Reprinted from Texas Medicine, Volume 91, Number 5, May, 1995. An overview of tick-borne relapsing fever with emphasis on outbreaks in Texas JULIE A. RAWLINGS, MPH Tick-borne relapsing fever (TBRF), a wo CAVE BIOLOGISTS 1927 (3); Arizona, Kansas, Nevada, disease ofhumans and other animals, has became ill after surveying a Utah, Washington, and Montana in been recognized in North America since T cave in Travis County during the 1930s (4,5,3,6,7); and Oklahoma, early in this century. Caused by Borrelia June 1994. They each entered the cave Oregon, Idaho, and New Mexico spirochetes, TBRF is transmitted by soft­ on June 9th and had onset of fever, (8-11) in the early 1940s. shelled Ornithodoros ticks, which may headache, chills, and malaise 6 and 7 Ornithodoros ticks are the vectors also act as reservoirs for the etiologic days later. This febrile episode was fol­ of TBRF in the United States. Weller agents. Initial symptoms include sudden lowed by two relapses. Neither patient and Graham established that onset offever, chills, headache, arthral­ was hospitalized, but one patient Ornithodoros turicata transmits dis­ gias, and myalgias. Persons with TBRF experienced a more severe illness than ease-causing spirochetes in Texas (12), may suffer several febrile episodes or the other, having developed a rash and Wheeler et al proposed that 0 relapses unless they are diagnosed and after the first episode and Bell's palsy hermsi is the vector in California (13). treated promptly because TBRF spiro­ during the second relapse. Both Two other species, 0 parkeri and 0 chetes are able to alter their outer su,face patients have remained well since talaje, harbor spirochetes and are able proteins and, thus, escape the infected being treated with doxycycline. to transmit organisms to laboratory host's immune response. Laboratory diag­ These patients represent the latest animals. On occasion, 0 parkeri is a nosis is made by detecting spirochetes in of ·13 cases of tick-borne relapsing vector to humans in the western peripheral blood specimens or by inocu­ fever (TBRF) reported to the Texas United States, although it rarely lating laboratory mice with blood col­ Department of Health since 1990. comes in contact with humans (14). lected during febrile episodes. In the Relapsing fever is a spirochetal illness Similarly, naturally infected O talaje 1930s and '40s, TBRF was reported caused by arthropod-borne Borrelia. have been found, but this species has commonly in Texas. More recently, fewer This genus of organisms, along with not been definitely incriminated as a cases have been reported, although 13 the treponemes and the leptospires, are vector to humans (15). cases were confirmed between 1990 and members of the family Treponemat­ Ornithodoros ticks, referred to as the first halfof1994. aceae, which contains all of the spiro­ soft-shelled (argasid) ticks, can survive chetal pathogens. Species within each prolonged starvation. They feed at of these genera produce disease in both night for less than I hour, so people humans and other animals and are often do not realize they have been well-documented agents of chronic, bitten (16). Adults feed repeatedly debilitating disorders. Relapsing fever and females may lay several hundred may be transmitted by lice or ticks. eggs after each blood meal ( 17). 0 Louse-borne relapsing fever or epi­ hermsi and O turicata are primary demic relapsing fever, caused by reservoirs because they pass spiro­ Borrelia recurrentis, is no longer found chetes transovarially, although a vari­ in the United States. Tick-borne ety of animal species (including relapsing fever is caused by a variety of rodents, rabbits, raccoons, opossums, Borrelia species and is endemic foxes, armadillos, dogs, cats, pigs, and throughout most of the world. monkeys) can be infected also (14,18,19). EPIZOOTIOLOGY The discoveries of TBRF in the United States generated interest in the The first report of TBRF in the relationships between spirochetes and United States came from Jefferson their hosts (20) . Researchers deter­ Send reprint requests to Ms Rawlings, Infectious Disease Epidemiology and County, Colorado, in 1915 (1). mined that, in the United States, each Surveillance, Texas Department of Health, Subsequently, TBRF was recognized species of Ornithodoros can carry a 1100 W 49th St, Austin, TX 78756. in California in 1922 (2) and Texas in strain of Borrelia that is specific to that TlXAS MEDICINE * MAY 1995 rick (20,6, 18). 0 turicata, which exists lacing blood berween relapses; reser­ notable exception is an outbreak that predominantly in the southwestern voir sites for organisms during these occurred in 1973 at the Grand United States (although the presence of periods include brain, liver, kidney, Canyon involving 62 persons infected chis species in Florida has been and spleen. Relapses are usually less with B hermsii (22). Five years earlier, reported), Mexico, and South America severe and of shorter duration than an outbreak of B hermsii relapsing (21-23), is found in caves frequented the original febrile attack. fever occurred in 11 of 42 boy scouts by sheep and goats or containing Laboratory diagnosis of TBRF may camping near Spokane, Wash (30). rodent and snake burrows (16). 0 be made by either ofrwo ways. The first In Texas, the disease was relatively hermsi, found in mountainous regions is by detecting spirochetes in peripheral common in the 1930s and '40s. At of the western United States and blood specimens either by dark-field lease 436 cases were reported from Canada, inhabits the crevices of old examination or by staining thick or 1930 through 1941 (31,32). From tree stumps and rodent-infested cabins. chin smears (early on, many laborato­ June 1942 through May 1949, an ries diagnosed cases of TBRF using additional 100 cases, primarily occur­ CLINICAL MANIFESTATIONS AND smears that had been submitted for ring in the central part of the state, LABORATORY DIAGNOSIS detection of malaria). The second way were confirmed at the Texas is by inoculating laboratory mice with Department of Health laboratory 0 turicata and O hermsi transmit blood collected during a febrile episode. (33). In more recent years, fewer cases spirochetes via their saliva; feedings of Organisms are rarely detected in smears have been reported: 21 cases berween less than 1 minute have resulted in from afebrile patients but will be found 1973 and 1986. Thirteen cases of infection (24,8). An average incuba­ in approximately 70% of specimens TBRF, associated with at least five tion period of 5 to 9 days is followed collected during febrile periods. caves in disparate geographic loca­ by sudden onset of fever, chills, Since species within the genus tions, were confirmed between headache, muscle and joint pain, Borrelia are closely related, patients November 1990 and July 1994. extreme muscle weakness, mental with TBRF will have false positive The first of the recent clusters of lethargy, nausea, vomiting, cough, indirect immunofluorescent antibody cases occurred in November 1990 and and phocophobia and/or delirium (IFA) and enzyme immunoassay involved 5 of 11 persons who had lasting 3 to 4 days (16,25). Ocher (EIA) tests for other rick-borne spiro­ been searching for Indian artifacts in symptoms may include hepatomegaly, chetoses, such as Lyme disease. and around a cave located on a rash, splenomegaly, meningitis, respi­ Antibody ricers, however, will be Crockett County (southwestern ratory manifestations, and iritis or iri­ higher when cultured B turicatae or B Texas) sheep ranch. The infected per­ docyclitis char can result in permanent hermsii is used as the test antigen sons spent nearly 5 hours in the cave visual impairment. Severe central ner­ (28,29, and unpublished data, Texas and sustained an average of 14 rick vous system involvement (cranial neu­ Department of Health). Because cases bites. In contrast, the ocher 6 were in ropathies, seizures, and coma) occurs of TBRF have been recognized in the cave less than 1 hour and averaged in l0% to 25% of patients. In preg­ locations where Lyme disease is also 7 bites. Because 2 of the 5 developed nant women, TBRF usually results in reported, an IFA test using B turicatae Bell's palsy and tested positive for abortion. Although the illness can be is available at the Texas Department of Lyme disease, these patients were serious, in many patients it is self-lim­ Health Laboratory. given initial diagnoses of Lyme borre­ iting and cases often go unrecognized. liosis. Symptoms common to all of A patient may have several febrile EPIDEMIOLOGY AND CLINICAL the patients included fever, headache, episodes (relapses) caused by antigenic EXAMPLES myalgias, and arthralgias. Four of the variation in spirochecal outer surface 5 had a rash. Four experienced one proteins, which allows these organ­ Tick-borne relapsing fever is endemic relapse, and 1 had two relapses; isms to escape the infected host's in the western United States. afebrile periods lasted 3 to 7 days. immune response (26,27). The TBRF Outbreaks are sporadic, however, and One person was hospitalized. These spirochetes usually vanish from circu- usually involve only a few people. A patients were treated with doxycy- VOLUME 91 * NUMBER 5 57 .. dine, penicillin, and, in one case, nausea, and severe fatigue. The patient mother dog was apparently unaffected intravenous cefrriaxone sodium. had visited the cave on February 4th although she had a positive antibody In January 1992, three United and 18th. During March, he experi­ titer. Young animals appear to be gen­ States Customs agents contracted enced four relapses. A petechial rash erally more susceptible to infection by TBRF after receiving between 10 and appeared on his legs with the final these spirochetes (17). 100 tick bites while inspecting a man­ febrile episode. In early April, the Although relatively few human made cave dug into the bank of the patient was given a prescription for cases have been reported in the United Rio Grande River in Starr County doxycycline but was asked to delay States, foci of TBRF continue to (southern Texas).