Mitchell, Fredericka H.H. (2019) Development of two rapid diagnostic tests for the detection of Bovine Salmonellosis in calves with scour. (PhD thesis), Kingston University, .
Abstract
Salmonellosis is a worldwide issue, that impacts human and animal health alike. Infection is often derived from foodborne contamination, causing gastroenteritis and in extreme cases, bacteraemia, and death. Current diagnostics for the detection of Salmonella sp. can take a minimum of three days. However once infected with Salmonella enterica serovar Dublin (S. Dublin), calves often die within 48 hours. Salmonellosis in calves is associated with scour, however it is not the only aetiological agent of diarrhoea in cattle. Antibiotics for potential salmonellosis are often administered before a definitive diagnosis is given, to reduce animal suffering and mortality rates. However, with the emergence of multi-drug resistant strains of Salmonella sp. efforts need to be made to ensure antibiotics are only prescribed when bacteria are the causal agent of infection. Rapid detection methods for pan-Salmonella are needed to prevent calf death and enable targeted treatment. This would reduce the impact of the disease on animal welfare, as well as to safeguard public health, reduce economic impacts, and enable the right treatment is prescribed for the right disease In this study two rapid diagnostic methods were developed: a nucleic amplification assay targeting Salmonella DNA known as loop-mediated isothermal amplification (LAMP), and a potentiometric mmunoassay targeting surface antigens on Salmonella bacteria using biosensors in the Vantix System. Both diagnostics were found to be rapid and robust, with high sensitivity and specificity to multiple Salmonella serovars. Fluorometric LAMP assays detected pan-Salmonella in 35 minutes, with visualisation under a UV light. Potentiometric immunoassays on the Vantix reader 2.0, were able to detect S. Dublin through undiluted calf scour in under an hour. Both diagnostic methods would enable rapid detection of Salmonella sp. in calves suffering from scour.
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