What is Lyme Disease?

Lyme Disease, or Borreliosis, is a bacterial disease that affects humans and other mammals. It is caused by the bacterial organism Borrelia burgdorferi, and is transmitted primarily by the deer tick, or Ixodes scapularis.

Deer Tick Life Cycle (brief summary)

There are four life stages of the deer tick: egg, larva, nymph and adult. Female deer ticks lay eggs, which hatch larvae in the spring. Larval forms become infected with Borrelia by attaching to/having a blood meal from infected white footed mice. Infected larvae will then lie dormant until the following spring, when they molt into nymphs. Nymphs later molt into adults. Both nymphs and adults will seek larger hosts (dog, human, and deer) to attach and have a blood meal. If infected with Borrelia, nymphs and adults will infect the host during the blood meal.

How is Lyme Disease transmitted?

Borrelia organisms live in the midgut of the tick. At the end of the blood meal, part of the contents of the tick's midgut will be regurgitated to its mouthparts and saliva. The organism is then transmitted to the host through the tick's saliva.

 This process requires at least 48 hours of tick attachment.

The organism replicates in the skin of the infected mammal and migrates throughout various tissues of the mammal. Borrelia is particularly good at hiding from the mammalian immune system. The organism does this by modifying the proteins on its surface, as well as changing shape. Clinical signs in the dog usually occur 2-5 months after exposure to the tick.

What are the signs of Lyme Disease in dogs?

Clinical signs are related to the dog's immune response to the Lyme organism. Dogs may exhibit any one of the following signs:

It is known that patients can have a latent infection for years. Latent infection refers to a condition where the patient is infected with disease but does not exhibit any outward clinical signs of disease. They may, in fact, never get sick at all.

It is believed that Lyme infected dogs can develop a type of immune-mediated kidney disease called Lyme Nephritis. Lyme Nephritis is the result of chronic antigen/antibody complex deposition in the kidneys. The antigen comes from Lyme, and the antibody is the dog's immune response to antigen. These complex molecules eventually cause damage to the kidneys, causing the kidneys to lose or "spill" protein into the urine. The concern is that even if the patient is treated for suspect Lyme Disease, the damage done to the kidneys may not be reversible. It is often recommended to complete lab work (Chemistry, CBC, and Urinalysis) at the time of diagnosis or at the end of treatment for Lyme Disease, in order to screen for evidence of kidney disease.

How do we test for Lyme Disease in dogs?

There are multiple tests that can be used to detect Borrelia infection. At Sterling Veterinary Clinic, we focus on Lyme C6 antibody testing. The Lyme C6 protein is a unique section of one of Borrelia's surface antigens and is expressed during Lyme infection. The canine immune system develops antibody against Lyme C6 protein when infected. There are two commercially available tests that detect canine antibody against Lyme C6 protein: the quantitative C6 antibody test and the SNAP 4Dx test. The quantitative C6 antibody test provides an actual measurement of the patient's antibody or "titer" level. A blood sample is obtained in clinic and sent to an outside lab for results within 24-48 hours. The SNAP 4DX test provides a "positive" or "negative" result. A positive result is indicative of active Lyme infection. This test requires a blood sample and can be run in-clinic for same day results. The Lyme vaccination does NOT contain Lyme C6 protein, so vaccinated dogs will not test positive, unless they have active Lyme infection.

 How do we treat dogs with Lyme Disease?

Treatment of dogs with Lyme Disease normally consists of a 3-4 week course of doxycycline, although amoxicillin or cefovecin can be effective alternatives. Obvious improvement in the patient's clinical signs is often seen within 48 hours from the start of treatment.

The goal of treatment is to bring the patient to a condition that is free of clinical signs of disease. Because the Borrelia organism is exceptionally good at hiding from the patient's immune system, it is often not possible to fully eradicate the organism from the patient's body - the organism is in the patient's body but is not causing active infection.  

How can we prevent Lyme Disease in dogs?

Lyme prevention in dogs can be achieved through a combination of three important practices, detailed below. Ideally, all three practices would be followed to minimize the Lyme infection rate in dogs.

1. Daily tick checks/tick removal - a practice that can be overlooked, but can be as valuable as monthly tick preventatives in prevention of disease. Transmission of Lyme Disease requires tick attachment for at least 48 hours. If dogs are checked daily, particularly after potential tick exposure, the probability of Lyme Disease transmission is lowered.  Click here to learn how to safely remove a tick from your pet.

    

2. Monthly tick preventatives - including topicals such as Frontline, Advantix and Revolution. All of these products aim to kill the tick or cause it to drop off prior to 48 hours.

    

3. Lyme vaccination - available and recommended in dogs living in tick endemic areas. At this time, there are several commercially available Lyme vaccinations. All primarily work by providing dogs with a specific antigen (OspA) that can be found on Borrelia's surface. When vaccinated, the dog's immune system will develop antibodies against OspA. When ticks attach for a blood meal, those antibodies enter the midgut of the tick (where Borrelia reside) and block migration of Borrelia from tick to dog.