I was at my parent's house earlier and I noticed my dog had lost a drastic amount of weight. Not to the point where I had to worry cuz he was getting a bit fluffy for a while there. My mom said it was from this new diet he is on which consists of tuna mixed with veggies. My dad on the other hand seems to think he could have a worm. He is the only animal at their house and he is always in the back yard. How does an animal contract worms and is it even a possibility for a dog such as him?