Abstract
Diarrhea in newborn calves is a serious global health problem. It poses challenges for animal industry, veterinarians and researchers due to the rapid onset of dehydration. Mixed infections make treatment complicated, and many young calves suffer high rates of illness and death from this condition. Numerous enteropathogens are associated with diarrhea in newborn calves, encompassing viruses, bacteria, parasites, and protozoa. Their occurrence differs by region, yet the most prevalent infections include E. coli, Salmonella species, Clostridium perfringens, Clostridium difficile, Rotavirus, Coronavirus, Cryptosporidium, Toxocara, Giardia and Eimeria. This review outlines the diagnostic techniques for diseases that lead to diarrhea in newborn calves. Diagnosis is based on clinical manifestations; however, the laboratory identification of etiological items is the only valid way for detecting the illness's aetiology and initiating treatment protocols. Classic methods such as bacterial culturing, fecal flotation, direct microscopy, and virus isolation help us understand pathogens better. Immunological assays like ELISA and immunochromatography are fast, accurate, affordable, and useful for on-farm detection. They help identify specific antigens or antibodies efficiently. Molecular methods including PCR (standard, multiplex, real time and digital), LAMP assays, DNA microarrays and whole-genome sequencing allow highly accurate and sensitive detection. They can identify pathogens effectively, even at very low levels. Nanotechnology-based assays introduce a novel level of sensitivity and specificity, often yielding quick results with minimal sample volumes. In conclusion, accurate and rapid diagnosis using advanced techniques is critical for managing and preventing diseases that lead to diarrhea in newborn calves.