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Rocky Mountain Spotted Fever in Pets

Although it is not as well-known as מחלת ליים, Rocky Mountain Spotted Fever (RMSF) is one of the most common tick-borne diseases in the USA. It has now also become a risk to pets in Canada, Mexico, and South America.

Once contracted, RMSF can be deadly without early intervention, but by knowing the risks, symptoms, and methods of prevention, you can help protect your pet from serious consequences.

What is Rocky Mountain Spotted Fever

This infectious disease is caused by the Rickettsia rickettsia bacterium, which is usually spread by feeding ticks. Once the bacterium is transmitted to the body is spreads through the bloodstream or lymph nodes, causing inflammation and damage in the blood vessels. Clinical signs of the disease usually develop within 2-15 days after the initial infection. If left untreated, Rocky Mountain Spotted Fever can cause irreparable damage to the nervous system or even death.

Cats are not natural hosts for Rocky Mountains Spotted Fever, but it is not unheard of for them to contract it. Owners should be aware of the risks and symptoms, particularly if they have an outdoor cat in areas where ticks are prevalent.

Risk factors

Don’t let the name fool you, RMSF is not restricted to the areas around the Rocky Mountains. The disease is a risk throughout the USA as well as in Canada, Mexico and some parts of South America. Rocky Mountain Spotted Fever is usually carried by the American dog tick (Dermacentorvariabilis), but may also be spread by the brown dog tick (Rhipicephalus sanguineus) and the Rocky Mountain wood tick (Dermacentorandersoni). Wherever these ticks are present, there is some risk of contracting RMSF.

Ticks generally inhabit wooded or grassy areas. They particularly like to live in the grass and shrubs along the side of trails where they can easily attach to hosts that walk past. City dogs are still at risk of coming into contact with ticks as shrubs and even medium length grass can provide a welcoming habitat. Some ticks do not survive well indoors, but the brown dog tick is often found in kennels or in the home, even creating infestations behind baseboards, moldings and in furniture.

Protecting your pet

Unfortunately, there is no preventative medication that can stop your pet from contracting Rocky Mountain Spotted Fever; the only way to prevent RMSF is to protect your pet from tick bites.

Regardless of the disease, you are trying to avoid, the advice for preventing tick bites is the same. Carefully check your dog for ticks each time you return from a walk. A tick only needs to be attached to your pet for as few as 5 hours to transmit the Rickettsia bacterium, so prompt removal of the tick is vital. Around the home, be sure to keep grass trimmed and clean up leaf litter.

The most effective way to prevent tick bites is with the use of a medicated tick product. Collars such as Seresto provide protection for up to 8 months but are not suitable for dogs who swim a lot. Monthly medicated options include topical or spot-on solutions including Frontline Plus or oral medications like Bravecto.

Symptoms of Rocky Mountain Spotted Fever

The symptoms of RMSF are variable and non-specific, which can make identifying the disease difficult for owners. Some dogs, including German shepherds and purebred dogs, are more likely to develop serious symptoms.

Some of the most common symptoms are:

High fever– this is one of the first symptoms a pet may display, usually within four days of initial infection.

תַרְדֵמָה – be aware of a change in energy levels in your pet. Normally energetic dogs may become reluctant to go on walks or play.

Loss of appetite/weight loss– Changes in an animal’s eating habits can be caused by many things, but a loss of appetite may be a symptom of RMSF.

Stiffness/lameness – slow movement, difficulty getting up or problems using the stairs may be an indication that your pet is suffering from joint or muscle pain, which are symptoms of the infection. You may also notice that the area around the joints is swollen and painful to the touch.

Bruising– as the infection develops, damage to the blood vessels often presents as bruising, most easily detected in the mucous membranes and around the genitals.

Bleeding – the damage to blood vessels may result in abnormal bleeding, such as nose bleeds and in the tissue around the eyes and mouth. You may also see signs of internal bleeding via blood in your pet’s urine or stools.

Swelling (edema)– a buildup of fluid will result in areas of the body becoming swollen or puffy. Edema usually occurs in the limbs, lips, and eyes, and may sensitive to the touch. Pets may also develop swollen lymph nodes.


Even if your pet exhibits the signs above, it is important that you visit your vet to confirm the diagnosis and rule out any other causes. Your vet will ask you about your dog’s full medical history and recent symptoms.

An initial diagnosis will be based on the symptoms and basic blood work, which will show your vet if an infection is present. A test to confirm the presence of Rocky Mountain Spotted Fever can be conducted in a laboratory, but the results take some time – the initial diagnosis will usually be enough for your vet to start treatment.

Treatment and prognosis

The prognosis for Rocky Mountain Spotted Fever is excellent if detected and treated early. Treatment for the infection itself consists of a course of antibiotics, usually Doxycycline, which is most effective when started within five days of the initial symptoms.

Your pet may also require treatment for the specific symptoms caused by the infection, such as corticosteroids for inflammation and iron supplements for anemia. Hospitalization may be necessary for animals that are refusing to eat, showing signs of organ failure, or in cases of edema where the vet needs to monitor fluid levels. If the damage to the blood vessels has caused severe anemia, a blood transfusion may be necessary.

Rocky Mountain Spotted Fever in humans

Humans are also at risk of contracting RMSF from infected ticks, and the consequences can be deadly if left untreated. Wear protective clothing when spending time in wooded or grassy areas, and check yourself for ticks afterward. There have also been cases of humans contracting RMSF from a tick’s body fluids when removing the tick from their pet. For this reason, it is important to wear gloves when removing and disposing of ticks.

Rocky Mountain Spotted Fever FAQs

Is there a vaccine for RMSF?
At this stage, there is no vaccine that will prevent your dog or cat from being infected with the disease. The only measure you can take is to prevent them from being bitten by ticks.

Can cats get RMSF?
Although cases are rare, cats can become infected with Rocky Mountain Spotted Fever.

Is RMSF contagious?
Rocky Mountain Spotted Fever is not directly contagious, meaning it cannot be transferred from dog to dog, or from dog to human. However, it is important to be aware that if a tick feeds on an infected pet, the tick can then transfer the infection to another animal or to you.

Rocky Mountain Spotted Fever

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