Interaction between Duddingtonia flagrans and dietary coccidiostats in lambs in reducing the development of Haemonchus contortus larvae

Authors: Burke, Joan; Rohila, Suman; MILLER, JAMES - Louisiana State University; PETERSSON, KATHERINE - University Of Rhode Island; VATTA, ADRIANO - Louisiana State University

Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2026
Publication Date: 5/13/2026
Citation: Burke, J.M., Rohila, S., Miller, J.E., Petersson, K., Vatta, A.F. 2026. Interaction between Duddingtonia flagrans and dietary coccidiostats in lambs in reducing the development of Haemonchus contortus larvae. Veterinary Parasitology. https://doi.org/10.1016/j.vetpar.2026.110798.
DOI: https://doi.org/10.1016/j.vetpar.2026.110798

Interpretive Summary: Gastrointestinal nematodes and coccidia are one of the greatest health challenges to sheep and goats due to ineffective pharmaceutical treatments, production losses and possible death associated with parasite infection. Control of these parasites to young lambs is essential to optimize animal health and production. A nematode-trapping fungus fed as spores to animals can aid in reducing the infective stage of nematode parasites on pasture, while coccidiostats control protozoan parasites, but it is not known whether both products can be fed together. Scientists from the USDA, ARS, Louisiana State University and the University of Rhode Island conducted studies using in vivo, in which animals were provided or not the fungus and the coccidiostat and fecal samples collected; and in vitro, in which the feces with nematode larvae were cultured to determine reduction of nematode larvae associated with each treatment. The fungus reduced the development of nematode larvae and there was no interaction between the fungus and the dietary coccidiostat. This is important for pasture based small ruminant production which is of great interest to farmers, extension specialists, veterinarians, the feed industry and scientists with an aim of maintaining healthy livestock.

Technical Abstract: Providing dietary spores of Duddingtonia flagrans leads to fewer gastrointestinal nematode (GIN) larvae on pasture, but little is known about interaction with dietary coccidiostats. The objective was to determine the efficacy of D. flagrans (Df) fed to sheep with or without coccidiostats, decoquinate (Study 1 and 2) or lasalocid (Study 3) to reduce the number of GIN larvae (predominantly Haemonchus contortus) in feces. All studies used a 2 × 2 factorial design (± Df × ± coccidiostat). Study 1: An in vivo experiment used 8 lambs/treatment using the recommended 5 × 105 chlamydospores/g carrier, but a post-study analysis indicated the package contained 10-fold fewer spores. There was no reduction in cultured larvae associated with Df. Studies 2 and 3: anthelmintic-treated lambs were fed a supplement with coccidiostat (+C; decoquinate or lasalocid in Study 2 or 3, respectively) or without (-C) for 7 (Study 2) or 14 (Study 3) days before fecal collection; within diet, Df was administered (+DF) daily or not (-DF) 1 to 3 days before fecal collection. Feces were cultured on agar plates for 7 days at 2 g/plate + 300 L3 of H. contortus or 5 g/plate + 1000 L3 (n = 3 to 4 plates/lamb) at 25°C. On the 2 g plates, Df reduced L3 recovery (P < 0.001) without an effect by coccidiostat in Study 2 (P = 0.38) or a slight increased recovery (P = 0.05) in Study 3, and no interaction between Df and coccidiostat. On the 5 g plates, Df reduced larval recovery (P = 0.001) and there was no effect of lasalocid or any interaction detected. Using these methods, dietary coccidiostats did not impair the action of Df (5 × 105 chlamydospores/g) on reducing infective larvae in feces.