Short communication Fusobacterium necrophorum, and not Dichelobacter nodosus, is associated with equine hoof thrush Kaloyan K. Petrov 1 , Leon M.T. Dicks * Department of Microbiology, University of Stellenbosch, Stellenbosch 7600, South Africa 1. Introduction Thrush of the equine hoof is recognised as an infection of the frog adjacent to the sulci. In severe cases, thrush may spread to the white line, sole, and sensitive layers of the foot, which may result in permanent lameness. Despite being a general problem in horses, little is known about the microorganisms associated with hoof thrush. Most of our understanding of the infection is gained from research published on Fusobacterium spp. isolated from sheep (Egerton and Roberts, 1971), goats (Bennett et al., 2009b), cattle (Sun et al., 2011) and pigs (Zhou et al., 2010) diagnosed with footrot. In earlier literature, footrot is described as an infection caused by the synergistic action of Fusobacterium necrophorum and Dichelobacter nodosus (Roberts and Egerton, 1969). In cattle F. necrophorum subsp. necrophorum and F. necrophorum subsp. funduliforme have been asso- ciated with footrot (Shinjo et al., 1991). Dorsch et al. (2001) have shown that Fusobacterium spp. isolated from oral-associated diseases in horses are genetically different from F. necrophorum and classified the strains as Fusobacterium equinum. F. equinum is a normal inhabitant of the gastrointestinal, respiratory, and genitourinary tracts of horses and is generally associated with abscesses and necrotic infections (Racklyeft and Love, 2000; Trevillian et al., 1998; Zicker et al., 1990). Although phenotypically similar than F. necrophorum, F. equinum does not produce alkaline phosphatase and tests negative for haemagglutination (Dorsch et al., 2001). Veterinary Microbiology 161 (2013) 350–352 A R T I C L E I N F O Article history: Received 6 June 2012 Received in revised form 17 July 2012 Accepted 19 July 2012 Keywords: Footrot Horses Fusobacterium necrophorum Dichelobacter nodosus A B S T R A C T The aim of this study was to determine which of the two species, Fusobacterium necrophorum or Dichelobacter nodosus, are associated with hoof thrush in horses. Fourteen hoof samples, collected from eight horses with thrush and 14 samples collected from eight horses with healthy hooves, were examined for the presence of F. necrophorum, Fusobacterium equinum and D. nodosus. Only isolates with phenotypic characteristics representing Fusobacterium could be cultured. Total DNA extracted from the 28 hoof samples was amplified by using DNA primers designed from gene lktA, present in F. necrophorum subsp. necrophorum, F. necrophorum subsp. funduliforme and F. equinum, and gene fimA, present in D. nodosus. The lktA gene was amplified from five of the 14 infected hoof samples and from one hoof sample without thrush. The DNA sequence of the amplified ltkA gene was identical to the lktA gene of the type strain of F. necrophorum (GenBank accession number AF312861). The isolates were phenotypically differentiated from F. equinum. No DNA was amplified using the fimA primer set, suggesting that F. necrophorum, and not D. nodosus, is associated with equine hoof thrush. Hoof thrush in horses is thus caused by F. necrophorum in the absence D. nodosus. This is different from footrot in sheep, goats, cattle and pigs, which is caused by the synergistic action of F. necrophorum and D. nodosus. ß 2012 Elsevier B.V. All rights reserved. * Corresponding author at: Department of Microbiology, University of Stellenbosch, Private Bag X1, Matieland 7602, Stellenbosch, South Africa. Tel.: +27 21 808 5849; fax: +27 21 808 5846. E-mail address: LMTD@sun.ac.za (Leon M.T. Dicks). 1 Current address: Institute of Chemical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria. Contents lists available at SciVerse ScienceDirect Veterinary Microbiology jou r nal h o mep ag e: w ww .els evier .co m/lo c ate/vetm ic 0378-1135/$ – see front matter ß 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.vetmic.2012.07.037