Raising Public Awareness Can Improve Control, Prevention Efforts for Soft Tick Relapsing Fever

The authors of a recent study concluded that the implementation of a standardized case definition as well as increased awareness of the disease among the public and clinicians could improve the effectivenss of STRF surveillance, prevention, and control efforts for individuals infected with the rare disease, soft tick relapsing fever (STRF).

“STRF often occurs in clusters because of common expo sures; inhabitants and visitors to a soft tick–infested structure can become infected over multiple decades,” wrote the researchers of this study. “Unrecognized or unreported cases are missed opportunities for intervention to prevent future exposures.”

The full case report study is published in Morbidity and Mortality Weekly Report by the CDC.

STRF is a rare, yet serious bacterial disease spread by Ornithodoros ticks that inhabit rodents, usually found in areas, such as cabins, caves, and camping sites. Antibiotic treatments to prevent complications from STRF that have been found to be highly effective include doxycycline, beta-lactam antibiotics: penicillin or ceftriaxone, and azithromycin.

However, if untreated for approximately 3 days, febrile episodes can recur every 7 to 10 days in infected individuals for 2 or more cycles. It can also cause complications, including neurologic and ocular disease, myocarditis, and acute respiratory distress syndrome. Additionally, infection during pregnancy can result in pregnancy loss, transplacental transmission, and neonatal death.

The study included confirmed, probable, or suspected cases of STRF data that was reported in 12 states: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Texas, Utah, Washington, and Wyoming. Of these states, 7 used case definitions that differed among one another.

Using linear regression analysis, the researchers aimed to better understand the geographic distribution and seasonal patterns of STRF.

A total of 251 cases were reported in 11 states, with a median of 24 cases per year (range, 15 [2020] to 41 [2014]), in which no significant change in the number of cases was identified during this timeframe (P = .21). Additionally, the median age at infection was 39 years (range, 2-92 years), 60% were male, no infected individual was reported pregnant at the time. Lastly, demographic data for 190 (76%) of participants found that 93% were non-Hispanic White.

The number of cases varied by state, with 4 states accounting for more than 75% of all cases. These states were California (33%), Washington (18%), Colorado (14%), and Oregon (12%).

Other states with reported cases included:

• Arizona (9%)
• Texas (5%)
• Idaho (4%)
• Utah (3%)
• Montana (1%)
• Nevada (1%)
• New Mexico (< 1%)

Of these cases, most patients (55%) were hospitalized, with no fatalities reported. Cases with STRF in counties of lower areas in Texas were more likely to be from cave exposure, and the summer peak from June to September had 154 (74%) of cases reported in 217 cases. These results suggest the geographic distribution and seasonal pattern of STRF has remained relatively constant since the 1990s.

The researchers acknowledge some limitations to the study, including the possible under recognition and underdiagnosis of STRF, especially among health departments who have also misdiagnosed STRF as Lyme disease. Additionally, the researchers note that the study may have been limited since state health departments rely primarily on provider reporting, in which STRF may have been underreported.

Despite these limitations, the researchers believe the study shows the importance of public and clinician awareness of clinical symptoms that may accompany STRF. Furthermore, the researchers hope that raising awareness of STRF may lead to new options for better diagnostic testing and improved public health reporting standards for symptomatic patients in STRF-exposed areas.

“Increased awareness of and access to molecular diagnostic testing for symptomatic patients with suspected STRF might improve recognition of cases at different stages of illness,” wrote the researchers of the study. “Coordinated improvements in surveillance, prevention, and diagnosis have the potential to prevent morbidity and mortality from STRF in the United States in the next decade.”

Reference

Beeson A, Kjemptrup A, Oltean H, et al. Soft Tick Relapsing Fever ¾ United States, 2012-2021. MMWR Morb Mortal Wkly Rep 2023;72:[777-781].