Rickettsial organisms are somewhat of a hybrid between viruses and bacteria. They generally must live and reproduce within the cells of another organism, like a virus, yet they contain some of their own metabolic enzymes as do bacteria. While this may seem like more information than most people need to know, it is important to understand that this is a separate life form unique to itself. Diseases caused by rickettsia always need a "third party" to transport the organism; they are not caught by direct contact.

Caused by the rickettsia Ehrlichia canis and rarely a few other subspecies, this disease is common in dogs in the Southwest United States as well as in other parts of the world. It is thought that the parasite may have been introduced to the US by dogs returning from Southeast Asia in the 60's and 70's. The organism is transmitted from dog to dog by ticks; most commonly the brown dog tick which itself is common in this part of the country. ((Ticks)) ((Nose Bleed from Ehrlichia))

The organism attacks blood cells and the bone marrow but may affect various other organs as time passes. Clinical signs are often vague and may mimic many other illnesses. Even dogs where an owner has never actually seen a tick can be infected as only one tick is all that is needed to pass on the disease. Two forms of the disease are recognized: an acute or quick onset form and a chronic form.

Dogs with the acute form will have a fever, possible enlargement of the lymph nodes, poor appetite and lethargy. In the chronic form of the disease, pets will have pale gums, weakness, weight loss, hemorrhages from the nose, mouth, genitals, digestive system and so forth and other organ dysfunctions including kidney failure, uveitis and encephalitis. Diagnosis is based on clinical signs, history of tick exposure (although not essential), blood counts and serum chemistries and a serologic test for the organism. ((Pale Gums))

For milder or early cases, tetracycline or doxycycline works well, but treatment must be continued for several weeks, and may need to be repeated until the disease is cured or under control. Repeated ehrlichia tests and blood counts are needed to monitor the progress of the treatment. Tick control is always important and vitamin supplements are often used to regenerate the blood.

Longer standing cases may be much more involved. The same basic treatment is utilized, but some dogs may loose so much blood or become so weak as to make fluid therapy and blood transfusions necessary. A few dogs have been known to develop immune-mediated hemolytic anemia, which greatly compounds the degree of treatment needed. Other drugs, known as anabolics, are sometimes employed to stimulate blood regeneration and appetite. Some dogs may never be able to fight the disease off but they can remain healthy with regular (every 4-6 months) rounds of antibiotics.

The blood parasite known as Hemobartonella canis can be transmitted to dogs by fleas and ticks, as well as from mother to pups and via blood transfusions. This disease actually is more common in cats than dogs and rarely makes a dog ill. A few weeks after this rickettsia enters the body, blood destruction can begin as the parasite multiples greatly in the blood stream. Clinical signs include fever, pale gums, lethargy, poor appetite and weight loss. Diagnosis is based on clinical signs, blood counts and serum chemistries, which includes identification of the parasite in the blood. This may not always possible.

Tetracycline type antibiotics usually work well if any treatment is needed. Cortisone type drugs and blood transfusions might be warranted in cases with severe hemolytic anemia which will sometimes occur secondary to the hemobartonellosis. Vitamins and anabolic drugs are also employed to help blood regeneration.

An interesting disease caused by the rickettsia Neorickettsia helminthoeca, dogs become infected by eating raw salmon that contain the fluke (worm) parasite Nanophyetus salmincola, which in turn harbors this rickettsia. This obviously can only occur where there are salmon, i.e., the Pacific Northwest. Once the salmon is digested, the fluke enters the digestive tract of the dog and releases the rickettsia.

Clinical signs will occur 5-10 days after eating the fish and may last for over a week. Dogs will exhibit a fever, depression, loss of appetite, vomiting and often-bloody diarrhea. Dogs will become dehydrated, loose weight, have enlarged lymph nodes and a discharge from the nose and eyes. Untreated, many dogs die. This disease can be confused with the symptoms of canine parvovirus. Diagnosis is based on history of eating a salmon, the clinical signs, blood counts, serum chemistries and fecal analysis. Aspirates taken from lymph nodes can be used to demonstrate the rickettsia.

Time is of the essence as the later treatment is begun, the less the chances are that the dog will survive. Dogs should be hospitalized and placed on IV fluids and electrolyte therapy, nutritional support and antibiotics. Survival is good if a quick response is given to dogs affected with this illness.

This is also a tick borne disease common through the United States more so in the Eastern United States. The organism Rickettsia rickettsii is transmitted to the dog via the bite of an infected tick. It then attacks the blood cells, liver, kidneys, nervous system and blood vessels. This condition is most commonly seen between April and September, corresponding to the time of year when ticks, too, are most active. Man also can become infected.

Clinical signs include fever, depression, dehydration, enlarged lymph nodes, loss of appetite, loss of weight, abdominal pain, small hemorrhages on the lips and gums, swelling to the limbs, muscle and joint pain, alterations in mental status and death. Diagnosis is based on the history, clinical signs, blood counts, serum chemistry, urinalysis, biopsy and a special IFA test for the organism. ((Ticks)) ((Petichia))

All dogs will need treatment with tetracycline type antibiotics, and more severe cases need to be hospitalized with fluid and electrolyte therapy. Control of any and all ticks is essential. Follow-up IFA testing and possible repeated blood tests is important to monitor the patient until remission.

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©2007 James W. Day D.V.M., P.C.