US - Farmers are set to benefit from greater accuracy in Johne’s disease testing thanks to the discovery of an antibody that is 100 per cent specific to the Mycobacterium avium (MAP) bacteria.
The discovery, announced last week, was achieved by a team of ARS research microbiologists headed by John Bannantine. It represents a considerable step forward in the battle against Johne’s which causes average yearly losses of $40-220 per animal, according to USDA data.
Prior to last week’s announcement, antibodies used to detect Johne’s disease reacted to a host of other bacteria. This included environmental and bovine tuberculosis bacteria meaning results could incorrectly show positive.
“You may think cattle are infected, based on a positive antibody test result, but they may simply have been exposed to nonpathogenic mycobacteria that are ubiquitously present in the environment,” explained Mr Bannantine.
The discovery comes after considerable efforts over recent years. Back in 2005 researchers were led on a ‘wild goose chase’ by an antibody developed from mice temporarily believed to be specific to K-10 a strain of MAP.
Eventually the team concluded that the antibody, Named UP1 (Unique Protein 1), was not an actual gene. This realisation was important in arriving at the current outcome.
Whilst not being a gene, UP1 had an epitope which is the name given to the part of the molecule where the antibody can bind.
Now researchers are able to accurately test for the Johne’s pathogen in certainty that the reaction is not to a contaminant from the environment.
An important step has also been taken in the examination of Johne’s vaccines cross reacting with bovine tuberculosis. Now scientists believe vaccinating for Johne’s does not interfere with TB tests.
The experiment looked at cross reactivity of an ‘effective’ US commercial vaccine with tuberculosis tests in calves.
Scientists at the National Animal Disease Centre took serology samples and skin tests over a year and noted no reactivity.
Lead Scientist at the Animal Disease Centre, Professor Judy Stabel said the results were ‘promising’ and aided by the relative ease of new serological tests.
Professor Stabel stated that the new serological tests have resulted in practical as well as knowledge benefits.
Rather than handling each animal twice to obtain a blood sample and then take a skin test, Prof Stabel said time and money can now be saved by only having to handle stock once for a single blood reading.