Efficacy of the nematophagous fungus Duddingtonia flagrans in reducing equine cyathostome larvae on pasture in south Louisiana

The effectiveness of Duddingtonia flagrans in reducing the free living thir d stage larvae (L-3) of equine cyathostomes on pasture when fed to horses h as been demonstrated in cold temperate climates. The objective of this expe riment was to assess the efficacy of D. flagrans against equine cyathostome s in the subtropical environment of southern Louisiana. Fecal pats were pre pared by mixing feces obtained from a parasite-free horse fed D. flagrans a t a dose of approximately 2 x 10(6) spores kg(-1), with feces containing cy athostome eggs from a parasitized horse. Control pats contained feces from a parasite-free horse mixed with feces containing cyathostome eggs. The fec al pats were placed on pasture in six replicates at 4-week intervals from M arch 1997 until January 1998. Comparison of recoveries of L-3 from non-trea ted control pats in the field with non-treated coprocultures maintained in the laboratory indicated that L-3 survival on pasture was reduced during th e months of May, June, July, August and September. The efficacy of the fung us was determined by L-3 recovery from grass surrounding the fecal pats of treated and control groups. D. flagrans significantly reduced L-3 during th e months of April, May, and October 1997 to January 1998 (range 66-99% redu ction, p=0.0001), and for the year as a whole (p=0.0001). (C) 2000 Elsevier Science B.V. All rights reserved.