Detecting MAP Immune Responses in Heifers

Disease Research Limited (DRL) has, over the last 3 years, tested over 5,000 heifers (18+ months old) to see how well we can detect an immune response using the Paralisa™ test combined with the absorbed ELISA test by IDvet.  The goal of testing heifers is to identify animals that may pose a higher risk to the herd, make management decisions around those animals, and control the spread of MAP to the next generation.

Testing Heifers to Control the Spread of MAP

In most cases, infection starts from birth to 6 months old, as a result of faecal-oral transmission, through milk, manure, contaminated bedding, or in utero.  Heifers that test positive were most likely infected at, or just after, birth.  Their infection has likely not progressed to clinical disease yet, they often appear healthy, and are not likely to be shedding MAP bacteria throughout the herd.  However, they pose a great risk to their calf, and, if their colostrum is included in the pool of milk delivered to other young stock, they are a threat to the healthy young stock.

Identifying these heifers, and their calves, as risk factors, can help limit the cycle of MAP infection on farm.  Removing their colostrum from the calf feeding program, and keeping a persistent eye on their production and overall condition, are just some of the management steps that help reduce the bacterial load presented to the rest of the herd.

In our study, across 12 herds and including over 5,000 heifers, we found the combination of the Paralisa™ and absorbed ELISA, increased positive immune response detection by over 5%, compared to using the absorbed ELISA alone.  The following diagram, prepared by Dr. Darryl MacKenzie of Proteus Research and Consulting, demonstrates the increased efficacy for farms that have MAP infections.