Your Pet and Lyme Disease
This information is not meant to be a substitute for veterinary care.
Always follow the instructions provided by your veterinarian.
What is Lyme disease?
Lyme disease is caused by the corkscrew-shaped bacteria, Borrelia
burgdorferi which is also called a spirochete. The bacteria are carried
by ticks which transmit the infection when they feed on animals and humans.
The disease can cause generalized illness in animals and humans worldwide.
||In the United States, Lyme disease occurs predominantly on
the Pacific coast and in the Midwest, and Atlantic coast
states. Regions in which the disease occurs commonly are called
endemic regions. About 75% of dogs living in endemic regions are
exposed to infected ticks, but only a small percentage of
exposed dogs develop signs of disease.
Lyme disease was first described in 1975 when an unusual outbreak of
rheumatoid arthritis occurring in children was reported in Lyme,
Connecticut. In 1982, the bacteria Borrelia burgdorferi was
determined to be the cause of that outbreak. Since Lyme disease was first
described in the early 1980's, the frequency of occurrence of disease has
increased twenty-five fold. Today, Lyme disease is the most common
vector-borne (transmitted by insects or arthropods) disease occurring in
people and probably in dogs in the United States. Dogs are most frequently
infected with the Lyme disease bacteria, but infections can also occur in
horses, cattle, and cats.
How is Lyme disease transmitted?
The bacteria live in mice, deer and other small mammals. The type of
ticks that can transmit the bacteria from these wildlife to humans and
domestic animals are the Ixodes
ticks. The bacteria replicate
(increase in number) in the wildlife without causing them to become sick.
When a tick feeds on the infected wildlife the tick picks up the bacteria,
then they transmit the bacteria to another animal the next time they feed.
If your pet is diagnosed with Lyme disease you are not at risk of
getting Lyme disease directly from your pet. The bacteria increase to
high levels in the blood of wildlife whereas humans and domestic animals
develop very low levels of the bacteria in their blood and these low
levels will not infect a feeding tick. Researchers have learned that
infected ticks must feed for about 24 hours to transmit the bacteria to
a susceptible animal so quick removal of ticks from your pet reduces the
chance of infection.
The most common sign of Lyme disease in dogs is arthritis, which causes
sudden lameness, pain ands sometimes swelling in one or more joints. Other
signs that may be seen include fever, lack of appetite, dehydration,
inactivity, and swollen lymph nodes. In severe cases, the infection can
cause kidney failure and death although this does not occur commonly in
dogs. The signs of heart and nervous system dysfunction seen in infected
humans are not often seen in animals.
||Humans often show a skin rash that looks like a target but
this is rarely seen in infected dogs.
A diagnosis of Lyme disease is usually made based upon a history of being
in an endemic area, signs of arthritis and favorable response to treatment.
There is a blood test that measures antibodies to the bacteria but many dogs
that live in endemic regions will have a positive blood test. A positive
blood test just means that the dog was exposed to Borrelia burgdorferi
but not all dogs that are exposed will show signs of disease. Early in the
disease dogs may not yet have a positive blood test. Dogs that have been
vaccinated for Lyme disease may have a positive blood test depending upon
the type of blood test that is performed. There are several other causes of
arthritis that occur in dogs that must also be considered.
Borrelia burgdorferi is easily treated with antibiotics. The
signs of Lyme disease usually regress rapidly in response to treatment. If
the disease remains untreated the disease becomes chronic and can cause
kidney damage although dogs are much less likely to develop chronic disease
than are people.
Animals in endemic areas are at greatest risk for infection. The best
method of prevention is to avoid tick infested areas, especially in the
spring when the young ticks are most active. When returning from a
tick-infested area do a thorough search for ticks on both yourself and your
animals. Ticks should be removed carefully with a tweezers, pinching the
tick near the point they enter the skin. There are also many highly
effective veterinary products that will kill ticks on your dog before the
tick can transmit the bacteria. Remember that early removal of ticks reduces
the chance that the tick will transmit Lyme disease.
There is a vaccine approved for use in dogs for Lyme disease
prevention. Most authors of veterinary articles on Lyme disease do not
recommend vaccinating dogs in non-endemic areas. Not all authors
agree on how effective the vaccine is in preventing Lyme disease and not
all authors agree that the vaccine should be given in endemic regions.
The vaccine can cause some blood tests for Lyme disease to become
positive. For more information about tick control products or Lyme
disease, consult your veterinarian.
For additional information on Lyme disease see: the
Centers for Disease
Control (CDC) website
This topic was written by Wendy Harless, Oregon State University, class
of 2002 with the guidance of Dr.Diana Stone, Washington State University.
Washington State University assumes no liability for injury to you or
your pet incurred by following these descriptions or procedures.
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