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Title: The role of Clostridium botulinum type C in the pathogenesis of equine grass sickness
Author: Hunter, Leonie C.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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This thesis investigates the hypothesis that EGS is caused by a toxicoinfection with C. botulinum type C, where the organism grows and produces toxin in the gastrointestinal tract (GI). The study has taken three main directions: 1) detection of the botulinum type C neurotoxin (BoNT/C) in the GI tract of horses with and without EGS. 2) isolation and characterisation of organisms phenotypically resembling C. botulinum type C, and 3) detection of antibodies to the type C neurotoxin and surface antigens in the serum, GI tract, colostrum and milk. BoNT/C was detected by ELISA both directly in GI contents and after enrichment of the sample in order to determine the presence of both preformed toxin-producing organisms. BoNT/C was detected by direct detection and/or enrichment in 74% of horses with acute grass sickness, 67% of horses with subacute grass sickness and 67% of horses with chronic grass sickness compared to 10% of controls. BoNT/C was also detected directly and/or after enrichment in the GI tract of 81% cats with feline dysautonomia. These results support the hypothesis that toxicoinfection with C. botulinum type C is involved in the aetiology of EGS and possibility other similar dysautonomias, such as feline dysautonomia. C. botulinum type C is phenotypically indistinguishable from C. botulinum type D and Clostridium novyi type A. These three organisms are grouped together as "Group III" botulinum strains and are differentiated on the basis of the major toxins they produce. However, the type C and D neurotoxins and the C. novyi alpha toxin are encoded on separate pseudolysogenic bacteriophages that can be readily lost. Loss of these phages results in loss of toxigenicity and non-toxigenic isolates are essentially indistinguishable from each other. Sixteen isolates phenotypically resembling Group III botulinum were isolated from the GI tract of nine horses, one cat and one hare. The animals from which these organisms were isolated all had some association with dysautonomia: five horses, one cat and one hare had dysautonomia at the time of sampling; two horses had recovered from EGS; two horses had been in recent contact with EGS.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available