Dracula's look is based on Count Orlok from the unauthorized adaptation Nosferatu: A Symphony of Horror (1922). This was also the model for the look of the vampire Barlow in the original Salem's Lot (1979).
Prior to learning about Dracula, the crew suspect that the animals' deaths are due to rabies, though they quickly dismiss the idea as it doesn't fit the situation. Vampirism, especially as described by Bram Stoker, is heavily based on the progression of the rabies virus in humans, and influences vampires' association with bats and wolves, two animals that commonly carry rabies.
Spent 20 years in development hell, having the directors, writers, and the script itself changed several times.
Dracula needed dirt from his homeland to regenerate his health, and ensure he rested well while living in foreign lands.
Director André Øvredal wanted Dracula to feel different, more animalistic, more feral, and wanted him to feel like he is fragile but also desperate and dangerous. Like an addict, who needs his blood.