positive feedback to producers in the program through a reduction in scores over time. Although a degree of subjectivity of the risk scoring system is inherent, the veterinarians completing the risk assessments did receive training and certification to complete this task.

One critical aspect of the VBJDCP is the identification of low-risk (test-negative) herds. A major risk factor for infected herd status is introduction of infected cattle,14 and results from the assessment revealed the continued risks posed for herds whose owners purchased cattle. Testing of randomly selected replacement cattle of unknown infection status is less effective in reducing risk of herd infection than is purchase of cattle from test-negative programs.15 Therefore, a ready source of identified low-risk cattle from herds participating in a low-risk herd classification program is necessary to meet the needs of the US dairy and beef industries. Results from the MNJDCP indicated a steady increase in the number of these low-risk herds.

Herds with more cows were more likely to participate in the Johne's Disease Management Program, compared with participation of herds with fewer cows, perhaps because of the higher likelihood of infection with M avium subsp paratuberculosis, which was reported in the most recent national study.1 This association was also reported in an earlier analysis of data from MNJDCP herds that included data up to February 2004.16 One reason for this increased likelihood of infection is that larger herds are more likely to introduce cattle from other herds than are herds with fewer cows.17 Some of these larger herds may have recently attempted herd expansions through purchase of cattle, which has the potential to result in high incidence of cows with clinical Johne's disease. Certainly, larger herds have a larger potential financial risk from Johne's disease, which may be reflected in higher participation rates in Johne's disease control programs.

Analysis of the results also revealed a reduction in risk of transmission of Johne's disease and a reduction in seroprevalence of Johne's disease over time for dairy herds in the MNJDCP Management Program, which is consistent with a positive effect of the control program. Because there were fewer beef herds participating in the program, less inference can be drawn for the beef herds. However, the available evidence indicates a similar beneficial effect in beef herds. The earlier analyses of MNJDCP data16 (which did not include approximately 3 years of program data included in the study reported here) revealed a similar reduction in risk scores from the first score to most recent score in program herds. However, a reduction in seroprevalence in herds participating in the program was not identified at that time.

The data reported here were consistent with results for Minnesota dairy herds in the NJDDHP. Results from the Minnesota demonstration herds,18 which were summarized as part of the NJDDHP, revealed that implementation of a Johne's disease control program through the use of management practices and test information resulted in a reduction in seroconversion and shedding of infectious organisms in feces. It was suggested in that study18 that reduction of environmental contamination of heifers < 1 year old had measurable impact on the success of the program and that the NJDDHP appeared more beneficial for herds that achieved a greater reduction of the risk assessment score.

As a state, Minnesota has the highest number of cattle herds participating in the VBJDCP (Table 1). One advantage of the program in Minnesota was the availability of state funding prior to initiation of federal funding, which generated early development and implementation of the program. Several other states also reported high participation rates, and the results reported here for the Minnesota producers were expected to be typical of results in other states with active Johne's disease control programs. The evidence from this study is consistent with the effectiveness of the control program, and continued funding is needed to support progress of the program. Currently, several funding options are available for the national program. These options include continuation of federal funding for the program (federal-funded program), reduction of federal funding for the program without replacement from an off-farm source (producer-funded program), or reduction of federal funding for the program and replacement with funding from another source (other-funded program).

At this time, the federal-funded option appears to be at risk because of other priorities of the USDA. Funding through APHIS has already decreased from a high of $21 million in 2003 to $12 million in 2007. Additional funding cuts are likely, especially without an increased focus and lobbying by producer groups. Without federal funds and without replacement of those funds from another source, the VBJDCP is at risk. Critical components of the program, including policy development and coordination, education, completion of risk assessments, and herd testing are expensive. Participation by herds is expected to decrease without funding support. The third option of replacement of some or all of the federal funds for this program by another funding source may be the best opportunity for long-term success of the program. Potential options available include state or industry funding. Whatever the source of funding, a sustained program is believed to be necessary for national control of this disease in cattle and other livestock species.

Despite the risk of reduction in federal funding for the VBJDCP, positive enhancements can be implemented to maintain critical program components while potentially increasing the efficiency of available funding. One critical component of the VBJDCP is communication between the certified veterinarians for each of the herds, federally employed veterinarians, and cattle producers. This relationship is necessary to ensure completion of risk assessments and herd plans (including review of principles for control of Johne's disease and identification of high-priority mitigations). In the study reported here, completion of risk assessments (with the associated education delivered as part of the process) was associated with reduced risk scores and reduced within-herd seroprevalence of infection over time for herds participating in the Johne's Disease Management Program. In addition, recent advances and understanding of diagnostic tests have identified alternatives that can reduce test costs through the use of less expensive tests and more efficient test strategies. The use of inexpensive testing options (including testing of milk with an ELISA) can reduce the cost of herd monitoring.19,20 In addition, new herd testing strategies can accurately identify herd infection status at a reasonable cost.21 Improved information about the value of specific on-farm management practices is expected in the near future as a result of clinical trials and related studies, such as the NJDDHP. Information generated from these and other studies is expected to help identify ways to reduce the overall cost of Johne's disease control programs.

Analysis of results for the study reported here indicated that in a state with high participation of dairy producers in the VBJDCP, an assessment of herds enrolled in the Johne's Disease Management Program revealed a reduction in risk of transmission of Johne's disease and in seroprevalence of Johne's disease over time. These data from Minnesota cattle herds with active Johne's disease control programs were consistent with confirmation of the effectiveness of the VBJDCP in reducing the incidence of Johne's disease in dairy and beef herds.

ABBREVIATIONS

CI

Confidence interval

MNJDCP

Minnesota Johne's Disease Control Program

NAHMS

National Animal Health Monitoring System

NJDDHP

National Johne's Disease Demonstration Herd Program

USAHA

US Animal Health Association

VBJDCP

Voluntary Bovine Johne's Disease Control Program

VS

Veterinary Services

a.

Carter M, USDA, APHIS, Veterinary Services, Riverdale, Md: Personal communication, 2007.

References

  • 1.

    USDA. Johne's disease on U.S. dairies, 1991–2007. No. N521.0408. Fort Collins, Colo: USDA, APHIS, Veterinary Services, Center for Epidemiology and Animal Health, 2008.

    • Search Google Scholar
    • Export Citation
  • 2.

    Ott SL, Wells SJ, Wagner BA. Herd-level economic losses associated with Johne's disease on US dairy operations. Prev Vet Med 1999;40:179192.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3.

    Dargatz DA, Byrum BA & Hennager SG, et al. Prevalence of antibodies against Mycobacterium avium subsp paratuberculosis among beef cow-calf herd. J Am Vet Med Assoc 2001;219:497501.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Committee on Diagnosis and Control of Johne's Disease, National Research Council. Diagnosis and control of Johne's disease. Washington, DC: National Academies Press, 2003.

    • Search Google Scholar
    • Export Citation
  • 5.

    Sweeney RW. Transmission of paratuberculosis. Vet Clin North Am Food Anim Pract 1996;12:305312.

  • 6.

    Rossiter CA, Hutchinson LJ & Hansen D, et al. Johne's disease prevention/control plan for dairy herds: manual for veterinarians. Bovine Pract 1999;33:193-1193-22.

    • Search Google Scholar
    • Export Citation
  • 7.

    Groenendaal H, Nielen M & Jalvingh AW, et al. A simulation of Johne's disease control. Prev Vet Med 2002;54:225245.

  • 8.

    Groenendaal H, Galligan DT. Economic consequences of control programs for paratuberculosis in midsize dairy farms in the United States. J Am Vet Med Assoc 2003;223:17571763.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9.

    Jubb TF, Galvin JW. Effect of a test and control program for bovine Johne's disease in Victorian dairy herds 1992–2002. Aust Vet J 2004;82:228232.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Jubb TF, Galvin JW. Effect of a test and control program for Johne's disease in Victorian beef herds 1992–2002. Aust Vet J 2004;82:164166.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    National Agricultural Statistics Service. Cattle. Washington, DC: USDA, 2007. Available at: www.usda.gov/nass/PUBS/TODAYRPT/catl0207.txt. Accessed Aug 22, 2008.

    • Search Google Scholar
    • Export Citation
  • 12.

    National Agricultural Statistics Service. Farms, land in farms, and livestock operations. 2006 summary. Washington, DC: USDA, 2007.

  • 13.

    National Johne's Working Group. Handbook for veterinarians and dairy producers: a guide for Johne's disease risk assessments and management plans for dairy herds. 3rd ed. St Louis: US Animal Health Association, 2003. Available at: www.johnes.org/handouts/files/Handbook%20for%20Vets%20and%20Dairy%20Producers%20final.pdf. Accessed Aug 22, 2008.

    • Search Google Scholar
    • Export Citation
  • 14.

    Wells SJ, Wagner BA. Herd-level risk factors for infection with Mycobacterium paratuberculosis in US dairies and association between familiarity of the herd manager with the disease or prior diagnosis of the disease in that herd and use of preventive measures. J Am Vet Med Assoc 2000;216:14501457.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Carpenter TE, Gardner IA & Collins MT, et al. Effects of prevalence and testing by enzyme-linked immunosorbent assay and fecal culture on the risk of introduction of Mycobacterium avium subsp. paratuberculosis–infected cows into dairy herds. J Vet Diagn Invest 2004;16:3138.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    Raizman EA, Wells SJ & Godden SM, et al. Characterization of Minnesota dairy herds participating in a Johne's disease control program and evaluation of the program risk assessment tool. Prev Vet Med 2006;75:2233.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17.

    USDA. Animal disease exclusion practices on U.S. dairy operations, 2002. No. N420.0804. Fort Collins, Colo: USDA, APHIS, Veterinary Services, Center for Epidemiology and Animal Health, 2004.

    • Search Google Scholar
    • Export Citation
  • 18.

    Ferrouillet C, Wells SJ & Hartmann WL, et al. Decrease of Johne's disease prevalence and incidence in six Minnesota, USA, dairy cattle herds on a long-term management program. Prev Vet Med 2008;87:in press.

    • Search Google Scholar
    • Export Citation
  • 19.

    Dorshorst NC, Collins MT, Lombard JE. Decision analysis model for paratuberculosis control in commercial dairy herds. Prev Vet Med 2006;75:92122.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20.

    Collins MT, Gardner IA & Garry FB, et al. Consensus recommendations on diagnostic testing for the detection of paratuberculosis in cattle in the United States. J Am Vet Med Assoc 2006;229:19121919.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21.

    Tavornpanich S, Muñoz-Zanzi CA & Wells SJ, et al. Simulation model for evaluation of testing strategies for detection of paratuberculosis in Midwestern US dairy herds. Prev Vet Med 2008;83:6582.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Figure 1—

    Funding for the MNJDCP for testing and risk assessments by certified herd veterinarians (triangles) and number of cattle herds in the MNJDCP (squares) since its inception in 1998.

  • 1.

    USDA. Johne's disease on U.S. dairies, 1991–2007. No. N521.0408. Fort Collins, Colo: USDA, APHIS, Veterinary Services, Center for Epidemiology and Animal Health, 2008.

    • Search Google Scholar
    • Export Citation
  • 2.

    Ott SL, Wells SJ, Wagner BA. Herd-level economic losses associated with Johne's disease on US dairy operations. Prev Vet Med 1999;40:179192.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3.

    Dargatz DA, Byrum BA & Hennager SG, et al. Prevalence of antibodies against Mycobacterium avium subsp paratuberculosis among beef cow-calf herd. J Am Vet Med Assoc 2001;219:497501.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4.

    Committee on Diagnosis and Control of Johne's Disease, National Research Council. Diagnosis and control of Johne's disease. Washington, DC: National Academies Press, 2003.

    • Search Google Scholar
    • Export Citation
  • 5.

    Sweeney RW. Transmission of paratuberculosis. Vet Clin North Am Food Anim Pract 1996;12:305312.

  • 6.

    Rossiter CA, Hutchinson LJ & Hansen D, et al. Johne's disease prevention/control plan for dairy herds: manual for veterinarians. Bovine Pract 1999;33:193-1193-22.

    • Search Google Scholar
    • Export Citation
  • 7.

    Groenendaal H, Nielen M & Jalvingh AW, et al. A simulation of Johne's disease control. Prev Vet Med 2002;54:225245.

  • 8.

    Groenendaal H, Galligan DT. Economic consequences of control programs for paratuberculosis in midsize dairy farms in the United States. J Am Vet Med Assoc 2003;223:17571763.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9.

    Jubb TF, Galvin JW. Effect of a test and control program for bovine Johne's disease in Victorian dairy herds 1992–2002. Aust Vet J 2004;82:228232.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Jubb TF, Galvin JW. Effect of a test and control program for Johne's disease in Victorian beef herds 1992–2002. Aust Vet J 2004;82:164166.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    National Agricultural Statistics Service. Cattle. Washington, DC: USDA, 2007. Available at: www.usda.gov/nass/PUBS/TODAYRPT/catl0207.txt. Accessed Aug 22, 2008.

    • Search Google Scholar
    • Export Citation
  • 12.

    National Agricultural Statistics Service. Farms, land in farms, and livestock operations. 2006 summary. Washington, DC: USDA, 2007.

  • 13.

    National Johne's Working Group. Handbook for veterinarians and dairy producers: a guide for Johne's disease risk assessments and management plans for dairy herds. 3rd ed. St Louis: US Animal Health Association, 2003. Available at: www.johnes.org/handouts/files/Handbook%20for%20Vets%20and%20Dairy%20Producers%20final.pdf. Accessed Aug 22, 2008.

    • Search Google Scholar
    • Export Citation
  • 14.

    Wells SJ, Wagner BA. Herd-level risk factors for infection with Mycobacterium paratuberculosis in US dairies and association between familiarity of the herd manager with the disease or prior diagnosis of the disease in that herd and use of preventive measures. J Am Vet Med Assoc 2000;216:14501457.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 15.

    Carpenter TE, Gardner IA & Collins MT, et al. Effects of prevalence and testing by enzyme-linked immunosorbent assay and fecal culture on the risk of introduction of Mycobacterium avium subsp. paratuberculosis–infected cows into dairy herds. J Vet Diagn Invest 2004;16:3138.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16.

    Raizman EA, Wells SJ & Godden SM, et al. Characterization of Minnesota dairy herds participating in a Johne's disease control program and evaluation of the program risk assessment tool. Prev Vet Med 2006;75:2233.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 17.

    USDA. Animal disease exclusion practices on U.S. dairy operations, 2002. No. N420.0804. Fort Collins, Colo: USDA, APHIS, Veterinary Services, Center for Epidemiology and Animal Health, 2004.

    • Search Google Scholar
    • Export Citation
  • 18.

    Ferrouillet C, Wells SJ & Hartmann WL, et al. Decrease of Johne's disease prevalence and incidence in six Minnesota, USA, dairy cattle herds on a long-term management program. Prev Vet Med 2008;87:in press.

    • Search Google Scholar
    • Export Citation
  • 19.

    Dorshorst NC, Collins MT, Lombard JE. Decision analysis model for paratuberculosis control in commercial dairy herds. Prev Vet Med 2006;75:92122.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20.

    Collins MT, Gardner IA & Garry FB, et al. Consensus recommendations on diagnostic testing for the detection of paratuberculosis in cattle in the United States. J Am Vet Med Assoc 2006;229:19121919.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21.

    Tavornpanich S, Muñoz-Zanzi CA & Wells SJ, et al. Simulation model for evaluation of testing strategies for detection of paratuberculosis in Midwestern US dairy herds. Prev Vet Med 2008;83:6582.

    • Crossref
    • Search Google Scholar
    • Export Citation

Advertisement