Clinical Diagnosis & Treatment of Rocky Mountain Spotted Fever

The summer season is approaching, and with it, an increased risk for tick-borne diseases such as Rocky Mountain Spotted Fever. In a recent webinar about the disease, experts with the Centers for Disease Control and Prevention (CDC) presented the latest information on its detection, diagnosis, and epidemiology.

Rocky Mountain Spotted Fever (RMSF) is a bacterial disease from the spotted fever group rickettsia, caused by the Gram-negative intracellular bacterium Rickettsia rickettsia. According to the CDC, the disease is the most deadly tick-borne infection in the world, and it is endemic throughout the Western Hemisphere. North Carolina, Tennessee, Oklahoma, Arkansas, and Missouri together report more than 60% of the cases in the United States. Ticks known to carry RMSF include the American dog tick, Rocky Mountain wood tick, and brown dock tick, and while they are most active in the summer months, in warm climates, tick bites can occur year-round. Similar to other illnesses, the first symptoms of a RMSF infection include fever and headache, which makes early diagnosis difficult. The condition can rapidly progress within 2 to 4 days to include a telltale rash, nausea, vomiting, stomach pain, and muscle pain. Severe symptoms such as vascular damage and death can occur within 1 week without treatment, and a RMSF infection can be cleared with the antibiotic doxycycline.

In a recent live webinar titled A Leopard without Spots: Clinical Diagnosis and Treatment of Rocky Mountain Spotted Fever — part of the CDC’s Clinician Outreach and Communication Activity series – epidemiologists presented discussed some of the latest data on RMSF. There were 4,269 cases of RMSF in the United States in 2016, said Paige Armstrong, MD, MHS, who presented one case of a 5-year-old child who died 6 days after first falling ill with the disease. After experiencing fever, headache, and flank pain for the first 2 days, the child went on to develop severe abdominal pain, respiratory failure with hypoxia, acidosis, hypotension, and sepsis by days 5 to 6. The lessons learned, said Dr. Armstrong, included that RMSF can mimic kidney infection and that up to 25% of cases can become fatal within 7 to 9 days without proper treatment.

Data from RMSF cases in Arizona from 2002 to 2011 emphasize the need for early treatment with doxycycline, said Dr. Armstrong, noting that no cases treated within the first 5 days were fatal, whereas 33% of cases untreated until day 6 were fatal; 50% of cases untreated at day 9 were also fatal. For children under the age of 10, the mortality rate of RMSF infections is 5 times higher than for adults.

To prevent RMSF, the CDC recommends avoiding tick habitats, treating clothing with the insecticide permethrin, using tick control products on pets, and applying insect repellants that use DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol as the active ingredient when going outdoors. After spending time outdoors, experts recommend checking clothing for ticks, taking a shower to wash away unattached ticks, and checking areas such as under hair, in and around ears, and in the underarms for ticks. If you find a tick, remove it immediately with a tweezer and watch for any signs of illness.

Feature Picture Source: CDC / Dr. Christopher Paddock. Picture Description: This 2008 photograph depicts a dorsal view of a male yellow dog tick, Amblyomma aureolatum, which is a vector of Rocky Mountain spotted fever (RMSF) in the country of Brazil.