Peculiarities of embryogenesis morphology and biometric parameters of Trichuris suis Schrank, 1788 eggs sampled from different organic substrates are described. The eggs of T. suis under laboratory conditions at a temperature of 27 °С reach the infectious stage in 40 days and pass through seven stages of embryogenesis. The study revealed significant differences in growth and development of eggs obtained from the nematode gonads and the faeces of infected animals (Sus scrofa domesticus Linnaeus, 1758), according to length and width of eggs and eggshell plugs. The excreted T. suis eggs were shown to be better adapted to environment (survivability 96.6 ± 0.33 %), than the eggs obtained from the gonads of female nematodes (survivability 89.3 ± 0.33 %).
Abundance and distribution of nematodes of the genus Trichuris Schrank, 1788 parasitizing domestic sheep (Ovis aries Linnaeus, 1758) were studied in Poltava, Kyiv and Zaporizhzhia Regions of Ukraine. Three species of Trichuris were found, Trichuris skrjabini Baskakov, 1924, Trichuris ovis Abildgaard, 1795 and Trichuris globulosa Linstow, 1901. Trichuris ovis and T. skrjabini were more common (54.9 and 35.7 %), whereas T. globulosa was relatively rare (9.4 %) in the studied material. New species-specific and sex-related morphological characters and metric indices were reviewed as useful in better identification of T. skrjabini, T. ovis and T. globulosa parasitizing sheep.