There is however a general move away from these products towards the non-organophosphate compounds. Systemic development inhibitors - eg Program. This works by preventing the development of the insect protein chitin which forms the external skeleton of the flea. It also prevents the eggs hatching by softening the 'egg-tooth' with which the flea larva cuts open its egg shell. Any larvae that do manage to hatch are prevented from moulting and cannot grow to maturity and pupation.
Program is given as tablets to dogs or a suspension on the food to cats once a month.
It should be given for at least six months as a course and can be given indefinitely if necessary. It must be given with food for proper absorption to occur and to achieve a month's effect. It has the advantage of being completely safe with no known side effects. It must be remembered that it has no effect on adult fleas and if there is an active population of fleas in the household an insecticide must be used for about two months. It is also wise to be prepared to use insecticides occasionally as the animal will from time to time bring in fleas from the outside.