Lyme disease, a tick-borne illness caused by the bacterium Borrelia burgdorferi, poses a significant health concern for both dogs and horses. While many infected animals remain asymptomatic, a portion can develop a range of clinical signs affecting their joints, general well-being, and in severe cases, their kidneys or nervous system. Recognizing these symptoms and understanding diagnostic tools are crucial for effective management. Cornell’s Lyme Multiplex assay offers a sophisticated method to pinpoint the stage of infection, assess treatment efficacy, and verify vaccination status, providing a more comprehensive picture than standard in-house tests.
Causes and Symptoms of Lyme Disease
The transmission of Borrelia burgdorferi occurs through the bite of infected blacklegged ticks, commonly known as deer ticks. In dogs, common symptoms include lameness, swollen lymph nodes, joint swelling, fatigue, and loss of appetite, with potential for serious kidney complications. Horses may exhibit shifting-leg lameness, stiffness, hypersensitivity to touch, weight loss, and poor performance. Neurological symptoms can also arise if the bacteria affect the central nervous system.
When Clinical Signs Appear
It’s important to note that only a small percentage of infected animals, estimated at 5-10%, will display clinical signs. These symptoms typically manifest during the chronic stage of the disease, appearing as early as 2 to 5 months post-infection, though they can emerge much later.
Diagnosing Lyme Disease
A veterinarian’s initial assessment involves observing clinical signs that align with Lyme disease. If suspected, a serologic test, such as the Lyme Multiplex assay, will be ordered. This advanced assay quantifies antibodies against specific proteins on the surface of Borrelia burgdorferi at different stages of the bacterial life cycle. This detailed profile helps determine if an animal has a recent or chronic infection and can monitor protective antibodies post-vaccination.
Differentiating Diagnostic Approaches
While a veterinarian can perform a rapid in-house assay, this test typically checks for antibodies against only one B. burgdorferi surface protein. It lacks the ability to detect early infection, confirm vaccination status, or quantify antibody levels. The Lyme Multiplex assay’s ability to quantify antibodies is vital for assessing successful treatment and confirming a cure.
Prevention and Vaccination
Preventing tick bites is paramount in reducing the likelihood of Lyme disease infection. This includes consistent tick control measures and, where appropriate, vaccination. Vaccination helps maintain antibodies against B. burgdorferi, offering further protection. However, the level and duration of vaccine-induced antibodies can vary among individuals, making it beneficial to verify an animal’s antibody response through testing to ensure robust and lasting protection.
Understanding Antibodies
Antibodies are proteins produced by the immune system to combat foreign substances like bacteria. They identify and attach to bacteria, aiding in their elimination from the body.
Treatment and Monitoring
If an animal shows clinical signs and tests positive on the Lyme Multiplex assay, discussing treatment options with a veterinarian is recommended. For seemingly healthy but positive animals, a discussion about the risks and benefits of treatment, along with a monitoring plan, is advisable.
Assessing Treatment Success
Successful antibiotic treatment typically leads to a decrease in antibody levels. For early-stage infections, antibody levels should drop by 40% or more within 6-8 weeks post-treatment. In chronic stages, this reduction may take up to 3 months.
Re-infection and Vaccination Status
Animals can still contract Lyme disease even after vaccination, often due to a low immune response or high exposure rates in their environment. Yearly checks of OspA titers are recommended for vaccinated animals to ensure adequate antibody development. The Lyme Multiplex assay can quantify vaccine antibodies as early as two weeks post-vaccination. Antibiotic treatment targets the bacteria but does not directly impact antibody levels. However, successful eradication of the pathogen leads to a decrease in antibody production.
Testing Protocols and Interpretation
For successfully treated animals, re-testing is recommended at specific intervals. For horses and dogs with positive OspF and negative OspC antibody values, re-testing is advised 3 months after treatment initiation. If OspC antibodies are also positive, re-testing can occur 6-8 weeks after treatment begins. A successful treatment is indicated by approximately a 40% drop in antibody levels.
For unvaccinated animals, if antibodies to OspA are positive but OspC and F are equivocal, re-testing in 2-3 weeks is recommended to observe potential antibody rises indicative of early infection. If an animal treated for Lyme disease shows no change in antibody levels upon re-testing, and exhibits clinical signs, retreatment or a switch to a different antibiotic may be considered. If no clinical signs are present, monitoring antibody status every 6-12 months is an option.
The Lyme Multiplex assay expresses results in Median Fluorescent Intensity (MFI) values, with higher MFIs indicating greater antibody concentration. While the assay detects total antibody levels, the pattern of antibodies to different surface proteins (Osp) helps differentiate between early and chronic infections.
Co-infections and Early Intervention
Ticks can carry other infectious organisms, such as Anaplasma, alongside Borrelia burgdorferi. Treatment immediately after a tick bite is not always necessary, as not all ticks are infected, and transmission requires at least 24 hours of feeding. If a tick is found, it can be submitted for PCR testing for B. burgdorferi and Anaplasma. Serological testing, including the Lyme Multiplex assay, can detect antibodies 3-4 weeks post-infection, allowing for early treatment if antibody levels are positive.
Vaccine-Specific Antibody Responses
Different vaccines induce varying antibody responses. Merial’s recombinant OspA vaccine should result in high OspA antibody levels while OspC and OspF remain negative, facilitating early infection detection. Intervet (Merck)’s vaccine, based on recombinant OspA and OspC, may interfere with early infection detection but allows identification of infected animals via OspF antibody values.
Understanding OspA Antibodies
Previously considered solely markers for vaccination, antibodies to OspA can now also indicate early infection or disease chronicity and severity in unvaccinated animals. While vaccinated animals typically develop high OspA antibodies, a low and transient OspA antibody response can occur early after infection in unvaccinated animals due to residual OspA on the bacterial surface.
Testing Other Fluids
For horses presenting with neurological signs, CSF samples can be submitted along with serum for comparative analysis. An elevated antibody level in CSF relative to serum can suggest local antibody production within the central nervous system, potentially indicating B. burgdorferi‘s involvement in the neurological condition. For other sample types, contacting the lab directly is advised.
