Abstract
Animal diseases are a significant source of lost revenue in livestock production systems. Reduction and control of diseases has traditionally been done under three management programs: eradication by test and slaughter, vaccination, and use of antibiotics. However, inadequate efficacy of vaccines and restrictions on the use of antibiotics in several countries have prompted the need to develop improved and novel methodologies to identify disease exposure and potentially implement intervention strategies to control various diseases. MicroRNAs (miRNAs) are small non-coding RNA molecules that have been proposed as biomarkers for disease in livestock. MiRNAs function by blocking protein translation, or through direct degradation of messenger RNA. As a result, miRNAs have been widely studied in humans, and their role in animal disease is now being assessed. This review encompasses a summary of miRNAs involved in animal diseases where miRNAs have been explored. This includes miRNAs associated with diseases in cattle, pigs, sheep and poultry. Reliability is necessary to propose a miRNA as a biomarker associated with a specific disease in any given livestock species. Results from the reviewed publications have identified miRNAs associated with the innate immune system; however, further research is necessary to establish miRNAs that are consistently dysregulated for each disease. The regulation of miRNAs appears to be dependent on the livestock species and pathogen evaluated. As research in this area continues, specific miRNA profiles will need to be supported by other assessments to establish their potential use in veterinary medicine in terms of prevention, diagnosis, or treatment of a disease. The possibility and challenges of using these molecules as biomarkers in animal health is discussed in this review.