Foot-rot in vaccinated and unvaccinated sheep. I. Incidence, severity and duration of infection
Egerton, J.R.; Morgan, I.R.; Burrell, D.H.
Veterinary Record 91(19): 447-453
1972
ISSN/ISBN: 0042-4900 PMID: 4647662 Document Number: 50741
In August 1970, 678 adult sheep were vaccinated with McMaster Laboratory Fusiformis nodosus vaccine and, together with 679 control sheep, were exposed to field challenge with foot rot on eight farms in Victoria. Foot rot outbreaks occurred on all farms among both vaccinated and control groups. At the peak of these outbreaks in early summer the infection rate among vaccinates ranged from 10.5 to 64% (mean 25.6%, SD 15.2) while that among controls ranged from 51.6 to 88.2% (mean 68.2% SD 6.0), whereas that among untreated controls was from 12.9 to 67.9% (mean 41.6%, SD 17.1). During the course of the outbreaks 274 of the vaccinates (40.4%) experienced foot rot at least once, compared to 535 (78.8%) of the controls. Foot rot in vaccinated sheep lasted a shorter time, was less invasive, and affected fewer feet than did foot rot in control sheep. Thus, of 233 affected vaccinates 154 (66%) had foot rot for less than two months; 257 of 356 affected controls (79%) had the disease for more than two months. Among affected vaccinated sheep 31.6% had severe infections that involved the matrix of the hard horn. In untreated controls 73.3% of sheep had similar extensive lesions. Of 233 affected vaccinates 59.6% were affected in one foot only, 24.8% in two feet, 8.0% in three feet and 7.6% in all four feet. Of 356 controls 26.9% had foot rot in only one foot, 30.3% in two feet, 17.3% in three feet and 23.5% in all four feet.