Lyme disease, a significant health concern for both dogs and horses, is caused by the bacterium Borrelia burgdorferi and transmitted through the bite of infected blacklegged ticks. While many infected animals remain asymptomatic, some can develop a range of clinical signs, including lameness, fatigue, loss of appetite, and, in severe cases, kidney complications in dogs or neurological issues in horses. Early and accurate diagnosis is crucial for effective management.
Diagnosing Lyme Disease with the Lyme Multiplex Assay
Traditional in-house tests performed by veterinarians can detect antibodies against a single B. burgdorferi surface protein, but they have limitations. These tests cannot identify early-stage infections, determine vaccination status, or quantify antibody levels. Cornell’s Lyme Multiplex assay offers a more comprehensive solution, providing a fully quantitative analysis of antibodies against specific proteins of B. burgdorferi at different life cycle stages. This allows for a clearer understanding of whether an animal has a recent or chronic infection and helps monitor protective antibodies after vaccination.
How the Lyme Multiplex Assay Works
The assay quantifies antibodies directed against specific B. burgdorferi surface proteins: OspA, OspC, and OspF. The antibody profile generated can indicate the stage of infection. For instance, in unvaccinated animals, positive antibodies to OspC and/or OspF are strong indicators of infection. Conversely, positive antibodies to OspA in unvaccinated animals can suggest chronicity and disease severity, or a transient response early after infection.
Interpreting Test Results
- Unvaccinated Animals:
- OspA positive, OspC/OspF equivocal: Retest in 2-3 weeks. A rise in OspC/OspF antibodies would confirm early infection.
- OspC and/or OspF positive: Indicates infection with B. burgdorferi.
- Vaccinated Animals:
- Vaccines primarily target OspA. Vaccinated animals should ideally show high OspA antibodies and negative antibodies to OspC and OspF.
- Infection can still occur despite vaccination, often due to a low individual immune response or high tick exposure. Yearly monitoring of OspA titers is recommended to ensure adequate antibody levels.
- The type of vaccine used can influence test interpretation. Vaccines based solely on OspA allow for easier detection of early infection. Vaccines incorporating OspC may interfere with early infection detection, but OspF antibody values can still identify infected animals.
Prevention and Treatment of Lyme Disease
Prevention Strategies
Preventing Lyme disease involves a two-pronged approach: tick control and vaccination. Implementing effective tick prevention methods significantly reduces the risk of infection. Vaccination can further protect animals by maintaining antibodies against B. burgdorferi.
Treatment and Monitoring
If an animal shows clinical signs of Lyme disease and tests positive on the Lyme Multiplex assay, discussing treatment options with a veterinarian is recommended. Antibiotic treatment targets the bacteria but does not directly affect antibody levels. However, successful treatment leads to a decrease in antibody levels as the bacteria are cleared.
Monitoring Treatment Success:
- Early Stage Infection (OspC- / OspF+): Antibody levels should decrease by 40% or more within 6-8 weeks after treatment begins.
- Chronic Stage Infection (OspC+ / OspF+ or OspC+ / OspF-): Antibody levels should decrease by 40% or more within 3 months after treatment begins.
Re-infection and Persistent Infection
Animals can be re-infected even while on treatment, as infected ticks may still bite. However, ongoing treatment usually prevents the establishment of a persistent infection. If antibody levels do not change significantly after treatment, and the animal remains symptomatic, re-treatment with a different antibiotic or an extended treatment duration may be considered. Alternatively, if the animal is asymptomatic, monitoring antibody status every 6-12 months is an option.
Understanding Antibodies and MFI
Antibodies are proteins produced by the immune system to fight foreign substances like bacteria. The Lyme Multiplex assay measures Median Fluorescent Intensity (MFI), where higher MFI values indicate a greater concentration of antibodies against B. burgdorferi. The assay detects total antibody levels, not specifically IgM or IgG, with the pattern of antibodies to different Osp antigens being key to determining infection status.
Other Tick-Borne Diseases
Ticks can transmit other infectious organisms besides Borrelia burgdorferi, with Anaplasma being a common co-infection. If a tick is found on an animal, it can be tested for B. burgdorferi and Anaplasma via PCR. Early treatment based on a positive tick test can be considered, but a serological test is needed to confirm transmission and infection. Antibodies can be detected as early as 3-4 weeks after infection, making the Lyme Multiplex assay a valuable tool for confirming infection and guiding treatment.
Testing Other Fluids
In cases of neurological signs in horses, CSF samples can be submitted along with serum samples. A relative increase in antibodies in CSF compared to serum can suggest local antibody production in the central nervous system, indicating B. burgdorferi‘s potential contribution to the neurological condition. For other sample types, contacting the laboratory is advised.
