Leptospirosis Flashcards
What is lepatospirosis?
Zoonotic infection caused by spriochetes (order) of genus leptospira.
mammalian hosts secrete leptospira from renal tubules - small rodents, environment contaminated
Ethology of leptosirosis
Caused by the pathogenic spirochetes of the genus Leptospira
Leptospires are thin, helically coiled, motile bacteria
Serologically classified into more than 200 pathogenic serovars (variant), diverse
Classification of leptospirosis
Based on serology - pathogenic or non pathogenic leptospira
or by molecular methods - divded as pathogenic, intermediate and saprophytic (doesn’t cause ilness)
Epidemiology of leptospirosis
- Broad geographic distribution due to wide spectrum of mammalian hosts
- animal hosts divided into maintenance hosts (small) and accidental hosts
reservoirs - rodents, dogs, domesticate and wild animals, shedding can be life long
stats on infection
Estimated 1.03 x 10^6cases and ~60K deaths annually
50-80% cases and deaths occur in adult males aged 20-49 years – based on occupational exposures
Greatest morbidity and mortality occur in resource-poor settings
60% global alerts between 2007 and 2013 reported from Americas
Most vulnerable are rural subsistence farmers and urban slum dwellers
Extreme weather events (eg flooding) associated with epidemics
Growth of urban slums worldwide has created conditions favourable to rat-borne transmission
Leptospirosis pathogenesis
Leptospires penetrate mucous membranes or abraded skin and multiply rapidly upon entering the blood stream
Spread to the kidney, liver, spleen, CNS, eyes, genital tract
Initial antibody response clears most organs except the kidneys where infection can remain and be shed for weeks to months
Leptospirosis causes severe vasculitis (complement mediated inflammation) with endothelial damage, kidney damage, shock, heart damage with arrhythmias.
Liver damage with icterus and low vit k levels
Eye disease-uveitis
Clinical presentation
Mild virus like syndrome
(anicteric leptospirosis) - systemic illness with aseptic meningitis
Iceteric leptospirosis - overwhelming disease in small proportion (Weil’s disease)
- vascular collapse
- thrombocytopenia
- haemorrhage
- hepatic and renal dysfunction
most cases subclinical, 85% won’t have recognisable illness.
Clinical disease
Estimated cause of 5-70% of undifferentiated fever
Acute symptoms develop 7-12 days after infection
Biphasic illness
- Acute – 3-7 days duration of fever, headache, myalgia
- Immune phase – appears during 2nd week of illness
Mild disease has case fatality rate <1%
10-15% of cases show severe disease (Weil’s disease with jaundice,
haemorrhage and renal failure with mortality of ~5-20%)
Differential diagnosis includes dengue, malaria, rickettsioses, flu, etc
What is Weil’s disease?
Severe leptospirosis with kidney and liver involvement
- fever
- jaundice
- renal failure
- haemorrhage
- respiratory distress
- meningitis
- mortality 5-20%
severe pulmonary haemorrhage syndrome
- 50-70% mortality rate
- rapid patient decline
What are the diagnostic tools for leptosirosis?
Serological detection - MAT, testing different serovars, agglutination = been infected by that serovar. available and pratical. can give false positives.
Molecular detection - PCR with blood or urine test
Isolation - semisolid or solid (MORU) media, takes time
Describe microagglutination tests /serological test MAT
Different serovars in culture and your test serum, add it to the different serovars
- complex and time consuming but invaluable for diagnosis, epidemiology and serological characterisation of leptospiral isolates
- high titres of 4 fold rise indicates recent/active infection
Treatment of leptospriosis
Mild lepto:
- Doxycycline
alternative:
- amoxicillin
- azithromycin dehydrate
moderate-severe
- penicilin G
alternative:
- ampicillin IV
- azithromycin dihydrate
- ceftriazone
- cefotaxime
Pre-exposure prohylaxis
Avoid high risk exposures or take personal protective measures
(boots, gloves, goggles, etc)
Pre-exposure antibiotic prophylaxis not routinely recommended
Where high risk exposure unavoidable, pre-exposure prophylaxis may
be considered for short-term exposures (doxycycline 200 mg once
weekly)
Post-exposure prophylaxis
single exposure:
- doxycycline, 2 capsules within 24/72 hrs
moderate risk: 2 capsules for 3-5 days
high risk, continuous exposure
- doxycycline once weekly until end of exposure
How can lepto be prevented?
- inactivated vaccine for dogs and bovines
- human vaccines in cuba and china, 3 strains of serovars and adjusvant
- but for most farmers it’s too expensive to vaccinate animals
focused education programmes in high risk occupational groups e.g those working with animals on farms
- pest control, wearing gloves, footwear, water proof plasters
