Rocky Mountain Spotted Fever

Condition Overview

Rocky Mountain spotted fever is a rickettsial disease caused by Rickettsia rickettsii and transmitted by several species of ticks. It is the most significant rickettsial disease in humans.

Symptoms

Signs of acute infection appear during the tick season and include listlessness, depression, high fever, loss of appetite, cough conjunctivitis, difficult breathing, swelling of the legs, and joint and muscle pains. Ocular signs such as uveitis may be present. Rarely, a rash will be noticed around the area of the tick bite.

These symptoms suggest canine ehrlichiosis, Lyme disease, or distemper. Central nervous system signs include unstable gait, altered mental state, and seizures. Inflammation of the heart muscle (myocarditis) can cause cardiac arrhythmias, resulting in sudden death.

1-2 weeks after the onset of the illness, some dogs develop a hemorrhagic syndrome similar to that seen with canine ehrlichiosis. Various bleeding problems, such as nose bleeds, subcutaneous hemorrhaging, and blood in the urine and stools may develop. This can cause shock, multiple organ failure, and death.

All symptoms +

Causes

Adult ticks transmit the disease to dogs when they attach and feed.

Diagnosis

Rocky Mountain spotted fever should be suspected in a sick dog with a history of tick infestation during April through September. Serologic diagnosis is best achieved by noticing a rise in micro-IFA antibody titer in paired serum tests - done at the time of illness and 2-3 weeks later.

Treatment

Tetracycline and its derivative, doxyxyxline, are the antibiotics of choice. Enrofloxacin is also effective. Antibiotics should be started as soon as Rocky Mountain spotted fever is suspected, even if the diagnosis is not confirmed. Mortality is high if treatment is delayed. Furthermore, dogs with Rocky Mountain spotted fever respond dramatically in 1-2 days, which confirms the presumptive diagnosis. Antibiotics are continued for 2-3 weeks.

Supportive treatment involves intravenous fluids and blood transfusions.

Prevention

Tick control is the mainstay of prevention. Keep grass and weeds trimmed below ankle height, as ticks will position themselves off the ground on vegetation. Remove brushy cover and rock piles, secure trash can lids, relocate wood piles and bird feeders away from the home. These steps will reduce the instance of tick carrying rodents being attracted to your property. Stick to trails while on hikes and avoid the longer grasses where ticks tend to hide.

Ticks must attach themselves for 5-20 hours before they are capable of transmitting infection. Accordingly, a daily inspection with removal of ticks will prevent many dogs from being infected. Ticks like being warm and protected, so pay special attention to the areas under your pet's legs and in or around the ears.

Treating a yard with tick control agents will help reduce the occurrence of ticks. Frontline Plus, Advantix, and Advantage all help to control flea and tick infestations.

Support

Please contact your veterinarian if you suspect your pet may be infected with this condition.