Can Dogs Get Rocky Mountain Spotted Fever from Humans?

Rocky Mountain spotted fever is a disease transmitted through tick bites to humans, dogs, and other animals. The disease is caused by an organism called Rickettsia rickettsii, which can only survive when it is in a host cell. This is a unique organism that it is not exactly a virus or a bacteria, but is something in between. The infectious organisms have been noted in North, South and Central America.

How do ticks get the disease? Infected ticks can get the disease from biting an infected animal and can have it passed on during mating or through their “tick mom”, who passes it to them when she produces eggs. So, can dogs get the disease from humans?

Can Dogs Get Rocky Mountain Spotted Fever from Humans?

Not directly, but perhaps indirectly. The disease is generally not transferable from dog to dog, human to dog, or dog to human. There is a slim chance that direct exposure to body fluids or tissues introduced into an open wound on another animal could transmit the disease, although this possibility is extremely low. However, if a tick bites an infected human, and then bites a dog, or passes it to their offspring who then bite the dog, the disease can be indirectly transmitted.

What is more common, is that infected ticks in an area will bite both pet owner and dog, resulting in both becoming ill from the disease being transmitted by multiple tick bites, not by being transmitted from one to the other by the same tick. So, do you need to worry about getting or giving Rocky Mountain Spotted Fever to or from your dog? No, but you do need to worry that if they were exposed to infected tick bites, you may have been too, and vice versa.

Does My Dog Have Rocky Mountain Spotted Fever?

R. rickettsii, which causes Rocky Mountain spotted fever, (RMSF), is transmitted through tick bites. Several different types of ticks in a variety of locations throughout America carry the disease. The highest prevalence is during tick season, which occurs from April to September.

There are two stages of RMSF, a subclinical and an acute stage. The subclinical stage occurs after the dog is bitten by an infected tick, but they do not show symptoms of the disease, abnormal laboratory results may reveal infection.

There is also an acute stage when symptoms appear. Symptoms are generalized and it can be difficult to distinguish them from other diseases. Symptoms include:

• Loss of appetite

• Fever

• Swollen lymph nodes

• Pain in muscles and joints

• Fluid accumulation in the face and legs

• Pneumonia

• Heart arrhythmia

• Sometimes vomiting and diarrhea

• Neurological symptoms such as depression, dizziness, stupor, seizures

• Hemorrhagic disorder, blood in the eye, stool or nose bleeds

• Kidney and liver disorder or failure
  
  

Symptoms usually occur within 2 to 14 days of being bitten by an infected tick. 

Several ticks including the American dog tick, the wood tick, the Rocky Mountain spotted fever tick, and the brown dog tick transmit the disease when they bite you or your dog and introduce the R. rickettsii into the bloodstream. In order to do this, the tick must feed on its host for 5 to 20 hours, so quick removal of ticks may prevent infection. Dogs are especially prone to tick bites when they run in tall grass and wooded areas. Ticks acquire the disease from biting an infected animal, from mating, or it can be transmitted from the female to her offspring. Not all ticks carry the disease, it is estimated that 3% to 5% of ticks in the US are infected.

If a dog develops symptoms and has had exposure to ticks or tick bites, a veterinarian can diagnose RMSF with a variety of blood tests. Some blood tests analyze the dog’s antibodies that fight infection, while others look for changes in blood chemistry indicating infectious disease. A tissue biopsy at the site of the tick bite can also be conducted to detect the presence of antigens, parts of the infecting organism present. The presence of a tick bite followed by symptoms is a good indicator of RMSF disease, however, since the disease looks very similar to a variety of other diseases, the presence of another cause needs to be ruled out. Tests to confirm RMSF may take several days or weeks, so treatment should be started prior to obtaining results if RMSF is suspected.

For more information, visit Rocky Mountain Spotted Fever in Dogs and Rickettsial Infection in Dogs.

How Do I Treat My Dog’s Rocky Mountain Spotted Fever?

At the subclinical stage, treated dogs usually recover uneventfully. However, the earlier treatment is received for dogs experiencing symptoms the better the recovery rate. Dogs experiencing RMSF are treated with antibiotics such as doxycycline, tetracycline or enrofloxacin. Antibiotics will need to be administered for 2 to 3 weeks. In addition, dogs that require supportive care such as intravenous fluids for dehydration, anticonvulsant or anti-seizure medication, or supportive care for shock may require hospitalization.

Antibiotics are usually successful in resolving the condition, if the dog receives treatment in the first several days of the disease. However, if the disease has progressed, causing organ and neurological damage, or if multiple tick bites are present overwhelming your dog's immune system, prognosis is more guarded.

Repelling ticks with commercial products and restricting your dog's movements in wooded areas with lots of underbrush during tick season will help reduce the chance they will be exposed to an infected tick. Also, controlling rodents that may harbor ticks can be helpful in reducing risk. Remove ticks from your dog as soon as possible, wearing protective gloves, as there is a possibility you could become infected from exposure to body fluids from the tick.

How is Rocky Mountain Spotted Fever Similar in Dogs, Humans and Other Animals?

Dogs, humans and other animals can all contract Rocky Mountain Spotted Fever.

• The disease is transmitted from tick bites, humans and dogs may get tick bites in the same area from infected ticks and both manifest disease

• Generalized flu-like symptoms are characteristic of the disease

• Antibiotics can usually successfully cure the disease if administered in a timely fashion

How is Rocky Mountain Spotted Fever Different in Dogs, Humans, and Other Animals?

Although very similar in nature, there are some differences in RMSF between species.

• The disease is usually mild in cats

• Humans are more prone to getting a rash

• Dogs are especially prone to acquiring tick bites due to their propensity for romping in wooded areas, and because they are low to the ground

Case Study

A Labrador Retriever and his owner are having a great hike in a heavily wooded area on a beautiful June afternoon while on vacation. The Lab is having a wonderful time romping through the bush, fetching sticks, and getting covered in mud, debris, and, unfortunately, a tick. Even more unfortunately, the tick, buried in the heavy hair behind the dog's upper leg, goes unnoticed by the owner and has a chance to get a good blood meal and pass on the Rickettsia organism it is harboring to the dog. Due to the stress of traveling and an irregular schedule, the dog’s immune system is somewhat compromised, and that combined with the undiscovered and untreated tick bite results in a Rocky Mountain spotted fever infection. The Lab becomes sick about a week after the woodland hike, exhibiting lethargy, fever, pain, and swollen lymph nodes.

A visit to a vet, who does a thorough evaluation of the dog including taking a history of the dog’s recent activities, discovers the canine was recently on vacation and hiking in wooded area where ticks are prevalent. A tick bite is suspected, although no sign of the bite can be discovered. The veterinarian takes a blood sample, and starts treatment with doxycycline. Within a day the Lab has perked up! Treatment is continued for a couple of weeks, by which time laboratory tests confirm the presence of the Rickettsia organism. Because the pooch received quick veterinarian attention and the vet was able to connect the possibility of an infected tick bite with the dog's illness, early treatment allowed the dog to make a complete recovery.