Johne's disease continues to receive considerable national attention as an important livestock disease. Previous research has indicated that this disease may cost the US dairy industry as much as $250 million annually. Reports concerning the possible role of the causative agent, Mycobacterium avium subspecies paratuberculosis (MAP), in Crohn's disease of humans and the finding of this organism in pasteurized milk have added new dimensions to the concern. Perhaps, the most tangible evidence of this concern is the availability of several million dollars in Federal funding over the past 3 to 5 years for research in Johne's disease and for efforts to control it.
In mid 2002, uniform standards for the Voluntary Bovine Johne's Disease Control Program (VBJDCP) were published by the USDA in cooperation with the National Johne's Disease Working Group and the United States Animal Health Association. This document outlines minimum standards for control of Johne's disease. The three basic elements are: 1) education, to inform producers about the disease and strategies to control it; 2) management, to provide producers with management and control strategies specific to their farm; and 3) guidelines for herd testing and classification programs to help separate infected herds from test-negative herds.
Ohio has been at the forefront of efforts to educate producers and assist them in the control of this disease. State and federally employed veterinarians and private practitioners have been valuable resources in this effort. The publishing of the VBJDCP program standards and the availability of Federal monies for support to the states have led to some changes. The first of these is the appointment of a Designated Johne's Disease Coordinator. Dr. Ned Cunningham of the Ohio Department of Agriculture's (ODA) Division of Animal Industry and Dr. Roger Krogwold of the UDSA APHIS serve as co-coordinators in Ohio. They provide oversight of all aspects of the program in Ohio. This includes providing additional training for private practitioners who are then called "Johne's Certified Veterinarians". Last year, in addition to seven educational producer meetings, four meetings were held to provide this training and certification to private practitioners. As well as providing new information on Johne's disease diagnosis and control, veterinarians were trained to conduct on-farm risk assessments and to develop specific farm management plans for Johne's disease.
Conducting a risk assessment involves a one-on-one meeting between the producer and the certified veterinarian and examination of several key areas where the disease may be introduced to the farm or where transmission of the infection may be more likely. These include such items as: a) examination of the calving area with attention to manure build up in the environment or on the cows and the time calves spend in the calving area; b) feeding and sanitation practices used in the management of pre-weaned calves; and c) management of calves post weaning with respect to opportunities for spread of the disease by contamination with infected manure. Each of six key areas is given a numerical score, and the weighted scores are totaled. This gives the producer an idea of "risk" on his/her farm and helps identify the areas that need the most attention for improvement. In practice, going through the risk assessment process is an educational activity and helps producers put the elements of Johne's disease control in perspective. Many people come to realize that the management strategies used to control transmission of Johne's disease are also very helpful in controlling other calfhood disease problems. When the risk assessment process is completed, a prioritized management plan is developed, and it is to be reviewed annually. Herd testing is not required for producers to participate in the risk assessment/management plan process. Currently, Federal monies of $350/farm are available to support the initial risk assessment/management plan. Support for subsequent risk assessments will likely be available, but the exact amount has not yet been determined.
Herd owners who do not know their herd's infection status or who believe they are infected, can elect to do some diagnostic testing. Currently, if they have completed the risk assessment process, their veterinarian can receive $4 per sample submitted (one time per cow yearly) to support the cost of sample collection. This is available as a result of the strong Federal support for Johne's disease control. Blood can be collected for ELISA screening or fecal samples can be submitted for culture. Whole herd cultures do have to be scheduled in advance and must be received early in the week in order for them to be processed.
Herd owners who believe their herd is not infected may want to enter the Ohio Johne's Disease Test Negative Status program. This program is designed and implemented for herd owners that wish to establish their herd's test negative status, and it is especially useful if they wish to market animals for breeding purposes. Negative ELISA results on all animals in the herd two years old or older will allow the herd owner to apply for Level 1 status. Herds advance through the five levels of the Test Negative Status Program by subsequent annual whole herd tests alternating between fecal culture and ELISA. Herd additions from off the farm are allowed, but all animals added must have had a negative fecal culture for Johne's disease within the previous twelve months or had a negative serum antibody test within thirty days after the animal was purchased. Click here for more information on the Test Negative Status Program.
An area of intense research has been in development of improved diagnostic tests. The Animal Disease Diagnostic Laboratory of the ODA has evaluated several new diagnostic tests and techniques. Polymerase chain reaction (PCR) technology is now available to confirm the presence of MAP in suspicious colonies found on the traditional solid culture medium and selected tissue specimens. The evaluation process for a new liquid culture media system has largely been completed. This system should allow a more rapid turnaround time of about 8 weeks for culture of fecal samples. In addition, this new system will have better sensitivity than the traditional solid media. This means that it is likely that more infected animals will be found on a herd test using this new method. It is anticipated that the laboratory will convert to use of this system for fecal cultures as soon as renovations can be completed to house the necessary equipment.
Three herds in Ohio have been identified for intense study and the generation of educational material. The first round of testing in these herds was conducted in the fall of 2004, and they will be tested again in the spring of 2005. Again, Federal monies have been available to support this educational effort in Ohio and 18 other states. Data from these herds is being submitted to the USDA for eventual analysis that will help us better understand control strategies that are most helpful. As a part of this effort, samples from the farm environment are being collected and cultured for MAP. Although it comes as no real surprise, preliminary data from our herds here in Ohio indicate that it is relatively easy to find MAP on the udder of cows on an infected farm, even if the cow herself has a negative fecal culture.
Although progress in the control of Johne's disease seems to be very slow, it is being made. The tools and knowledge we already have can allow us to make substantial improvement in reducing the disease's impact on individual farms. Producers should talk with their veterinarian about conducting a risk assessment and development of a management plan to control the disease or to prevent its introduction to the herd.