The rise in outdoor temperatures is a sure sign that spring is here, and with the change come ticks.
When the weather warms it's safe to assume that ticks are out looking for their next meal. Although the arachnids are found throughout the United States, deer ticks, also known as blacklegged ticks, are common carriers of Lyme disease. They often are found in wooded areas and along forest trails, primarily where their preferred host, the white-tailed deer, is located.
For veterinary clinics, spring is a time to educate pet owners about flea and tick season, and to recommend preventive measures such as parasitic control and vaccination against Borrelia burgdorferi, or Lyme disease.
Signs of Trouble
When a tick attaches itself to a host, the transfer of Lyme disease isn't immediate."The general consensus is it takes at least 24 to 48 hours," said Jeremy Smith, DVM, owner of Oak Knoll Animal Hospital in St. Louis Park, Minn.
Symptoms don't necessarily show themselves right away, either. Dogs are more affected than cats—a fact that some attribute to felines being more fastidious groomers. However, cats are at a disadvantage because there is no Lyme vaccine for them and they have been found to harbor B. burgdorferi antibodies but show no clinical signs.
Generally, infected dogs show symptoms weeks or sometimes months after the initial bite. Signs include:
- Shifting leg lameness.
- Swollen joints.
- Enlarged lymph nodes.
- Lethargy.
- Fever.
- Anorexia.
- Depression.
Because symptoms are not evident right away—or sometimes at all—diagnosing Lyme disease can be difficult. Symptoms often are thought to be indicative of other illnesses, and in some cases, the pet shows no signs and the disease is caught only during a yearly physical.
Dr. Smith recommends routine screening.
"Most of the positive cases we see here turn up … as part of the dog's annual heartworm screening," he said. "In these cases we're hopefully getting on top of the infection before the dog become symptomatic."
Ann Valenti, DVM, owner of Inver Grove Heights Animal Hospital in Inver Grove Heights, Minn., noted that a typical case at her clinic presents itself with fever and shifting leg lameness.
"The fever usually causes a loss of appetite, and a 'walking on eggshells' appearance has been described," Dr. Valenti said.
In these cases, even if the owner never saw ticks on the dog, Valenti and her team test for Lyme disease. Inevitably the test comes back positive.
Looking for Confirmation
Diagnosing the Lyme infection may be tricky when a veterinarian relies on symptoms alone. However, several tests can be used, including:
- 4DX Lyme C6 antibody screening.
- Chemistry tests to evaluate how the kidney, liver and pancreas are functioning.
- Blood parasite screening.
- Urinalysis to check for Lyme nephritis.
- Fecal tests to rule out any intestinal parasites.
Sara Williams, DVM, MPH, the owner of Northwest Animal Hospital in Plymouth, Minn., routinely does 4Dx screening on some patients and has seen unexpected positive test results. Upon a positive test, Dr. Williams' next steps are to "send out a Quant C6 to quantify the amount of circulating Lyme antibody," she said, "which usually indicates their levels are really high and require immediate treatment."
She noted a misperception among veterinarians, one that's important to know: "Some believe Lyme vaccinations will interfere with the test results on a 4Dx. The 4Dx test looks at the C6 antibodies from the Lyme organism itself, and the vaccine induces a different type of antibody formation in the dog. So the vaccine does not interfere with the test."
Now What?
The most common treatment of Lyme disease is a course of doxycycline, although other options, such as minocycline, may be considered, depending on the severity of the symptoms.
Because her clinic is located in Minnesota, Williams has treated many patients who tested positive for Lyme disease. Some cases also presented as Lyme-associated renal disease. However, Williams noted that many ticks may be co-infected with Anaplasma and Ehrlichia. Even though Lyme disease takes a minimum of 18 hours to transmit, these tick-borne diseases may begin the process in as little as three hours, of transferring and infecting the host animal.
Most uncomplicated cases of Lyme disease will respond to doxycycline within 24 hours of treatment. Williams has had patients unable to walk and appearing near death, but they rebounded within 24 hours of beginning treatment.
In some cases, symptoms never fully disappear, despite full treatment. Smith has worked with patients who suffered lingering joint or kidney problems.
"For these," he said, "titer levels are watched closely in order to catch recurrence or reinfection early."
Valenti pointed out that if the kidneys are infected, "antibiotics are still an integral form of treatment, but more intensive supportive care also is required because Lyme nephropathy, which affects the kidneys, is much more serious and often fatal."
Time to Teach
One of the best ways to prevent Lyme disease in patients is by educating owners.
Knowing how widespread ticks are in a given area is the first step. A great resource is the Companion Animal Parasite Council's Parasite Prevalence Maps at www.capcvet.org. With just a few clicks, visitors can select their location in the United States and view how many dogs have been tested for Lyme disease and of those how many tested positive.
Veterinarians also should encourage clients who take their pets outdoors to always check for ticks upon their return home. Pay close attention to the inside of the thighs, the ears and the belly trunk. If they don't find anything, it's important to check again the following day. Ticks can be hard to find, but they're easier to spot once they've fed for a while.
Practitioners located in Lyme-prevalent areas may recommend vaccinations. In addition, monthly preventives and even prescription-strength collars will help prevent tick bites. If a client is an avid hunter, camper or outdoors person, a combination might be necessary.
Stephanie Duncan is the communication coordinator at the Veterinary Hospitals Association, a cooperative based in South St. Paul, Minn.
Originally published in the May 2016 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today!
