Fly Strike Protector for Small Animals. Fly Strike can be a very serious and sometimes fatal health problem, especially for Rabbits and Guinea Pigs. Spray every 7 days during warmer weather to deter flies and help protect against Fly Strike. Cleanliness and hygiene in hutches, cages etc. is vital to avoid attracting flies. Fly Strike Protector also kills fleas, lice and other insect pests. Contains effective permethrin for lasting protection.