Study urges milk-based tests for Johne’s disease detection
Pictor research shows variability in milk test results
30 October 2025
1 minute read
By: New research from Pictor Holdings shows that while commercial antibody tests for Johne’s disease produce consistent results when used on serum, their performance on milk samples varies more widely, according to a press release from Pictor. The findings highlight the need for milk-specific diagnostic standards to improve herd-level disease monitoring.
Johne’s disease costs the US dairy industry an estimated $198 million each year. Caused by a bacterial infection that damages the gut of cattle, it reduces nutrient absorption and milk yield and spreads mainly through contaminated faeces, milk, or feed.
The study found that two commercial antibody tests agreed strongly when used on serum but showed greater variability when used on milk. Researchers say this underscores the need for tests specifically designed for milk, with clear cutoff values to ensure reliable results.
Moderate agreement was also observed between ELISA and PCR tests, which detect different signs of infection and provide complementary information for herd management.
John Bannantine, retired USDA-ARS research microbiologist, said Johne’s disease remains one of the most under-recognised burdens in dairy production, affecting both profitability and animal welfare.
“Our research is focused on finding faster, more reliable ways to detect infection early, because every day of delay compounds the loss,” he said.
Jamie Platt, CEO of Pictor Holdings, said the findings emphasise that repurposing serum-based assays is not ideal.
“Veterinarians, dairy farmers, and testing laboratories need cost-effective tests developed specifically for milk,” he said.
The study recommends three key steps to strengthen Johne’s disease control: adopt milk-first surveillance using assays designed for milk, align on standardised cutoff values, and combine milk antibody testing with PCR in higher-risk herds.
The research analysed samples from New Zealand dairy herds and was co-funded by Pictor Ltd. and Massey Ventures Ltd. The abstract is now available, with the full paper set for publication in Tuberculosis (Elsevier).
