The York-based company announced the succession plans alongside a half year trading update which showed strong first half results and a positive outlook for the full year to June 2013.
Dr Menneer is taking over as chief executive with immediate effect.
Mr Wildridge will remain with the business until October as director of strategy and business development, driving forward Animalcare’s key product development programmes and assisting Dr Menneer with the overall strategy for the group. He will continue as a board director until October.
Mr Wildridge, 56, is credited with transforming Animalcare from a mainly agricultural business to a niche pet drugs company. He said he is keen to take on another role at a company that needs turning around.
“I enjoy taking a business and building something strong. I’m not sure I’d take on another long term chief executive’s role, but if someone needs help for a couple of years I’d look at it,” he said.
He added that his homebase will always be Yorkshire although he could travel further afield for work.
Analyst Chris Glasper, at N+1 Singer, said: “Stephen has been the architect of growing the business since 2003 and revenues in that period have grown from £6.1m to £10.9m in 2012, with the margin profile transformed.
“He will remain with the group until October to assist in an orderly handover and in implementing the foundations for the next leg of growth.
“Iain has also been with the business since 2003 and has held a number of marketing, managerial and business development roles, including working on the new product development programme. As such, he is ideally positioned to take the business to the next stage of its development.”
Dr Menneer was promoted to the board as director of marketing in 2011 and was appointed managing director last March.
James Lambert, chairman of Animalcare, said: “Whilst we will miss Stephen’s experience, he leaves the group in a strong position and with a proven, capable successor in Iain Menneer to take over as chief executive.”
In a trading update yesterday Animalcare said first half revenues rose by 13 per cent to £6.1m.
Gross profits increased by 16 per cent.