Adaptation to Biological Stressors: Diseases

Adaptation to Biological Stressors: Infectious Disease

• This presentation covers infectious diseases, including malnutrition, human adaptations, epidemiological transitions, historical disease contexts, and modern city disease/culture.

Introduction

• Malnutrition
• Infectious diseases
  • Humans, disease, and adaptations
  • Epidemiological Transition
  • History of disease
  • Modern cities, disease, and culture

1. Humans and Disease

• Co-evolving for thousands of years
• Have we adapted?
  • Yes
  • No
  • Somewhat

Infectious Diseases

• Vector-borne diseases
  • Malaria (Plasmodium falciparium, Anopheles mosquitoes, human and mosquito reproductive cycles)
• Direct-contact diseases
  • Ebola
• Intimate-contact diseases
  • HIV
• Poor sanitation diseases
  • Cholera

Malaria Adaptations

• Hb variants
  • HbS: Sickle cell trait
  • Thalassemia
  • G6PD deficiency

Ebola Virus Disease (EVD)

• Direct-contact/Zoonosis
  • Highly virulent in humans
    • Pathogen's ability to infect/damage a host
• Fruit bats are natural hosts
  • Close contact (blood, secretions, organs) with infected animals leads to spread
• Monkeys and apes
  • Human-to-human transmission via direct contact

Ebola Virus Ecology and Transmission

• Animal-to-animal transmission involves bats
• Spillover events occur when animals/humans are infected
• Human-to-human transmission through blood and body fluids from sick or deceased individuals

Ebola Virus Disease (EVD): Symptoms

• Symptoms include fever, fatigue, muscle pain, headache, sore throat, vomiting, diarrhea, rash, and impaired kidney/liver function
• Both internal/external bleeding can occur in some cases
• Transmitted via contact with bodily secretions
• 50% fatality rate (25-90% range)
• First outbreak in Central Africa (1976)

EVD: Treatment and Adaptations

• Rehydration with oral/IV fluids
• Monoclonal antibody treatments
• Bind to virus proteins like natural antibodies
• RCTs during the 2018-2020 outbreak in DRC
• Vaccine (one approved, effective against one virus)
• Population-specific adaptations (future considerations)

HIV: Intimate-Contact Disease

• Human Immunodeficiency Virus
• Weakens immune system
• Destroys CD4 (T) cells
• Harder to fight infections/cancer
• Originated in West Africa from chimpanzees and sooty mangabeys
• Existed in the U.S. during the mid-to-late 1970s

HIV Adaptations

• Varying degrees of resistance (some live 20+ years, some die within a year)
• Chemokine receptor 5 (CCR5)
  • Allows HIV to enter cells
• CCR5-432 variant (mutation)
• Lack of receptors
  • Homozygous carriers resistant to certain HIV strains

HIV Treatment

• Antiretroviral therapy (ART)
  • Can reduce viral load to undetectable levels
    • Prevents or reduces transmission if undetectable
• Pre-exposure prophylaxis (PrEP)
  • Reduces risk of infection
• Post-exposure prophylaxis (PEP)
  • Taken within 72 hours of exposure

Cholera

• Poor sanitation
• Water-borne disease
• Vibrio cholerae (fecal contamination)
• Symptoms
  • Dehydration, diarrhea, and vomiting
• 2.9 million cases, 95,000 deaths yearly, 10% severe symptoms can die in hours
• Variation in susceptibility (Type O more susceptible)
• Hyperactivation of key intestinal signaling molecules causing inflammation
• Excretion of electrolytes and water

Cholera Adaptations

• Variation in susceptibility
  • Type O blood more susceptible
• Lack of A or B antigens
• Hyperactivates a signaling molecule, leading to inflammation, electrolyte/water excretion.

Malnutrition & Infectious Disease

• Under-nutrition linked to infections
• Poverty affects food security, access to healthcare, and living conditions
• These create higher pathogen loads and enteropathy (enteric disease). Non-immunological factors like respiratory muscles, dehydration, and cardiac functions are impacted by these conditions.

2. Epidemiological Transition

• Explains shifts in disease patterns over the past 10,000 years
• Abdel Omran (1971) - How patterns of mortality change
• Disease burden shifted from infectious to chronic illnesses (communicable to non-communicable)
• Ongoing issue in low and middle-income countries

Epidemiological Transition - Now/Future

• Age of pestilence & famine
  • Emergence of infectious and nutritional diseases
• Age of receding pandemics
  • Industrial Revolution
• Age of chronic and man-made diseases
  • “Degenerative disease” (late 20th century)
• Novel diseases (re-emergent infections)
  • Increasing microbial resistance (antibiotic resistance)
  • Increasing zoonotic diseases
  • Rapid spread due to globalization

3. Diseases of the Past

• Hunting-gathering/foraging prior to 10,000 years ago
  • Small populations, temporary settlements
  • Diseases of exposure/parasites/zoonoses
• ~10,000 years ago (Neolithic)
  • Agriculture
  • Increased population densities
  • Sanitation issues
• Preindustrial cities (~3000 BCE)
  • Very high densities
  • Food/water contamination, sewage
  • Typhoid fever, cholera, etc.

Communicable Diseases of the Past

• Originated from animal viruses (measles, rubella, mumps, chicken pox, smallpox)
• Sweep through populations every few years
• Children not previously exposed susceptible

Modern Cities, Disease, and Culture

• Culture influences relationships with physical & biological environments
• Modern city challenges
• Legionnaire's disease (pneumonia-like symptoms, Legionella bacteria, AC ducts, hot tubs)

Next Steps: Disease Warriors (2006)

• Work of early researchers to understand & fight disease
• Vaccines (past, present, future)

This quiz explores the adaptations humans have made in response to infectious diseases. It covers topics from malnutrition to the epidemiological transitions and the historical context of diseases. Additionally, it discusses specific diseases like malaria and Ebola, and their impacts on human evolution.