Parasites are living organisms that live on other organisms. Parasites do not have their own metabolic systems. Keeping that in mind humans can not be termed as parasites.
If you are talking about humans being parasites in the figurative way, well in that case too my answer above holds.
Humans are right above the food chain. They have been given total privileges to mess with their own eco systems.
But Animals Can be Parasitic in Nature
A few examples of parasites are tapeworms, fleas, and barnacles. Tapeworms are segmented flatworms that attach themselves to the insides of the intestines ofanimals such as cows, pigs, and humans. They get food by eating the host's partly digested food, depriving the host of nutrients.