The disease monocytic ehrlichiosis in dogs often results from a rickettsia infection by Ehrlichia canis or by other kinds of Ehrlichia. Microorganisms called rickettsiae, though similar to bacteria, cannot live outside their host cells. Ticks are the carriers of this organism. When transmitted to dogs, these rickettsiae infect the WBC of a particular type, resulting in several symptoms, including fever. Another kind called, Ehrlichia ewingi infects granulocytes, which are a different type of WBC. This infection is seen not only in dogs but also in people living in Western and Southern areas of the US. A rickettsia named Anaplasma platys causes cyclic thrombocytopenia characterized by periodic lowering of platelets. It results in abnormalities in the clotting of blood.
Rickettsiae such as Anaplasma and Ehrlichia have a worldwide distribution. Different types of ticks such as the black-legged tick, lone star tick and the brown tick get infected with them when they suck the blood of animals that have this infection. The ticks harboring the microbes then transmit them to other dogs. People as well as domestic animals like cats can become carriers and transmit the disease to dogs.
The symptoms and duration of the rickettsia infection caused by Ehrlichia ewingi are determined by the strain that infects the dog as well as the immunity of the animal. It can be either short-term or prolonged. Fever accompanied by inflamed lymph nodes and low platelet count is the first symptom. The spleen may be enlarged. Lack of appetite and strength and listlessness, are other common symptoms. Stiffness and swelling of legs make the dog reluctant to walk. Respiratory symptoms such as breathing difficulties and cough may be present. Ticks being more active in summer, short-term type of disease occur during this season. The infected dog may get well soon enough without any treatment and may stop displaying the symptoms. Fatalities rarely occur during this period. However, in some dogs, the disease later develops into long-term type.
All breeds of dogs that are infected by Ehrlichia canis may be affected by long-term type of ehrlichiosis, but some breeds are more prone to it. German shepherd is an example. Long-term type of infection by Ehrlichia canis may develop anytime, irrespective of the season. Depending on the organs that are affected by the disease, symptoms vary. Kidney failure or inflammation of various vital organs such as lungs, spinal cord and brain may occur. Spleen may be enlarged. Eyes may be affected too. The dog may lose weight considerably. Loss of coordination, partial paralysis and excessive sensitivity to pain may result if the disease affects the nervous system.
Anaplasma platys infection is not as symptomatic even when the platelets contain this organism. Infections by other rickettsiae result in symptoms like that of short-term type of disease caused by Ehrlichia canis, and are self-limiting in most cases. Fever followed by lameness is the usual symptom. The lameness in one leg may change to the other leg. Infections by other types of Ehrlichia do not usually cause long-term type ehrlichiosis.
Antibiotic therapy is the main treatment for all types of rickettsia infections. The veterinarian may prescribe the medication for 10-21 days. The fever may subside within a day or two of starting the treatment. The abnormalities in the blood may continue for up to six months in dogs having the long-term type of the disease. Other symptoms get resolved much earlier. If severe blood loss has occurred due to low platelet count, blood transfusion or platelet transfusion may be necessary. The dog may require supportive treatments and good nursing care too.
Since ticks are the usual carriers of this disease, controlling them is the best preventive measure. Areas that have high chance of harboring ticks should be avoided. Medications that prevent tick infestation in dogs also can be used. Prompt removal of the ticks from the dog’s body may go a long way in preventing disease transmission.
When plucking the ticks off the dog’s body, the tick’s head should be grasped tight with pointed tweezers and pulled straight back without squeezing the body. If the dog has severe infestation, get the help of the vet to remove them.