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Leptospirosis is spread in the urine of infected animals most commonly rats, mice, cows, pigs and dogs. Start antibiotics on basis of clinical signs before cultures are available

About

• Leptospirosis is a zoonotic infection due to the organism Leptospira interrogans

Pathology

• Live in the renal tubules of chronically infected asymptomatic mammals
• Bacteria are then shed through the urine of these animals
• Bacteria can survive for weeks to months in shaded, warm, and humid conditions

Risks

• Animal workers, sewage workers.
• Those involved with water sports are at risk
• Pets and bites rare
• Human-to-human transmission is exceptional.

Aetiology

• Gram negative coiled bacteria. No capsule, non-sporing.
• Spirochetes with hooked ends
• Gain entry to human hosts via mucous membranes or abraded skin

Hosts

• Rat - Rattus Norvegicus shed living in convoluted tubules in huge numbers in rat urine

Clinical

• Symptoms come on 1-2 weeks following exposure
• Fever with conjunctival suffusion hyperaemia is a useful sign
• Oliguric renal failure with renal casts and proteinuria and haematuria
• Tender hepatosplenomegaly and jaundice but liver failure and encephalopathy are classically not seen. There may be a prolonged PT and haemorrhage.
• ARDS and total bilateral pulmonary consolidation with a "pulmonary syndrome" has been seen more in Asia and can lead to multi-organ failure, ARDS and very high mortality, haemoptysis, patchy lung infiltrates on CXR and respiratory failure.
• Bleeding leads to skin and bruising, epistaxis, haematemesis, melaena, bloody pericardial/pleural effusions or bloody subarachnoid space
• Aseptic meningitis resembling a viral meningitis (increased neutrophils and elevated AST)
• Myocarditis, Encephalitis

Classical Presentations

• Mild influenza-like illness
• Weil's syndrome characterized by jaundice, renal failure, haemorrhage, and myocarditis with arrhythmias,
• Meningitis/meningoencephalitis
• Pulmonary haemorrhage with respiratory failure.

Differential

• Dengue, Typhoid fever, Malaria, Scrub typhus, Hantavirus

Investigations

• FBC - ↓ platelets, ↑ WCC (classically neutrophils)
• U&E - ↑ Creatinine, proteinuria, haematuria
• LFT: ↑PT, ↑ ↑ AST ↑ ALT ↑ Bilirubin ↑ CK
• LP/CSF - ↑ protein and normal glucose
• Before day 10 - positive blood cultures. After 7 days - positive urine cultures
• Positive IgM serology after 1st week so treat on suspicion
• Microscopic agglutination test (MAT): seroconversion or ↑ x4 in titre between acute and convalescent sera is confirmatory
• PCR to detect leptospiral DNA blood or urine (after day 8 and for months)

Prevention

• Wash your hands with soap and water after handling animals or animal products and clean any wounds as soon as possible
• Cover any cuts and grazes with waterproof plasters
• Wear protective clothing if you're at risk through your job
• Shower as soon as possible if you've been in potentially infected water
• Vaccinate dogs (there isn't a vaccine for people)
• Don't touch dead animals with your bare hands
• Don't drink water from rivers, canals or lakes that hasn't been boiled

Complications

• Oliguria caused by acute renal failure
• Haemorrhage can also be a major concern.
• Severe pulmonary haemorrhage often needs ventilation
• Aseptic meningitis
• ARDS, Haemolytic anaemia
• Guillain-Barre syndrome.
• Circulatory collapse

Management

• Usually supportive as usually self-limiting.
• Transfuse for significant haemorrhage
• Renal support/replacement can be life-saving. AKI typically resolves

Antibiotic (Several choices)

• Severe Disease: IV Benzylpenicillin 1.5 MU 6 hourly for 1 week or Ceftriaxone 1 g daily for one week.
• Oral Doxycycline 100 mg bd for 1 week for mild disease
• A mild Jarisch-Herxheimer reaction may occur with Penicillin therapy. High mortality > 10%

Prevention

• Doxycycline 200 mg weekly has been shown to help in high-risk individuals