Neonatal calf diarrhoea (NCD) is a common problem in Australian beef and dairy enterprises. The disease epidemiology is complex and traditionally diagnosis is difficult. Prompt, accurate and cost-effective diagnosis is imperative, so our research group is exploring the application of real-time quantitative polymerase chain reaction (qPCR) and loop mediated isothermal amplification (LAMP) for calf faecal and environmental samples as tools to add to the diagnostic armoury for this disease.
Faeces are a notoriously difficult matrix to work with. This is particularly so when using nucleic acid detection tests such as PCR. A lot of research has focused on better nucleic acid extraction from samples and this is an important part of our current research project. There are significant and worthwhile advantages of PCR-based tests over more traditional methods of diagnosis, including turn-around time, the scope for high throughput and use of extracted DNA for further testing.
Real-time PCR assays have been developed at EMAI for common viral, bacterial and protozoal agents involved in calf scours, namely bovine rotavirus type A, bovine coronavirus, bovine torovirus and bovine pestivirus/bovine viral diarrhoea virus, Salmonella spp., Escherichia coli K99/F5, Cryptosporidium spp. and Giardia spp.. The plan is to combine these assays, thus lowering the cost, and to offer them as diagnostic commercially available tests.
Potentially, this technology can be applied in such a way as to provide meaningful quantitative answers about pathogen load in various samples. This in turn would assist with tackling the epidemiological issues surrounding this complex disease syndrome, such as source of infection. This emphasises the need to collect and submit samples in a systematic way from a number of affected (and sometimes unaffected) animals to provide an accurate picture of the disease syndrome. Many serious calf scours outbreaks involve multiple pathogens, which have complex interactions. Additionally, this technology could potentially assist with assessing the effectiveness of management and other interventions to assist in disease control on cattle properties with ongoing problems.
Meat & Livestock Australia for funding this project; Staff at the Elizabeth Macarthur Agricultural Institute (Virology, Bacteriology and Parasitology Laboratories), Menangle; Staff in the Shute Building, University of Sydney, Camden.