Disease Ecology

Question 1

What are some different definitions of Health and Disease?

Answer 1

“Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity” (WHO)

“States of health or disease are the expressions of the success or failure experienced by the organism in its efforts to respond adaptively to environmental challenges” (Dubos, 1965)

Question 2

What is the link between biodiversity loss and infectious diseases?

Answer 2

Research has shown that high biodiversity can reduce rates of pathogen transmission and lower disease risk for human beings, wildlife, livestock, and plants.

e.g. West Nile Virus
Low avian diversity -> species that amplify WNV may be able to dominate -> high infection prevalence in mosquitoes and people.

Question 3

How might climate change affect infectious diseases?

Answer 3

Long-term changes in climate and short-term climatic disruptions will continue to alter the distribution and prevalence of infectious diseases.
Rising temperatures and changes in rainfall patterns can alter the biogeographic patterns of:
- microbes
- insect vectors
- animal reservoirs
- susceptible humans
Intensification vs. spread to new areas

Question 4

What is the impact of climate change on human health?

Answer 4

Heat-related illness and death
Forced migration (mental health)
Malnutrition
Poor water quality e.g. cholera
Malaria, dengue, WNV
Asthma

Question 5

What health risks do urbanisation present?

Answer 5

1) Poor housing/sanitation/waste management -> proliferation of insect and rodent vector diseases
2) Inadequate water supplies -> poor water storage practices -> standing water for vectors

3) Lack of effective fuel and ventilation systems -> respiratory tract infections
4) Density of inhabitants -> close contact between people -> hot spots for rapid spread of emerging infectious diseases such as SARS and avian flu

Question 6

What is the ‘State of Health’ triangle made up of?

Answer 6

Population
Concerned with humans as biological organisms – as the potential hosts of disease
Ability of a population to cope with insults depends on genetic susceptibility/resistance, nutritional status, immunological status, physiological status

Behaviour
Cultural norms, economic constraints, individual psychology

Habitat
That part of the environment within which people live and which directly affects them

Question 7

What is landscape epidemiology?

Answer 7

A geographic delimitation of the territory of a transmitted disease in order to identify pathways for disease control

Question 8

Describe May’s (1958) multi factor zone model.

Answer 8

It models areas where transmissible diseases were present, due to multiple factors occurring and overlapping to create a disease system.

Each factor has its own spatial distribution, and all must coincide in space and time to create the disease conditions.
4 factors: agent, reservoir, vector, human host.