Disease & other Testing

The “basics” – required for interstate transport and most sales:

  • Bovine Tuberculosis (TB) test
  • Brucellosis (“Bangs”) vaccination

Major dairy diseases of consideration:

  • Johnes
  • Bovine Leukosis (BLV)

(There are many, many, many diseases and tests available – speak with your vet or local farmers to see which other tests may be relevant to your area. Some others potentially relevant to dairy are: Neospora, Anaplasmosis, Mycoplasma, Q-Fever, BVD.)

Other (non-disease) testing:

  • Milk testing (for lactating animals)
  • Preg Testing (If animal is being sold as “pregnant”)

A word about disease testing:

Animals may be exposed to a number of various diseases. It’s up to you how extensively you want to test. Keep in mind, this testing can become very expensive. Also, be aware of false-positives. If you are unsure about a test result, consider re-testing with a different type test (ie: PCR vs. Elisa, milk vs. blood vs. stool) or a different lab and compare results.

Buy from credible sources that are aware of disease and prevention. Paying a little more for a healthy cow will save $$ in the long run. We like to see a maternal line that has longevity, which is a great indicator of health!



  • Most states are TB free. Bovine tuberculosis CAN be transmitted to humans and make them sick. So therefore, though it is not very prevalent, it is important to be aware of TB. (TB testing is required in our state for raw milk producers.) Clinical signs of the bacterial infection are not easy to identify as TB.
  • A TB test is done by a vet. They will stick a small amount of fluid (tuberculin) under the skin of the cow and come back in 72 hours to read the results (a raised bump = positive). If positive, ask your vet about re-testing to eliminate error. [Keep in mind, this test requires a vet to make TWO visits.]
  • Prevention: If in California, people have become sick from TB from cattle, so definitely extra caution in that state. Avoid housing animals in enclosed areas with poor ventilation. Avoid feeding/watering where wild animals can co-mingle with your herd. If you attend a fair, avoid “community watering” areas for the animals!
Sample definition of results
Sample definition of results


  • You may have heard an older person speak of “undulant fever” – they are referring to Brucellosis. In the cow world, it is known as “Bangs” or “contagious abortion.” Brucellosis is eradicated within the United States, thanks to a federal eradication program, EXCEPT for populations near Wyoming, where officials refuse to vaccinate wild bison populations. Many states do not allow transportation of animals unless they are Brucellosis vaccinated, so check before moving or selling cattle!
  • Most animals are vaccinated. To tell if your animal is vaccinated, check the animal’s RIGHT ear. In the ear should be a tattoo, a “shield” (looks like a flower, kind of) that has a letter on one side and a number on the other side. These reference the year of vaccination. In addition, most cattle have a ear tag, which is a long skinny metal tag of silver or orange color that is clipped to the top edge part of the ear close to the head (The first two letters on the metal tag identify the state in which the cow was vaccinated.). [Click here for photos]
  • If not vaccinated, Brucellosis can be checked for in milk or blood samples.
  • To vaccinate an animal:
    • A vet is required to vaccinate/tattoo/tag/record your animal.
    • The animal should be vaccinated between 4-12 months old.
    • If not vaccinated as a calf, an adult cow can often be vaccinated after a blood test confirms she is negative for the disease.
  • If you have a breed-specific registered & tattoo identified animal, you can ask for the vet to NOT put in the metal tag. Instead of the tag number, they will use the animal’s registration number.
  • Prevention: Vaccinate calves. Adults can be vaccinated after being tested and proven negative.


Sample definition of results
Sample definition of results


  • M. paratuberculosis: Pronounced “Yo-nees”, is an infectious bacterial infection of the digestive tract.  Johnes is in the same group as leprosy & tuberculosis. The most distinct sign of Johnes is long-lasting, foamy/bubbly diarrhea and chronic weight loss. Cattle infected at a young age that are shedding the bacterial spores and show symptoms tend to be cows around three years of age, often getting ready to have their second calves. Johnes is tricky in that it may not show symptoms in a cow until late in life (perhaps even to 10 years of age or older, carriers that do not show symptoms until late in life!). Johnes DOES spread from manure and any identified sick cow should be removed immediately, as the bacteria can spread to other cows and survive in the soil. Any land where a Johnes infected cow has been should not have cows on that land for at least a year as a precaution. This disease affects the white blood cells. More info: http://www.aphis.usda.gov/publications/animal_health/content/printable_version/faq_johnes_cattle3-06.pdf
  • Why is Johnes so important to test for? Because Johnes is very likely linked to Chron’s disease in humans: http://www.wnd.com/2004/10/26829/ 
  • Blood (Elisa/AGID, antibodies) and manure (PCR, organism) tests. We always tested the herd with blood and manure samples at the same time. PCR is best for detecting already sick cows, but AGID is better for cows not showing symptoms, so both tests are valuable. For more in-depth discussion on testing types: Johnes: What Tests?
  • Your vet should be able to help you send in a sample for Johnes testing. Note: testing can take up to 6-8 weeks to get results back!
  • Prevention: If you test your animal, before purchase, this is probably THE most important test to do! Because testing is the only way to monitor Johnes in your herd! There is NO cure. In the dairy industry, Johnes is a very touchy subject and not every state is as intense about eradicating Johnes as others. Most herds have dealt with Johnes, whether they know it or not.
  • There is a Johnes vaccine, but the use should be carefully discussed with your veterinarian before deciding whether to give or not.
  • Do not feed raw milk to calves from their own mother if the mother has signs of Johnes. (Powdered colostrum and powdered/pasteurized milk are safer alternative feeds in this situation.) If the calf is a heifer that you plan to raise as a replacement, the calf should be removed immediately from the pen, ideally without the calf touching anything in the birthing environment. The heifer should also be carefully monitored through testing throughout her life.
  • Resource: http://johnesdisease.org/
Sample definition of results
Sample definition of results

BLV – Bovine Leukosis:

  • September 2015 study: http://medicalxpress.com/news/2015-09-virus-cattle-linked-human-breast.html
  • Bovine Leukosis Virus is most noticed when a cow loses weight and cannot gain weight no matter how hard you try. This disease is often uniquely and visibly noticeable for tumors and swollen lymph nodes (this is a key indicator suggesting leukosis over Johnes as a diagnosis). She will usually dramatically drop in production if milking, perhaps even dry up completely. Stress, such as calving, can be fatal to a cow showing clinical signs of this disease.  More info: Cause for Concern: Bovine Leukemia Virus (WSU)
  • Types of testing for BLV are Elisa, AGID and PCR. Elisa is an inexpensive “screening” test that can have false readings. AGID is similar to Elisa and can also have false readings. PCR is more accurate by testing for DNA of the actual virus, and therefore is the testing of choice. Here’s more about the testing types: Available Tests for BLV
  • Where to get testing done: Available Labs
  • Prevention: Spreads via blood contamination. Never share needles between animals. Test new animals before adding them to herd. Ask vet to use a new obstetrical glove when checking each individual animal. Disinfect any equipment that comes in contact with blood. For example, always disinfect between animals at dehorning, tagging, vaccinating, AI, etc. MERCK
Sample definition of results
Sample definition of results


  • Probably the most useful test to anyone purchasing a dairy cow is milk testing!
  • Prevention is all about cow health from udder health to general cleanliness.
  • “Somatic cell” testing is a cheap, useful indicator of general health and udder health.
  • Bacterial cultures or DNA testing from individual quarter(s) can help identify specific pathogens.
  • Click here for more information on how to do milk testing: MILK TESTING


  • Seeing accurate signs of pregnancy are often difficult or impossible.
  • To verify pregnancy, we highly recommend preg checking cows, otherwise you assume the risk of a non-pregnant cow going 9 months unbred at your cost.
  • For details on pregnancy tests, click here: PREGNANCY TESTING


When a sample is returned, it should contain the animal’s name/identifying number, indication of which test was performed, test results, and sometimes a number:

BVDSome also contain a number (for example: SP ratio) in addition to the result of negative/suspicious/positive/inconclusive:

JohnesAnother style of sampling, disease testing through milk:



10 thoughts on “Disease & other Testing

    1. If her milk is clean (mastitis free, milk handling equipment properly cleaned, etc.) then it should be fine to drink. Most cow diseases are potentially harmful to the cow, rarely is the risk to humans. It’s my opinion that raw milk is safer to drink than pasteurized milk, but that’s a debate everyone needs to read up on and decide on their own. 🙂


  1. Sheree Gruber

    What are the chances my new heifer has any of these diseases? I bought her as a bottle calf off a small Amish dairy in Maryland. She is a jursey and she is already in my heart. She will be our homestead family milk cow for raw milk consumption. What tests should I absolutely have done? Getting a vet here is 100$ travel expenses +++.


      1. Leah Pascua

        I loved your article on diseases in cattle. I just got a positive for Q fever on a cow I bought from a dairy 2 weeks ago. I was hoping you had any information on this disease? I am so worried. I don’t know if my cow will recover, or if I should put her down. I only have 2 mini jerseys and she was to be my heifers compainion and our family milk cow. Now I am looking at whatever I can find on it and I am lost! I couldn’t figure out how to comment, please excuse my message on your post.


      2. Your cow will likely never show any signs of being a carrier of Q fever. The risk, however small or big, is more for humans. Definitely re-test your cow to confirm positive status (you might even try a different lab). If the next test also comes back positive, I would definitely let the prior owner know. At this point, if you purchased the cow without any stipulations on testing, then there’s nothing the prior owner is obligated to do. If I were you, I’d probably call the lab and talk to them and/or contact your local vet to see if they’ve dealt with any cases. If the cow is positive and if you’re able to make the decision whether or not to keep her (positive cows are condemned in some states, not in others), then it’s really up to you to weigh the information and decide whether to risk it or not. Where you’re wanting her for your family milk cow, raw milk I’m guessing, I’d be a bit leery of drinking raw milk from a positive cow…

        Q fever is much better known in Australia. Friends of mine from there have commented on it occasionally: http://familycow.proboards.com/thread/49384/fever
        You can probably find most accurate information about the disease by looking at AUS sources: http://www.dairyaustralia.com.au/Animal-management/Animal-health/Animal-health-fast-facts/Abortion-and-infertility/Q-fever.aspx Keep in mind, the US is relatively “unaware” of this disease, there is no vaccine for humans or animals in the US (that I’m aware of), and if your animal tests positive, it may be recorded in a registry.

        I took Q fever off my list of recommended testing…. I had some cows tested for it and was disappointed how unreliable the test was. If you would like to know more about Q fever in America, here are links: http://www.doh.wa.gov/Portals/1/Documents/5100/QFever-in-WA2011.pdf http://www.waddl.vetmed.wsu.edu/search-tests http://waddl.vetmed.wsu.edu/animal-disease-faq/q-fever


  2. FAQ: If I had a cow with BLV, can another cow get it even if the infected cow is long gone?

    I compared BLV to HIV. First, some people get HIV and never AIDS. Second, think of how HIV/AIDS is transmitted – through blood. So, occasionally a calf can get it inside the mother. It helps me to think of HIV as a comparison.I’d recommend anyone purchasing a cow to have thorough testing done beforehand. “Cheap insurance” It puts everyone on a level field of honesty and then if the cow comes up positive for something 6 months later, you know you all did the best you could to get a healthy cow and that’s life.Buying a lot of cows from different places can bring in all sorts of problems. I see you have multiple animals, and that can be a consequence of “buying around”. As close as you can get to a closed herd (meaning no buying of animals from different farms) the more protected you will be against new diseases. Staph Aureus is a terrible plague at a farm I know. They sold off all but about 15 older cows and then calved in 40 young cows. Guess what? Those young cows are coming in with huge staph counts. 😦 Very sad.


  3. FAQ: A person got bit by a tick, wondered about Lyme’s disease, and then wondered if cows get tick-borne disease?

    Keep an eye on the spot where the tick was. If you get a bullseye, head to your dr asap. Might not hurt to get checked for lymes, too.. For cows, I got to researching and remembered when we moved our cows to PA, one thing we had to test for was anaplasma. It’s a tick-borne disease for dairy cattle. Because of insecticides (is that the right word? Anyway, whatever chemicals they use to kill ticks).. ticks are resistant to many chemicals now, and are increasing. In Maryland, the incidences of tick-borne diseases has skyrocketed!! Anyway…I was going to add some info, but if you’re really curious, just read this link: http://veterinarynews.dvm360.com/dvm/Vet…./d etail/501075
    QUOTE: ” In non-endemic areas, the goal is to prevent the disease from coming into a herd. Herd additions should be screened with the cELISA or purchased from test-negative herds. Because of the potential for possible false negatives on the cELISA during the incubation phase and the potential for wildlife reservoirs, the disease still can sneak in. Therefore, a new needle should be used for all animals and equipment should be washed/disinfected between animals.If available, vaccination, especially of the most valuable animals, should also be considered. The only vaccine available is produced by University Products and is offered in 14 states via a U.S. Department of Agriculture experimental approval. However, work is ongoing to allow availability nationwide. Visit http://www.anaplasmosis.com for more information about the vaccine. ”

    (Before you panic about your cow having anaplasmosis: I’ve spoken to several vets and none have ever had anaplasmosis issues.)


Please comment here!

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s