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Leptospira interrogans

ISSN 2398-2950

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Introduction

Classification

Taxonomy

  • Order: Spirochaetales.
  • Family: Leptospiraceae.
  • Genus: Leptospira.
  • Species: Leptospira interrogans.
  • More than 180 serovars.

Etymology

  • Greek: spira- a coil; chaete- a hair.

Significance

  • Leptospirosis in animals and man.

Active Forms

Active Form 1

Morphology

  • Gram-negative, slender, motile, flexous bacteria.
  • Helically-shaped bacteria.
  • The outer sheath is a multilayered membrane which surrounds the protoplasmic cylinder.
  • Wound around the protoplasmic cylinder inside the outer sheath are periplasmic flagellae, between 2 and 100 per cell, depending on the species. One end of each flagellum is inserted near a pole of the protoplasmic cylinder and the other end is unattached.

Tolerances

Temperature
  • Optimal growth at 29-30°C.
  • Killed by heating to 50°C for 10 mins.
Humidity
  • Desiccation inactivates organism.
Ultraviolet
  • Inactivated by direct sunlight.
Other
  • Inactivated by acidic urine.

Development

Growth
  • Aerobe.
  • No growth on blood agar or other routine media.
  • Grows in broths, eg Korthof or Stuart.
Reproduction
  • Generation time averages 12 hours.
Longevity
  • Can survive for around 3 months in moist, temperate environments.

Resting Forms

Clinical Effects

Epidemiology

Habitat

  • Survive in contaminated water.
  • Areas of high rainfall and poor drainage harbor infections.

Lifecycle

  • Long generation time (12 hours).

Transmission

  • Reservoir hosts include rodents. Reservoir hosts become infected with host-adapted serovars.
  • Leptospira spp are found in the mammalian kidney and excreted in the urine. The reservoir host shows none or only mild clinical signs.
  • Direct or indirect - contact with mucous membranes or damaged skin.
  • Indirect - depends on wet conditions.

Pathological effects

  • Antibodies important for clearance.
  • Damage vascular epithelium.
  • Damages parenchymal tissue in organs to which it is disseminated.

Diseases associated with L. interogans

  • Subclinical with L. canicola.
  • Acute hemorrhagic disease, L. icterohemorrhagiae.
  • Less acute icteric type, L. canicola or L. icterohemorrhagiae.
  • Uremia, L. canicola.
  • Chronic hepatitis, L. grippotyphosa.
  • Acute renal failure, L. grippotyphosa.

Control

Control via chemotherapies

Control via environment

  • Prevent contact with urine-contaminated water, especially near rodent habitats.

Vaccination

Diagnosis

Useful samples

  • Mid-stream urine - dark field examination or attempted culture, PCR.
  • Blood - serology, PCR.
  • Kidney/liver tissue - histopathology and fluorescent antibody, PCR.

Specimen storage

  • Urine for culture - specialist transport medium.
  • Tissue for fluorescent antibody testing - snap frozen in liquid nitrogen.
  • Alternatively, can make tissue impression smears, or urine sediment smears, for FA testing.

Transport of samples

Field diagnosis

  • Direct visual demonstration on wet mounts from urine samples, examined by dark field or phase-contrast microscopy.

Laboratory diagnosis

  • Serology - serovar-specific; microscopic agglutination test.
  • Immunofluorescent antibody staining.
  • Silver impregnation of fixed tissue.
  • Polymerase chain reaction for bacterial genetic material; blood during bacteremia; urine, kidney.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kalin M, Devaux C, DiFruscia R et al (1999) Three cases of canine leptospirosis in Quebec. Can Vet J 40 (3), 187-191 PubMed.
  • Birnbaum N, Barr S C, Centre S A et al (1998) Naturally acquired leptospirosis in 36 dogs: serological and clinicopathological features. JSAP 39 (5), 231-236 PubMed.
  • Weekes C C, Everard C O & Levett P N (1997) Seroepidemiology of canine leptospirosis on the island of Barbados. Vet Microbiol 57 (2-3), 215-222 PubMed.
  • Rentko V T, Clark N, Ross L A et al (1992) Canine leptospirosis. A retrospective study of 17 cases. JVIM (4), 235-244 PubMed.