From epidemiologic considerations of onchocerciasis the compartmental structure of the onchocerciasis infection process - as example for a class of infection processes of endemic diseases where two states of infection (susceptible and infective) may be classified - is worked out. It consists in the main compartments of fresh susceptible states and the main infective states (first infective state and blindness state at the end). Virtual sub-compartments, with a common unidirectional transition rate between them, are inserted within the main compartments in order to generate gamma-distributed compartmental residence times in each.
The governing system of forward differential equations for the probabilities of location in the main compartments is solved by using Laplace transform techniques giving for two situations the probability profiles. Further, the effect of application of control measures on the infection process is discussed and may be modelled as a piecewise homogeneous compartmental process. These models are applicated for two age-prevalence data sets from WHO studies.