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Lyme Disease – The Key Is Prevention

3 August 2009 No Comment View all Articles by: Pamela

By: Carolyn C. Cassidy

Lyme disease, caused by the spirochete Borrelia burgdorferi, remains pervasive throughout many parts of the United States and Europe both in humans and dogs. The incidence of infection is highest in the Northeastern states (70-90% of dogs) followed by the upper Midwest and then the far West. Out of the infected dogs, 5-10% will become ill from Lyme disease. Veterinarians are faced with the challenge of not only recognizing and treating ill dogs, but preventing the disease in healthy dogs.

Lyme disease is transmitted by the Ixodes ticks during a blood meal and does not occur at least for the first 24 hours of attachment- some suggest it is 36-48 hours. Dogs are the most common animal to show symptoms of the disease, with cattle and horses occasionally becoming ill, and cats only showing exposure but no signs. No breed, age, or gender predilection has been reported in dogs. But Shetland Sheepdogs and Labrador and Golden Retrievers have been more likely than other breeds to develop Lyme nephritis (kidney disease). Clinical signs of Lyme disease usually occur 2-5 months after the infection and may include fever, lethargy, lameness, enlarged lymph nodes, and arthritis of one or multiple joints. Less common signs are skin lesions, kidney disease, heart disease and neurologic disease. A chronic recurrent form of the disease has been suggested, but there is no clear evidence.

There are a variety of tests available to screen for Lyme infection in dogs. Currently, our hospital employs the SNAP 4Dx test (qualitative) as part of a screening program for outwardly healthy dogs (performed yearly) or when Lyme disease is suspected. This test also screens for 2 other tick borne diseases- Anaplasmosis and Erchlichiosis. The C6 Antibody Quantitative test is performed when the SNAP 4Dx test is positive and the dog is a candidate for Lyme treatment. This test enables us to compare antibody levels and follow trends, thereby identifying treatment success or failure.

Since the majority of infected or seropositive dogs will remain asymptomatic, our hospital has formulated a Lyme disease prevention and treatment program to address the three different categories our patients fall into based on their physical health and the SNAP 4Dx test results. These categories with the accompanying recommendations for animal care are outlined below.

Asymptomatic Dogs with a Negative SNAP 4Dx Test
A. Practice daily tick removal. Transmission of the disease to humans from the tick during removal is unlikely due to damaged mouth parts, but some caution should be used.
B. Apply tick control products. We recommend Frontline which protects against other diseases and has proven to be successful in preventing Lyme infection.
C. Vaccinate in endemic areas. Vaccines appear safe and effective for this group. Preventing infection is the goal, since it is believed that most dogs will remain carriers of the bacteria, even after treatment, which could potentially cause problems in the future. Dogs do not have a good natural immunity to Lyme infection.
D. We do not recommend the indiscriminate use of antibiotic therapy to prevent infection since there is no proven benefit and this could contribute to drug resistance, if repetitive and widespread, and unnecessary drug reactions (anorexia, esophagitis, and liver abnormalities).

Asymptomatic Dogs With a Positive SNAP 4Dx Test
A. Perform a comprehensive blood panel and urinalysis with urine P/C ratio. If protein present in the urine indicative of Lyme nephritis, recommend blood pressure and antibiotic therapy. Additional diagnostics and medication may be warranted.
B. Monitor for urine protein every 3-6 mos.
C. Perform C6 Quant. Test and repeat in 6 mos., then as needed.
D. If treatment warranted, Doxycycline is our first choice for antibiotic treatment at 10 mg/kg twice a day for 4-6 weeks.
E. Tick removal and control measures stressed for all groups of dogs.

Symptomatic Dogs with a Positive SNAP 4Dx Test
A. Perform comprehensive blood panel and urinalysis with urine P/C ratio. Since other diseases can manifest with similar clinical signs as Lyme disease, it is important we keep an open mind to alternative diagnoses and the possibility of a co-infection. Additional tests that may be warranted include x-rays, ultrasound, urine culture, joint aspirate, autoimmune testing and kidney biopsy to name a few.
B. Perform C6 Quant. Lyme test as earlier described.
C. Initiate therapy with Doxycycline and any other medications that may be deemed necessary.
D. Monitor.

Lyme disease has proven to be a challenging disease for veterinarians. The hallmark for prevention continues to be daily tick removal and tick control measures. The disease’s insidious nature warrants a proactive effort to prevent infection in dogs and, thereby, avoid the risk of sometimes long term illnesses and eliminate a reservoir for the disease in humans.

Carolyn C. Cassidy, V.M.D. graduated from University of Pennsylvania in 1988 and then completed an internship and residency in large animal medicine at New Bolton Center. She worked for 1 year at a large animal practice in Lebanon, PA before accepting a position at Windcrest Animal Hospital. She worked at Windcrest full-time for
15 years and then became part-time after starting a family. Her interests include ultrasonography and internal medicine.