What Is Rocky Mountain Spotted Fever in Dogs?
Rocky Mountain Spotted Fever (RMSF) in dogs is a tick-borne illness caused by the bacterium Rickettsia rickettsii. This bacterium, which can only survive within cells, enters the bloodstream through tick bites and infects the cells lining blood vessels, leading to inflammation and affecting various organs. RMSF commonly impacts both dogs and humans.
Initially identified in 1896 in Snake River Valley, Idaho, RMSF earned its name due to the distinctive rash it causes in humans. This rash typically starts as small red spots and spreads from the wrists and ankles to the arms and legs. In advanced stages, the skin around the rash may turn black, hence the term “black measles.”
Geographically, RMSF has been reported across North, South, and Central America. In the United States, it has been documented in every state except Vermont and Alaska, with higher prevalence in states like North Carolina, Tennessee, Oklahoma, Arkansas, and Missouri. RMSF is particularly prevalent in dogs during tick season, with diagnoses peaking between April and October.
Symptoms and Types
Symptoms of Rocky Mountain Spotted Fever (RMSF) in dogs typically manifest within 2 to 14 days after a tick bite. These signs are often nonspecific and can include:
- Fever (up to 105°F)
- Lethargy
- Loss of appetite/weight loss
- Muscle or joint pain, swelling of joints, lameness
- Swollen lymph nodes
- Swelling in the legs (peripheral edema)
- Red spots (petechiae) or bruising (ecchymosis) on the skin or mucous membranes
- Coughing
- Vomiting/diarrhea.
Causes
The primary cause of Rocky Mountain Spotted Fever (RMSF) in dogs is typically through tick bites, commonly by the Rocky Mountain wood tick (Dermacentor andersoni), the American dog tick (Dermacentor variabilis), and the brown dog tick (Rhipicephalus sanguineus).
It’s important to note that dogs cannot transmit RMSF to other dogs or humans. However, transmission can occur through a tick bite, which usually requires 5 to 20 hours of attachment, ingestion of an infected tick, or direct contamination of a wound by tick feces.
Swift removal of ticks is crucial to prevent RMSF. When removing ticks, humans should wear gloves not only for cleanliness but also for protection, especially if there are cuts on the hands. Failure to wear gloves can lead to potential infection from tick feces or blood/fluids during the removal process.
Diagnosis
To diagnose Rocky Mountain Spotted Fever (RMSF) in dogs, veterinarians typically begin with a thorough physical examination to check for signs such as fever, joint swelling, or enlarged lymph nodes. It’s important to provide information about recent travel or tick exposure.
As part of the diagnostic process, a veterinarian will likely recommend a complete blood count, serum blood chemistry, and urinalysis to establish a baseline evaluation of the dog’s health.
If RMSF or another tick-borne illness is suspected, specialized laboratory testing may be recommended. This can include antibody titers to detect immune response (antibodies) to the bacterium Rickettsia rickettsii. Another option is polymerase chain reaction (PCR) testing to identify the presence of Rickettsia rickettsii bacteria. PCR testing may be performed as part of a tick PCR panel designed to detect multiple tick-borne diseases.
Treatment
Timely antibiotic treatment plays a critical role in effectively managing Rocky Mountain Spotted Fever (RMSF) in dogs. Veterinarians typically initiate antibiotics promptly, even before confirmatory tests are available, as any delay in treatment can exacerbate the disease and its prognosis.
Depending on the severity of the illness, dogs may require hospitalization for intravenous (IV) fluids to address dehydration and to commence supportive care, which may include appetite stimulants or pain relievers. Antibiotics are essential for eliminating the bacteria responsible for RMSF. The veterinarian will select the most appropriate antibiotic for your pet, with Doxycycline being a commonly prescribed option.
Recovery and Management
Rocky Mountain Spotted Fever (RMSF) can be fatal for dogs if treatment is delayed, with approximately 1-10% of infected dogs experiencing a fatal outcome. However, the majority of dogs can recover and thrive with early antibiotic therapy and supportive measures.
While some dogs may be managed as outpatients, many will necessitate hospitalization, typically involving two to three days of intravenous (IV) fluids, supportive care, and antibiotics. Discharge usually occurs once the dog’s fever subsides, and they consistently resume eating and drinking on their own.
RMSF is not transmissible from dog to dog. However, if multiple pets were exposed to the same area with ticks, it’s advisable to consult with a veterinarian regarding testing and potentially treating all dogs in the household.
Moreover, although RMSF is not zoonotic (transmissible between animals and humans) through dog-to-human transmission, humans can contract RMSF from tick bites or from tick feces/bodily fluids while removing a tick. If there’s suspicion of exposure to RMSF, prompt medical attention should be sought.
Prevention
Preventing Rocky Mountain Spotted Fever (RMSF) in dogs primarily involves mitigating tick exposure. Monthly flea and tick prevention is strongly advised since ticks are the primary carriers of the infection. Both topical and oral flea/tick prevention options are available, and it’s recommended to consult your veterinarian to determine the most suitable choice for your pet. Additionally, it’s advisable to keep pets away from dense brush or wooded areas where ticks tend to reside. As there is no RMSF vaccine available, tick protection remains the most effective prevention method.
Regularly inspecting your dog for ticks after outdoor activities, especially during the months of April through October when ticks are more prevalent, is essential. Swift tick removal reduces the risk of disease transmission. When removing ticks, wearing latex gloves is recommended, and ensuring the entire head/mouthparts are removed is crucial. Tick removal tools can facilitate this process, or you can seek assistance from your veterinarian or a technician for proper tick removal techniques.
Rocky Mountain Spotted Fever in Dogs FAQs
What are the symptoms of Rocky Mountain Spotted Fever in dogs?
Dogs may not develop the classic rash seen in humans. Instead, symptoms often include fever, lethargy, loss of appetite, joint swelling/pain, and enlarged lymph nodes.
Is Rocky Mountain Spotted Fever in dogs treatable?
Yes, early antibiotic therapy can effectively treat RMSF in dogs, often resulting in immunity after successful treatment.
How long does Rocky Mountain Spotted Fever last in dogs?
Most dogs show improvement within 24 to 48 hours of starting antibiotic therapy. Severe cases may require hospitalization for supportive care, including IV fluids, appetite stimulants, pain medications, along with antibiotics.
Can Rocky Mountain Spotted Fever be fatal to dogs?
Untreated RMSF can be fatal to dogs, but the prognosis is generally favorable with prompt antibiotic therapy.
How common is Rocky Mountain Spotted Fever?
While RMSF is the most prevalent rickettsial disease in both dogs and humans in the United States, it is still considered relatively rare.