Safety is also a consideration. In September 2018 the US Food and Drug Administration (FDA) released a statement warning about the risk of tremors and seizures in animals treated with products containing drugs in the isoxazoline class, which are used to combat fleas and ticks. However, the FDA said it still considers the products "safe and effective".
Ideally, dogs should be taken to council-designated areas where they can be safely let off the leash to run free. It is important to use these specifically designated areas not only to ensure their own safety (preventing the risk of being hit by a car) but also the safety of farm livestock and wildlife which can be threatened by a dog let loose in their habitat.
Puppy Roundworms can infect humans. To prevent this infection, puppies should be wormed regularly throughout their first year of life, and owners should be thorough with their own personal hygiene after having interacted with the dog. Tapeworms, Hookworms, and Whipworms can also infect dogs, and your veterinary surgeon can advise when to worm the dog.