Effectiveness of an inactivated paratuberculosis vaccine in Iranian sheep flocks using the subsp 316F strain.

Background And Objectives: Paratuberculosis (PTb) (John's disease) is an incurable chronic intestinal infection that mainly affects ruminants. PTb is caused by subspecies (MAP) with a global distribution. Despite evidences on MAP contribution in Crohn's disease its causal role is still a matter of controversy. In ruminant farming, vaccination is broadly accepted as an effective control measure of PTb. This article describes preparation and field trial of an inactivated PTb vaccine made from the MAP 316F strain.

Materials And Methods: Formulation of the vaccine was conducted based on the method traditionally used in the UK. Identity of the MAP strain was authenticated by PCR-IS and PCR-F57 tests. In the field, a group of 100 lambs (3-8 weeks old) were subcutaneously inoculated with the vaccine preparation under study. These animals, pre-vaccination, were all PTb ELISA negative. Serum level of antibody was determined by ELISA on days 0, 30, 60, 120 and 240, post-vaccination.

Results: In PCR- and PCR-F57, the MAP 316F strain produced two fragments of 560 and 704 bp length respectively, a confirmation of its identity as MAP bacterium. In the field trial and at the arranged time intervals, the achieved blood serum levels of antibody, attributable to the vaccine formulation, displayed considerably high values.

Conclusion: Given that the PTb-caused economical losses in the Iranian environment are dramatically high and also the fact that future of state policy on control of PTb remains unknown, we belive vaccination of animals is the best recommendable practice.