The quickest way to test for Lyme and other tick-borne diseases (Ehrilichia and Anaplasma) is through the use of a 4Dx test.  This test detects heartworm, Lyme disease, Ehrlichia, and anaplasmosis.  Heartworm is transmitted by mosquitoes, while the other three diseases are transmitted by ticks.  This test is run annually during your dog's physical examination or if there is suspicion of infection.  

The 4Dx test is an antibody test, which means that it detects your dog's immune response to the Borrelia organism.  A positive test means that your dog has been exposed to the Borrelia (bitten by an infected tick and invaded by the organisms) within the past few years.  It does not necessarily mean that there is still Borrelia infection in your dog's body.  Beyond keeping your pet healthy, it's important to know your dog's status as he/she may be a carrier of the disease which could be transmitted to human family members (for this to occur your pet would need to have an active infection, a tick would need to bite the dog, and then tick bites you).

Clinical Signs of Lyme Disease:

• Fever of unknown origin
• Lethargy
• Not eating
• Depression
• Joint pain
• Intermittent lameness

Clinical Signs of Ehrlichiosis:

• Fever of unknown origin
• Difficult breathing
• Weight loss
• Skin Hemorrhages
• Bloody Nose
• Low platelet count
• Low white blood cell count
• Anemia
• High urinary protein

Clinical Signs of Anaplasmosis:

• Lethargy
• Fever of unknown origin
• Swollen, painful joints
• Vomiting

SOURCE: https://waunakeevetclinic.com/information-on-lyme-disease-and-4dx-testing.html