Abstract :
Twosheep farms with clinical footrot for several years were selected to compare the efficacy
of paucivalent-specific vaccines with a commercially available vaccine (Footvax®). Furthermore,
it was also investigated whether specific DQA2-haplotypes may cause enhanced
footrot-tolerance. Prior to the trial and vaccination of animals, Dichelobacter nodosusstrains
isolated from both flocks were used to produce a pentavalent vaccine (containing
serogroups A, B, G, H und I) for flock 1 and a quadrivalent vaccine (containing serogroups B,
E, G and I) for flock 2. The trial included 695 ewes of German Mutton Merino (n = 347), German
Merino (n = 115) and German Blackheaded Mutton (n = 175). During the 16-week trial,
the ewes were examined thrice, on weeks 1, 4 and 16. Vaccination was performed during
the first and second examination. Prevalence of footrot (evaluated by the number of digits
with underrun horn) decreased from 20.2 to 5.9%. Depending on the kind of vaccination,
prevalence decreased from 12.3 to 2.5% within the Footvax®-group, whereas sheep vaccinated
with the autogenous vaccine showed a reduction of under-running footrot from 28.4
to 8.9%. Taking into account that vaccination with Footvax® caused a significantly (p < 0.001)
greater number of local reactions, the autogenous vaccines containing milder adjuvants are
recommended for reasons of animal welfare. The DQA2-locus of 538 ewes was analysed to
assess the genetic basis of footrot-tolerance. A total of 21 alleles and 96 genotypes were
detected. The most common DQA2-allele to be found was D (n = 263), which was also part
of the most frequent genotype B1/D (n = 44). Of all confirmed alleles, 23.4% consisted of a
DQA2-allele accompanied by an additional DQA2-like sequence. The likelihood that animals
carrying such a duplicated DQA2-haplotype, had under-running footrot was significantly
lower than the odds of ewes lacking the duplication (OR = 1.76 [95% confidence interval:
1.08–2.88], p = 0.02). Comparing single DQA2-alleles with each other leads to the result that
the likelihood of a footrot infection is smaller for ewes having one of the duplicated alleles
G and J2 than for ewes carrying the unduplicated alleles E and L (OR L/J2 = 2.09 [95%
confidence interval: 1.07–4.10], p = 0.03).
