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, ocassionally other tick species.
The disease occurs in 3 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.
2-4 weeks after the onset of the acute phase, the dog enters a sub-clinical phase that lasts weeks to months. Some dogs eliminate the infection during the sub-clinical phase, while others progress to the chronic phase.
There appears to be a breed disposition for developing chronic ehrlichiosis. German Shepards and Doberman Pinschers are at increased risk.
During the chronic phase, which appears 1-4 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.
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 and not just during tick season.
A serologic blood test (IFA) is sensitive for E canis. However, the test may not be positive ntil 2-3 weeks after the tick bite. A new ELISA test has been developed that checks for Lyme disease, ehrlishiosis, anaplasmosis, and heartworm.
Tetracycline and doxycycline are highly effective against rickettsiae, and should be given fr at least 1 month. Improvement in the acute phase begins within 1-2 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.
Tick control is the mainstay of prevention. Keep grass and weeds trimmed below ankle height, as ticks will position themselves off the ground on vegetation. Remove brushy cover and rock piles, secure trash can lids, relocate wood piles and bird feeders away from the home. These steps will reduce the instance of tick carrying rodents being attracted to your property. Stick to trails while on hikes and avoid the longer grasses where ticks tend to hide.
Ticks must attach themselves for 5-20 hours before they are capable of transmitting infection. Accordingly, a daily inspection with removal of ticks will prevent many dogs from being infected. Ticks like being warm and protected, so pay special attention to the areas under your pet's legs and in or around the ears.
Treating a yard with tick control agents will help reduce the occurrence of ticks. Frontline Plus, Advantix, and Advantage all help to control flea and tick infestations.
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 .45kg of body weight) or doxycycline (0.45 to 0.90 mg per pound or .45kg of body weight)every 24 hours. This is rarely necessary.
Please contact your veterinarian if you suspect your pet may be infected with this disease.
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