Johne's disease, or JD, is a chronic and incurable bacterial infection of the lower intestinal tract of ruminant animals. Most commonly a disease of cattle, sheep and goats, it can infect any ruminant including deer, elk, bison, llamas and alpacas. The vast majority of infected animals appear completely normal although many of them are already shedding the organism and are therefore infectious to others. The clinical signs, which are weight loss and diarrhea, generally do not appear until animals are in the most advanced stage of the disease. The time from first becoming infected until development of clinical signs is often two or more years.
Johne's disease is spread by ingestion of the organism which is shed in the manure and sometimes also the milk of an infected animal. Susceptibility to infection is greatest in young animals: the younger the animal the greater the susceptibility. The most effective management principle in reducing the infection rate in a herd is to prevent the exposure of young stock to adult animals, their milk and their manure.
The Bureau of Animal Health and Diagnostic Services, in collaboration with USDA, has developed several voluntary programs designed to aid herds in their efforts to detect, reduce infection rates, and/or prevent the introduction of Johne's disease.
PA Johne's Herd Certification
The Pennsylvania Johne's disease Herd Certification Process provides a structured framework that veterinarians, herd owners and herd managers can use to develop a meaningful herd management plan. Herds that develop and implement such a plan can be recognized for their participation by being classified as a "Management" or "Testing and Classification" herd.
The Management Option is designed for herds that would like to use management changes to minimize the risk of Johne's disease entering or spreading within the herd, but do not & wish to participate in regular testing of its animals for Johne's disease. Both infected and uninfected herds may enroll in this level. No claims concerning the level of JD in the herd can be made by herds participating at the Management Level since no structured diagnostic testing is carried out. Herd owners have the option of adding some level of strategic diagnostic testing to their management protocol if they and their veterinarian decide that it would benefit their ability to assess the level of infection in the herd and/or to monitor the prevalence of disease over time in response to management changes which are instituted.
The Testing and Classification Options are for herds that have not had any recent evidence of Johne's disease or wish, through regular testing and management changes, to eventually eliminate the disease from the herd. Herds in this option, through prescribed testing methods, can document the level of infection in the herd and work to reduce the infection rate over time with the ultimate goal of demonstrating that the herd has become free of Johne's Disease. This option consists of utilizing management changes and annual testing protocols determined by the size of the herd to first evaluate the level of infection and then work to reduce it. There are six levels in this option with level one herds having the highest rates of infection and levels Four through six limited to herds with no test positive animals. Although level six herds have had at least three years of all negative test results, the nature of Johne's disease is such that they cannot be considered free of infection. And, in fact, most scientists agree that once infected, few herds can ever again be declared to be unequivocally free of Johne's disease.
In order to participate in the PA Johne's Herd Certification Process, interested herd owners must work with a Johne's Certified Veterinarian to complete an enrollment application and carry out a risk assessment in order to develop a herd management plan. The application must be completed and submitted to the Department along with the Johne's disease Risk Assessment and Herd Management Plan for Dairy or Beef herds. Further details regarding participation at each level, and more information regarding the PA Johne's Herd Certification Process can be found at the following website: http://www.johnesdisease.org.
Johnes Certification for Veterinarians
Veterinarians wishing to become certified to participate in Pennsylvania's Voluntary Bovine Johne's Disease Certification Program should contact David Zellner, PA Department of Agriculture, at 717-783-8555 or at firstname.lastname@example.org. Certified veterinarians must renew their recertification every five years. Recertification training is available online.
GOATS and SHEEP
While Pennsylvania's program is designed for cattle, the decision has been made to offer a management option program to sheep and goat producers who are interested in addressing Johne's disease in their flocks and herds. This program is available to producers who are willing to adopt the risk assessment/herd management format utilized by beef and dairy herds. In order to be considered for the program, the producer must work with a PA Johne's Certified veterinarian, enroll in the program and follow the best management practice guidelines outlined in the beef and dairy management handbooks, but with the appropriate species alterations. Participating herds and flocks will qualify for the same reduced laboratory testing fees offered to enrolled cattle herds.
The Testing and Classification option is not available to sheep flocks and goat herds because the model it employs was designed around the epidemiology of the disease in cattle. That same model cannot be applied to the disease in small ruminants. If such a model is developed in the future, Pennsylvania will consider offering a Testing and Classification option for sheep and goats as well.