Transmission

Q&A

What age is the animal at the highest risk of becoming infected?

 

Animals are most susceptible from birth to when they are weaned. It is possible for an adult animal to become infected with Johne’s disease, but in a farm setting it’s not likely, old animals or animals that have a suppressed immune system can also be at risk.

 

“I had been told that once an animal reaches 2 years old it is can’t become infected, is that true?”

 

A 2 year old goat is less likely to become infected. At 2 yrs old goats are usually strong and healthy and usually have good resisitance to the organism. Again, it should be noted that its possible to infect a healthy goat if given high doses of the organism. This scenario is not likely to occur in a farm setting.

 

How long does it take for an infected animal to start having positive test results?

Newly infected animals won’t test positive until at least a year after they have become infected. This can vary depending on the health of the animal.

When is that animal likely to start shedding the disease?

Animals are likely to start shedding the disease when they start testing positive. This can be periodic and they will start to shed the organism more frequently and in larger quantities as the disease progresses.  The Fecal PCR test can produce positive results before the animal starts shedding with regularity. ( by regularity I mean shedding to a degree that puts other animals at risk)

When would that animal develop symptoms?

A goat can start showing clinical signs of Johne’s disease at anytime in its life. Animals will start testing positive before they have symptoms. There are certain events in an animal’s life (stress, kidding, injuries) that can advance the infection in the animal.
REMEMBER:  by doing regular tests you can catch the infection before the animal starts showing clinical signs.

 

Can Johne’s disease be spread via semen? No.

Can you catch Johne’s at a goat show? No.

 

Example Scenerio:

 

A doe is bred annually and tested each year before she kids. She has negative results but at age 6 she tests positive for Johne’s disease.
What kids are at risk?

The most concern would be for the kids that she had at age 5 and if she kidded at age 6. If she was tested annually kids that were born before the age of 5 are not likely to have contracted the disease in utero.

If kids from years 1-4 were pulled from the dam and bottle fed pasteurized milk, it would be unlikley for them to be infected.

 **remember, in this case I am assuming that all the other adults in the herd have also tested negative annually.

 

This scenario illustrates why it is important to test annually. It’s best to set up a plan with your veterinarian to determine when /if you reach a point where annual testing is not necessary.