Will the New Zealand Footrot Gene Marker Test be Useful in Uruguay?

Abstract

Since 2001 New Zealand sheep breeders have been using a technology that rates sheep on their susceptibility to under-running footrot caused by Dichelobacter nodosus. The technology is based on DNA typing of the ovine MHC-DQA2 gene and related DQA2-like sequences and the associations seen between particular sequences and susceptibility (or tolerance) to footrot. This is a proprietary technology which is jointly owned by Lincoln University and Ovita NZ Ltd. Rather than reveal the specific alleles of the ovine MHC-DQA2 gene and related MHC-DQA2-like sequences, of which there are at least 22 in total, the test codifies the sequences into a ‘1’ to ‘5’ range of scores with ‘1’ being defined as “least susceptible” to footrot and ‘5’ being “most susceptible”. Typed sheep receive two scores reflecting their diploid genome and the expression of the alleles or sequences is assumed to be co-dominant. Using linear modelling there is nearly a 10-fold difference in susceptibility to footrot between sheep carrying the “worst” and “best” alleles found in the New Zealand flock and under conditions of a severe challenge from under-running or virulent footrot. No Dichelobacter nodosus strain-specific variation in the susceptibility has been seen, but this would be very difficult to investigate conclusively given the immense variation seen in NZ strains, the observation that different “multi-strain” infections occur on different sheep in the same flock and the extensive polymorphism of the MHC-DQ region.  ...