Equis ISSN 2398-2977

Leptospirosis

Synonym(s): Periodic ophthalmia, Equine periodic ophthalmia, Equine recurrent uveitis, Moon blindness

Contributor(s): Tom Divers, Melissa Kennedy, Alex Morrow, Vetstream Ltd

Introduction

  • Leptospirosis is a worldwide zoonotic bacterial disease affecting humans, wildlife and domestic animals.
  • Cause: various serovars ofLeptospira interrogans  Leptospira interrogans  .
  • Seven species based on genetics; many serovars (>200) based on antigenicity.
  • Infections are frequently insidious or subclinical.
  • Signs: pyrexia, icterus and abortions with the development of recurrent uveitis (periodic ophthalmia) later.
  • Diagnosis: history, signs, serology.
  • Treatment: oxytetracycline, penicillin or streptomycin.
  • Prognosis: good except guarded in newborn foals or adults which develop recurrent uveitis.

Pathogenesis

Etiology

  • Genus:Leptospira.
  • Species:interrogans,kirschneri.
  • Within these species both pathogenic and non-pathogenic serovars exist.
  • Serovars belonging to thepomona,icterohaemorrhagiae,australis,grippotyphosa,Hebdomadis,tarassovi,autumnalis,ballumandcanicolaserogroups have been isolated from horses with clinical syndromes suggestive of leptospirosis.
  • L. interrogansserovarpomonaappears to be more pathogenic in horses than serovarbratislavafor which the horse is the maintenance host. Cattle, pigs and wildlife are the definitive hosts ofL. pomona.
  • Serovarpomonastrainkennewickiiis the most common cause of disease in North America.
  • L. interrogansserovarbratislavais reported to be common in North America, Ireland and northern Europe, but is generally considered to be host adapted and of minimal pathogenicity.
  • L. interrogans icterohaemorrhagiaeis the predominant serogroup in seroprevalence studies in Japan, Sweden, Scotland, Holland, Chile and Brazil.
  • L. interrogans copenhageniis common in Brazil.
  • L. kirschneri grippotyphosastrains predominate in Germany, Poland and Czechoslovakia and are important in France, Russia and Egypt.
  • L. interrogansserovarsejroewas the predominant serovar in horses in Japan.
  • Ballumis important in Venezuela.
  • Autumnalisstrains predominate in West Indies.

Specific

  • Leptospiraorganisms are obligate aerobes with an optimal growth temperature of 27.7-30°C/82-86°F.
  • Leptospiral growth is greatest in stagnant neutral or slightly alkaline pH.
  • Leptospiradie quickly when exposed to dryness, freezing temperatures and most chemical disinfectants.
  • Exposure to water contaminated by urine of the maintenance host.
  • Severity of infection depends on pathogenicity of the strain involved and the hosts' immune status.
  • Virulence of the infecting serovar is more important than the challenge dose.

Pathophysiology

  • Exposure of horses to leptospires appears to be common but clinical disease is rare, most infections being asymptomatic.
  • An animal may be infected either by leptospires which are adapted to and carried by members of that species (maintenance host, host adapted) in their kidneys, eg serovarbratislavain horses, or by leptospires carried by another animal species which shares the same environment, in which case infection of an incidental or accidental host tends to be more pathogenic.
  • Bratislavahas been reported in disease outbreaks in foals.
  • Geographical differences in the seroprevalence of the various serotypes is probably a reflection of the level of exposure to serotypes maintained by other domestic or wild animals.
  • Leptospires enter the vascular space through conjunctival, nasopharyngeal, small intestinal and genital mucous membranes. Abraded or soft moist skin may also be a portal of entry.
  • Bacteremia occurs with invasion of internal organs. The severity of organ involvement depends on the presence or the rapid development of a humoral immune response.
  • Opsonised bacteria are rapidly eliminated. Once tissue invasion has taken place infection may persist, especially with host adapted serovars, despite the presence of circulating antibodies.
  • Tissue damage is due to bacterial virulence factors (lipooligosaccharide enzymes) and the inflammatory response.
  • The organism is retained in the proximal kidney tubules, genital tract, eye or CNS. In this situation animals can remain carriers/shedders for the rest of their life.
  • In accidental infections in which the animal is infected with non-host-adapted strains, infection tends to be short and urinary shedding brief or non-existent.
  • Renal and liver dysfunction have occasionally been reported.
  • Fetal infections occur following localization of the organism in the pregnant uterus (placenta, umbilicus and fetus) and results in abortions, still births or weak neonates.
  • Uveitis is likely to be the result of persistent leptospiral infection or antigen in the eye and/or an induced auto-immune recognition of self-antigens because of partial identity with leptospiral antigens. Recurrent episodes of uveitis may be associated with epitope spreading within the uveal tissues.
  • Recurrence of acute eye lesions results in chronic sequelae.

Timecourse

  • Bacteremia occurs in 4-10 days after infection and may persist for hours to days.
  • Fever lasts for up to 2-3 days.
  • Clinical uveitis develops 1-24 months after infection - interval between recurring attacks is often between a week and a month.

Epidemiology

  • The horse would appear to be the maintenance host for serovarbratislava.
  • Hedgehogs are an important carrier animal forbratislavain some European countries.
  • Pigs and wildlife are reported to be reservoir hosts for serovalpomona.
  • Kennewickitype has frequently been found in wild rodents and skunks. Wild animals are important reservoirs, including rodents which may infest stored feed.
  • Domestic animals, especially cattle can also be a source.
  • Pathogenic serovars ofL. interroganslocalize in the kidneys or genital tract especially of the maintenance hosts. Transmission is generally through urine although all body secretions may contain leptospires during the acute stage of the disease.
  • Generally the organism does not survive long in the environment but under favorable conditions they may survive for several weeks.
  • Moderate temperature and moisture provide optimal conditions for transmission.
  • Prevalence of infection is highest in the autumn in some countries.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references fromPubMed andVetMedResource.
  • Hamond Cet al(2014)Urinary PCR as an increasingly useful tool for an accurate diagnosis of leptospirosis in livestock.Vet Res Commun38(1), 81-85PubMed.
  • Arent Z J & Kedzierska-Mieszkowska S (2013)Seroprevalence study of leptospirosis in horses in northern Poland.Vet Rec172(10), 269PubMed
  • Martins G & Lilenbaum W (2013)The panorama of animal leptospirosis in Rio de Janeiro, Brazil, regarding the seroepidemiology of the infection in tropical regions.BMC Vet Res9(1), 237PubMed.
  • Verma A, Stevenson B & Adler B (2013) Leptospirosis in horses.Vet Microbiol167(1-2), 61-66PubMed.
  • Broux Bet al(2012)Acute respiratory failure caused by Leptospira spp. in 5 foals.J Vet Intern Med26(3), 684-687PubMed.
  • Gilger B Cet al(2010)Long-term outcome after implantation of a suprachoroidal cyclosporine drug delivery device in horses with recurrent uveitis.Vet Ophthal(5), 294-300PubMed.
  • Yan Wet al(2010)Experimental Leptospira interrogans serovar Kennewicki infection of horses.J Vet Intern Med24(4), 912-917PubMed.
  • Bernard W (2009)Leptospirosis.Equine Vet Educ21(9), 485-486.
  • Divers T Jet al(2008)Ocular penetration of intravenously administered enrofloxacin in the horse.Equine Vet J 40(2), 167-170PubMed.
  • Odontsetsed Net al(2005)Serological prevalence ofLeptospira interrogansserovar Bratislava in horses in Mongolia.Vet Rec157(17), 518-519PubMed.
  • Sebastian Met al (2005)Funisitis associated with Leptospiral abortion in an equine placenta.Vet Pathol 42 (5), 659-662PubMed.
  • Faber N A, Crawford Met al(2000)Detection of Leptospira spp in the aqueous humor of horses with naturally acquired recurrent uveitis.J Clin Microbiol38(7), 2731-2733PubMed.
  • Wollanke B (1998)Intraocular and serum antibody titers to Leptospira in 150 horses with equine recurrent uveitis (ERU) subjected to vitrectomy.Berl Munch Tierarztl Wochenschr111(4), 134-139PubMed.
  • Bernard W V (1993)Leptospirosis.Vet Clin N Am Eq Pract9, 435-444 (comprehensive review)PubMed
  • Poonacha K Bet al(1993)Leptospirosis in equine fetuses, stillborn foals and placentas.Vet Pathol30, 362-369PubMed.
  • Roberts S J (1969)Comments on equine leptospirosis.JAVMA155(2), 442-445PubMed.

Other sources of information

  • Hines M (2014)Leptospirosis.In: Equine Infectious Disease.2nd edn. Eds: Sellon D C & Long M T. Elsevier, St Louis, Missouri. pp 302-311.
  • Hanson L E, Martin R J, Gibbons R W & Schnurrenberger P R (1969)Equine leptospirosis.In: Proc Ann Meeting Anim Health Assoc.73, 169-180.


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