Identification of Johne’s Disease is not easy
By ANDREA JOHNSON, Assistant Editor
Thursday, February 16, 2006 11:47 AM CST
Two cattle – a healthy looking bull and a razor thin cow with severe scours. Which one has Johne’s Disease?
Both of them.
An infected animal may harbor the organism for two to five years before testing positive or developing disease signs.
Johne’s Disease is a chronic, contagious inflammation of the intestine characterized by persistent and progressive diarrhea, weight loss, debilitation and eventually death.
More than 20 percent of dairy herds across the U.S. are infected with the organism that causes Johne’s disease.
The infection causes the walls of the small intestine to thicken to the point that the bovine cannot absorb nutrients.
According to the Johne’s Information Center, University of Wisconsin, animals infected with the M. paratuberculosis bacteria usually develop diarrhea and lose weight.
Because of the slowly progressive nature of the infection, signs of Johne’s disease are usually not seen until animals are adults. Signs tend to start within a few weeks after calving but could happen anytime in the cow’s reproduction cycle.
“The rule of thumb is when you have one clinically affected animal, there are five to seven animals that are subclinical and 10-15 others that are in some earlier stage of infection,” said Dr. Steve Just, a federal district veterinarian with the Minnesota Board of Animal Health. Just works out of Morris, Minn.
“When you see that one animal that has scours and is very thin, that’s just the tip of the iceberg,” said Just, speaking at Minnesota Cow/Calf Days in Glenwood. “You also have reduced production, decreased milk production – because they are not getting all the nutrients and it’s not going to the calves, and you get lower weaning weights.”
Just encourages producers to compare weaning weight records over the years. Even though Johne’s may not be causing death loss, the disease could still be affecting the herd’s performance.
It is estimated that a 10 percent level of Johne’s infection in a 100-cow dairy results in the loss of $20,000 each year, and the disease often leads to premature culling and decreased cull value.
“Also, the increased replacement cost and increased disease susceptibility,” said Just. “When an animal is not on a good nutritional plane, their immune system is going to be suppressed and they are going to be vulnerable to all other infections.”
Minnesota dairy and beef producers are invited to participate in a voluntary control program for Johne’s, said Just. The purpose of the program is to help producers eliminate the disease from their herds and prevent introduction of the disease from other sources.
According to Minnesota Board of Animal Health information, Minnesota is recognized as a national leader in Johne’s disease control.
The state instituted its volunteer program in 1998, and since that time, over 435,000 cattle have been tested in approximately 5,606 herds.
Minnesota Board of Animal Health offers free on-farm consultations called risk assessments. Either a state or federal district veterinarian, such as Just, or a trained veterinarian in private practice completes the risk assessments.
The goal is to identify a producer’s highest risks for spreading the disease.
The veterinarian then works with the producer to develop a herd plan that can help stop the spread of Johne’s.
The state pays for some testing to help producers identify infected animals, said Just.
Those herds that do not have Johne’s can participate in the Test Negative Status Program. The state offers free risk assessments to help these herds remain free of infection. The program also covers fees and testing for some animals at the beginning of the program.
“Status Program Herd replacement animals have brought premiums,” said Just, and he encourages producers to work with the Board of Animal Health to minimize Johne’s in Minnesota.
For more information, call the Minnesota Board of Animal Health at 651-296-2942. You may also visit: http://www.johnes.org/ or http://www.bah.state.mn.us/diseases/johnes/johnes_disease.htm for more information.