This is a question that comes up nearly daily in our veterinary practice. If a pet tests positive for Lyme Disease or Cat Scratch Disease but seems healthy, does that mean he/she isn’t really sick? The answer to this question is…..”Yes…..and…..maybe No” It can be as confusing for veterinarians as for pet owners. So what do we do? Many tests we perform daily are extremely sensitive. The purpose of this testing is often to “screen” to see if there has been an exposure to a specific disease. For example, if you have found ticks on your dog recently, you may be concerned with whether he/she has contracted Lyme disease or Anaplasmosis. With an in office screening test we can determine if any of these ticks were carrying Lyme disease or Anaplasma bacteria when they bit your pet. If this screening test is positive, then the answer is “yes”. However, just because your pet was exposed to these bacteria, it doesn’t mean they will develop the disease. So do we treat or do we not? If your pet appears ill with symptoms that could be attributed to the specific disease, then of course we would start the appropriate antibiotics. But if your pet appears healthy, then what? At this point we send out an additional test to further evaluate your pet’s response to the exposure. If your pet’s response is strong, as evidenced by they’re making of an abundance of antibodies, then we may choose to treat with antibiotics even though there are no obvious signs present. Although the measurement of this response is accurate, the testing laboratory often makes recommendation as to how high it should be before we choose to treat. If the patient’s number is in a gray area, we may choose to treat or may chose to retest one month later.
Fortunately, for cat owners, things are a bit simpler. When dealing with Feline Leukemia Virus or Feline Immunodeficiency Virus, a positive test is significant whether or not the pet is sick. In the case of Bartonella (Cat Scratch Disease) testing, the same test that screens also quantifies. A positive may be a “weak” positive (+1) or “moderately weak” positive (+2) in which case we would only treat if there were compatible signs of illness. But a “positive” (+3), “strong (+4) positive” or “very strong positive” is treated whether there are signs or not.
Follow up on all of the above can be a bit tricky. For Cat Scratch Disease, a repeat test is performed 6-12 months later and that quantification will be compared to the previous present response in order to assess how successful we have been with our treatment. However, in the case of Lyme Disease or Anaplasmosis, the “in house” screening test may remain positive for several years. In that case a quantitative test needs to be submitted separately to see if the response to the bacteria is now weaker. If so the patient is considered successfully treated.
Is all of this a bit confusing? Absolutely. It should be mentioned that not all practitioner’s take the same approach and not all doctors choose the same “trigger numbers” before treating. The take away is this; If your pet tests positive for any disease and the doctor chooses not to treat, make sure you clearly understand the reasoning. Ask as many questions as you can in order to be clear on the logic for your pet’s treatment. If you are uncomfortable with the response, seek another opinion. After all, these companions are also our very best friends. It is important to be comfortable with decisions made on their behalf.