If a dog is infected with gastrointestinal parasites, such as roundworms and whipworms, it will cause diarrhea. Dogs infected with roundworms and tapeworms often cause vomiting. , if the dog is infected with intestinal parasites, the dog will lose weight, because the parasites will weaken the dog's nutrient absorption, and the dog will lose weight over time. There are usually two types of external parasites, one is fleas, and the other is ticks. They can be judged by whether the dog has hair loss and other phenomena.