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NAHMS Study: Johne's Disease on U.S. Dairies, 1991-2007

Dairy 2007 study suggests that at least one-fourth of U.S. dairy operations may have a relatively high percentage of Johne's-infected cows in their herds.

The U.S. Department of Agriculture’s National Animal Health Monitoring System’s (NAHMS) fourth study of the U.S. dairy industry, Dairy 2007, focused on Johne’s disease, a disease caused by Mycobacterium avium subspecies paratuberculosis (MAP). MAP has a long incubation period, with clinical manifestation of Johne’s commonly occurring two or more years after initial infection. Clinical signs of Johne’s include chronic diarrhea, weight loss despite a normal appetite and decreased milk production.

Dairy 2007 involved 17 of the nation’s major dairy states. West region states included California, Idaho, New Mexico, Texas and Washington. East region study states included Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, Vermont, Virginia and Wisconsin. The 17 states involved in the study represented 79.5 percent of U.S. dairy operations and 82.5 percent of U.S. dairy cows.

The two key objectives of Dairy 2007 were:

To estimate herd-level prevalence (number of herds infected with MAP) in the United States.
To compare and evaluate management practices related to perceived risks of MAP transmission between the previous NAHMS dairy studies.

The following information is a summary of Dairy 2007. The complete APHIS/VS Info Sheet is available by clicking on http://nahms.aphis.usda.gov/dairy/dairy07/Dairy2007_Johnes.pdf. Also, see the APHIS/VS Info Sheet on "Off-Site Heifer Raising on U.S. Dairy Operations, 2007."

Producer Familiarity

Percent of producers who are “fairly knowledgeable” about Johne’s disease: Dairy 1996 study, 17.7 percent; Dairy 2007 study, 57.9 percent.
Percent of producers who had not heard of Johne’s disease: Dairy 1996, almost 10 percent; Dairy 2007, 1.5 percent.
Percent of producers who were fairly knowledgeable or knew some basics about the disease: Dairy 1996, 54.8 percent; Dairy 2007, 94.1 percent.

Percentage of Operations by Level of Familiarity with Johne’s Disease and by Study Year

Management Practices

31.7 percent of dairies surveyed in the Dairy 2007 participated in a Johne’s disease certification or control program.
Although separating calves from cows and their manure immediately after calving reduces the potential of newborn calves ingesting MAP, only 55.9 percent of producers in the Dairy 2007 study removed calves immediately after birth.

Bringing animals onto an operation can introduce new diseases or add to the disease burden of the herd. Careful scrutiny of the source of new additions and a brief isolation or quarantine once the animals are on the dairy are good management practices.

Less than one in five operations, 17.2 percent, that brought cattle onto the operation during the previous year required herd-of-origin information regarding MAP-infection status.
11.4 percent of operations tested individual animals brought onto the operation.
A higher percentage of medium operations, 16.6 percent, tested purchased animals compared to large operations, 7.2 percent.
For operations that did not individually test animals brought on, 22.3 percent reported that testing had been done by the herd-or-origin.
For operations that did not individually test animals brought on, 28.6 percent reported that MAP infection was not a concern to their operation.

Johne’s Testing

Organism detection and measuring antibody response are the two main methods used to test for MAP infection. During the 12 months prior to the Dairy 2007 study:

A higher percentage of operations with 100 to 499 cow performed any testing for Johne’s disease compared with small operations with fewer than 100 cows: 46.7 percent vs. 30.7 percent. This finding was consistent with the Dairy 1996 and Dairy 2002 studies.
Compared to Dairy 1996, the percentage of all operations testing for Johne’s disease increased in 2002, and an increase was seen again in 2007.

Percentage of Operations That Tested for Johne's Disease, by Study Year and by Herd Size

Confirmed Johne’s Disease in the Herd

More than two of 10 operations—22.7 percent—reported Johne’s disease was confirmed in their herd during the previous 12 months.
17.4 percent of small operations—fewer than 100 cows—confirmed Johne’s disease in their herds during the previous 12 months.
35.0 percent of medium operations—100 to 499 cows—confirmed Johne’s disease in their herds during the previous 12 months.
34.1 percent of large operations—500 or more cows—confirmed Johne’s disease in their herds during the previous 12 months.
23.6 percent of operations in the East region confirmed Johne’s disease compared to 12.8 percent in the West region.

Johne’s Vaccination Practice

The percent of operations that normally vaccinate heifers against Johne’s disease has remained essentially unchanged since 1996, with 5.0 percent of operations reporting this practice in 2007.

Environmental Sample Testing, Culture Results

To establish Johne’s herd-level prevalence for the Dairy 2007 study, six composite environmental samples were taken from each of 524 participating operations. The environmental samples were taken from six different adult-cow areas where manure accumulates. Positives were confirmed by PCR methods.

MAP was isolated from at least one environmental sample on 68.1 percent of operations during the Dairy 2007 study.
Prevalence of MAP increased as herd size increased.
There were no differences in MAP prevalence between operations in the West and East study regions.

Part I: Reference of Dairy Cattle Health and Management Practices in the United States, 2007
Part II: Changes in the U.S. Dairy Cattle Industry, 1991-2007
Part III: Not yet published

For more information, contact:
USDA/APHIS/VS/CEAH
NRRC Building B, MS 2E7
2150 Centre Ave
Fort Collins, CO 80526-8117
Phone: 970.494.7000
E-mail: NAHMS@aphis.usda.gov
http://nahms.aphis.usda.gov

A cooperative effort of the National Institute for Animal Agriculture and USDA, APHIS, Veterinary Services,
in association with the National Johne's Working Group & United States Animal Health Association