There is plenty of advice to be found on t'internet to suggest that it 'might' help. Faced with no other treatment option available, I would certainly go through with Oxytet if I had a storm again (not routinely every year like a lot round here do for Enzo though).
Just a couple of the links I found in a few minutes on Google:
http://www.farmhealthonline.com/disease-management/sheep-diseases/campylobacteriosis/
http://www.westpointfarmvets.co.uk/sheep-abortion/
First link says no evidence it does anything. I've complained about the second link and will see if I can get it adjusted or taken down. Have a look on something like NADIS if you want good quality impartial advice with expert oversight (any one can put any old crap on the internet). http://www.nadis.org.uk/bulletins/abortion-in-ewes.aspx
Re your comment " I would certainly go through with Oxytet if I had a storm again ", see my reply to the post below:
Very hard not to try everything when you're at the pit face
Well yes and no. We are talking batch treatment of animals with antibiotic. I hope to hell you on't have enough antibiotic in stock to treat all these animals and therefore you are going to have to source a reasonably large volume from your vet. Very simply I would not prescribe it or allow you to have it in the situation where we had confirmed campylobater abortion.
The use of antibiotics in this way is not your decision, it's down to a professional to prescribe them. Those professionals are under a hell of a lot more pressure to reduce the use and reliance on antibiotics.
does the capitals mean you are shouting?!
Yes! It bloody does.