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Fast and precise diagnosis of infectious and non-infectious animal diseases and their targeted treatments are of utmost importance for their clinical management. The existing biochemical, serological and molecular methods of disease diagnosis need improvement in their specificity, sensitivity and cost and, are generally not amenable for being used as points-of-care (POC) device. Further, with dramatic changes in environment and farm management practices, one should also arm ourselves and prepare for emerging and re-emerging animal diseases such as cancer, prion diseases, COVID-19, influenza etc. Aptamer – oligonucleotide or short peptides that can specifically bind to target molecules – have increasingly become popular in developing biosensors for sensitive detection of analytes, pathogens (bacteria, virus, fungus, prions), drug residues, toxins and, cancerous cells. They have also been proven successful in the cellular delivery of drugs and targeted therapy of infectious diseases and physiological disorders. However, the in vivo application of aptamer-mediated biosensing and therapy in animals has been limited. This paper reviews the existing reports on the application of aptamer-based biosensors and targeted therapy in animals. It also dissects the various modifications to aptamers that were found to be successful in in vivo application of the aptamers in diagnostics and therapeutics. Finally, it also highlights major challenges and future directions in the application of aptamers in the field of veterinary medicine.

Context Mastitis is an inflammation of mammary gland parenchyma, and is an unending cause of economic loss to the dairy industry. The interest in research on biomarker discovery for the diagnosis of bovine mastitis stems largely from the need to identify reliable biomarkers. Aim To determine the putative biomarkers of mastitis by using bioinformatics analysis, and experimental validation of pro-inflammatory cytokines and oxidative stress biomarkers of the mammary gland in healthy and diseased animals. Methods Various in silico analysis tools were applied to screen for gene expression in mastitis. Milk, as well as blood samples, was collected aseptically from the animals, which were then classified into three groups; namely, clinical, subclinical and control. Samples were subjected to assay of pro-inflammatory cytokines and oxidative biomarkers using enzyme-linked immunosorbent assay kits and the prescribed methodology respectively. Key results In silico analysis revealed that mastitis reduces the expression of fat metabolism and immune system-related genes, whereas it increased the expression of inflammatory genes. On laboratory analysis of cytokines and acute phase protein, it was revealed that interleukin-1∝, interleukin-8 and haptoglobin were significantly (P < 0.01) increased in both blood serum and milk whey in subclinical and clinical mastitis cows. On analysis of oxidative biomarkers, our results showed that oxidative stress was significantly (P < 0.05) increased with progression of mastitis in dairy cows. There was a significant (P < 0.05) increase in the blood serum level of malondialdehyde and nitric oxide, and a decrease in the level of anti-oxidant enzymes – glutathione peroxidase, superoxide dismutase and catalase – compared with healthy animals. Conclusion In conclusion, bioinformatics analysis of high-throughput gene expression revealed the involvement of multiple pathways, including the inflammatory pathway, fatty acid pathway and triglyceride synthesis pathway, in mastitis. Experimental validation confirmed that interleukin-8 and haptoglobin are putative early diagnostic markers for mastitis in dairy cattle. This study also concluded that milk can be used for the detection of cytokines as a non-invasive technique.

Mastitis is a multi-etiological complex disease of dairy cows and negatively affects the quality and quantity of milk. Milk is a nutritious food for human being; milk quality is negatively affected by intramammary infection of dairy cows. A total of 300 milk samples were collected from mastitis dairy cows irrespective of parity and stage of lactation, 235 (78.33%) samples were culturally positive and yielded 1,100 bacterial isolates. Staphylococcus aureus was found to be the prime etiological agent involved in the mastitis of dairy cows, followed by Escherichia coli and other environmental pathogens. On the molecular characterization of isolates obtained from the milk culture, various toxic genes such as nuc, seb, hla, stx1, stx2, hly, and Sagl were found on different isolated bacteria. Milk somatic cell counts (SCC) were found to be directly related to the severity of mastitis. On drawing the SCC correlation with milk components, it was found that SCC had a significant negative correlation with fat, lactose, solid not fat (SNF), and ash. It was concluded that mastitis-affected milk contains numerous pathogenic bacteria, toxins, and reduced milk quality, which is unfit for human consumption.

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