| Relapsing fever | |
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| Specialty | Infectious diseases  |
Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus Borrelia , [1] which is transmitted through the bites of lice, soft-bodied ticks (genus Ornithodoros ), or hard-bodied ticks (Genus Ixodes). [2] [3]
Most people who are infected 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. [4]
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. [5] Louse-borne relapsing fever is more severe than the tick-borne variety.[ citation needed ]
Louse-borne relapsing fever occurs in epidemics amid poor living conditions, famine and war in the developing world. [6] It is currently prevalent in Ethiopia and Sudan.[ citation needed ]
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 ]
Lice that feed on infected humans acquire the Borrelia organisms that then multiply in the gut of the louse. 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 mucous membranes and then invades the bloodstream. No non-human, animal reservoir exists.[ citation needed ]
Tick-borne relapsing fever is found primarily in Africa, Spain, Saudi Arabia, Asia, and certain areas of Canada and the western United States. Other relapsing infections are acquired from other Borrelia species, which can be spread from rodents, and serve as a reservoir for the infection, by a tick vector.[ citation needed ]
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 ]
Borrelia miyamotoi , which is transmitted by Ixodes ticks, was reported as a cause of tick-borne relapsing fever in 2011. [7] [3]
The diagnosis of relapsing fever can be made on blood smear as evidenced by the presence of spirochetes. Other spirochete illnesses (Lyme disease, syphilis, leptospirosis) do not show spirochetes on blood smear. Although considered the gold standard, this method lacks sensitivity and has been replaced by PCR in many settings. [8]
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 ]
Tetracycline-class antibiotics are most effective. These can, however, induce a Jarisch–Herxheimer reaction in over half 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 ]
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 are binding to and clearing 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 ]
Relapsing fever has been described since the days of the ancient Greeks. [9] 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. [9] 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. [10] 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. [9] The disease was not successfully produced in an inoculated subject until 1874. [9] In 1904 and 1905, a series of papers outlined the cause of relapsing fever and its relationship with ticks. [11] [12] [13] [14] 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. [15] In 1984, it was renamed Borrelia duttoni . [16] In 1907, Frederick Percival Mackie discovered that human body louse can transmit Borrelia recurrentis, which causes relapsing fever as well. [17] The first time relapsing fever was described in North America was in 1915 in Jefferson County, Colorado. [18]
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. [19] [20] 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.[ citation needed ]
Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by Borrelia bacteria, which are spread by ticks in the genus Ixodes. The most common sign of infection is an expanding red rash, known as erythema migrans (EM), which appears at the site of the tick bite about a week afterwards. The rash is typically neither itchy nor painful. Approximately 70–80% of infected people develop a rash. Early diagnosis can be difficult. Other early symptoms may include fever, headaches and tiredness. If untreated, symptoms may include loss of the ability to move one or both sides of the face, joint pains, severe headaches with neck stiffness or heart palpitations. Months to years later, repeated episodes of joint pain and swelling may occur. Occasionally, shooting pains or tingling in the arms and legs may develop. Despite appropriate treatment, about 10 to 20% of those affected develop joint pains, memory problems, and tiredness for at least six months.
Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. The economic impact of tick-borne diseases is considered to be substantial in humans, and tick-borne diseases are estimated to affect ~80 % of cattle worldwide. Most of these pathogens require passage through vertebrate hosts as part of their life cycle. Tick-borne infections in humans, farm animals, and companion animals are primarily associated with wildlife animal reservoirs. Many tick-borne infections in humans involve a complex cycle between wildlife animal reservoirs and tick vectors. The survival and transmission of these tick-borne viruses are closely linked to their interactions with tick vectors and host cells. These viruses are classified into different families, including Asfarviridae, Reoviridae, Rhabdoviridae, Orthomyxoviridae, Bunyaviridae, and Flaviviridae.
Borrelia burgdorferi is a bacterial species of the spirochete class in the genus Borrelia, and is one of the causative agents of Lyme disease in humans. Along with a few similar genospecies, some of which also cause Lyme disease, it makes up the species complex of Borrelia burgdorferi sensu lato. The complex currently comprises 20 accepted and 3 proposed genospecies. B. burgdorferi sensu stricto exists in North America and Eurasia and until 2016 was the only known cause of Lyme disease in North America. Borrelia species are Gram-negative.
Alkhurma virus (ALKV) is a zoonotic virus of the Flaviviridae virus family. ALKV causes Alkhurma hemorrhagic fever (AHF), or alternatively termed as Alkhurma hemorrhagic fever virus, and is mainly based in Saudi Arabia.
Borrelia is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme borreliosis, a zoonotic, vector-borne disease transmitted by ticks. Other species of Borrelia cause relapsing fever, and are transmitted by ticks or lice, depending on the species of bacteria. A few Borrelia species as Candidatus Borrelia mahuryensis harbor intermediate genetic features between Lyme disease and relapsing fever Borrelia. The genus is named after French biologist Amédée Borrel (1867–1936), who first documented the distinction between a species of Borrelia, B. anserina, and the other known type of spirochete at the time, Treponema pallidum. This bacterium must be viewed using dark-field microscopy, which make the cells appear white against a dark background. Borrelia species are grown in Barbour-Stoenner-Kelly medium. Of 52 known species of Borrelia, 20 are members of the Lyme disease group, 29 belong to the relapsing fever group, and two are members of a genetically distinct third group typically found in reptiles. A proposal has been made to split the Lyme disease group based on genetic diversity and move them to their own genus, Borelliella, but this change is not widely accepted. This bacterium uses hard and soft ticks and lice as vectors. Testing for the presence of the bacteria in a human includes two-tiered serological testing, including immunoassays and immunoblotting.
Wilhelm Burgdorfer was a Swiss-American scientist and an international leader in the field of medical entomology. He discovered the bacterial pathogen that causes Lyme disease, a spirochete named Borrelia burgdorferi in his honor.
Lyme disease, or borreliosis, is caused by spirochetal bacteria from the genus Borrelia, which has 52 known species. Three main species are the main causative agents of the disease in humans, while a number of others have been implicated as possibly pathogenic. Borrelia species in the species complex known to cause Lyme disease are collectively called Borrelia burgdorferisensu lato (s.l.) not to be confused with the single species in that complex Borrelia burgdorferi sensu stricto which is responsible for nearly all cases of Lyme disease in North America.
Ixodes scapularis is commonly known as the deer tick or black-legged tick, and in some parts of the US as the bear tick. It was also named Ixodes dammini until it was shown to be the same species in 1993. It is a hard-bodied tick found in the eastern and northern Midwest of the United States as well as in southeastern Canada. It is a vector for several diseases of animals, including humans and is known as the deer tick owing to its habit of parasitizing the white-tailed deer. It is also known to parasitize mice, lizards, migratory birds, etc. especially while the tick is in the larval or nymphal stage.
Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by Anaplasma phagocytophilum, an obligate intracellular bacterium that is typically transmitted to humans by ticks of the Ixodes ricinus species complex, including Ixodes scapularis and Ixodes pacificus in North America. These ticks also transmit Lyme disease and other tick-borne diseases.
Borrelia recurrentis is a species of Borrelia, a spirochaete bacterium associated with relapsing fever. B. recurrentis is usually transmitted from person to person by the human body louse. Since the 1800s, the body louse has been known as its only known vector.
Ticks are insects known for attaching to and sucking blood from land-dwelling animals. Ticks fall under the category of 'arthropod', and while they are often thought of in the context of disease transmission, they are also known to cause direct harm to hosts through bites, toxin release, and infestation. Infestation can cause symptoms ranging from mild to severe and may even cause death. Hosts can include any number of vertebrates, though humans and livestock are more likely to be the interest of researchers.
Ornithodoros hermsi is a species of soft tick. It can be infected with Borrelia hermsii.
Borrelia duttoni is a species of Borrelia. It is the endemic causative agent of tick-borne relapsing fever in parts of sub-Saharan Africa, and Madagascar. It is transmitted by the soft-bodied tick Ornithodoros moubata which sheds the pathogen in its saliva and coxal fluid. Vertical transmission occurs in ticks which thus appear to represent the major reservoir of this pathogen. Humans appear to be the sole vertebrate host of B. duttoni. Human disease is characterised by a long incubation period, numerous brief recurrences, and frequent ocular involvement. Infection results immunity which is enduring but strain-specific.
Ornithodoros moubata, commonly known as the African hut tampan or the eyeless tampan, is a species of tick in the family Argasidae. It is an ectoparasite and vector of relapsing fever in humans, and African swine fever in pigs.
Ornithodoros turicata, commonly referred to as the relapsing fever tick, is a soft tick found in the midwestern and southwestern United States. It is a known vector of Borrelia turicatae, a spirochete responsible for tick-borne relapsing fever in humans. Additionally, vector competence for the transmission of Leptospira pomona, the agent of canine jaundice, has been demonstrated in a laboratory setting.
Borrelia miyamotoi is a bacterium of the spirochete phylum in the genus Borrelia. A zoonotic organism, B. miyamotoi can infect humans through the bite of several species of hard-shell Ixodes ticks, the same kind of ticks that spread B. burgdorferi, the causative bacterium of Lyme disease. Ixodes ticks are also the primary vector in the spread of babesiosis and anaplasmosis.
Borrelia garinii is a species of spirochete bacterium in the genus Borrelia. It is endemic to parts of Eurasia where it is one of the causative organisms of human Lyme disease. It is transmitted by hard-bodied ticks of the Ixodes genus, infecting various wild woodland mammals.
Borrelia turicatae is a bacterial species of the spirochaete class of the genus Borrelia. It is one of the relapsing fever spirochaetes, which are globally distributed yet understudied agents of tick-borne relapsing fever. The tick vector Ornithodoros turicata transmits B. turicatae, which causes relapsing fever, an arthropod-borne infection of humans and other mammals caused by different Borrelia species. B. turicatae is long and spiral-shaped, as is typical for all spirochaetes. It is a Gram-negative bacterium and visible with light microscopy. Few epidemiological studies have been performed and few molecular data exist for B. turicatae and its arthropod vector O. turicata.
Borrelia coriaceae is a species of spirochete bacteria and member of the genus Borrelia. Strains of this species have been isolated from the soft tick Ornithodoros coriaceus and from mule deer.
Borrelia mayonii is a Gram-negative, host-associated spirochete that is capable of causing Lyme disease. This organism can infect various vertebrate hosts such as humans via the bite of a black legged tick.
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