An Investigation of Embryo and Eggshell Development in

Nematodes of the GenusТrichuris (Nematoda, Trichuridae) Parasitizing Sheep in Central and South-Eastern Regions of Ukraine. Yevstafi eva, V. A., Yuskiv, I. D., Melnychuk, V. V., Yasnolob, I. O., Kovalenko, V. A., Horb, K. O. -Abundance and distribution of nematodes of the genus Тrichuris Schrank, 1788 parasitizing domestic sheep (Ovis aries Linnaeus, 1758) were studied in Poltava, Kyiv and Zaporizhzhia Regions of Ukraine. Th ree species of Тrichuris were found, Trichuris skrjabini Baskakov, 1924, Trichuris оvis Abildgaard, 1795 and Trichuris globulosa Linstow, 1901. Trichuris оvis and T. skrjabini were more common (54.9 and 35.7 %), whereas Т. globulosa was relatively rare (9.4 %) in the studied material. New species-specifi c and sex-related morphological characters and metric indices were reviewed as useful in better identifi cation of T. skrjabini, Т. оvis and Т. globulosa parasitizing sheep.

The genus Heterakis Dujardin, 1845 is one of the most widely distributed genera of nematode parasites of domestic and wild birds. Geographically and ecologically predominant species include Heterakis gallinarum Schrank, 1788 and Heterakis dispar Schrank, 1790. Prevalence and occurrence of these nematodes in the domestic goose (Anser anser dom.) depend on their biological and morphological specifics which ensure the highest viability, fast growth and maximum fertility in the host. This study presents the abundance and species composition of nematodes of the genus Heterakis in the domestic goose in Ukraine. Comparative study of morphological and metrical characteristics of H. gallinarum and H. dispar adult females and males is presented. Additional morphometric characteristics are proposed for easier identification of the two species. Stages and periods of embryonic development of H. gallinarum and H. dispar nematodes obtained from domestic geese are established according to morphological and metrical characters. Of the two species, H. dispar is prevalent in domestic geese from Poltava, Kharkiv and Kyiv regions. Abundance index of this species is 9.8 specimens, and intensity of infection index is up to 62 specimens. H. gallinarum is rarer, its abundance index is 1.2 specimens and maximum intensity of infection is 30 specimens. Species-specific morphological differences are more distinct in male nematodes in the size and structure of the spicules, lateral wing-like protrusions of pseudobursas, numbers and position of tail papillae. Additional metrical characteristics differ between H. gallinarum and H. dispar nematodes, allowing us to identify not only adult specimens but also eggs. Embryonic development of both species occurs in four morphologically distinct stages: protoplast, blastomere cleavage, formation of first and second stage larvae. Eggs of H. gallinarum nematodes become infectious in eight days at 27 °С, eggs of H. dispar in four days, their viability in laboratory culture is 84.3 ± 0.58 and 91.3 ± 1.53% respectively.

One of the most common ectoparasites on domestic carnivores are fleas from the genus Ctenocephalides. This group of blood sucking insects are one of the most important in medical and veterinary terms, as they can serve as carriers of dangerous infectious and may cause other invasive diseases. Research studies have established a variety of fleas and other contagions parasitizing domestic dogs in Poltava, Ukraine. Certain peculiarities of these ectoparasitic studies, as a part of mixed infestations of dogs, have recently been determined. The results of the studies have shown that the species composition of the fleas was represented by two main species. The dominant species was Ct. felis, and their prevalence was 36.05 %. Another species (Ct. canis) was diagnosed less often and had a prevalence of 27.94 %. It was found that in 31.18 % of the dogs, the blood-sucking insects were mostly parasitizing in the form of an associations with: nematoda (Toxocara canis, Trichuris vulpis, Uncinaria stenocephala), Cestoda (Dipylidium caninum), protozoa (Cystoisospora canis), and another ectoparasite (Trichodectes canis). Overall, 33 types of mixed infestations were detected. Moreover, the number of different parasitic species in each dog ranged from one to seven. Fleas of the genus Ctenocephalides (in the composition of two species of parasites) were registered the most often (14.60 %). The infestation of dogs with other forms of mixed infestations was 0.69—8.01 %. The most frequent co-members for Ct. felis were Cestoda [D. caninum (13.47 %)], for Ct. canis—Cestoda [D. caninum (11.23 %)] and Nematoda [T. vulpis (8.29 %)].

This study aimed to study the current state of the fauna of pathogens of nematodoses of the digestive tract of sheep in the Poltava region. The work was performed based on the Laboratory of the Department of Parasitology and Veterinary Sanitary Examination of Poltava State Agar University and in the conditions of sheep farms of various forms of ownership in the Poltava region. According to the conducted research, for the first time, a detailed description of the fauna of nematodes parasitizing in the gastrointestinal tract of sheep in the climatic conditions of the Poltava region is given. Generic and species identification of isolated helminths was performed. Indicators of intensity and invasions and abundance index of detected nematodoses of sheep were established. It was determined that the fauna of nematodes of the digestive tract of sheep is represented by 15 species of helminths belonging to 2 classes: Adenophorea and Secernentea, 5 series: Trichurida, Enoplida, Strongylida, Rhabditida, Oxyurida, and 12 genera: Trichuris, Haterongia, Haemonchus Trichostrongylus, Nematodirus, Aonchotheca, Oesophagostomum, Scriabinema, Chabertia, Strongyloides, Cooperia, Bunostomum. Detected nematodes are geohelminths that cause the following diseases in sheep: trichuriasis, haemonchosis, ostertagiosis, trichostrongylosis, nematodirosis, oesophagostomosis, chabertiosis, cooperosis, bunostomosis, scriabinemosis, capillariasis, and strongyloidosis. It was found that the total infestation of sheep by nematodes was 78.10 %, the intensity of the invasion ranged from 1 to 93 specimens, and the abundance index – from 0.01 to 21.39 samples. The most common in the study region were nematodes of four species: H. contortus (P – 60.81 %, II – 24.15 spec./head, AI – 14.69 spec.), O. circumcincta (P – 60.81 %, ІІ – 29.75 spec./head, AI – 18.09 spec.), T. colubriformis (P – 59.08 %, ІІ – 36.21 spec./head, AI – 21.39 spec.) and T. ovis (P – 55.04 %, II – 24.19 spec./head, AI – 13.31 spec.). Isolated nematodes of T. colubriformis and H. contortus are pathogens of zooanthroponoses and are dangerous to humans, indicating the study's relevance and importance. The obtained scientific data will increase the effectiveness of measures to control and prevent nematodoses of the gastrointestinal tract of sheep in farms of the Poltava region.

The parasitic nematode Trichuris vulpis Frölich, 1789 is the pathogen of trichuriasis in domestic and wild carnivores, and humans. This helminth species is distributed world-wide in populations of domestic dog (Canis lupus familiaris). The prevalence of T. vulpis in dogs depends to a large degree on the morphofunctional and biological adaptations of the parasite which support its high survivability in various environmental conditions. The present study considers the species-specific peculiarities of morphology, and metric parameters of the mature and embryonic stages of Trichuris nematodes parasitizing in C. lupus familiaris. We studied the periods of stages of development and infectious egg formation, and their survivability under optimal conditions for T. vulpis in laboratory culture. The differential characteristics of both female and male adult T. vulpis nematodes include the metric characteristics of cuticular protrusions at the surface of the anterior body part. The male T. vulpis nematodes can be distinguished from males of other species by the specifics of spicule sheath ornamentation, the shape and size of spicule, and the width of spicule sheath at different sections. In identification of the female nematodes of this species, it is necessary to consider the presence and size of papillary processes in the vulval area and metric parameters of vulva location. Nine metric characters of sexual dimorphism are described for T. vulpis nematodes. In laboratory conditions, five embryonic stages were observed for T. vulpis: protoplast, blastomere cleavage, and formation of bean-like embryo, larva and mobile larva. These stages are characterized by specific morphological features. The egg develops to the infectious stage at 27 °С in 18 days of culture, and their survivability is up to 76.6%. The egg development is associated with changes in their metric characters, such as decreasing egg length and width of egg shell, and increasing egg width and egg plug width.

Morphological characteristics were studied in adult and embryonic Amidostomum anseris (Zeder, 1800) obtained from domestic goose Anser anser domesticus Linnaeus, 1758. The studied characters included species-specific morphometric indices of male and female specimens and differential characters of sex-related dimorphism in that species. Stages and periods of embryonic development, and viability of the nematodes were studied at laboratory conditions. Size dimorphism in A. anseris was considerable, females were significantly larger (by 10.09–27.98 %) than males by 11 parameters. Additional metric characters were proposed to enhance effectiveness of differentiation of female and male A. anseris specimens. Under laboratory conditions, embryonic development of A. anseris occurs in four stages: blastomere cleavage; larval formation; formation of non-infective larvae I and II; formation of infective larva III which hatches from the egg. Infective larvae develop at 23 °С in six days, and their viability was up to 78.33 ± 2.08 %.

Biological specifics of Trichuris оvis Abildgaard, 1795 and T. globulosa Linstow, 1901 parasitizing domestic sheep were analyzed enhancing the species identification of these nematode species. The embryonic development of nematodes was timed, survival of embryonic stages was determined taking into account their morphological and metric specifics in laboratory culture. Trichuris eggs were isolated from gonads of adult female nematodes collected from caeca of dissected sheep. Then the eggs were cultured at optimal temperature to the formation of eggs with mobile larvae. Six morphologically distinct stages of embryogenesis were established in T. оvis and T. globulosa nematodes. The protoplast stage lasted from the 1st to the 12th day in T. оvis and to the 18th day in T. globulosa. Blastomeric formation occurred from the 3rd to the 18th day in T. оvis and from the 3rd to the 21st day in T. globulosa. Bean-shaped embryos formed from the 6th to the 21st day in T. оvis, and from the 9th to the 30th day in T. globulosa. Tadpole-like embryos developed from the 12th to the 24th day in T. оvis and from the 18th to the 33rd day in T. globulosa. Larvae formed in eggs of T. оvis from the 18th to the 27th day, and in eggs of T. globulosa from the 21st to the 36th day. Mobile larvae formed from the 21st to the 30th day in T. оvis, and from the 30th to the 39th day in T. globulosa. At 27 °С, mature eggs with mobile larvae developed in 30 days in T. оvis and in 39 in T. globulosa. The egg survival in laboratory culture was 84.3 ± 4.2 % and 76.3 ± 1.5%, respectively. Developmental changes of metric parameters in Trichuris nematode eggs (length and width of eggs, plug length, eggshell thickness) were species-specific.