title: Outbreak-specific monovalent/bivalent vaccination to control and eradicate virulent ovine footrot.
abstract: Footrot is a contagious disease of small ruminants which is caused by the bacterium Dichelobacter nodosus. In its virulent form there are severe economic losses and a very significant animal welfare issue. Sheep and goats can be vaccinated for treatment and prevention of the disease. There are 10 different serogroups of D. nodosus (A-I and M) and immunity is serogroup-specific. When all 10 serogroups are presented together in a vaccine, protection persists for only a few months due to "antigenic competition". Consequently we evaluated the use of sequential monovalent or bivalent vaccines to control/eliminate/eradicate virulent footrot in a longitudinal intervention study on 12 commercial farms in southeast Australia with flock sizes of approximately 1200-4200 sheep. Overall, virulent footrot was eradicated from 4 of the flocks, 2 of which had 2 serogroups, and the others 4 or 5 serogroups. Where there were only 1 or 2 serogroups (3 farms) the clinical response was rapid and dramatic; prevalence was reduced from 45 to 50% before vaccination to 0% (2 farms) or 0.4% (1 farm) after one round of vaccination. In the remaining 9 flocks there were more than 2 serogroups and successive bivalent vaccines were administered leading to eradication of virulent footrot on 2 farms over 4 years and control of the disease on all but 3 of the others. Of the latter farms, 1 discontinued, and 2 initially had poor response to vaccine due to misdiagnosis of serogroup 'M', which was previously unknown in Australia. Control was achieved after administration of a serogroup M vaccine. These results provide clear evidence for control, elimination and eradication of virulent footrot by outbreak-specific vaccination in Australia.
authors: Farm Animal and Veterinary Public Health, Faculty of Veterinary Science, The University of Sydney, 425 Werombi Road, Camden, NSW 2570, Australia. om.dhungyel@sydney.edu.au
authors: Om
authors: O
authors: Dhungyel
authors: Natalie
authors: N
authors: Schiller
authors: Jeff
authors: J
authors: Eppleston
authors: Deb
authors: D
authors: Lehmann
authors: Paul
authors: P
authors: Nilon
authors: Andrew
authors: A
authors: Ewers
authors: Richard
authors: R
authors: Whittington
mesh_terms: D000818:Animals; D001315:Australia; D001428:Bacterial Vaccines / Q000008:administration & dosage* / Q000276:immunology; D020376:Dichelobacter nodosus / Q000145:classification / Q000276:immunology / Q000302:isolation & purification*; D004196:Disease Outbreaks; D005535:Foot Rot / Q000453:epidemiology* / Q000517:prevention & control / Q000628:therapy; D015995:Prevalence; D012703:Serotyping; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology* / Q000517:prevention & control / Q000628:therapy; D016896:Treatment Outcome; D014611:Vaccination / Q000379:methods*
chemical_list: D001428:Bacterial Vaccines