A class of distributions applicable to the description of the number of nematodes parasitizing birds.

We define the class of bivariate binomial distributions as Poisson distributions transformed by a binomial dilution and mixing with a gamma distribution. They are used to study the number of nematodes, considering the sex ratio, parasitizing birds.

Estimation of distribution parameters of some avian parasites.

Occurrence of nematodes (mostly dominating and common species of Porrocaecum ensicaudatum and P. semiteres) in host populations of birds (Turdus merula, T. philomelos, Sturnus vulgaris and Scolopax rusticola) was summarized in frequency distributions, and tests of agreement with the Poisson model as well as the modified binomial have been computed.

Population dynamics in the co-culture of Shigella flexneri 1b original strain and its antigenic 3b mutant carrying a prophage.

The antigenic mutant Shigella flexneri 3b showed selective prevalence when subcultured with the original strain 1b. Mathematical analysis of such co-cultures showed that the dynamics of bacterial growth may be described by equations of the Lotka-Volterra type. The analysis of serial cultivations suggests that parameters of the equations may be realizations of random variables characterizing strains and media.