Our second stop on the nasty tick disease tour is with Rocky Mountain Spotted Fever. Before Lyme, this was the scary tick disease everyone worried about in New England. That said, it wasn’t that common and was easily treated, even in people. Much like today, it tended to re-appear as small outbreaks in certain geographic areas, then decrease with no true pattern. So, as vets, we must always keep it in the back of our minds and stay vigilant regarding its clinical signs.
Like Lyme, this is caused by a bacteria (Rickettsia rickettsia). Unlike Lyme, this disease is carried and passed by American Dog Ticks. The tick must be attached for at least 2 hours before the bacteria can pass from an unfed tick. Once in the infected patient’s body, the bacteria immediately begin causing inflammation of the walls of the blood vessels leading to leakage of fluid into the surrounding tissue (vasculitis). This causes progressive damage to organs throughout the body. Between 2-10 days after infection, patients will begin acting sick. Humans usually start with a severe headache and fever. In dogs, the same fever happens, and they will begin showing lethargy and behavioral changes that are likely also associated with some head pain. Without treatment, this will progress to tissue swelling, skin sloughing, internal bleeding, and even death.
It can take up to 14 days before a test for Rocky Mountain Spotted Fever to show a positive result, so diagnosis is not always a formal one. Mostly, we look at the clinical signs and blood testing results indicative of vasculitis (signs of internal bleeding, organ damage, etc.). Treatment is the same as for most tick diseases where doxycycline antibiotic is used. Most dogs are better within 48 hours of treatment, but we usually treat for several weeks to ensure we clear the infection. Prognosis for dogs treated early is excellent with most developing lifelong immunity after this. For those with delayed treatment, many require hospitalization. Some of these patients can also have long-lasting issues related to kidney failure and neurologic damage.
There is no vaccine for this disease, so prevention is key. Since transmission can occur in under 2 hours, effective tick preventive products should be used. As topicals and collars have variable effectiveness based on lifestyle, the oral forms are still ideal. Discuss with you vet which products they prefer.