Rocky Mountain Spotted Fever

 

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Original Editors - David Grinnell from Bellarmine University's Pathophysiology of Complex Patient Problems project.

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Definition/Description

 Rocky Mountain Spotted Fever (RMSF) is a tick born disease, due to an intracellular pathogen known as Rickettsia rickettsi (JEADV)¹.  This pathogen is carried by ticks and is transmitted to humans via a bite from an infected tick.  Three known ticks in the United States carry this pathogen: the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni) and the brown dog tick (Rhipicephalus sanguineous).  The American dog tick carries the pathogen in the western United States, and the wood tick carries the pathogen in the eastern United States.  (Medline reference)².  This infection was first described in the Rocky Mountains in Idaho in 1896. Howard Ricketts found the causative agent in the early 1900’s. (JEADV)¹.  This systemic infectious disease is treatable, however, if left untreated can be fatal.

Prevalence

United States

Between 1993 and 1996, there were 1253 reported cases of Rocky Mountain Spotted Fever.  This amount of confirmed incidence is roughly 2.2 cases per million. (JEADV). Since that time period there has been some increase in confirmed cases.  In 2008, the number of cases has jumped to approximately 8 per million.  However, the number of fatalities has decreased and currently is about 0.5%. ³

Even though the disease is known as Rocky Mountain Spotted Fever, it is more commonly found in the eastern United States. Georgia, Maryland, North Carolina, Oklahoma, South Carolina, Tennessee, and Virginia are among the states that have confirmed the largest number of cases.⁴

Worldwide

Other cases of RMSF have been confirmed in Canada, Mexico, Central America, Columbia, as well as Brazil.  Currently, there haven’t been any confirmed cases of RMSF beyond the boarders of the American continents.³

Characteristics/Clinical Presentation

The R. ricketttsii pathogen can have numerous systemic manifestations affecting the: cardiac, pulmonary, gastrointestinal, renal, neurological, ocular, musclecoskeletal, and integumentary systems. If infected the individual may face moderate to severe illness.  The initial symptoms usually will begin 2-14 days after being bitten by an infected tick.

Initial symptoms include

• high fever - reaching temperatures to 102 degrees Fahrenheit (38.9 degrees Celsius) or greater
• chills
• severe headache
• nausea
• vomitting
• fatigue
• loss of appetite
• abdominal pain - may present as appendicitis
• conjunctival infection

Additional signs and symptoms that may develop include the following:

• a red-spotted rash that spreads to a majority of the body -this rash occurs in approximately 90% of those infected with RMSF and usually 2-5 days after the fever has been present
• restlessness
• diarrhea
• aches & pains
• delirium

After completing a thorough examination, a patient's laboratory workup may show the following results:

• usually normal periphearl WBC count
• thrombocytopenia
• elevated aminotransferase levels
• hyponatremia
• anemia
• ielevated bilirubin level
• elevated level of creatine kinase
• elevated CSF and WBC count with monocyte predominance
• serological tests negative until convalescence

Associated Co-morbidities

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Medications

Doxycycline is the standard medication prescribed when physicians are suspicious of RMSF (CDC).  Adults are prescribed to take 200mg by mouth or IV two times per day. Children who weigh less than 100lbs are to take 2mg/lb by mouth and those children who weigh above 100lbs are suggested to take the same dosage as an adult, 200mg by mouth or IV, two times per day. (emedicine article). Medical treatment should be continued for a minimum of 3 days after one's fever had decreased. Typically, medical treatment of this disease will last anywhere from 7-14 days in length. (CDC article)

If an allergy to doxycycline exists, there are other forms of treatment that exist. Chlorampenicol is another antibiotic that may be prescribed, however, this medication has some adversve side effects such as: aplastic anemeia and grey baby syndrome (CDC article). General spectrum antibiotics have not been found to be effective against RMSF and sulfa drugs may actually worsen the infection.

Tetracyclines have been found to increase hypthrombiemic effects of anticoagulants, and they have also been found to decrease the effectiveness of common oral contratceptives (e medicine article)

Diagnostic Tests/Lab Tests/Lab Values

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Etiology/Causes

RMSF is a possibly fatal tick-bourn illness. Three known ticks in the United States carry the pathogen R. rickettsii: the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni) and the brown dog tick (Rhipicephalus sanguineous). The American dog tick primarily carries the pathogen in the United States, primarily in the western United States.  The Rocky Mountain wood tick primarily carries the pathogen in the eastern United States and the brown dog tick is thought to be the vector for the pathogen in Mexico. In addition, there are other tick species that are thought to carry the pathogen. In Central and South America, the Cayenne tick is thought to be the vector for the pathogen.

Rrickettsii is transmitted to humans via a bite of an infected tick.  The tick bites do not cause pain, and many don't know they were exposed to the ticks.  The transmission process can be completed in as little as 4 hours extending up to 24 hours. Most cases of RMSF occur between the months of April and September and usually occur in rual settings, however, they are not confined to just the rual community.

R rickettsii

Kingdom	Bacteria
Phylum	Proteobacterai
Class	Alphaproeobacteria
Order	Rickettsiales
Family	Rickettsiaceae
Genus	Rickettsia
Species	Rickettsia rickettsii

Currently, there is no vaccine that will protect against RMSF. With precaution one can prevent the transmission of the disease by following these general recommendations:

• avoid habitats where ticks thrive - wooded, grassy areas, stream banks and trails
• take protective measure to limit tick exposure - wear light-colored long sleeves and pants, and tuck pant legs into your socks, wear insect repellents that contain DEET
• frequently examine yourself in you are in suspected tick infested areas

If an attached tick is found, it is important to remove it as quickly as possible. Health professionals recommened that protective gloves be worn during this process. It is best to remove the tick via tweezers as close to the skin as possible and carefully pull it out. Take precaution to not squeez  or twish the tweezers upon removal. As soon as possible, disinfect the wound area as well as your hands. It is not advised to burn ticks out or topical application of petroleum jelly.

Systemic Involvement

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Medical Management (current best evidence)

Please see above section entitled "medication."

Physical Therapy Management (current best evidence)

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Alternative/Holistic Management (current best evidence)                                                                                                                                    

• Meningoceccemia
• Enteroviral infection
• Typhus
• Ehrlichiosis
• Other rickettsial dieseases
• Immune complex vasculitis
• Typhoid fever
• Leptospirosis
• Dengue
• Infectious mononucleosis
• Bacterial sepsis
• Gastroenteritis or acute abdomen
• Bronchitis
• Pneumonia

Case Reports/ Case Studies

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Resources

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Recent Related Research (from Pubmed)

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References

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