A rapid test for tilapia lake virus moves closer to on-farm diagnosis

Early detection of tilapia lake virus (TiLV) is essential to reducing the risk of disease spreading across aquaculture farms. However, the molecular methods commonly used to confirm infection require specialised equipment, trained personnel and, in many cases, samples to be sent to external laboratories.

A rapid test that could be used directly on farms would help speed up the identification of infected fish and the implementation of biosecurity measures, without initially having to wait for laboratory results.

To bring diagnosis closer to the point of production, a team of Thai researchers has developed a lateral flow immunoassay (LFIA), which works in a similar way to other rapid diagnostic tests.

The device uses two monoclonal antibodies that recognise a structural protein encoded by segment 8 of the TiLV genome. As described by the authors in a study published in Aquaculture, the procedure involves preparing a gill tissue sample and applying it to a test trip, which provides a visual result approximately 15 minutes after the sample is applied.

To assess its performance, the researchers analysed 61 samples collected from tilapia on commercial farms and compared the results with those obtained using semi-nested RT-PCR, a molecular technique used as the reference method.

This method identified 48 positive and 13 negative samples. The rapid test agreed with moleculr diagnosis in 60 of the 61 cases, correctly identifying 47 positive samples and all 13 negative samples. It therefore achieved a relative diagnostic sensitivity of 97.92%, specificity of 100% and overall accuracy of 98.36% in the sample set evaluated.

Alongside this high level of agreement, the researchers identified other characteristics that could facilitate its use outside the laboratory. No cross-reactivity was observed with the bacterial and viral pathogens included in the specificity tests, and the stability of the strips was assessed through accelerated ageing tests.

The findings suggest that the strips could retain their diagnosis performance for approximately two years at room temperature, a potential advantage for distribution and storage in production areas with limited access to specialised laboratory services. However, the estimate will need to be confirmed through storage studies under real-world conditions.

Despite these promising results, the test still has limitations when detecting infections involving low viral loads.

A negative result cannot completely rule out infection when the amount of viral antigen is below the device’s detection limit.

The authors therefore highlight the need to improve sensitivity for detecting early-stage or subclinical infections and to expand validation using a larger number of samples.

The reported accuracy must also be interpreted in the context of the sample set analysed, rather than as a guarantee of identical performance across all farming conditions.

For tilapia producers, the main value of this technology lies in obtaining an initial diagnostic result where the first fish health decisions need to be made.

Its eventual integration into surveillance protocols could help identify potentially infected batches and support the early implementation of containment measures, while retaining molecular testing for confirmation when required.

The next step will be to assess its performance under different production conditions and determine whether it can genuinely reduce diagnostic turnaround times and costs.

Although its use has not yet been shown to reduce mortality or economic losses, the study represents progress towards more accessible disease detection tools for aquaculture.

Scientific reference: Ponpukdee, N., Wangman, P., Chaivisuthangkura, P. & Longyant, S. (2026). Development and evaluation of a highly specific lateral flow immunoassay (LFIA) strip for the rapid detection of Tilapia lake virus in fish samples. Aquaculture, 625, 744330. DOI: 10.1016/j.aquaculture.2026.744330