The disease is detected in Central Yakutia and deserves the closest attention from practicing veterinarians. In village dogs infected with and suffered from dirofilariasis, the main pathomorphological changes were localized in the heart and were represented by atrophic, dystrophic and necrobiotic processes. In addition, the products of the nematode metabolism led to the appearance of circulatory disorders. First of all, the researchers paid attention to the study of blood smears, which showed the microfilariae in the smears. The authors also examined guard dogs that died from this disease, and an incomplete examination of organs and tissues when dissecting the heart, lungs and parenchymatous organs, showed sexually mature Dirofilaria in the heart of the dissected animals. Subsequently, methods for diagnosing dirofilariasis were applied using the method of peripheral blood examination, where live microfilariae larvae were found in sick dogs. As the authors of the article note, cardiac dirofilariasis subsequently had a destructive effect on red blood cells, erythrocytes, and was observed in the development of hemoglobinemia, and hemoglobinuria, and in some cases leads to liver and kidney failure. In the respiratory system, there were also typical clinical signs of chronic dry cough, difficult breathing and shortness of breath, and foci of pulmonary rales detected. During the disease, pulmonary thromboembolism was developed in the animals, which characterized by the occurrence of fever and the release of sputum with blood. In the treatment of canine dirofilariasis, the authors observed a fatal outcome in two cases, and made dissections to study the organs and tissues affected by nematodes.

The results are presented for the study on the distribution of the trematode Alaria alata in the red fox Vulpes vulpes (Linnaeus, 1758) in Yakutia. Sexually mature forms of the trematode Alaria alata were found in the small intestine of the fox, and the prevalence of invasion was 31.6% with an invasion intensity of 52±0.2 specimens. In the last decade, the number of foxes in Yakutia has increased. According to the Republican Department of Hunting Economy, the number of these animals totaled up to 23 thousand specimens in 2020. Sharp fluctuations in the number of foxes in Central Yakutia are associated with a decrease in the number of the Arctic hare (Lepus timidus) and the muskrat (Ondatra zibethicus). The number of foxes is greater in the Republic’s "hare" regions of Verkhoyansky, Eveno-Bytantaisky and Kobyaysky uluses, where the dynamics of the number of foxes repeats the "hare" regions with a lag of 2–3 years. Foxes live throughout the territory of Yakutia, usually closer to taiga-lake lowlands with an abundance of meadow-lake, bottomland and shrub habitats where the meadow mouse and the muskrat can be found. The authors find remains of the muskrat, squirrel, chipmunk, pikas, mouse-like rodents and ungulates in the diet of the fox. Additionally, insects, mollusks, berries and herbaceous plants are found among food objects. Red foxes are of significant importance in the epizootology of alariosis as the main source of the trematode spreading in nature.

Nematophagous hyphomycetes were found almost in all parts of the world and in different climatic zones. Therefore probably many researchers separate predatory fungi from all soil samples, wherever nematodes can exist. Currently, the prevention and treatment of nematodoses of herd horses by practicing veterinarians is limited to single deworming with the use of known semi-synthetic anthelmintic drugs. It should be noted that the strategy of anthelmintic treatment is aimed at disinfectation directly in the body of animals. Most anthelmintic drugs have antiparasitic properties, and are highly toxic to any endothermic organism. Chemical components of antiparasitic drugs after animal use are excreted in the environment with feces, and, being practically unchanged, continue their strong toxic effect on the pasture biocenosis components. The nematophagous fungi isolated from the permafrost soil of Yakutia belong to the genus Arthrobotrys according to the description of the species, and by morphological and physiological characteristics; 2 strains of predatory fungi L3-1 and L3-2 have been identified. Nematophagous fungi of the genus Arthrobotrys occupy a certain place in the system of microbiomes that are able to control nematodes.

Reindeer husbandry is the basis of the economy and way of life, the traditional occupation of the indigenous inhabitants of the North, Siberia and the Far East, and the most important branch of animal husbandry in the Republic of Sakha (Yakutia). Reindeer husbandry is associated with the cultural traditions, lifestyle and economy of the small national communities of the north. Yakutia is the traditional centre and the region of breeding domestic reindeer. Further development of reindeer husbandry, and increasing of the productivity and profitability of reindeer husbandry in Yakutia are impossible without proper organization and effective protection of domestic reindeer from various diseases, including parasitic ones, which cause significant damage to reindeer farms in the Republic. Reindeer are infected with 37 species of helminths. The results of the research of the authors of the article showed that all the studied deer had different types of helminths, and 100% were infected with gadfly larvae. The most frequent parasitic diseases in deer are monieziasis, larval echinococcosis, parenchymal, muscular and serosal cysticercosis, dictyocaulosis, nematodirellosis and elaphostrongylosis; moreover other parasitoses – edemagenosis and cephenomyosis – are recorded in 100% of deer. The authors of the article consider the infection of deer with larvae of subcutaneous and nasopharyngeal gadflies to be the number one problem.

Horse herd farming based on the year-round pasture management of horses has become one of the main branches of animal husbandry and the basis of the lifestyle and economy of the Yakutia population. Herds are formed according to their sex and age: stallions, mares, and foals are kept in the herd. Helminth infections are widespread among herd horses and are chronic in most cases without pronounced clinical manifestations. Horses seem to be completely healthy from the point of view of the usual visions of the disease. Therefore, no preventive or treatment measures are often applied. In cases of asymptomatic helminth infections (subclinical forms), the huge economic damage caused by them is determined not so much by the death of animals, but it is very difficult to endure wintering in Yakutia with a high invasion degree, and loss of fatness and weight. The Authors of the Article studied the interspecific relationships of equine intestinal nematodes in mixed invasion, and detected changes in the population density of individual nematode species in horses of different age and in different seasons of the year. The Strongylata incidence and infection rate in herd horses was studied based on the results of quantitative coproovoscopic and larvoscopic studies of faeces from herd horses, and on the results of incomplete helminthological dissections on horse ranches of Central Yakutia.