** Shares in Virbac VIRB.PA fall 5% after the French animal drugs company posted weak H1 results, with lower operating income margin hurt by one-off events and higher costs
** Virbac reports H1 EBITA of EUR 135 mln ($158 mln), down from EUR 150.4 mln a year ago
** Analysts at Midcap Partners and Portzamparc highlight that profitability was hit by higher-than-usual stock destruction and a temporary halt in antigen production for plant maintenance
** The brokerages add that margins were also squeezed by a front-loading of R&D expenses and a rise in operating costs during H1
** The stock heads for its worst day in 11 months, if losses persist
($1 = 0.8522 euros)
(Reporting by Hugo lhomedet)
((hugo.lhomedet@thomsonreuters.com))