By Dr. Jennifer Morrow
We are getting more and more calls at the Minden Animal Hospital asking about ticks, owners wondering what the risks are to their dogs, what prevention they should be using and worried about their dog contracting Lyme disease.
Ticks are relatively new to our area, and every year we are seeing more and more of them. There’s a good explanation for this – they are a hardy species and once they have migrated into an area, they are here to stay. Migration occurs by being carried on an animal – domestic or wild mammal or birds. Ticks have exceptional reproductive capacity, with the females laying up to 2000 eggs at once! Adults survive the winter, males remaining on their host and females will bury themselves under leaves and debris, so even our coldest winters don’t deter them.
Without going into all the details of the life cycle, the basics include an egg hatching into larva, which feeds on a small host, the larva then falls off and molts into a nymph (think teenager with fewer hormones), which feeds on a slightly bigger host, falls off and then molts into an adult. This transformation takes approximately 2 years. When adults come out of “hibernation” to feed there’s often still snow on the ground! This is the time you need to start thinking about tick prevention.
It is helpful to know where Lyme disease comes from in order to understand how your dog can become infected. Lyme disease is transmitted by a tick called Ixodes scapularis, commonly known as the deer tick. The larvae or nymph stages become infected when they feed off an infected white-footed mouse. The areas where Lyme disease is endemic, are the areas the infection is endemic in the mouse population. When an infected tick bites your dog (or you), it injects an anti-coagulant into them, so that the blood doesn’t clot, and it can continue feeding. It is at this time, when they will regurgitate the Lyme bacteria into your dog. The good news is that it takes at least 48 hours for this to occur; therefore, this is our key window for prevention.
Lyme disease is caused by a bacterium, known as a spirochete, because of its shape. It can change its outer proteins, and it is these outer proteins that our immune system relies on to identify invaders and destroy them. It is also what scientists rely on to differentiate bacteria from each other when testing or creating vaccines. Because of this, Lyme bacterium is called as a master of disguise. As well, once infected, the animal or human is infected for life.
There are some important differences regarding infection in people versus dogs. Infected people have an 80% chance of developing clinical signs. Symptoms include; a red target like lesion, flu-like illness, followed by joint pain, occasionally neurological signs and rarely heart arrhythmias.
In people clinical signs usually present within the first few weeks of being bitten by the tick. Dogs only have a 10% chance of becoming ill after being infected. The majority of dogs will never show signs of illness, although will remain infected (the bacteria present in their system), usually for life. The dogs that do become ill, however, take weeks to months before showing symptoms. Signs mainly include fever for a few days or intermittent arthritis. Neurological signs or heart issues are very rare. In some dogs, a more serious illness occurs that is associated with the kidneys. Immune-mediated complexes (clumps of antibodies) get lodged in the kidneys and cause damage. It often takes months to years for this to occur, which makes it difficult to treat and hard to associate to Lyme disease.
Some people have wondered if their dog gave them Lyme disease. This is very unlikely, and what typically happens is co-infection. When walking your dog through the bush, both of you get bitten by ticks that are carrying Lyme disease (in endemic areas, it is very common for numerous ticks to be carrying the bacteria).
Treatment in dogs can be relatively easy and typically consists of a month of antibiotics. The challenging aspect is determining which dogs need to be treated. Arthritis is the most common clinical sign, but shows up months after being bitten by a tick and is often associated with aging, rather thanLyme disease. By the time kidney disease shows up years later, the thought of a tick bite (if known) is a distant memory.
Prevention of ticks is the best course of action to protect your dog. Ticks can cause painful or irritating swelling at the insertion site. If removed improperly, the mouthparts of the tick can create an abscess. Some ticks are small and we may never notice them, but can still infect your pet with diseases. Although Lyme disease, or other tick-borne illnesses, are not endemic in our area at this time, the environment is constantly changing and chances are high that we will be affected one day.
Checking yourself and your dogs each day and removing any ticks immediately is the best prevention. At Minden Animal Hospital we have several products that can aid in killing ticks and we recommend their use from March through until November as an added measure of protection.
To see a Map of where Lyme disease is prevalent in Ontario visit http://mindenanimalhospital.com/