Vaccination Against Paratuberculosis (Johne's Disease)

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Abstract
Summary: A total of 289 lambs, on farms where Paratuberculosis (Johne's disease) of sheep was prevalent, were vaccinated over a period of 3 years with one or two injections of heat killed Mycobacterium paratuberculosis suspended in mineral oil. This type of vaccine was known previously to elicit a powerful and protracted immunological response. A total of 266 lambs on the same farms were left unvaccinated as controls. During the experimental period 16 of the unvaccinated animals, but none of the vaccinated sheep, succumbed to Paratuberculosis. The experiment was terminated 3½ years after it was started, and the intestines of the remaining sheep were carefully searched for lesions of Paratuberculosis. Such lesions were found in 4 of the vaccinated animals but in 21 of the unvaccinated controls. Both these differences are statistically highly significant, and it may be concluded that under the conditions of the present experiment the vaccine has provoked a satisfactory resistance to subsequent infection. This vaccine does not contain living bacilli, and has proven to be safe for field use also in other respects.