4DX Testing

We recommend running annual 4DX tests on our canine patients. Read below to learn about heartworm and three common tick-borne diseases.

Heartworm Disease

Heartworm disease is transmitted through mosquito bites. A positive test indicates the presence of worms in the dog’s heart. Often a secondary test is done to confirm infection before initiating treatment. Heartworm disease is very dangerous, with the worms causing serious heart and lung disease. Treatment is typically $500 – $1000 and must be carried out over a six month period to decrease the risk of complications from killing the worms. In the past five years, just under 1000 cases have been diagnosed in Maine.

Lyme Disease

Lyme disease is caused by a bacterium transmitted by the bite of a deer tick. The disease typically causes stiff joints, fever, loss of appetite, but rarely can cause kidney failure also. A positive 4DX test says that your dog has been exposed to to the bacteria. It does not mean that your dog has an active infection. If your dog has symptoms of the disease we recommend treatment with antibiotics. If your dog does not have symptoms, we usually recommend further diagnostics to ensure that the bacteria has not caused any other problems. Most dogs that are positive on the 4DX test will continue to show up positive on future rests, but will only be treated if symptoms arise.


Anaplasma is a bacterium, also transmitted by deer tick bites. The symptoms are almost identical to Lyme disease, except that it also has the potential for platelet loss and bleeding disorders. A positive 4DX test for Anaplasma means that the dog has been exposed to the organism, but does not necessarily mean there is an active infection. Our current recommendation for a positive 4DX test is to treat the dog with antibiotics, check a CBC to evaluate platelet numbers, and to recheck that CBC in 6 months to check for long-term changes in platelet numbers. Much like Lyme, once a dog has come up positive, they will likely continue to be positive on subsequent tests.


Elhrlichia is another bacterium transmitted by ticks. It’s primary symptoms are bleeding disorders, fever and joint pain. At this time, it is still fairly rare in the northeastern United States, but prevalence has been rising. A dog testing positive on 4DX for Ehrlichia will most often require treatment with antibiotics and further testing to determine the extent of any impact on the immune or vascular systems. Similar to Lyme and Anaplasma, dogs that are positive tend to stay positive on the 4DX test in later years.