Relapsing fever causes: Difference between revisions
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*More than 15 additional Borrelia species can cause tick-borne (endemic) relapsing fever which is transmitted to humans through the bite of infected “soft ticks” of the genus Ornithodoros. Soft ticks (family Argasidae) differ in many ways from the so-called hard. also, Borrelia species are usually associated with specific species of ticks. For example, B. hermsii is transmitted by O. hermsi ticks, B. parkerii by O. parkeri ticks, and B. turicatae by O. turicata ticks. Each tick species has a preferred habitat and preferred set of hosts. They live in the nests of squirrels, chipmunks, and other small animals like chicken & pigs. They feed very quickly(less than a half-hour) and painlessly. | *More than 15 additional Borrelia species can cause tick-borne (endemic) relapsing fever which is transmitted to humans through the bite of infected “soft ticks” of the genus Ornithodoros. Soft ticks (family Argasidae) differ in many ways from the so-called hard. also, Borrelia species are usually associated with specific species of ticks. For example, B. hermsii is transmitted by O. hermsi ticks, B. parkerii by O. parkeri ticks, and B. turicatae by O. turicata ticks. Each tick species has a preferred habitat and preferred set of hosts. They live in the nests of squirrels, chipmunks, and other small animals like chicken & pigs. They feed very quickly(less than a half-hour) and painlessly. | ||
*When rodents or other natural hosts vacate a cabin, humans may become the only available host. Patients usually are unaware of a tick bite or exposure. | |||
*In the United States, TBRF is caused by one of three Borrelia species: ''B. hermsii'', ''B. parkerii'', and ''B. turicatae''. | *In the United States, TBRF is caused by one of three Borrelia species: ''B. hermsii'', ''B. parkerii'', and ''B. turicatae''. | ||
Revision as of 00:09, 10 August 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Relapsing fever is a bacterial infection caused by several species of spirochete bacteria in the Borrelia family. TBRF is caused by more the 15 Borrelia species: Borrelia hermsii, Borrelia turicatae, Borrelia parkeri, Borrelia duttonii, Borrelia johnsonii, B miyamotoi. The bacteria species associated with LBRF is Borrelia recurrentis which has a genome so similar to B. duttonii and B. crocidurae (causes of East and West African tick-borne relapsing fever). Louse-borne relapsing fever is more severe than the tick-borne variety. Humans are the sole reservoirs of B recurrentis, while small mammals (eg, pets, ground and tree squirrels, chipmunks) and reptiles (lizards, snakes, gopher tortoises) may serve as a reservoir for tickborne Borrelia species.
Causes
Causative agent
- Relapsing fever is an infection with certain spirochete in the genus Borrelia which transmitted by ticks and lice. Borrelia recurrentis causes louse-borne (epidemic) relapsing fever; and more than 15 additional Borrelia species can cause tick-borne (endemic) relapsing fever.
- Borrelia are gram-negative, helical, 8-30 11m long, 0.2-0.5 11m wide, and have 3-10 loosely coiled spirals. They are visible with light microscopy.they are flagellated and highly motile, and they divide by binary fission, with doubling times. They have a unique process of DNA rearrangement in their linear DNA. Each time the DNA is read a different antigenic marker, also known as a variable major protein, is created, which allows the organism to evade the immune system and therefore cause recurrent patterns of fever and other symptoms.
- They are difficult to cultivate on artificial media and, because of frequent antigenic variation, difficult to serotype, and also identifying of Borrelia species by standard bacteriologic methods is problematic, so the nomenclature has relied on the vector specificity of these organisms.
Louse-borne relapsing fever
Borrelia recurrentis is the only agent of louse-borne disease. Pediculus humanus, is the specific vector. Louse-borne relapsing fever is more severe than the tick-borne variety.
- Borrelia recurrentis causes louse-borne (epidemic)relapsing fever.
- Transmission of LBRF is confined to the human body louse Pediculus humanus corporis, 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.
- 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 animal reservoir exists
- A single louse can only infect one person, but Nosocomial infections are possible from contamination by infected blood.
- Louse-borne relapsing fever occurs in epidemics amid poor living conditions, famine and war in the developing world;[1] it is currently prevalent in Ethiopia and Sudan.
Tick-borne Relapsing Fever
- More than 15 additional Borrelia species can cause tick-borne (endemic) relapsing fever which is transmitted to humans through the bite of infected “soft ticks” of the genus Ornithodoros. Soft ticks (family Argasidae) differ in many ways from the so-called hard. also, Borrelia species are usually associated with specific species of ticks. For example, B. hermsii is transmitted by O. hermsi ticks, B. parkerii by O. parkeri ticks, and B. turicatae by O. turicata ticks. Each tick species has a preferred habitat and preferred set of hosts. They live in the nests of squirrels, chipmunks, and other small animals like chicken & pigs. They feed very quickly(less than a half-hour) and painlessly.
- When rodents or other natural hosts vacate a cabin, humans may become the only available host. Patients usually are unaware of a tick bite or exposure.
- In the United States, TBRF is caused by one of three Borrelia species: B. hermsii, B. parkerii, and B. turicatae.
- Other relapsing infections are acquired from other Borrelia species, such as Borrelia hermsii or Borrelia parkeri, which can be spread from rodents, and serve as a reservoir for the infection, via a tick vector. Borrelia hermsii and Borrelia recurrentis cause very similar diseases although the disease associated with Borrelia hermsii has more relapses and is responsible for more fatalities, while the disease caused by B. recurrentis has longer febrile and afebrile intervals and a longer incubation period.
