We have an 18 month old male cat who has been neutered for a year. Recently (past 2 months) he has begun releasing a very pungent odored substance when petted. He is very affectionate and likes being brushed and petted. We have tried to make sure we don't touch his hindquarters but lately just petting will cause this reaction. He seems surprised when this happens and cleans himself thoroughly. Any ideas on how to stop this gross smelling spraying? He is a completely indoor cat and his sister has been neutered as well. No other cats in the vicinity. There is someone home all day with the cats and they are played with and petted. He has received all his shots and is on Iams Indoor Cat dry food.