Disease Management through Environmental Modification

Abstract

Disease management through manipulation of elements of the environment, other than the causative agent or the population of animals, is based on the concept that disease is a result of interactions among agent, host and environment, or that disease has a multifactorial basis (see Chapter 1). In both of these concepts, a population of susceptible animals and a disease agent or risk factor may be present in an area much or all of the time with disease occurring only when certain environmental factors are also present. The task of the disease investigator is to identify the specific environmental factors that are associated with the occurrence of disease. When this has been done, the disease may be managed by ensuring that this specific combination of environmental factors does not occur. Disease management in this manner is obviously much less direct than is management that removes the host population from the area or that eliminates the causative agent but the indirect approach may be possible in situations where neither of the more direct actions are feasible. However, manipulation of environmental factors requires a much better understanding of the ecology of a disease than simple identification of a cause:effect relationship between agent and disease. The more thoroughly the ecology of a disease is understood, the greater is the likelihood of discovering one or more loci at which control can be accomplished through habitat modification. As stated by Leopold (1933), the “the very complexity [of disease mechanisms] increases the possible points of attack, one of which may some day be used for control measures”.

“We have only recently studied some facets of these control possibilities. There are now a few gaps in our ignorance” (Bergstrom and Robbins, 1980).