One Health Concept in Community Medicine

Definition

"One Health is a global collaborative, multisectoral, and transdisciplinary approach to disease that recognizes the interconnection between people, animals, plants, and their shared environment." — Fishman's Pulmonary Diseases and Disorders

Historical Background

The Three Pillars (Interconnected Spheres)

        HUMAN HEALTH
             ↕
       ANIMAL HEALTH
             ↕
   ENVIRONMENTAL HEALTH

Governing Bodies — The One Health Quadripartite

1. WHO (World Health Organization) — human health dimensions
2. WOAH/OIE (World Organisation for Animal Health) — animal health
3. FAO (UN Food and Agriculture Organization) — food systems & agriculture
4. UNEP (UN Environment Programme) — environmental dimensions (newest member)

Six Focus Areas (WHO/Quadripartite Framework)

Why It Matters — Key Statistics

• ~60% of emerging infectious diseases globally originate from animals (wild or domestic)
• Over 30 new human pathogens detected in the last 3 decades — 75% originated in animals
• Factors driving emergence: deforestation, climate change, global travel/trade, ecotourism, intensive agriculture, urbanization

Applications in Community Medicine

1. Zoonosis Prevention & Control

2. Antimicrobial Resistance (AMR)

• Antimicrobial stewardship in hospitals and outpatient settings
• Regulation of antibiotic use in food animals
• Environmental surveillance of resistance genes

3. Pandemic Preparedness

4. Food Safety

5. Environmental Health

One Health vs. Traditional Approaches

Relevance to Public Health Practice

• Community level: local zoonosis surveillance, food safety inspections, vector control
• National level: integrated disease reporting systems, agricultural policy
• Global level: WHO/FAO/WOAH joint outbreak investigations, pandemic preparedness frameworks

Summary

1. Most emerging infections are zoonotic in origin
2. AMR is a cross-species, cross-environment problem
3. Climate and ecological change continuously reshape disease geography
4. Effective prevention requires breaking down silos between human medicine, veterinary science, and environmental science

One Health Approach in Leptospirosis

Why Leptospirosis is a Model One Health Disease

"Leptospirosis is a clear example of why we need collaboration between clinicians, veterinarians, environmental authorities and communities. Only a truly integrated approach can reduce the risk of outbreaks." — Dr Jane Sykes, WSAVA / WOAH (2025)

The Pathogen — Quick Background

Leptospira interrogans — helical spirochete with hooked ends (Goldman-Cecil Medicine)

• Over 25 serogroups and 250 serovars with different geographic distribution and host specificity
• Organisms colonize the renal tubules of reservoir animals → persistent urinary shedding for months to years
• Survive in humid soil and water for many months → environmental reservoir

The Three Dimensions of Leptospirosis (One Health Lens)

1. HUMAN DIMENSION

2. ANIMAL DIMENSION

3. ENVIRONMENTAL DIMENSION

• Leptospira survives in warm, moist soil and stagnant/slow-moving freshwater (pH 6.0–8.0)
• Some strains form biofilms on surfaces, resisting antibiotics and environmental degradation — explaining outbreaks months after flooding
• Flooding is the major environmental trigger: washes leptospires from rodent burrows into water supplies
• Climate change → more extreme rainfall events → increasing leptospirosis incidence projected
• Land use: deforestation, agriculture, urbanization increase human–animal–environment contact

One Health Framework Applied to Leptospirosis

        HUMAN SECTOR          ANIMAL SECTOR
        (clinicians, public   (veterinarians, farmers,
         health, epidemiology) animal health workers)
                    \              /
                     \            /
                   ONE HEALTH APPROACH
                     /            \
                    /              \
       ENVIRONMENTAL SECTOR    LABORATORY SERVICES
       (ecologists, urban       (shared surveillance,
        planners, WASH)          diagnostics, serovars)

One Health Interventions — Structured by Sector

A. Human Health Sector

1. Clinical awareness: Recognizing leptospirosis in febrile illness, especially in at-risk occupational groups and after floods
2. Chemoprophylaxis: Doxycycline 200 mg/week for high-risk short-term exposures (military, adventure travelers)
3. Treatment: Penicillin G or doxycycline (mild–moderate); ceftriaxone/penicillin IV for severe disease
4. Personal protection: Waterproof boots/gloves for occupational exposure; avoid wading in floodwaters; cover cuts before water exposure
5. Public health messaging: Community education about flood risk, animal contact, and safe water practices
6. Integrated surveillance: Mandatory reporting, standardized case definitions, data sharing with animal and environmental sectors

B. Animal Health Sector

1. Vaccination of companion animals: Dogs — annual leptospirosis vaccines (bivalent/quadrivalent) are effective; all dogs at risk regardless of urban/rural setting
2. Vaccination of livestock: Cattle vaccination (Hardjo serovar) reduces urinary shedding on farms
3. Veterinary surveillance: Monitoring serovar distribution in animal populations; linking animal serovar data to human case serogroups
4. Rodent control (vector control):
   • Reduction of rodent habitats in urban areas
   • Rodent sentinel surveillance programs — identifying Leptospira-positive rodent populations
   • Rodent baiting and trapping in high-risk areas
5. Farm hygiene: Restricting livestock access to water sources; keeping livestock areas clean to reduce urine contamination

C. Environmental Sector

1. WASH (Water, Sanitation, Hygiene): Clean water supply; sewage management; reduce human contact with contaminated water
2. Flood control infrastructure: Urban drainage systems, early flood warning — critical in slums/informal settlements where rodent access to homes is high
3. Land use planning: Buffer zones between wildlife habitats and human settlements; slaughterhouse siting
4. Environmental monitoring: Testing water sources (rivers, canals, floodwater) for Leptospira DNA using PCR
5. Climate adaptation: Planning for increased flood frequency and leptospirosis risk under climate change models

D. Laboratory and Surveillance (Cross-Sector)

• Integrated sentinel surveillance: Indonesia's pilot program (WHO/Ministry of Health + Agriculture + Environment) monitors rodents, water, and human cases simultaneously
• Shared diagnostics: MAT (Microscopic Agglutination Test — gold standard), PCR, IgM ELISA used across human and veterinary labs
• Molecular typing: Linking human outbreak serovars to animal reservoirs via genomic methods
• Data systems: One integrated platform for human, animal, and environmental leptospirosis data (operationalized in Brazil, Malaysia, Chile as models)

Real-World One Health Case Studies

One Health Duties in Leptospirosis — Ethical Dimension

• Physicians: Prevent contagion, treat the infected
• Veterinarians: Immunize animal reservoir hosts; reduce urinary shedding
• Environmental authorities: Maintain safe water; control rodent populations; mitigate flood damage
• Policymakers/planners: WASH infrastructure, urban design, climate preparedness

Key Message for Community Medicine

• Goldman-Cecil Medicine, International Edition (Chapter 298 — Leptospirosis)
• Harrison's Principles of Internal Medicine, 22E (2025) (Chapter 189 — Leptospirosis)
• Fishman's Pulmonary Diseases and Disorders
• WHO Integrated Leptospirosis Surveillance (2022)
• WOAH World Zoonoses Day Report (2025)
• PMC9696530 — One Health: An Effective and Ethical Approach to Leptospirosis Control in Australia