The Bat People (1974)

Dr John Beck recently married decides to take his wife Cathy spelunking in Carlsbad Cavern While there Dr Beck who specializes in bats is bitten by a fruit bat He is then inexplicably transformed into a vampire bat While he escapes and seeks help from another doctor it is clear the treatments are not working In fact they are aggravating his condition Dr Beck unwittingly goes on a killing spree catching the attention of Sergeant Ward