Experimental infection of pregnant sheep with attenuated Salmonella typhimurium

A.M. KHALIL, R.G. McFARLANE, N.A. SHAND, S.E. LESLIE AND N.H.CHRISTENSEN

Animal and Food Sciences Division, PO Box 84, Lincoln University, New Zealand

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Proceedings of the New Zealand Society of Animal Production 2001. 61: 74-77

Salmonellosis occurs in many animal species including sheep, and may cause pathology of the gut and possible abortion. If attenuated strains were to be used for future control, their establishment in the host and shedding pattern needs to be determined. Fifty-one pregnant ewes were obtained from the Lincoln University Research Farm and assigned randomly to five treatment groups. At approximately 1 month before lambing, the groups were given attenuated S. typhimurium (cya^-, crp^-) by different routes and doses as follows: 10¹⁰ colony-forming units (cfu) intranasally (i.n.), 10⁹ cfu i.n., 10¹⁰ cfu subcutaneously (s.c.), 10⁹ cfu s.c., and control (saline i.n. and s.c.). Selected animals were slaughtered at days 4 and 14 post infection for bacteriological culture from the mesenteric and retropharyngeal lymph nodes, intestinal contents and lamb stomach contents. The experimental organisms were isolated using selective cultures and identified by latex agglutination test and fermentation reactions. Following infection there were no changes in rectal temperature or significant clinical signs except two cases of abortion in the 10^{10 cfu s.c. group. The number of
animals shedding organisms in their faeces decreased with time from 12
ewes at day 1 to one ewe at day 4 and day 7. Most of them were from the
10,sup>10} i.n. group. Subcutaneous injection of 10¹⁰ cfu induced abortion in two of 11 ewes, as organisms were detected in their faeces and the aborted lambs. However, no organisms were detected in faeces, intestinal contents or the lamb stomach contents of the ewes that were killed at days 4 or 14. In the two ewes that had received 10¹⁰ cfu i.n. and were killed at day 4, organisms were detected in the mesenteric and retropharyngeal lymph nodes. In summary, the administration of the attenuated S. typhimurium (cya^-, crp^-) at 10¹⁰ cfu caused asymptomatic short-term faecal shedding and abortion when given i.n. and s.c., respectively.

Keywords: NZSAPAB; attenuated; Salmonella typhimurium,/i>; pregnant sheep

Last Updated 7/08/01