Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

88 •DOG OWNER’S HOME VETERINARY HANDBOOK
occasionally, other tick species. Ehrlichiosis occurs mainly in the Gulf Coast
area, the eastern seaboard, the Midwest, and California. Outside the United
States it is distributed worldwide. Some of the Ehrlichia species have been
renamed and are now listed in scientific literature as Anaplasma platys.
Ticks acquire the rickettsia by feeding on an infected host. A variety of
wild and domestic animals serve as reservoirs. Because of its chronic nature,
cases of ehrlichiosis are seen year-round, not just during the tick season.
The disease occurs in three phases. During the acute phase, the dog develops
fever, depression, loss of appetite, shortness of breath, enlarged lymph
nodes, and, occasionally, signs of encephalitis. These symptoms may suggest
Rocky Mountain spotted fever, Lyme disease, or canine distemper.
Two to four weeks after the onset of the acute phase, the dog enters a subclinical
phase that lasts weeks to months. Some dogs eliminate the infection
during the subclinical phase; others progress to the chronic phase. There
appears to be a breed disposition for developing chronic ehrlichiosis; German
Shepherd Dogs and Doberman Pinschers, for example, are at increased risk.
During the chronic phase, which appears one to four months after the tick
bite, the disease attacks the dog’s bone marrow and immune system, producing
weight loss, fever, anemia, a hemorrhagic syndrome with spontaneous
bleeding and nose bleeds, swelling of the limbs, and various neurological
signs. These signs may suggest leukemia. Infections of E. ewingii usually show
arthritis as well.
A serologic blood test (IFA) is sensitive for E. canis. However, the test may
not be positive until two to three weeks after the tick bite. A new ELISA test
has been developed that checks for Lyme disease, ehrlichiosis, anaplasmosis,
and heartworm.
Treatment: Tetracycline and doxycycline are highly effective against rickettsiae,
and should be given for at least one month. Improvement in the acute
phase begins within one to two days. Supportive treatment involves intravenous
fluids and blood transfusions. The outlook for recovery is excellent if
treatment is started before the dog develops bone marrow suppression.
Prevention: Tick control is the mainstay of prevention (see Ticks, page
123). Ticks do not infect dogs until they have been attached for 5 to 20 hours.
Therefore, examining pets who have been roaming in tick-infested areas, and
promptly removing ticks, can prevent many infections.
Dogs living in areas where the disease is endemic can be protected by giving
a low dose of oral tetracycline (1.3 mg per pound or .45 kg of body weight)
or doxycycline (0.45 to 0.90 mg per pound or .45 kg of body weight) every 24
hours. However, this is rarely necessary.
Using Frontline or Advantix to control fleas also kill ticks for up to 30 days
following a single application. Collars containing amitraz are also effective in
controlling ticks.