Ehrlichiosis, also known as canine typhus, is caused by the bacterial organism Ehrlichia canis. One of many tickborne diseases, ehrlichiosis is primarily a disease of dogs, although cats can be affected in rare instances.
The disease is spread from dog to dog by the bite of the brown dog tick, Rhipicephalus sanguineus. First reported in the United States in 1963, this disease is most prevalent in the midwestern and southern states. Left undetected, ehrlichiosis can be quite devastating and ultimately fatal to its host.
Once they gain entrance into the body, these parasitic bacteria set up housekeeping in various organ systems throughout the body within a week or two. As a result, clinical signs can be quite variable once they start to appear.
Acute signs of infection include general depression, weakness, fever, weight loss, eye and nose discharges, and swollen lymph nodes. As the disease progresses over time and the organisms colonize the bone marrow, dogs will often become anemic and immunosuppressed.
As a result, secondary pneumonia is a frequent finding in infected canines. Nosebleeds and bruising of the skin might also become apparent as the body’s blood clotting mechanisms are interfered with.
Finally, in severe instances, the kidneys and brain might become affected, leading to kidney failure and nervous system disorders. Noticeable drops in the total number of white blood cells, red blood cells, and platelets (structures that play a vital role in the body’s blood clotting mechanism) within an obtained blood sample are usually the first parameters that tip veterinarians off to a possible infection with Ehrlichia.
In fact, in many cases, the Ehrlichiaorganisms can be seen microscopically within the actual white blood cells themselves. Clinical signs related to a bleeding disorder or involving a high fever also provide clues leading to such a diagnosis.
Specific Ehrlichia antibody detection tests are also available through veterinarians, and can help confirm what is already suspected. Current treatment of ehrlichiosis in dogs employs high doses of special antibiotics until clinical signs go into remission.
Owing to the organism’s ability to hide within blood cells and bone marrow, ehrlichiosis is difficult to treat. The sooner treatment is instituted after the appearance of clinical signs, the better the chances are for a complete recovery.
Chronic long-term infections, however, might never clear up totally with antibiotic therapy. Drugs such as doxycycline and imidocarb dipropionate have shown some promise in many of these cases.
Continuous low-dose administration of antibiotics, combined with supportive therapy, including occasional blood transfusions, might be needed to keep these long-term infections controlled. To date, there is no vaccine available to protect against ehrlichiosis.
As a result, a good tick-control program is still the best way to prevent this disease.