Logarithmic normal distribution of incubation times for canine diseases (Sartwell's model).

The distribution of incubation periods for most infectious diseases follows a logarithmic normal distribution (Sartwell's model). The same is true for human neoplastic diseases of known cause and for genetic diseases, when the age at onset of the disease was used as a surrogate measure of the incubation period. In this study, a similar distribution was observed when Sartwell's model was applied to canine diseases of known genetic cause, but not to diseases of an environmental cause. The model was also applied to canine diseases of suspected multifactorial causes for the purpose of distinguishing between the relative importance of genetic and environmental factors that act before or after birth. Limitations of this method were discussed.