GENERAL INTRODUCTION: SPIROCHAETES

SPIROCHAETES

A General Introduction has been added to each disease chapter in an attempt to give a brief updated overview of the taxonomic, biological and other characteristics of the virus family or group of bacteria /protozoa that cause disease in livestock and, where relevant, involve wildlife. As the text of the three-volume book Infectious Diseases of Livestock is currently under revision the Editors are aware that there are inconsistencies between the updated introductions to chapters and the content of the chapters themselves. Once the chapters have been updated – a process that is currently underway – these inconsistencies will be removed.

Members of the order Spirochaetales are helical, motile, unicellular bacteria 0,1–3,0 × 5,0–250 µm in size. Spirochaetes have periplasmic flagella (ranging from two to more than 100 per cell) which are encased in an outer sheath and are responsible for their typical snake-like motility. The lack of free flagella distinguishes the spirochaetes from other motile bacteria. The spirochaetes are propelled along by rotating on their longitudinal axis and by flexing motions which are elicited by the action of the sheathed flagella.2

The order Spirochaetales contains two families, Leptospiraceae and Spirochaetaceae. The genera Brachyspira, Leptospira and Borrelia contain species that are of veterinary importance.

The members of the genus Brachyspira (formerly Serpulina) are usually found in the intestinal tract of animals.5 Brachyspira hyodysenteriae is responsible for swine dysentery and B. pilisicoli for spirochaetal diarrhoea in pigs. Both diseases are found wherever pigs are farmed. Brachyspira alvinopulli is enteropathogen of chickens.6

Borrelia spp., with the exception of B. suilla, are usually transmitted by ticks or lice that have been infected with them. Borrelioses in animals occurs throughout the world and is caused by a number of Borrelia spp. which initiate diverse disease conditions in a variety of animal species. Borrelia theileri infection has been associated with anaemia, lymph node enlargement and petechiation of the mucous membranes in horses, cattle and sheep, while Borrelia suilla has been isolated from necrogranulomatous skin lesions in pigs. Infection by both these species are rarely diagnosed.

Borrelia burgdorferi has been incriminated as the cause of fever, lymphadenopathy, lymphocytic proliferative synovitis, arthralgia, recurrent lameness and encephalitis in horses, dogs and humans. It may also cause abortion in mares.1

The family Leptospiraceae is divided into three genera, Leptospira, Leptonema and Turneriella, but only Leptospira contains pathogens. Leptospira is currently divided into 22 genome-species of which 10 are known to be pathogenic in animals and humans, and five species that show intermediate pathogenic characteristics.4 In total, more than 250 pathogenic serovars are recognized.

Leptospira bacteria are transmitted by direct or indirect (e.g. through contaminated environments) contact with infected urine or tissues of infected carrier animals.3 A wide range of mammals including livestock and domestic animal species may act as carriers of Leptospira. Clinical manifestations include haemolytic crisis, chronic interstitial nephritis, mastitis, abortion and, recurrent uveitis (periodic ophthalmia) in horses.3 Livestock may also act as a source of Leptospira infection for humans as chronic urinary shedding may persist for months to years after clinical or subclinical infection.

References

  1. BARANTON, G., POSTIC, D., SAINT GIRONS, I., BOERLIN, P., PIFFARETTI, J. C., ASSOUS, M. & GRIMONT, P. A. D., 1992. Delineation of Borrelia burgdorferi sensu stricto, Borrelia garinii sp. nov., and group VS461 associated with Lyme borreliosis International Journal of Systematic Bacteriology. 42, 378–383.
  2. CANALE-PAROLA, E., 1984. The spirochetes. In: KRIEG, N. R. & HOLT, J. G., (eds). Bergey’s Manual of Systematic Bacteriology. Vol. I Baltimore, London: Williams & Wilkins
  3. ELLIS, W.A., 2015. Animal Leptospirosis. In: Leptospira and leptospirosis, Adler, B. Current Topics in Microbiology and Immunology, Springer.
  4. PICARDEAU, M., 2017. Virulence of the zoonotic agent of leptospirosis: still terra incognita? Nature Reviews Microbiology. 15, 297-307
  5. OCHAI, S., ADACHI, Y. & MORI, K., 1997. Unification of the genera Serpulina and Brachyspira, and proposal of Brachyspira hyodysenterica comb. nov., Brachyspira innocens comb. nov. and Brachyspira pilosicoli comb. nov. Microbiology and Immunology. 41, 445–452.
  6. STANTON, T. B., POSTIC, D. & JENSEN, N. S., 1998. Serpulina alvinipulli sp. nov. a new Serpulina species that is enteropathogenic for chickens. International Journal of Systematic Bacteriology. 48, 669–676.