Rover was very sick. It took a few weeks, but we diagnosed a new tick borne disease in our area. We have seen an increasing amount of tick transmitted diseases in our area. The Rickettsial organisms are small, bacteria that require a host cell to live. In the order Rickettsiales, there are two families—Anaplasmataceae and Rickettsiaceae—that contain species that infect dogs.
All of these require one of a variety of ticks that act as a vector and then the bacteria cause clinical disease in humans, dogs, and other domestic animals. Perhaps our most commonly diagnosed rickettsial disease is Ehrlichiosis.
Rover was positive for Ehrlichia, but that didn’t help us much. (The signs didn’t match Ehrlichia.) It is easy to test for the genus of Ehrlichia, but the different species vary in their disease process. Canine ehrlichiosis from E. canis infection can cause a fever, muscle pain, enlarged spleen and lymph nodes and a decrease in platelet availability caused bleeding disorders. E. ewingii and E. chaffeensis are usually only lethargy, fever, shifting lameness, lymph node enlargement, peripheral edema, and thrombocytopenia, but E. Chaffeensis can progress to more severe neurologic abnormalities. Regardless of disease severity, all the Ehrlichia species cause disease that is usually long-term, especially if not treated early. Rover’s advanced tests were negative for the most dangerous E. canis, so Rover had one of the less likely to cause disease strands.
Lyme disease is our next most common rickettsial disease. The spiral-shaped bacterium is called Borrelia burgdorferi. The tiny deer ticks that carry Lyme disease are especially likely to be found in tall grasses, thick brush, marshes, and woods. A tick can transmit the disease once it has been attached to a dog for 24 to 48 hours. Unfortunately, Lyme disease is fairly common. Dogs can have a fever, loss of appetite, reduced energy, shifting, intermittent, and/ or recurring lameness with generalized stiffness, discomfort or pain, and swelling of the joints. This can progress to kidney failure and death or serious cardiac and neurological effects.
Anaplasmosis is another group of tick borne diseases. The severity of the disease depends on the species involved. A. phagocytophilum often causes a fever and lameness due to a neutrophilic polyarthritis. Like other tick-borne infections, lymph node and spleen enlargement are also possible. Many positive dogs remain clinically normal, but clinical signs may appear later in combination with another disease. A. platys causes a bacterial invasion and destruction of platelets in a waxing and waning thrombocytopenia and a bleeding disorder.
Rover was negative for Lyme and Anaplasmosis, two tick borne diseases that are common enough that we have an in hospital test for it. Rover’s CBC was very high and it did not respond to normal antibiotics. In fact on some of our best antibiotics, the white blood cell count continued to rise.
Rover had Rocky Mountain Spotted Fever (RMSF). Of the rickettsial diseases of dogs, RMSF, caused by Rickettsia rickettsia, is the most life threatening. Unlike Ehrlichia, Lyme and Anaplasmosis, RMSF must be sent off for a test. Although it is seen throughout the US, it is unusual in our area. The intracellular parasite (Rickettsia rickettsia) is transmitted to dogs through the bite of an infected Rocky Mountain wood tick, American dog tick, or brown dog tick. This tick has to be attached to your dog for more than 10 hours.
Two to 14 days later symptoms begin to occur. R. rickettsii infects vascular endothelial cells, which causes vasculitis that shows up as a variety of clinical signs depending on where the infection develops and how disseminated it is. Many of the symptoms of this disease are common to other conditions which can make diagnosis challenging. Please, let your veterinarian know if and when your dog may have been exposed to ticks. The symptoms can range from mild to severe and life-threatening. The more common signs include poor appetite, non-specific muscle and/or joint pain, lameness, abdominal pain, vomiting, diarrhea, facial or leg swelling, fever, lethargy, eye and/or nose discharge or nosebleeds, cough, enlarged lymph nodes and/or petechiae (tiny hemorrhages visible in the skin) and about 1/3 of infected dogs will experience symptoms related to the central nervous system such as spinal pain, lack of coordination, weakness, balance problems, or seizures.
Sometimes months or years later, dogs may begin to exhibit leg edema, lymph node and spleen enlargement and head or leg tremors. Late-stage disease signs commonly include necrosis of the extremities: ears, feet, scrotum, and lips. Neurologic abnormalities, muscle pain, polyarthritis, and other signs of multiorgan failure are indicative of more severe, disseminated infection and carry a worse prognosis. Early initiation of treatment is the key to preventing the progression of this disease.
Rover didn’t play by the rules. He had some of these signs, but also had a rash that was not petechiae. Rover was supposed to have a low platelet count, anemia, and abnormal white blood cell counts. Other diagnostic tests could have pointed to a diagnosis, but didn’t. I still started the right antibiotics.
The primary treatment for RMSF in dogs is specific antibiotics. Most dogs respond well to the antibiotic treatment, and can improve within 24 to 48 hours after starting treatment. The entire course of antibiotics must be given or a recrudescence of the infection can occur. That said, dogs suffering from a severe case of the disease may not respond to treatment at all. Some dogs need IV fluids, a blood transfusion, or corticosteroids to get through the severe, acute phase of disease. Corticosteroids help with damage caused by the vasculitis, but should be used with caution, as can cause a recrudescence of the latent rickettsial infections. For dogs that are diagnosed and treated for RMSF early, the prognosis is good with few complications. In fact, lifelong immunity will often occur after the infection has been cleared up.
Advanced RMSF that is not treated in the early stages, means a higher risk of severe complications such as kidney disease, neurological disease, vasculitis, and coagulopathies.
With a disease that is so hard to diagnose during the window for treatment, the best bet is prevention. We have extremely good tick preventatives that can be used now. Limiting exposure to areas of high ticks, particularly during peak tick months from March through October can also help. If your does is in areas known to have ticks, inspect them closely for any hitchhikers. The sooner the tick is removed the less ikely infection will occur. (Wear gloves or wash your hands to avoid your own infection.)
Rover seems to be okay, but I doubt his owners have any idea how hard I worked to save him and I still worry that it was not enough.