Chapter 22: One Health - Interconnected Health of Environment, Humans, and Animals

Chapter 22: One Health - The Interconnected Health of the Environment, Humans, and Other Animals

Overview

  • Chapter 22 focuses on One Health, highlighting the connections among human health, animal health, and environmental health.

  • Importance: This interconnectedness arises from global travel, movement of plants and livestock, climate change, and rising human populations bringing humans and animals into closer contact.

Historical Context

  • One Health is not a new concept; it dates back to the 1800s.

    • Pasteur and Koch recognized the links between human and animal health.

    • The concept has evolved to encompass the health and sustainability of entire ecosystems.

Environmental Disruption and Pathogen Transmission

  • Environmental disruptions can facilitate the transmission of pathogens among animals and humans.

  • Changes in ecosystems can lead to the evolution of new microbial traits and the persistence of pathogens in the environment.

  • Example of Environmental Disruption: The Black Death (14th century)

    • Bacterium: Yersinia pestis.

    • **Process:

    • Lake turnover led to Yersinia pestis being brought to the surface.

    • Rats drank the water, became carriers (without showing disease).

    • Fleas that bit the rats then bit humans, leading to widespread illness.

    • Result: Approximately 25 million deaths, about a third of Europe’s population at that time.

    • Four organisms involved: Bacterium, rats, fleas, humans.

  • Global Mixing Bowl Concept

    • Interplay of microbes, animal hosts, and humans fosters the evolution of new pathogens and zoonotic diseases (diseases transferred from animals to humans).

Zoonosis

  • Definition: The transfer of disease-causing microorganisms from animals to humans.

  • Zoonotic diseases can move back and forth between humans and animals through ecological disturbances.

Example of Zoonosis and Global Mixing Bowl

  • Avian and Human Viruses in Swine:

    • Swine infected by both avian and human viruses.

    • Genetic mixing occurs, which can lead to new strains of viruses that may return to humans.

Emerging and Reemerging Infectious Diseases

  • Increase in infectious diseases in humans and animals over the past four decades:

    • About 75% of newly emerging human diseases are zoonotic.

  • Examples: Measles and mumps, linked to lower vaccination rates.

    • 2015 Measles Outbreak:

    • 18 states reported cases, with many linked to an outbreak in Disneyland.

    • Lyme Disease:

    • First identified in Lyme, Connecticut in 1976.

    • Caused by the bacterium Borrelia burgdorferi.

    • Spread influenced by urban development and climate change.

    • Involves mice, ticks, deer, and humans.

Lyme Disease Cycle

  1. Newly hatched tick larvae feed on infected mice.

  2. Larvae become infected but do not show disease.

  3. Ticks mature to nymphs and bite humans and deer.

  4. Nymphs mate; females lay eggs.

  5. Cycle continues with new larval ticks feeding on mice.

Water and Infectious Disease

  • Pathogen-Free Water in the US: Most tap and bottled water is free from human pathogens.

  • Global Water Access:

    • According to the World Health Organization:

    • 1 billion people lack access to clean water.

    • 2.6 billion lack basic sanitation.

  • Impact of Unsafe Water:

    • Waterborne diarrheal diseases account for 4.1% of the daily global disease burden.

    • More than 3.4 million deaths annually related to unsafe drinking water.

    • Daily deaths: Approximately 4,000 children, often from contaminated water.

  • Water Monitoring:

    • Focus on detecting E. coli as an indicator of water safety.

    • Testing Method: Membrane filter technique using selective media (e.g., endo agar).

    • Results indicate presence of E. coli by visible growth or fluorescence.

Foodborne and Environmental Pathogens

  • Infections can occur from food sources, particularly when they are contaminated by fecal matter from infected animals.

  • Common sources: contaminated beef or produce (e.g., lettuce, spinach).

  • Foodborne Illness Examples:

    • Infections may also arise from damaged food processing systems.

Climate Change and Its Effects

  • Climate change influences pathogen spread:

    • Droughts can increase pathogen prevalence.

    • Increased rainfall can lead to the increase in vectors (organisms that carry pathogens).

    • Predictions indicate that a 2-3 degree increase in temperature will drastically increase malaria cases.

Hantavirus Outbreak of 1993

  • Occurrence: Unusual respiratory illness in healthy adults across the American Southwest.

  • Factors: Wetter conditions from El Niño led to increased populations of deer mice, which are carriers of hantavirus.

Benefits of Microbes

  • Not all microbes are harmful; many are beneficial:

    • Microbes assist in breaking down waste and pollutants in the environment.

    • New York City: Microbes in wastewater treatment plants manage over 1 billion gallons of sewage daily, removing 65% of organic matter.

Composting Process

  • Definition: Anaerobic process carried out by diverse aerobic microbial communities.

    • Initial decomposition leads to a shift from mesophilic (moderate temperature) to thermophilic (high temperature) organisms.

Bioremediation Examples

  • **Oil Spill Clean-ups:

    • Exxon Valdez (1989):** More oil present than microbes could degrade; bioremediation aided by nutrient addition.

    • Deepwater Horizon (2010): Microbes biodegraded half of the dispersed oil within two to six days, 90% in a month.

    • Key organisms involved: Oceanospirillales and Corynebacterium.

Conclusion

  • One Health embodies the interconnectedness of environment, human health, and animal health, and it highlights the critical importance of addressing ecological disturbances, climate change, and public health threats in a unified manner.