rickettsii is transmitted transovarially to tick progeny from one generation to the next. 311-1) and in Central and South America (Argentina, Brazil, Colombia, Costa Rica, Mexico, and Panama). RMSF is prevalent in at least 44 states in the United States ( Fig. It is the major tick-transmitted rickettsiosis recognized in America, 3 along with Rickettsia africae in the West Indies, Rickettsia parkeri in the southern states of the United States, and, perhaps, “ Rickettsia philipii.” It was described first in the 19th century in the western United States. Rocky Mountain spotted fever (RMSF), the most severe of tick-borne rickettsioses, 2 is caused by Rickettsia rickettsii ( Table 311-2). Lee Goldman MD, in Goldman-Cecil Medicine, 2020 Epidemiology 15, 16 Uncomplicated cases may be effectively treated with oral doxycycline, and the cases complicated by meningoencephalitis responded to intravenous therapy with ceftriaxone or penicillin G. 296.5), and Ixodes pacificus, the western black-legged tick ( Fig. miyamotoi infections are transmitted by the same ixodid ticks that carry Lyme disease: Ixodes scapularis, the eastern black-legged tick ( Fig. In two cases, immunocompromised patients developed meningoencephalitis. This initial clinical presentation more closely resembles other hard tick–transmitted diseases, especially anaplasmosis and Lyme disease without a significant rash, rather than soft tick–transmitted classic relapsing fever. 16 In most cases, patients present with fever, malaise, fatigue, headache, myalgias, and arthralgias, and they do not have recurrent fevers. 15 Since 2011, more than 50 patients with acute febrile illnesses resembling Lyme disease without erythema migrans have been described as having B. 14 In 2013, 1% to 3% of surveyed residents of New England states where Lyme disease is endemic were seropositive for prior B. In 2011, the first human cases of relapsing fever caused by tick-transmitted Borrelia miyamotoi were reported from Russia. 12 In a seemingly unending era of new discoveries in tick-transmitted diseases, another new and unanticipated vector for RMSF- Rhipicephalus sanguineus, the brown dog tick-was identified in the United States in 2005 ( Fig. burgdorferi complex were identified, a new relapsing fever Borrelia species was isolated, and anaplasmosis was exported to Europe from the United States. 10,11īy 2004, ticks were recognized as the most common vectors of all arthropod-borne infectious diseases in Europe, five new spotted fever (SF)–causing rickettsiae were described, four new subspecies of the Lyme disease–causing B. This new borreliosis would soon be named the southern tick-associated rash illness (STARI) or Masters disease, but its causative agent, Borrelia lonestari, a new Borrelia species, would not be identified until 2004. 7,8 In 1997, Kirkland and colleagues 9 described a new erythema migrans–like rash illness in North Carolina, a nonendemic region for Lyme disease, transmitted by the Lone Star tick, Amblyomma americanum ( Fig. 6 These latest discoveries have been spawned by new immunodiagnostic technologies, especially by nucleic acid identification technologies, particularly the polymerase chain reaction (PCR) assay.īy the 1980s and 1990s, the causative agents of the ehrlichioses were stratified as newly emerging, Rickettsia-like species, and later (2001) they were completely reorganized into separate genera, Ehrlichia and Anaplasma. 5 Since the 1970s, every decade now describes emerging or rediscovered tick-borne infectious disease and new vectors for previously described tick-borne diseases, such as RMSF. 4īy the early 1990s, Lyme borreliosis (LB) had become the most common arthropod-borne infectious disease in the United States and Europe. 3 The emergence and recognition of Lyme disease in the early 1970s in the United States, whose causative agent, the spirochete Borrelia burgdorferi, was not identified until 1982, sparked renewed interest in tick-borne diseases in the United States and Europe ( Fig. Ricketts identified the wood tick, Dermacentor andersoni, as the vector of Rocky Mountain spotted fever (RMSF) in 1906 and firmly established the insect vector theory of infectious disease transmission (see Fig. Tick-borne infectious diseases have challenged researchers and physicians since Dr. Bennett MD, in Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 2020 Epidemiology of Tick-Borne Infectious Diseases
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