A multi-antigen proteomic approach to Johne's Disease monitoring in dairy herds

25 March 2026

4 minute read

By: Jamie Platt, PhD

Johne's disease costs the U.S. dairy industry an estimated $200–250 million annually. Yet the animals driving those losses are rarely the ones showing clinical signs. 

The real economic burden comes from subclinical infection — cows that appear healthy and productive while shedding Mycobacterium avium subspecies paratuberculosis (MAP) into the environment, reducing milk yield, compromising reproduction, and increasing culling rates long before diarrhea or weight loss appear. 

For herd managers, the challenge is clear: you can't manage what you can't see. 

Current serological testing helps, but it's built on a simplifying assumption — that measuring antibody response to a single MAP antigen is enough to characterize immune exposure across a herd. In reality, MAP infection triggers a complex, variable immune response. Some animals mount strong antibody responses early. Others don't seroconvert until late-stage disease. Some may never produce detectable antibodies at all. 

If immune responses vary this much, does it make sense to keep measuring just one? 

Why single-antigen serology has limits 

Most commercially available ELISA platforms for Johne's disease rely on detection of antibodies against a limited, non-specific MAP antigen. These assays are practical, scalable, and widely used — but they are not specific and reflect only one slice of the immune response. 

MAP infection doesn't produce a uniform antibody profile. Reactivity depends on disease stage, individual immune dynamics, and the specific antigens an animal's immune system happens to recognize. Relying on a single target means some infected animals may show strong reactivity, while others — equally exposed or infected — show little to none. 

For producers running control programs, this creates interpretive challenges. Is a negative result truly negative, or did that animal simply not produce antibodies to the antigen being measured? Is a borderline result meaningful, or noise? 

These aren't hypothetical questions. They show up in herd data as inconsistent test-retest results, animals that seroconvert late, and subclinical shedders that remain seronegative on standard assays. 

Expanding the antigen target profile 

Recent work in targeted proteomics has explored whether measuring antibody responses to multiple MAP antigens simultaneously could provide a more complete picture of immune exposure. 

The rationale is straightforward: if immune responses vary across animals and infection stages, measuring a broader panel of antigen targets should capture more of that variability. 

In a small validation cohort of dairy cows (n=15), we evaluated antibody reactivity to several MAP-associated proteins using a targeted proteomic assay. Samples were also tested using commercially available single-antigen ELISA platforms for comparison. 

The results were notable: 

• The targeted proteomic assay showed higher overall antibody agreement compared to single-antigen platforms 
• Antibody signals were detected in animals that showed limited or inconsistent reactivity on single-target assays 
• The broader antigen panel appeared to capture immune responses that single-antigen testing missed 

These findings are preliminary and based on a limited sample size. Larger field studies will be required to define sensitivity, specificity, and predictive value across diverse herd conditions. But the data suggest that broader antigen coverage may help characterize the heterogeneity in humoral immune responses — particularly in subclinical animals where variability is highest. 

Why subclinical monitoring matters 

The economic impact of Johne's disease is driven largely by what you don't see. Reduced milk production, reproductive inefficiency, and premature culling often begin years before clinical signs appear. 

For herd managers, this creates a visibility problem: 

• Clinical animals are obvious. 
• Subclinical animals are not. 

Monitoring strategies that characterize immune exposure patterns more broadly may support more informed herd-level decision-making — particularly when integrated with culling policies, replacement strategies, and biosecurity planning. 

No single test provides a complete answer. Effective Johne's control programs combine testing with management practices, hygiene protocols, and long-term surveillance. But tools that reflect the biological complexity of MAP infection — rather than simplifying it — may offer a more nuanced view of herd health over time. 

Practical considerations for dairy operations 

Any new testing approach must work operationally, not just scientifically. 

Key considerations include: 

1. Sample Type 

Milk-based testing offers logistical advantages in dairy operations already accustomed to milk recording workflows.  

2. Testing Frequency 

Herd-level surveillance relies on periodic testing and trend analysis over time, not one-time snapshots. Consistency matters. 

3. Cost per Animal 

Expanded antigen profiling must remain cost-competitive with existing tools to support routine adoption. 

4. Data Interpretation 

Targeted proteomic assays using multiple antigens generate data that more accurately reflects the complex biology of disease and increases the robustness and reliability of the results Clear interpretive frameworks will be necessary to support field use by veterinarians and producers. 

In practice, proteomic assays may also serve as complementary tools within broader Johne's disease control strategies, in addition to a replacement for some existing methodologies. 

Integrating targeted proteomics into herd health programs 

Targeted proteomics allows simultaneous analysis of antibody responses to multiple defined MAP antigens within a single assay. This multiplex capability may offer advantages in: 

• Research settings seeking to characterize immune response dynamics 
• Herd-level surveillance programs evaluating exposure patterns 
• Development of next-generation platforms 

However, widespread adoption will depend on additional validation across larger and more geographically diverse herds, different management systems, and varied stages of infection. Robust field performance data remain essential. 

A shift toward broader immune characterization 

Johne's disease control has historically relied on incremental improvements in management practices and testing protocols. Advances in proteomic technologies may represent another step in that evolution. 

Rather than focusing solely on the presence or absence of antibody reactivity to a single, mixture of proteins, specific multi-target analysis approaches reflect the biological complexity of MAP infection. Whether this broader immune characterization ultimately improves herd-level monitoring strategies will depend on continued research, transparent data reporting, and collaboration between producers, veterinarians, and testing developers. 

As dairy operations face increasing pressure to optimize productivity and biosecurity, tools that support more nuanced understanding of herd health patterns may play a role in long-term disease management frameworks. 

The data suggest that expanding antigen targets in testing warrants further investigation — particularly in the context of subclinical infection monitoring, where variability in immune response remains a central challenge.