Proceedings of the 10th International Colloquium on Paratuberculosis

#181 Continued shedding <strong>of</strong> MPtb from Australian sheep vaccinated with Gudair TM
Jeff Eppleston, Jeff Eppleston, Peter A Windsor, Evan Sergeant, Navneet K Dhand, Richard J Whittington,
Tablelands LHPA, Australia; University <strong>of</strong> Sydney, Australia; AusVet Animal Health Services, Australia
GudairTM was registered in Australia to control paratuberculosis in sheep after our previous research demonstrated
its efficacy for reducing mortalities and shedding <strong>of</strong> Mycobacterium avium subsps. paratuberculosis in
treated lambs. Subsequently a national risk-based trading scheme was developed that allowed trade in ‘lowrisk’
vaccinated sheep. However our original study was conducted in high challenge environments while in
practice vaccine has also been used in lower prevalence flocks. There has also been a recent trend to not vaccinate
we<strong>the</strong>r lambs because <strong>the</strong>y are being sold at young ages. We report 2 fur<strong>the</strong>r studies investigating <strong>the</strong>
impact <strong>of</strong> vaccination on faecal shedding in flocks <strong>of</strong> variable prevalence, and <strong>the</strong> risk associated with leaving
we<strong>the</strong>rs unvaccinated.
In a longitudinal study we monitored <strong>the</strong> prevalence <strong>of</strong> shedders across 4 generations <strong>of</strong> vaccinated
lambs in 11 flocks that varied in <strong>the</strong>ir initial disease prevalence. Cultures from 3, 4, 5 and 6 year-old sheep
were collected every 2 years on 3 occasions. Vaccinates had significantly less shedding than non-vaccinates
(0.63% versus 1.66%; P < 0.001) with unvaccinated sheep 7.9 times more likely to be pool positive compared
to vaccinates. The flock prevalence declined from 2.1% at Sampling 1 when all age groups were unvaccinated,
to 0.9% at Sampling 3 when all age groups were vaccinated. However at Sampling 3, 10 <strong>of</strong> <strong>the</strong> 11 flocks had
detectable shedding (range 0.1% -1.3%) indicating that despite almost no mortalities in flocks vaccinating for
<strong>the</strong> 6 years <strong>of</strong> <strong>the</strong> study, shedding persists at levels capable <strong>of</strong> spreading disease.
In Study 2 shedding in 1-2 year old ewes vaccinated as lambs and <strong>the</strong>ir unvaccinated we<strong>the</strong>r cohorts was
compared across 6 flocks. Shedding was detected in 5 <strong>of</strong> <strong>the</strong> 6 we<strong>the</strong>r flocks but in only 2 <strong>of</strong> <strong>the</strong> 6 ewe flocks.
The implications for flock and national control programs will be discussed.
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