The Spirochetes (4)

Family 2: TREPONEMATACEAE

Genus 1: Borrelia

The genus was named after the French biologist Amédée Borrel (1867 – 15 September 1936), a French biologist.* The study of Borrelia has become increasingly important as more of its pathology is understood. As the causative agent of Lyme disease, understanding its structure and function is now a major focus of modern medicine. One recent study took a strange turn when it concluded that in Dublin, Ireland small rodents were relatively unimportant as reservoir hosts of Borrelia burgdorferi s.l., and suggested that songbirds (Passeriformes) were the most significant hosts.

In Mosby's Medical Dictionary (8th edition. © 2009, Elsevier) its defined as: a genus of coarse, unevenly coiled helical spirochetes, several species of which cause tickborne and louseborne relapsing fever. The organism is spread to offspring from generation to generation. This does not occur in lice. Many animals serve as reservoirs and hosts for Borrelia. The spirochete may be identified by microscopic examination of a smear of blood stained with Wright's stain; it is also easily inoculated onto culture media for bacterial culture and identification.

* See: http://www.pasteur.fr/infosci/archives/bor0.html

Borrelia burgdorferi .Under a magnification of 201X,  this scanning electron micrographic (SEM) image depicted a dorsal view of an unidentified engorged female tick, which had been extracted from the skin of a pet cat while in the process of obtaining its blood meal.

Habitat: Parasites of wild rodents and small mammals, and also arthropods associated with these animals

Oxygen Relationships: Microaerophilic

Major Characteristics: Pathogenic , causing louseborne or tickerborne relapsing fever in humans

Pathology: Lyme disease (named for the town in which it was first identified) can be caused by any number of different species in the genus Borrelia, such as: B. andersonii, B. japonica, B. valaisiana, B. lusitanie, B. turdae. B. tunakii, B. bissettii, and B. lonestari.

Borrelia inhabits the lumen of a tick's digestive tract. The disease is transmitted to humans from a tick bite when the bacteria migrates up to the ticks salivary glands, and through the opening created by the tick. Ticks increase salivation during gorging, prompting the migration of the saliva from the digestive tract. Because migration from the gut takes a few days, transmission of the disease usually does not happen until after the first 24 hours of attachment.

Classic bulls-eye rash (Erythema Migrans) caused by Borrelia

Tick-borne relapsing fever is found primarily in Africa, Spain, Saudi Arabia, Asia in 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, via a tick vector.

• Borrelia hermsii
• Borrelia parkeri
• 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 miyamotoi

Borrelia hermsii and Borrelia recurrentis cause very similar diseases. However, one or two relapses are common with the disease associated with Borrelia 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. B. recurrentis has longer febrile and afebrile intervals and a longer incubation period thanBorrelia hermsii.)

Scanning electron micrograph image of Borrelia burgdorferi.

Treatment of Relapsing Fever:  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 that tumor necrosis factor-alpha (TNF-alpha) may be partly responsible for this reaction. 
Species: 

1. Borrelia afzelii
2. Borrelia americana
3. Borrelia anserina]
4. Borrelia baltazardii
5. Borrelia brasiliensis
6. Borrelia burgdorferi
7. Borrelia carolinensis
8. Borrelia caucasica
9. Borrelia coriaceae
10. Borrelia crocidurae
11. Borrelia dugesii
12. Borrelia duttonii
13. Borrelia garinii
14. Borrelia graingeri
15. Borrelia harveyi
16. Borrelia hermsii
17. Borrelia hispanica
18. Borrelia japonica
19. Borrelia latyschewii
20. Borrelia lusitaniae
21. Borrelia mazzottii
22. Borrelia miyamotoi
23. Borrelia parkeri
24. Borrelia persica
25. Borrelia recurrentis
26. Borrelia sinica
27. Borrelia spielmanii
28. Borrelia tanukii
29. Borrelia theileri
30. Borrelia tillae
31. Borrelia turcica
32. Borrelia turdi
33. Borrelia turicatae 
34. Borrelia valaisiana Wang et al. 1997, sp. nov.
35. Borrelia venezuelensis

(For more information: http://www.bacterio.cict.fr/b/borrelia.html)