We have categorised the Physical Factors and Environmental Events / Factors into
the groups listed above to aid the end-user in considering similar factors together. Physical factors influence disease at a number of levels. They may
have a direct effect on the host species, on the reproduction and transfer of infectious
agents or on the transfer (presence or absence) of chemical agents. Currently, this section covers only those physical factors which have a
direct effect on the host species (Waterfowl) and is used for linking these factors to the
relevant disease pages.
features/events are instrumental in providing an environment that will foster the
development of disease. Different basic environmental components associated with these
features/events are detailed in this section. (See also Environmental
and Population Management).
- Climate Features / Events -
The environment in which animals live, either enclosed or natural, is usually most
strongly influenced by both macro and micro-weather conditions. Weather is important for
the stressors that it places on the animal, and its affect on the persistence of disease
- Topography / Enclosure - An
animal's living area or home range, be it 10 hectares or 10 square meters, defines many
components of its existence. Free-ranging animals in savannahs or prairies have evolved
behaviour suited to those surroundings. Species from mountainous or arid regions have
developed the necessary anatomical and physiologic features. Design of captive enclosures
must address these needs. Topography has a significant affect on weather effects and
therefore the presence and transmission of disease agents. Animals restricted to a small
valley with stagnant air might be significantly effected by introduced pollutants. A
similar situation would exist in a poorly designed housing.
- Soil / Substrate - Soils
have a direct impact on vegetation and the nutritional composition of forage; excesses and
deficiencies in macro and micro-nutrients can occur. Contaminants can reside in soils for
extended periods of time and can cause intoxication in natural and artificial
environments. Disease agents have been demonstrated to be associated with specific soil
types. Captive animals often have intimate and chronic exposure to limited soil and/ or
substrates. Enclosure floors and soils should be chose with the type of animals to be
housed in mind.
- Food & Water Quality -
These play a significant role in health and disease. All animals require a balanced diet
with most animals requiring a consistent supply of palatable drinking water. These provide
a ready medium for exposure to infectious organisms and toxic substances.
- Human Disturbance / Land Use -
Humans have been altering the natural environment for thousands of years; many of these
ecosystem changes can directly or indirectly contribute to the initiation or amplification
of disease processes. Examples of these changes are:
- Introduction of toxic substances, directly
- Translocations and reintroductions causing
disease spread and amplification.
- Modification of topographic features, such
as water sources and impoundments, create new new reservoirs for agents and
- Land clearing and development reduces
available habitat and can lead to increased populations, increased agent
concentrations, reduced food resources and the associated stresses.
- Human disturbance is important on the
individual/population level, as well as the ecosystem level. Most animals have a flight
distance within which they feel threatened and will often either retreat or attack when a
human intrudes. In free-ranging animals and large enclosures, the impact may be limited,
but is an important factor to be considered in cage design.
- Habitat Disturbance/Vegetation -
Toxic plant poisoning is known in both free-living and captive wildlife. Infectious
diseases are sometimes associated with specific vegetation types and ecosystems.
Investigation of wild mortality, and selection of vegetation for exhibits should consider
N.B. Detailed information
on the general influence and the control of Environmental Events/ Factors associated with
disease in general is available in the Environmental
and Population Management section of "How to..." -
Guidance on best practice husbandry and veterinary techniques and on the management of
species, diseases and habitats".