Evaluation of a lateral flow test to diagnose liver fluke in cattle and sheep.

Fasciola hepatica (the liver fluke) is an important parasite of cattle and sheep globally. Current diagnostic tests are laboratory based, which involve costs for sample collection and time taken for results to be returned. This can discourage farmers from engaging with the industry message to test before treating. Treatment in the absence of a diagnosis can contribute to the development of resistance to anthelmintics. We have developed a lateral flow test (LFT) to detect antibodies to fluke in whole blood, which can be used on-farm to detect exposure in cattle and sheep within 10 min. LFT performance was evaluated though on-farm trials sampling 10 sheep on 24 farms, and where possible, up to 10 cattle. Results were compared to those obtained with an in-house antibody detection ELISA. Linear regression analysis showed a positive correlation between LFT and ELISA results. Bayesian analysis assuming no gold standard indicated that the LFT had a sensitivity (Se) of 77 % (95 % Credible Interval [CI] 61-91 %) and specificity (Sp) of 80 % (CI 70-89 %) in cattle and 67 % Se (CI 47-94 %) and 71 % Sp (CI 62-82 %) for sheep. Sub-setting for first season lambs gave 96 % Se (CI 85-100 %) and 74 % Sp (CI 65-84 %). A group interview with the farmers who participated in on-farm trials indicated they found the LFT easy to use and thought it would be a useful tool to guide treatment decisions. The LFT will enable farmers to better engage with fluke management on their farms and encourage appropriate use of anthelmintics.