Rocky Mountain Spotted Fever in Dogs
Rocky Mountain Spotted Fever continued...
Treatment: Tetracycline and its derivative, doxycycline, are the antibiotics of choice. Enrofloxacin is also effective.
Antibiotics should be started as soon as Rocky Mountain spotted fever is
suspected, even if the diagnosis is not confirmed. Mortality is high if
treatment is delayed. Furthermore, dogs with Rocky Mountain spotted fever
respond dramatically in one to two days, which confirms the presumptive
diagnosis. Antibiotics are continued for two to three weeks. Supportive
treatment is the same as that described for Canine Ehrlichiosis.
Canine Ehrlichiosis and Anaplasmosis
This is a relatively common rickettsial disease caused by the organisms E.
canis and E. ewingii, although several other rickettsia are capable of causing
ehrlichiosis. The disease is transmitted by the bite of the brown dog tick and,
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.