Relapsing fever

{{Short description|Infectious disease caused by Borrelia bacteria}} {{Infobox medical condition | name = | synonym = | image =  | image_size = | alt = | caption = | pronounce = | specialty =  | symptoms = Fever, headache, muscle pain, nausea, rash | complications = | onset = | duration = | types = | causes = | risks = | diagnosis = | differential = | prevention = | treatment = | medication = | prognosis = | frequency = | deaths = }} '''Relapsing fever''' is a vector-borne disease caused by infection with certain bacteria in the genus ''Borrelia'',<ref name=Schwan_1996>{{cite journal |author=Schwan T |title=Ticks and Borrelia: model systems for investigating pathogen-arthropod interactions |journal=Infect Agents Dis |volume=5 |issue=3 |pages=167–81 |year=1996 |pmid=8805079}}</ref> which is transmitted through the bites of lice, soft-bodied ticks (genus ''Ornithodoros''), or hard-bodied ticks (genus Ixodes).<ref name=Schwan_2002>{{cite journal |author=Schwan T, Piesman J |title=Vector interactions and molecular adaptations of Lyme disease and relapsing fever spirochetes associated with transmission by ticks |journal=Emerg Infect Dis |volume=8 |issue=2 |pages=115–21 |year=2002 |pmid=11897061 |doi=10.3201/eid0802.010198 |pmc=2732444|last2=Piesman }}</ref><ref name="Hoornstra">{{cite journal |last1=Hoornstra |first1=Dieuwertje |last2=Azagi |first2=Tal |last3=van Eck |first3=Jacqueline A |last4=Wagemakers |first4=Alex |last5=Koetsveld |first5=Joris |last6=Spijker |first6=René |last7=Platonov |first7=Alexander E |last8=Sprong |first8=Hein |last9=Hovius |first9=Joppe W |title=Prevalence and clinical manifestation of Borrelia miyamotoi in Ixodes ticks and humans in the northern hemisphere: a systematic review and meta-analysis |journal=The Lancet Microbe |date=October 2022 |volume=3 |issue=10 |pages=e772–e786 |doi=10.1016/S2666-5247(22)00157-4|pmid=36113496 |hdl=10029/626087 |hdl-access=free }}</ref>

== Signs and symptoms == Most infected people develop sickness between 5 and 15 days after they are bitten. The symptoms may include a sudden fever, chills, headaches, muscle or joint aches, and nausea. A rash may also occur. These symptoms usually continue for 2 to 9 days, then disappear. This cycle may continue for several weeks if the person is not treated.<ref name=Sherris>{{cite book |author=Ryan KJ; Ray CG |title=Sherris Medical Microbiology |pages=432–4 |edition=4th |publisher=McGraw Hill |year=2004 |isbn=978-0-8385-8529-0}}</ref>

==Causes== ===Louse-borne relapsing fever=== Along with ''Rickettsia prowazekii'' and ''Bartonella quintana'', ''Borrelia recurrentis'' is one of three pathogens of which the body louse (''Pediculus humanus humanus'') is a vector.<ref name="Fournier">{{cite journal |url=https://www.cdc.gov/ncidod/eid/vol8no12/02-0111.htm |last=Fournier |first=Pierre-Edouard |title=Human Pathogens in Body and Head Lice |journal=Emerging Infectious Diseases |year=2002 |volume=8 |issue=12 |pages=1515–8 |doi=10.3201/eid0812.020111 |pmid=12498677 |pmc=2738510 |access-date=October 17, 2010}}</ref> Louse-borne relapsing fever is more severe than the tick-borne variety.<ref>{{Cite web |date=2018-04-11 |title=Relapsing Fever |url=https://www.columbia-lyme.org/relapsing-fever |access-date=2026-04-30 |website=Lyme Disease |language=en}}</ref>

Louse-borne relapsing fever occurs in epidemics amid poor living conditions, famine, and war in the developing world.<ref name=Cutler_2006>{{cite journal |author=Cutler S |title=Possibilities for relapsing fever reemergence |journal=Emerg Infect Dis |volume=12 |issue=3 |pages=369–74 |year=2006 |pmid=16704771 |doi=10.3201/eid1203.050899 |pmc=3291445 }}</ref> It is currently prevalent in Ethiopia and Sudan.<ref>{{Cite journal |last=Perine |first=P. L. |last2=Reynolds |first2=D. F. |date=1974-11-30 |title=Letter: Relapsing-fever epidemic in the Sudan and Ethiopia |url=https://pubmed.ncbi.nlm.nih.gov/4139567 |journal=Lancet |volume=2 |issue=7892 |pages=1324–1325 |doi=10.1016/s0140-6736(74)90189-5 |issn=0140-6736 |pmid=4139567}}</ref>

Mortality rate is 1% with treatment and 30–70% without treatment. Poor prognostic signs include severe jaundice, severe change in mental status, severe bleeding, and a prolonged QT interval on ECG.{{Citation needed|date=July 2020}}

Lice that feed on infected humans acquire the ''Borrelia'' organisms that then multiply in the louse's gut. When an infected louse feeds on an uninfected human, the organism gains access when the victim crushes the louse or scratches the area where the louse is feeding. ''B. recurrentis'' infects the person via the mucous membranes and then invades the bloodstream. No non-human animal reservoir exists.<ref name=Warrell_2019>{{cite journal |author=Warrell David A |title=Louse-borne relapsing fever (''Borrelia recurrentis'' infection) |journal=Epidemiol Infect |volume=147 |pages=e106 |year=2019 |pmid=30869050 |DOI=10.1017/S0950268819000116|pmc=6518520 }}</ref>

===Soft tick-borne relapsing fever=== {{Unreferenced section|date=April 2026}} Soft tick-borne relapsing fever (STRF) is found primarily in Africa, Spain, Saudi Arabia, Asia, and certain areas of Canada and the western United States. STRF is caused by a variety of ''Borrelia'' species through the bite of infected soft body ticks. Rodents serve as a reservoir for the infection, which is then spread to humans by the tick vector.<ref>{{Cite web |last=CDC |date=2024-07-19 |title=About Soft Tick Relapsing Fever (STRF) |url=https://www.cdc.gov/relapsing-fever/about/about-strf.html |access-date=2026-04-30 |website=Tick and Louse-borne Relapsing Fevers |language=en-us}}</ref> *''Borrelia crocidurae'' – occurs in Egypt, Mali, Senegal, Tunisia; vectors – ''Carios erraticus'', ''Ornithodoros sonrai''; animal host – shrew (''Crocidura stampflii''){{Citation needed|date=March 2026}} *''Borrelia duttoni'', transmitted by the soft-bodied African tick ''Ornithodoros moubata'', is responsible for the relapsing fever found in central, eastern, and southern Africa. *''Borrelia hermsii'' *''Borrelia hispanica'' *''Borrelia parkeri'' *''Borrelia turicatae'' *''Borrelia persica''

''B. hermsii'' and ''B. recurrentis'' cause very similar diseases. However, one or two relapses are common with the disease associated with ''B. hermsii'', which is also the most common cause of relapsing disease in the United States. (Three or four relapses are common with the disease caused by ''B. recurrentis'', which has longer febrile and afebrile intervals and a longer incubation period than ''B. hermsii'').{{citation needed|date=May 2021}}

===Hard tick-borne relapsing fever=== ''Borrelia miyamotoi'', which is transmitted by ''Ixodes'' ticks, was reported as a cause of tick-borne relapsing fever in 2011.<ref>{{cite news |last=McNeil |first=Donald |title=New Tick-Borne Disease Is Discovered |newspaper=The New York Times |pages=D6 |date=19 September 2011 |url=https://www.nytimes.com/2011/09/20/health/20tick.html |access-date=20 September 2011}}</ref><ref name="Hoornstra"/>

==Diagnosis== The diagnosis of relapsing fever can be made on blood smear as evidenced by the presence of spirochetes. Other spirochete illnesses (e.g., Lyme disease, syphilis, leptospirosis) do not show spirochetes on blood smears. Although considered the gold standard, this method lacks sensitivity and has been replaced by PCR in many settings.<ref name="pmid26618151">{{cite journal |vauthors=Fotso Fotso A, Drancourt M |title=Laboratory Diagnosis of Tick-Borne African Relapsing Fevers: Latest Developments |journal=Frontiers in Public Health |volume=3 |pages=254 |year=2015 |pmid=26618151 |pmc=4641162 |doi=10.3389/fpubh.2015.00254 |bibcode=2015FrPH....3..254F |doi-access=free }}</ref>

==Treatment== {{Unreferenced section|date=April 2026}} Relapsing fever is easily treated with a one- to two-week course of antibiotics, and most people improve within 24 hours. Complications and death due to relapsing fever are rare.{{citation needed|date=May 2021}}

Tetracycline-class antibiotics are most effective. These can, however, induce a Jarisch–Herxheimer reaction in over half of those treated, producing anxiety, diaphoresis, fever, tachycardia and tachypnea with an initial pressor response followed rapidly by hypotension. Recent studies have shown tumor necrosis factor-alpha may be partly responsible for this reaction.{{citation needed|date=May 2021}}

==Research== {{Unreferenced section|date=April 2026}} Currently, no vaccine against relapsing fever is available, but research continues. Developing a vaccine is very difficult because the spirochetes avoid the immune response of the infected person (or animal) through antigenic variation. Essentially, the pathogen stays one step ahead of antibodies by changing its surface proteins. These surface proteins, lipoproteins called variable major proteins, have only 30–70% of their amino acid sequences in common, which is sufficient to create a new antigenic "identity" for the organism. Antibodies in the blood that bind to and clear spirochetes expressing the old proteins do not recognize spirochetes expressing the new ones. Antigenic variation is common among pathogenic organisms. These include the agents of malaria, gonorrhea, and sleeping sickness. Important questions about antigenic variation are also relevant for such research areas as developing a vaccine against HIV and predicting the next influenza pandemic.{{Citation needed|date=July 2020}}

==History== Relapsing fever has been described since the days of the ancient Greeks.<ref name="Cutler2010">{{cite journal |last=Cutler |first=S.J. |date=April 2010 |title=Relapsing fever – a forgotten disease revealed |journal=Journal of Applied Microbiology |volume=108 |issue=4 |pages=1115–1122 |language=en |doi=10.1111/j.1365-2672.2009.04598.x |issn=1365-2672 |pmid=19886891|s2cid=205322810 |doi-access=free }}</ref> After an outbreak in Edinburgh in the 1840s, relapsing fever was given its name, but the etiology of the disease was not better understood for a decade.<ref name="Cutler2010" /> Physician David Livingstone is credited with the first account in 1857 of a malady associated with the bite of soft ticks in Angola and Mozambique.<ref name=Livingstone1857>Livingstone D (1857) Missionary travels and researches in South Africa. London: John Murray</ref> In 1873, Otto Obermeier first described the disease-causing ability and mechanisms of spirochetes, but was unable to reproduce the disease in inoculated test subjects and thereby unable to fulfill Koch's postulates.<ref name="Cutler2010" /> The disease was not successfully produced in an inoculated subject until 1874.<ref name="Cutler2010" /> In 1904 and 1905, a series of papers outlined the cause of relapsing fever and its relationship with ticks.<ref name=Cook1904>{{cite journal |author=Cook AR |year=1904 |title=Relapsing fever in Uganda |journal=J Trop Med Hyg |volume=7 |pages=24–26}}</ref><ref name=Ross1904>{{Cite journal |pmid=20761784 |year=1904 |last1=Ross |first1=P. H. |title=Tick Fever. |journal=British Medical Journal |volume=2 |issue=2291 |pages=1453–4 |last2=Milne |first2=A. D. |pmc=2355890 |doi=10.1136/bmj.2.2291.1453}}</ref><ref name=Dutton1905>{{cite journal |vauthors=Dutton JE, Todd JL |year=1905 |title=The nature of human tick-fever in the eastern part of the Congo Free State with notes on the distribution and bionomics of the tick |journal=Liverpool School Trop Med Mem |volume=17 |pages=1–18}}</ref><ref name=Wellman1905>{{cite journal |author=Wellman FC |year=1905 |title=Case of relapsing fever, with remarks on its occurrence in the tropics and its relation to "tick fever" |journal=J Trop Med |volume=8 |pages=97–99}}</ref> Both Joseph Everett Dutton and John Lancelot Todd contracted relapsing fever by performing autopsies while working in the eastern region of the Congo Free State. Dutton died there on February 27, 1905. The cause of tick-borne relapsing fever across central Africa was named ''Spirillum duttoni''.<ref name=Novy1906>{{Cite journal |doi=10.1093/infdis/3.3.291 |jstor=30071844 |url=https://archive.org/details/jstor-30071844 |title=Studies on ''Spirillum obermeieri'' and related organisms |journal=Journal of Infectious Diseases |volume=3 |issue=3 |pages=291–393 |year=1906 |last1=Novy |first1=F. G. |last2=Knapp |first2=R. E.|hdl=2027/hvd.32044106407547 |hdl-access=free }}</ref> In 1984, it was renamed ''Borrelia duttoni''.<ref name=Kelly1984>Kelly RT (1984) "Genus IV. Borrelia Swellengrebel 1907" in Krieg NR (ed.) Bergey's Manual of Systematic Bacteriology. Baltimore: Williams & Wilkins</ref> In 1907, Frederick Percival Mackie discovered that human body louse can transmit ''Borrelia recurrentis'', which causes relapsing fever as well.<ref>{{Cite book |last1=Mullen |first1=Gary Richard |title=Medical and veterinary entomology |last2=Durden |first2=Lance A. |date=2019 |publisher=Academic press, an imprint of Elsevier |isbn=978-0-12-814043-7 |edition=3rd |location=London |pages=2}}</ref> The first time relapsing fever was described in North America was in 1915 in Jefferson County, Colorado.<ref>{{Cite journal |last=Davis |first=Gordon E. |date=1940-01-01 |title=Ticks and Relapsing Fever in the United States |journal=Public Health Reports |volume=55 |issue=51 |pages=2347–2351 |doi=10.2307/4583554 |jstor=4583554}}</ref>

Sir William MacArthur suggested that relapsing fever was the cause of the yellow plague, variously called ''pestis flava, pestis ictericia, buidhe chonaill'', or ''cron chonnaill'', which struck early Medieval Britain and Ireland, and of epidemics which struck modern Ireland in the famine.<ref>{{cite journal |author1=Bonser, Wilfrid |author2=MacArthur, Wm |year=1944 |title=Epidemics during the Anglo-Saxon period, with appendix: Famine fevers in England and Ireland |journal=Journal of the British Archaeological Association |volume=9 |pages=48–71|doi=10.1080/00681288.1944.11894687 }}</ref><ref>{{Cite journal |pmid=20248471 |year=1947 |last1=MacArthur |first1=W |title=Famine fevers in England and Ireland |journal=Postgraduate Medical Journal |volume=23 |issue=260 |pages=283–6 |pmc=2529527 |doi=10.1136/pgmj.23.260.283}}</ref> This is consistent with the description of the symptoms experienced by King Maelgwn of Gwynedd as recorded in words attributed to Taliesin and with the "great mortality in Britain" in 548 CE noted in the Annales Cambriae.<ref>{{cite web |title=The Mystery of the Missing Plague |url=https://www.youtube.com/watch?v=nMA6SFyjO80 |website=youtube.com |publisher=Cambrian Chronicles |language=en |format=video |date=September 9, 2025}}</ref>{{Self-published source|date=September 2025}}

==References==  {{Reflist|35em}}

== External links == * [https://www.cdc.gov/relapsing-fever/ CDC: Relapsing Fever] {{Medical resources | DiseasesDB = 4428 | ICD11 = {{ICD11|1C1J}} | ICD10 = | ICD9 = | ICDO = | OMIM = | MedlinePlus = | eMedicineSubj = | eMedicineTopic = | MeshID = }} {{Gram-negative non-proteobacterial bacterial diseases}} {{Tick-borne diseases}}

Category:Bacterial diseases Category:Tropical diseases Category:Zoonoses Category:Tick-borne diseases Category:Rickettsioses