Features of exogenous development of Trichuris globulosa (Nematoda, Trichuridae)

Parasitic nematodes of the genus Trichuris Röderer, 1761 are hematophagous helminths, capable of parasitizing many different hosts including humans. The domestic and wild ruminants are hosts of several Trichuris species, with Trichuris globulosa (Linstow, 1901) one of the most prevalent parasites found in cattle. The exogenous stages of the helminth’s life cycle develop in the outer environment, and their activity and survival depend on the abiotic factors. Thus the aim of the work was to determine the influence of temperature on the rate and success of development of infectious eggs of T. globulosa in laboratory culture considering their morphological and metric changes. The results of experimental studies showed that the embryogenesis of T. globulosa eggs, cultured in laboratory conditions and obtained from gonads of female nematodes, occurs in six stages regardless of the temperature regime. At the same time, the rate of transition from one stage to another, the term for the formation of infectious eggs and their viability directly depends on the temperature of the external environment. At the optimal temperature for the development of T. globulosa eggs, 25 °C, 76.3% of eggs reached the mobile larva stage. A decrease in temperature to 20 °C and an increase to 30° C led to an increase in the egg mortality of up to 26% and 32%, respectively, and the viability of eggs decreased. Under such temperature conditions, 74% and 68% of eggs of Trichuris reached the mobile larva stage. With an increase in the culture temperature, the time of embryogenesis decreased and amounted to 56 days at 20 °C, 48 days at 25 °C, and 32 days at 30 °C. Depending on the temperature regime, the zygote stage lasted from the release of eggs from the gonads of female nematodes to 12 days, the stage of blastomere formation from 4 to 12 days, the stage of the bean-shaped embryo from 8 to 24 days, the stage of the tadpole embryo from 16 to 36 days, the stage of larval formation lasted from 16 to 48 days, the stage of mobile larva from days 20 to 56. The formation of the infectious T. globulosa egg from a non-infectious one is shown in an experiment to include the metric changes confirmed by metric indicators. Mature eggs with a mobile larva are shorter and wider, with shorter and narrower plugs and a thinner shell than eggs at the zygote stage. The obtained research results on the influence of temperature on the exogenous development of Trichuris globulosa will make it possible to predict the epizootic situation of trichurosis in animal husbandry, as well as take timely measures to arrest the embryonic stages of nematode development in the external environment.

Ovocidal action of glutaraldehyde and benzalkonium chloride mixture on Aonchotheca bovis (Nematoda, Capillariidae) embryogenesis

Deinvasion, aimed at elimination of environmental exogenic stages of invasion agents and avoidance of their invasion to host organism, occupies an important place in the complex of sanitary and prophylactic activities against animal helminthosis diseases. Application of glutaraldehyde and benzalkonium chloride at vital activity and embryogenesis of Aonchotheca bovis (Schnyder, 1906) obtained from nematode female gonads was investigated with different concentration and exposures. Two test-cultures were used in the experiment. The first culture contained non-invasive eggs of A. bovis, the second contained invasive ones, obtained by the laboratory culturing of gonadic eggs until mobile larva maturing. It was established that glutaraldehyde and benzalkonium chloride mixture has a deinvasive capacity against A. bovis eggs, parasitizing on sheep. Ovocidal efficiency indexes appeared higher with use of the test culture against the non-invasive capillaria eggs’ test-culture. So, the high level of ovocidal efficiency of glutaraldehyde and benzalkonium chloride mixture against non-invasive A. bovis eggs culture was established at the concentration of 0.5% and exposure of 10–60 min (93.6–100.0%), and against the invasive A. bovis egg culture – at the concentration of 0.5% and exposure of 30 and 60 min (90.3–94.6%) and 1.0% at all exposures (100.0%). Ovocidal activity of the examined mixture was accompanied by specific morphological changes of nematode eggs structure. Destruction of the egg envelope, embryo loosening and decay and its dissolution were observed. Such changes are proved by metric indexes of width and length of capillaria eggs, envelope thickness and cap length, indicating the violation of embryogenesis of A. bovis. Thus, glutaraldehyde and benzalkonium chloride mixture of 1.0% concentration is a promising deinvasive agent suitable for effective fight against and prophylaxis of sheep-breeding nematodosis.