Lesson 17:

#Leptospirosis

Parajuli SB, 2026 (www.suryaparajuli.com.np)

For
Community Medicine (Kathmandu University) | MBBS 6th Semester |
Birat Medical College Teaching Hospital

#🔹 Specific Learning Outcomes (SLOs)

At the end of the session, the learner will be able to

• define leptospirosis and explain its zoonotic nature.

• describe agent, host, and environmental factors.

• explain transmission and risk groups.

• explain complications of leptospirosis, including Weil’s disease and pulmonary hemorrhage, and assess their impact on mortality

• differentiate clinical types (anicteric vs icteric).

• outline diagnosis, treatment, and prevention.

#📘 1. Definition

Leptospirosis is a zoonotic infection caused by Leptospira (spirochete), transmitted from animals to humans through contaminated water, soil, or direct contact.

👉 Simple idea:
“Disease from animal urine → enters through skin → spreads in body”

#🌍 2. Public Health Importance

Most widespread zoonotic disease

Common in tropical countries (like Nepal)

Strongly linked with:

• floods

• heavy rainfall

• poor sanitation

📊 Burden

• ~1 million cases/year

• ~60,000 deaths

👉 Often underdiagnosed

#🔬 3. Epidemiological Determinants

#🧫 A. Agent Factors

Organism: Leptospira interrogans

Type: spirochete (thin, motile, spiral)

Has many serovars (>200)

👉 Important:

• Only some strains are pathogenic

• Cross-reactivity seen in tests

#🐀 B. Reservoir (VERY IMPORTANT)

Main reservoir:

👉 Rats (most important) ⭐

Other animals:

• Dogs

• Cattle

• Pigs

• Sheep

👉 Key concept:
Animals carry infection without symptoms

#🧍 C. Host Factors

Age:

Common: 20–45 years

Sex:

More in males
👉 Due to occupational exposure

Occupation ⭐ (High yield)

• Farmers

• Sewer workers

• Rice field workers

• Abattoir workers

• Veterinarians

👉 Exposure to contaminated water = key

Immunity:

Serovar-specific immunity

👉 Infection with one type does NOT protect against others

#🌍 D. Environmental Factors ⭐

👉 Core concept:
Leptospirosis = environmental disease

Risk conditions:

• Flooding

• Water logging

• Poor sanitation

• Rodent infestation

Survival of organism:

Survives weeks in:

• water

• moist soil

Best conditions:

• Warm temperature (~22°C)

• Alkaline pH

#🔄 4. Mode of Transmission

#1. Direct Transmission

Contact with:

• urine

• tissues of infected animals

Entry via:

• skin cuts

• mucous membrane

#2. Indirect Transmission ⭐ (Most common)

Contaminated:

• water

• soil

• food

👉 Example:
Walking barefoot in flood water

#3. Droplet Transmission (Rare)

Inhalation of contaminated droplets

#⏳ 5. Incubation Period

Average: 10 days

Range: 4–20 days

#🤒 6. Pathogenesis

• Entry through skin/mucosa

• Spread via blood (leptospiremia)

Damage to:

• liver

• kidney

• blood vessels

👉 Leads to:

• hemorrhage

• organ failure

#🤒 7. Clinical Features

👉 Very important: Wide spectrum

#🟢 A. Anicteric Leptospirosis (Mild) – Most common

Symptoms:

• Fever + chills

• Headache

• Myalgia (especially calf muscle) ⭐

• Conjunctival suffusion ⭐ (red eyes without pus)

Other features:

• Kidney involvement

• Cough, chest pain

• Mild bleeding

👉 Biphasic pattern:

• symptoms improve

• then reappear

#🔴 B. Icteric Leptospirosis (Severe)

Symptoms:

• Jaundice

• Severe myalgia

• Vomiting, diarrhea

• Renal failure

• Hypotension

#⚠️ Weil’s Disease ⭐ (Most Important)

👉 Severe form of leptospirosis:

• Liver failure (jaundice)

• Kidney failure

• Hemorrhage

👉 High mortality

#💀 Fatality

• Mild: low

• Severe: 5–15%

• Pulmonary hemorrhage: >50%

#🔬 8. Diagnosis

❗ Clinical diagnosis is difficult

Because:

symptoms mimic other diseases (dengue, malaria)

#🧪 Laboratory Diagnosis

#1. Culture

Blood → early stage

Urine → after 1 week

👉 Slow (takes weeks)

#2. Serology ⭐

• Microscopic agglutination test (MAT)

• ELISA

👉 IgM ELISA:
positive as early as 2 days

#3. Rapid Tests

Leptodipstick

#💊 9. Treatment

🔹 Drug of Choice

👉 Penicillin

🔹 Alternatives

• Doxycycline

• Amoxicillin

• Ampicillin

🔹 Severe cases

IV penicillin

👉 Early treatment = prevents complications

#🛡 10. Prevention & Control

#🌍 A. Environmental Measures ⭐

• Rodent control

• Proper drainage

• Safe water supply

• Waste disposal

#🧤 B. Personal Protection

• Avoid contaminated water

• Wear boots, gloves

• Maintain hygiene

#💊 C. Chemoprophylaxis

Doxycycline (in high-risk exposure)

#💉 D. Vaccination

Available in some countries

Must match local serotypes

👉 Not widely used globally

#📚 REFERENCES

• World Health Organization (WHO). Managing Epidemics: Key Facts About Major Deadly Diseases. WHO, 2018.

• World Health Organization (WHO). Weekly Epidemiological Record. No. 27, 7 July 2000.

• Centers for Disease Control and Prevention (CDC). Leptospirosis Fact Sheet. 30 January 2018.

• World Health Organization (WHO). Weekly Epidemiological Record. No. 6, 4 February 2011.

• World Health Organization (WHO). World Health, October 1978.

• National Centre for Disease Control (NCDC). National Guidelines for Diagnosis, Case Management, Prevention and Control of Leptospirosis. DGHS, New Delhi, 2015.

• World Health Organization (WHO). World Health, July 1985.

• Coghlan JD. Postgraduate Doctor, May 1983.

• Tierney LM Jr, McPhee SJ, Papadakis MA. Current Medical Diagnosis and Treatment. 38th Edition. 1999.