Semi-automated motility assay speeds the hunt for new liver fluke drugs

Researchers have developed a semi-automated screening assay that tracks the movement of newly excysted juveniles of Fasciola hepatica, the trematode parasite behind fasciolosis, using microscopic live imaging. The method, described as standardized and objective, is designed to fill a gap in the drug-discovery toolkit for a disease classified alongside other food-borne trematode infections as a neglected tropical disease and one that also causes substantial agricultural losses in ruminants. The motivation is pressing.

No vaccine exists against F. hepatica, and control depends heavily on drug treatment, particularly triclabendazole (TCBZ). Four decades of intensive TCBZ use have driven rising rates of treatment failure and the emergence of drug-resistant parasites, making the identification of new treatment options an urgent priority. Yet the tools currently available for drug screening against this parasite remain limited, which is what the new motility-based assay sets out to address.

To validate the platform, the team tested a panel of ten compounds with known anthelmintic properties. Among them were TCBZ itself, which showed a half-maximal inhibitory concentration (IC50) of 1.5 µM, and benzamidoquinazolinone, an activator of the F. hepatica transient receptor potential melastatin (TRPMPZQ) ion channel, which came in at an IC50 of 1.05 µM. Both are established reference points for activity against the juvenile stage, and their performance in the assay supported its reliability.

Beyond confirming known actives, the screen flagged three compounds as particularly promising because they acted quickly and inhibited parasite motility at nanomolar concentrations. All three are salicylanilides: MMV665807 with an IC50 of 44 nM, niclosamide with an IC50 of 32 nM, and niclosamide ethanolamine, the ethanolamine salt of niclosamide, with an IC50 of just 9 nM. Complementary live/dead staining, however, added an important caveat.

Only TCBZ displayed parasiticidal activity in the test window. The other compounds, including the highly potent salicylanilides, caused parasite paralysis but did not kill the parasites within 72 hours. Scanning electron microscopy of drug-treated parasites provided a further layer of characterization.

At concentrations corresponding to the measured IC50 values, the researchers observed no significant damage to the parasite surface. The authors position the motility assay as a robust method for discovering novel anthelmintic compounds and as a practical contribution to ongoing efforts against fasciolosis. By replacing subjective visual scoring with automated imaging-based monitoring of juvenile motility, the approach offers a standardized readout that can be applied across compound panels, supporting the search for alternatives to triclabendazole at a time when resistance continues to spread.

Subject of Research: Development of a semi-automated motility-based drug screening assay for the juvenile stage of the liver fluke Fasciola hepatica

Article Title: A new semi-automated, motility-based screening assay for discovery of compounds with activity against the juvenile stage of Fasciola hepatica

Article References: Bernal, A., Gliga, D. S., Colangeli, G., Preza, M., Irobalieva, R. N., Frey, C. F., Hemphill, A., Lundström-Stadelmann, B., & Wiedemar, N. (2026). A new semi-automated, motility-based screening assay for discovery of compounds with activity against the juvenile stage of Fasciola hepatica. PLOS Neglected Tropical Diseases, 20(10), e0014491. https://doi.org/10.1371/journal.pntd.0014491

Image Credits: AI Generated

DOI: 10.1371/journal.pntd.0014491

Keywords: Fasciola hepatica, fasciolosis, drug screening, motility assay, triclabendazole, niclosamide, salicylanilides, newly excysted juveniles, anthelmintics, neglected tropical disease, TRPM ion channel, drug resistance