During your dog’s annual examination you are likely asked about heartworm prevention, as well as flea and tick prevention. If preventatives haven’t been given consistently, or if there has been a lapse in administration a 4DX test (or “Lyme test”, in our office we call it the “HWLET”) is often mentioned. This is a quick test that can be performed in the office with a small sample of your pet’s blood. It tests for four diseases; Heartworm, Lyme, Anaplasma, and Ehrlichia. The test detects antigen for Heartworm disease, meaning it finds the molecules that cause the body to produce an immune response. So a positive result for Heartworm disease indicates an active infection. Unfortunately, the results for the tick-borne diseases (Lyme, Anaplasma, and Ehrlichia) are not as straight forward. The test can only detect antibodies for the tick-borne diseases; this means a positive result tells you there has been as exposure to the disease, but not whether or not an infection is actively present. Antibodies are the compounds a body produces when exposed to antigen.
So what are the symptoms you need to look for?
Heartworm disease is transmitted to your pet by mosquitoes. The microscopic larva migrates through your dog’s body into his bloodstream where it begins to grow in the chambers of the heart and inside some of the arteries. It is not a worm that lives in the intestines, as in other parasites we deworm for. Early symptoms of Heartworm disease are typically undetectable. As the worms begin to grow in the heart and arteries infected animals may experience persistent coughing, lethargy, exercise intolerance, decreased appetite, and weight loss.
The tick-borne diseases are transmitted through hard ticks (the small ones that are hard to see). The individual diseases are actually caused by different bacteria the tick passes to your pet while feeding. The bacteria then typically make their way to the bloodstream where they can affect the red blood cells, platelets, or joint fluid. If the diseases are left untreated they can begin to damage the bone marrow or kidneys. Generally the symptoms of tick-borne diseases can be lameness (limping or favoring a leg/legs), lethargy, decreased appetite, bruising, neurological signs (seizures or convulsions), and fever.
Why test annually?
The Companion Animal Parasite Council (and the doctors at FWVH) recommends yearly testing for Heartworm, Lyme, Anaplasma, and Ehrlichia. Because the body may take several months to mount an immune response and show outward clinical signs the 4DX test can help facilitate earlier detection of disease. Earlier detection allows for earlier treatment, and makes more serious, life-threatening side effects less likely. Because the test indicates exposure to the tick-borne diseases it can also give us a better picture of what tick control measures are reliable and which ones may not be as effective.
What happens when the 4DX has a positive result?
Heartworm disease: If the 4DX is positive for Heartworm disease the result is then verified with a second test. Another test to test for the microscopic larvae may be sent to the lab, or your pet’s blood may be examined under the microscope. Often, a combination of the aforementioned are performed. X-rays of your pet’s heart and lungs are often taken to evaluate for signs of heart enlargement or heart failure (often causing fluid to back up into the lungs). A complete blood count (CBC) and serum blood chemistry will be performed to look for signs the disease has impacted the organs, as well as red and white blood cells. After further testing has been performed treatment is often initiated.
Lyme disease: There is a special antibody test, called the QC6, which can measure the amount of antibodies to Lyme disease present in your pet’s bloodstream, when a 4DX is positive for Lyme that test is typically recommended. A low value is thought to indicate previous exposure, not active infection. If a QC6 comes back with a high value, treatment is typically initiated. Because more serious forms of Lyme disease can affect the kidneys when an animal tests positive the serum blood chemistry (part of this panel checks specific kidney enzymes) as well as the urine are tested. If a positive pet has elevated kidney enzymes or protein present in its urine, it is likely the Lyme disease is affecting the kidneys and treatment should be started.
Anaplasma and Erhlichia: As with the other diseases a CBC and chemistry are performed to assess for organ damage, as well as signs the red and white blood cells, and platelets are affected. If Erhlichia is present the urine will typically be checked for protein as well. If the tests show signs of infection then treatment will be started.
Treatment for Heartworm disease is usually a series of injections of high doses of a chemical dewormer, as well as oral antibiotics and heartworm preventative. The tick-borne diseases are treated with an oral antibiotic, usually over the course of one month.
How can I prevent my pet being exposed to these diseases?
The very best prevention is monthly heartworm prevention and monthly flea and tick prevention. The preventatives are available in many different forms; from topical liquid, to oral chews, to collars. In our area yearly administration of preventatives is recommended, our weather is no longer consistently cold enough to eliminate ticks. Yearly administration also helps to develop a pattern of administration, making missed doses less likely.
During your pet’s next wellness visit you may hear the recommendation for annual 4DX testing. It could diagnose a disease early, allow for early treatment, and even a negative test can give you information about the effectiveness of your monthly preventatives. Our clinic has recently implemented a Wellness Profile that includes a 4DX. The profile also includes all of the follow-up tests that are typically performed for the tick-borne diseases, a urine protein quantification test and QC6 (for Lyme antibody) are usually add on tests that require an extra charge, they are now included for no extra charge. Consider testing your pet yearly to increase their longevity and your peace of mind!