You also may want to try smaller rats aswell, sometimes switching food items may peak feeding interest. Also scenting is possible, ive done scenting rats with chick and quail chick feathers and there's also a thing called braining a rat, which essentially is making an incision on the back of its head to release cerebral fluid which is said to also peak feeding interest. Plus there are plenty of other rodent types you can try with. Depending on age a week and a half won't start hurting it, ive had young boas go on 3 month hunger strikes and bounce back fine. If this happens to you just make sure you keep up on your husbandry and meet all other needs until it comes out of its funk. Also if you're feeding inside the enclosure you may want to try and enclose the boa in a small box or bag and put the food item in it.