Virulent footrot diagnosis

Summary

Virulent footrot costs the sheep industry $32M pa. This project delivered new, fully validated diagnostic approaches:

1. PCR for serogroup M
2. all conventional PCR serogrouping tests upgraded to a modern real-time format and multiplexed, and
3. direct PCR detection of D. nodosus serogroups from lesion swabs, all of which will improve sensitivity and reduce test times and costs.

A validation study of recently published qPCR virulence tests based on protease genes surprisingly revealed that they should not be used due to risk of false-positive diagnoses.

In an attempt to further develop new molecular virulence tests, single nucleotide polymorphisms in 11 potential virulence-associated genes were evaluated but were found to be not suitable virulence markers.  Collectively, these studies indicate that our understanding of the molecular basis of virulence is incomplete, which hinders the development of a simple diagnostic test.  Future diagnostic approaches await a better understanding of the microbiome of footrot lesions. We trained postgraduate students to meet the future need for expertise to service industry and we conducted a National Workshop.

Producers should demand the application of validated diagnostic procedures by the state jurisdictions. There are considerable risks in the application of non-validated novel technologies. Furthermore, there is a risk that footrot is driven underground and subsequently spread more widely through lack of reporting by producers (due to stigma, risk of quarantine being applied) unless the quality of diagnosis is improved nationally and the means of diagnosis harmonised.