DIVA Diagnostics After BCG Vaccination: What Practicing Veterinarians Need to Know

One of the major challenges associated with BCG vaccination for bovine tuberculosis (bTB) control is its interference with conventional tuberculin-based surveillance programs. In countries where bTB control relies on "test-and-slaughter" policies, distinguishing vaccinated animals from truly infected animals becomes essential. This is where DIVA (Differentiating Infected from Vaccinated Animals) diagnostics become an important component of vaccination programs, allowing disease surveillance to continue alongside vaccination¹. 

Why Conventional Testing Becomes Challenging 

BCG vaccination can interfere with the tuberculin skin test because vaccinated animals may develop immune responses that are difficult to distinguish from those produced by natural infection. In regions where routine tuberculin testing is central to regulatory disease control, this limitation can complicate herd surveillance, movement decisions, and eradication programs¹. 

Rather than preventing vaccination, this challenge highlights the need for diagnostic tools capable of differentiating vaccinated cattle from those infected with Mycobacterium bovis. 

How DIVA Diagnostics Work 

The DIVA approach takes advantage of an important biological difference between field strains of M. bovis and the BCG vaccine strain. 

Field strains express the proteins ESAT-6, CFP-10, and Rv3615c, whereas these proteins are absent from the BCG vaccine. These antigens can therefore be incorporated into interferon-gamma (IFN-γ) assays to distinguish infected cattle from vaccinated animals¹. 

Studies using these antigens have demonstrated a sensitivity comparable to the traditional tuberculin test while achieving a specificity of approximately 97%–99%. In addition, infection with M. bovis or M. tuberculosis does not compromise the interpretation of the DIVA test¹. 

Advances in Intradermal DIVA Testing 

In addition to IFN-γ assays, compatibility between BCG vaccination and an intradermal DIVA test has also been demonstrated. 

A fusion reagent (DSF-F) containing ESAT-6, CFP-10, and Rv3615c has shown encouraging diagnostic performance, with approximately 90% sensitivity and 95% specificity in intradermal testing^2,3. 

Although these findings are promising, the performance of this approach under natural field challenge across different production systems and geographical regions still requires further validation^2,3. 

Practical Clinical Implications 

For veterinarians working in regions with active bTB control programs, DIVA diagnostics offer several practical advantages. 

They can support¹: 

• Continued disease surveillance in vaccinated herds. 

• More confident interpretation of diagnostic results following vaccination. 

• Improved compatibility between vaccination programs and existing control policies. 

• Better support for cattle movement and disease monitoring where vaccination is adopted. 

The availability of DIVA-compatible testing may also facilitate the broader implementation of BCG vaccination without compromising disease control objectives. 

Where DIVA Testing May Be Less Critical 

Not all production systems rely heavily on routine tuberculin testing. In some regions with endemic bTB, formal control programs are limited or animal movement is minimal. Under these circumstances, interference with the tuberculin test may have relatively little practical impact. 

In such herds, vaccination can still provide value, while program effectiveness may instead be monitored through indicators such as tuberculosis lesions detected during meat inspection and the number of carcass condemnations at slaughterhouses¹. 

Practical Clinical Insights 

Before recommending BCG vaccination, veterinarians should understand how disease surveillance will continue after vaccination. Where official control programs require tuberculin testing, DIVA-compatible diagnostics become an essential part of the overall vaccination strategy rather than an optional addition. 

Selecting an appropriate diagnostic approach before implementing vaccination can help maintain confidence in surveillance results while supporting long-term tuberculosis control. 

Take-Home Message 

Successful BCG vaccination extends beyond vaccine administration; it also requires reliable post-vaccination diagnosis. DIVA diagnostics allow veterinarians to distinguish infected cattle from vaccinated animals, supporting surveillance, cattle movement, and disease-control programs. As these diagnostic tools continue to develop, they have the potential to make BCG vaccination increasingly compatible with national tuberculosis control strategies. 

Reference 

1. Milián-Suazo F, González-Ruiz S, Contreras-Magallanes YG, Sosa-Gallegos SL, Bárcenas-Reyes I, Cantó-Alarcón GJ, Rodríguez-Hernández E. Vaccination strategies in a potential use of the vaccine against bovine tuberculosis in infected herds. Animals. 2022 Dec 1;12(23):3377. https://www.mdpi.com/2076-2615/12/23/3377 

2. Bayissa B, Sirak A, Zewude A, Worku A, Gumi B, Berg S, Hewinson RG, Wood JL, Jones GJ, ETHICOBOTS consortium, Vordermeier HM. Field evaluation of specific mycobacterial protein‐based skin test for the differentiation of Mycobacterium bovis‐infected and Bacillus Calmette Guerin‐vaccinated crossbred cattle in Ethiopia. Transboundary and emerging diseases. 2022 Jul;69(4):e1-9. https://onlinelibrary.wiley.com/doi/pdf/10.1111/tbed.14252 

3. Jones GJ, Konold T, Hurley S, Holder T, Steinbach S, Coad M, Neil Wedlock D, Buddle BM, Singh M, Martin Vordermeier H. Test performance data demonstrates utility of a cattle DIVA skin test reagent (DST-F) compatible with BCG vaccination. Scientific Reports. 2022 Jul 14;12(1):12052. https://www.nature.com/articles/s41598-022-16092-8.pdf