Are some cows genetically susceptible to Johne’s Disease?

Citation

Are some cows genetically susceptible to Johne’s Disease?

Plain language summary

A research project led by Nathalie Bissonnette (Agriculture and Agri-Food Canada (AAFC)-Sherbrooke) and Kapil Tahlan (Memorial University of Newfoundland) is investigating genetic markers in dairy animals that may be associated to Johne’s disease susceptibility or resistance. The project called, Unraveling the genetic susceptibility to Johne’s disease, is financed by Agriculture and Agri-Food Canada and Lactanet with in-kind contributions by Holstein Canada under the Dairy Research Cluster 3.

Mycobacterium avium subspecies paratuberculosis (MAP) is the pathogen that causes Johne’s disease. For dairy producers, Johne’s disease translates to significant financial losses related to reduced milk production, decreased pregnancy rates, increased premature culling, and decreased slaughtered carcass weight, not to mention diminished animal welfare Economic losses in the Canadian dairy sector resulting from Johne’s disease are recently estimated at $21.5 million to $34.1 million . Controlling Johne’s disease is difficult due to unpredictable disease progression and weak sensitivity of diagnostic tests in some animals that may look healthy but can shed the bacterium in the environment and transmit the disease.

Previous research showed the potential for genetic resistance to Johne’s disease in cattle, which may be useful to complement other farm management strategies to prevent infections. Nathalie Bissonnette and her team had repeated serum and fecal samples collected from over 3,150 cows during a longitudinal study and determined with accuracy the development of paratuberculosis over time.
In this new project, the researchers are using the data collected previously combined with other diagnostic tests to classify the animals as infected and infectious, infected and assumed resistant, or healthy. Genotyping the cows using two proven genetic testing methods, (Single nucleotide polymorphisms (SNP) panel and genotyping-by-sequencing), will help identify genetic markers and genes associated with susceptibility to Johne’s disease. In recent publications (January 20202, November 2020 , March 20214,5), the team validated the role of specific immune cell, SNP, and long non-coding RNA response to Johne’s Disease and confirmed data that associates genetic changes to the ability of the disease to “hide” from its host.
The team has profiled the epigenetic regulation of gene expression in infected and healthy animals and present the genetic diversity of MAP strains from animals at different stages of the disease. Their analyses will define which factors affect the performance of diagnostic tests and can explain disease progression. 3
The team will also characterize the different strains of MAP to identify variants that could be more virulent. They will use up-to-date molecular tools reported in their recent publication (December 2020 7) to identify the causative MAP variants for the mixed genetics infection identified in the 23 Canadian herds screened in the recent years. The identification of the variants will be an asset for the development of vaccination program.
The identification of new genetic markers associated with Johne’s disease may help improve natural disease resistance through genetic selection. It will also strengthen researchers’ understanding of the epidemiology and host-pathogen relationship to support the development of diagnostic tools and vaccines in the future.

Abstract

A research project led by Nathalie Bissonnette (Agriculture and Agri-Food Canada (AAFC)-Sherbrooke) and Kapil Tahlan (Memorial University of Newfoundland) is investigating genetic markers in dairy animals that may be associated to Johne’s disease susceptibility or resistance. The project called, Unraveling the genetic susceptibility to Johne’s disease, is financed by Agriculture and Agri-Food Canada and Lactanet with in-kind contributions by Holstein Canada under the Dairy Research Cluster 3.

Mycobacterium avium subspecies paratuberculosis (MAP) is the pathogen that causes Johne’s disease. For dairy producers, Johne’s disease translates to significant financial losses related to reduced milk production, decreased pregnancy rates, increased premature culling, and decreased slaughtered carcass weight, not to mention diminished animal welfare Economic losses in the Canadian dairy sector resulting from Johne’s disease are recently estimated at $21.5 million to $34.1 million . Controlling Johne’s disease is difficult due to unpredictable disease progression and weak sensitivity of diagnostic tests in some animals that may look healthy but can shed the bacterium in the environment and transmit the disease.

Previous research showed the potential for genetic resistance to Johne’s disease in cattle, which may be useful to complement other farm management strategies to prevent infections. Nathalie Bissonnette and her team had repeated serum and fecal samples collected from over 3,150 cows during a longitudinal study and determined with accuracy the development of paratuberculosis over time.
In this new project, the researchers are using the data collected previously combined with other diagnostic tests to classify the animals as infected and infectious, infected and assumed resistant, or healthy. Genotyping the cows using two proven genetic testing methods, (Single nucleotide polymorphisms (SNP) panel and genotyping-by-sequencing), will help identify genetic markers and genes associated with susceptibility to Johne’s disease. In recent publications (January 20202, November 2020 , March 20214,5), the team validated the role of specific immune cell, SNP, and long non-coding RNA response to Johne’s Disease and confirmed data that associates genetic changes to the ability of the disease to “hide” from its host.
The team has profiled the epigenetic regulation of gene expression in infected and healthy animals and present the genetic diversity of MAP strains from animals at different stages of the disease. Their analyses will define which factors affect the performance of diagnostic tests and can explain disease progression. 3
The team will also characterize the different strains of MAP to identify variants that could be more virulent. They will use up-to-date molecular tools reported in their recent publication (December 2020 7) to identify the causative MAP variants for the mixed genetics infection identified in the 23 Canadian herds screened in the recent years. The identification of the variants will be an asset for the development of vaccination program.
The identification of new genetic markers associated with Johne’s disease may help improve natural disease resistance through genetic selection. It will also strengthen researchers’ understanding of the epidemiology and host-pathogen relationship to support the development of diagnostic tools and vaccines in the future.