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Abstract
Extract
Disease surveillance systems can take many forms, depending upon what is desired of them. Surveys of mortality can be useful as an integral part of any surveillance system, both as a record of the losses and as an indication as to which conditions may be responsible for lowering the thrift of the population. Both these sources of loss are important in reducing the monetary return from a stock population as a whole. Surveys of mortality can indicate the importance of low incidence diseases and can be used to identify conditions previously unknown in the area. Totally new diseases can also be detected in this manner. Many individual disease conditions as well as surveys of groups of diseases (Hartley and Kater, Citation1962; O'Hara and Shortridge, Citation1966; Shortridge and Cordes, Citation1971) have been reported from material submitted to New Zealand laboratories and mortality studies on groups of animals have been undertaken elsewhere (Everitt and Evans, Citation1970; Jackson et al., Citation1972).