The Animal Health Diagnostic Center (AHDC) at the Cornell University College of Veterinary Medicine is now offering a new Lyme test for Dogs. The AHDC is one of just seven members of the National Animal Health Laboratory Network (NAHLNN) that monitors for disease outbreaks in animals and has an impact on the standards for testing for different diseases in dogs, horses, cattle, and other animals. The new Lyme disease test for dogs will replace the current ELISA test and Western Blot that have been found lacking in specificity, sensitivity and accuracy when testing for Lyme disease in dogs (and humans). The new test to detect antibodies to Borrelia burgdorferi, the Lyme multiplex assay, is hoped to do away with some of the speculation and controversy surrounding Lyme disease, its diagnosis, and treatment.
The Lyme multiplex assay is now available for both dogs and horses and is said to combine the better aspects of the ELISA and Western blot tests whilst avoiding their pitfalls. Antibodies to different specific antigens of B. burgdorferi are detectable with the Lyme multiplex assay, along with the ability to differentiate between antibodies produced in response to spirochaetes and those resulting from Lyme disease vaccination. The new Lyme disease test for dogs can be carried out using serum (blood) and/or cerebrospinal fluid (CSF).
Lyme Disease Causes, Symptoms, and Tests
The cause of Lyme disease is the bacteria Borrelia burgdorferi sensu lato, with B. burgdorferi sensu stricto responsible for infections in North America. The infection is transmitted by tick bite with some dogs developing the Lyme disease rash, although not all do. Ticks are more likely to feed on a dog’s blood for longer by remaining unobserved in their fur, increasing the risk of bacterial transmission. Symptoms of Lyme disease in dogs may not arise for two or more months after the initial tick bite. Symptoms in dogs include fever, sudden onset of arthritis or lameness, sickness, loss of appetite, mood changes, and fatigue. ELISA testing can be carried out four to six weeks after exposure and a follow-up Western blot is considered standard for confirmation of Lyme disease in most cases.
The new Lyme multiplex assay has the advantages of being able to distinguish between early and chronic stages of Lyme disease infection, along with increased specificity and sensitivity over the ELISA and Western blot tests. Quanititive measurements of individual antigens, namely OspA, OspC, and OspF (outer surface proteins), is also possible with the new Lyme test for dogs. The test can identify if the antibodies to B. burgdorferi are present due to vaccination or infection which helps in deciding treatment strategies and avoids the risks of treating a dog unnecessarily with antibiotics or missing an active infection in a vaccinated dog. The test will also help determine the response to Lyme disease vaccinations and may prevent a dog having unnecessary booster shots for Lyme.
How the Lyme Disease Test for Dogs Works
The new Lyme multiplex assay for dogs is based on fluorescent bead technology that allows a single sample of serum or CSF to be used for detection of three antibodies to Lyme disease antigens all at the same time. OspA is expressed by the Borrelia bacteria to enable it to adhere to the gut wall of the tick and remain in place whilst waiting for the tick to feed. When the tick bites a new host, the bacteria begin to express OspC in order to facilitate the movement of the spirochaetes into the tick’s salivary glands from where it is transmitted to the host.
If OspC-antibodies are detected using the new Lyme multiplex assay then this is likely to indicate early infection with Lyme disease as the bacteria once again change their outer surface protein expression when disseminated in the host environment. Detecting antibodies to OspF indicates a chronic stage of infection. The intensity of fluorescence detected by the Lyme multiplex assay indicates the level of free antibodies that have been conjugated (joined) to the fluorescent bead technology. These values are described as median fluorescent intensities (MFIs) and the test turn-around time is just two to three days for most samples.
Early Lyme Disease Detection and Treatment
A positive value for OspA is usually a sign that the dog has been vaccinated for Lyme disease with those dogs naturally infected with Borrelia most likely having undetectable levels of antibodies to OspA as the expression of this outer surface protein is quickly downregulated during infection. High OspC-antibody MFIs can indicate early infection and these antibodies are detectable two to three weeks after infection using the new Lyme test for dogs. Low or undetectable levels of OspC-antibodies may indicate an absence of infection or a chronic infection if OspF-antibodies are detected as OspC levels drop off after three to five months of infection. OspF-antibodies begin to develop six to eight weeks after infection and remain afterwards.
The most common Lyme disease vaccine for dogs induces antibodies to OspA only, but some other vaccines also induce antibodies to the other outer surface proteins found in Borrelia. Knowing which vaccine was used is important when conducting a Lyme multiplex assay for dogs in order to differentiate natural infection from vaccine-induced antibody production. The current C6 assay, used to differentiate a vaccinated dog from an infected dog following a positive ELISA/Western blot test, had a high agreement rate with the new Lyme multiplex test but the availability of a single Lyme disease test for dogs will streamline the process considerably. Lower costs, higher specificity and sensitivity, the ability to tell early infection from chronic infection, and the relative speed of the test (compared to PCR, for example) all make the new Lyme test for dogs look highly advantageous over the current testing modalities.