Abstract. Marek's disease virus is an oncogenic avian herpesvirus and the problem of oncogenicity of this virus for humans remains unexplored. This pathology appeared in broiler chickens of 30 days and older, that is from now on the contact with poultry meat carries the risk of infecting people. This article analyzes the risks of the emergence of the epidemic potential of the Marek's disease virus in the Russian Federation taking into account the characteristics of modern pig and poultry farming. It was found that COVID 19 can serve as an additional factor in reducing the resistance of the population to herpesvirus infections. The COVID 19 epidemic is accompanied by folic acid deficiency which also increases the risk of contamination of diseases associated with DNA viruses, including an extended risk of animal viruse infection. Since, according to our estimates, Marek's disease occurred in at least 25% of broiler poultry farms in the Russian Federation, a possible expand in mortality from neoplasms of the reproductive system for the Russian Federation as a whole can contribute to the dynamics of oncological diseases of reproductive organs and breast cancer. Since 2011 a contagious form of intestinal pathology, vesicular enteritis, has widely spread at poultry farms in the Russian Federation. During periods of extending incidence of vesicular enteritis, we recorded cases of inflammation of the facial nerves and subfebrile temperature in contact persons, bursts of oncological diseases in veterinary personnel (ovarian cancer, breast cancer), abnormal and synchronous increases in the incidence of infectious larengotracheitis and Marek's disease in chickens under the age of 40 days which requires additional monitoring studies.

MicroRNAs (miRNAs) are small endogenous RNAs that regulate gene expression post-transcriptionally by targeting either the 3′ untranslated or coding regions of genes. They have been reported to play key roles in a wide range of biological processes. The recent remarkable developments of transcriptomics technologies, especially next-generation sequencing technologies and advanced bioinformatics tools, allow more in-depth exploration of messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs) including miRNAs. These technologies have offered great opportunities for a deeper exploration of miRNA involvement in farm animal diseases, as well as livestock productivity and welfare. In this review, we provide an overview of the current knowledge of miRNA roles in farm animal diseases with a particular focus on diseases of economic importance. In addition, we discuss the steps and future perspectives of using miRNAs as biomarkers and molecular therapy for livestock disease management as well as the challenges and opportunities for understanding the regulatory mechanisms of miRNAs related to disease pathogenesis.