Tick-Borne Diseases in Dogs
but in doing so we expose them to some potentially serious infections. Escalating deer populations and chang- ing habitat are bringing us in proximity to wildlife and the ticks they carry. Combined with this is the rise of rescue groups and internet adoptions importing dogs from other parts of the country into our state, introducing species of ticks as well as infectious agents that had previously not been present in Connecticut. Tick populations seem to be thriving in Con- necticut’s climate. Most ticks require several hosts to com- plete their life cycles, and in the process of feeding on sequential hosts, they have the ability to transmit infections. For example, the deer tick, which transmits Lyme disease, may feed on the white-footed mouse and white-tailed deer as well as on people or dogs during the completion of its life cycle. The most common tick-borne disease seen in Connecticut is Lyme disease, which is caused by the spirochete Borrelia burg- dorferi. It is contracted when a dog is bitten by Ixodes scapularis, or the deer tick. The life cycle of this tick involves several hosts and takes two years to complete. During the feeding process the different stages of the tick can acquire the spirochete and pass it on to the next host. When that host is a dog, it may contract Lyme disease. Lyme disease in dogs manifests differently from the infec- tion seen in humans. In people, 80% will
W
e love to include our dogs in our outdoor activities,
develop a characteristic rash and/or flu-like symptoms after being bitten by an infected tick, and within weeks they may develop joint pain, neurologic abnormalities, and heart rhythm disturbances. Dogs, on the oth- er hand, develop symptoms weeks to months following the tick bite, with most dogs devel- oping signs of arthritis, possibly with fever. Heart and neurologic signs are rare. Clinical signs respond quickly to appropriate anti- biotic therapy. The most serious long-term complication is glomerular disease, a type of kidney damage that results from long-term exposure of the immune system to a latent infection, and which can cause dangerous protein loss through the kidneys. Diagnosis of Lyme disease is based on identification of antibodies to the organism (or parts of it) in the dog’s blood. There are now several types of rapid in-house tests that your veterinarian can perform on just a few drops of blood. It must be kept in mind, however, that antibodies may be detected in the majority of dogs in endemic areas, and this does not always indicate active illness, so test results must be interpreted in con-
junction with clinical signs and response to treatment. Treatment usually involves a 2-4 week course of an ap- propriate antibiotic (usually doxycycline or amoxicillin), and usually results in a no- ticeable improvement in most dogs, often within 48 hours. Eradication of the organism is not expected, as the spiro- chete hides in the body, but the goal is to prevent active infection. There are several vac-
cines against Lyme disease available to vet- erinarians, with varying degrees of efficacy and potential for vaccine reaction. The differ- ences are based on the fact that the spiro- chete produces different surface proteins at different stages. The risk versus the benefit of vaccination is something that should be discussed with your veterinarian. The decision on whether or not to vaccinate should be based on your dog’s lifestyle, risk of exposure, and other health concerns. There is a wide range of opinion within the veterinary community as to whether or not to vaccinate all dogs, so don’t be afraid to ask questions and do your own research. There is no one right answer for all dogs.
Seen less commonly, though with increasing frequency are Ehrlichia canis, and Anaplasma phagocytophilum (formerly known as Ehrlichia equi), bacteria that live in white blood cells. Ehrlichia canis infection may be acute, subclinical or chronic. In the acute phase dogs may be listless, have de- creased appetite, and enlarged lymph nodes or fever. The disease causes destruction of platelets (cells necessary for proper clotting of blood) and in its chronic form may cause abnormal bleeding, uveitis (an inflammation affecting the eyes), neurologic signs, and glo- merlonephritis (which can cause dangerous protein loss through the kidneys). Diagnosis may involve a blood test for antibodies, or other serological testing, and supportive lab findings such as decreased platelets, or ane- mia. As for Lyme disease, there is a quick, in- house blood test that your veterinarian can perform if Ehrlichiosis is suspected. Also like Lyme disease, treatment involves a course of appropriate antibiotic (usually doxycycline) but may also include prednisone or another
32 Natural Nutmeg May 2012
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