CLM is caused most often by the larvae of the dog and cat hookworm Ancylostoma brasiliense or the the larvae of the dog hookworm Ancylostoma caninum. Medical literature does mention that CLM has been attributed to the larvae of cattle hookworm Bunostomum phlebotmum, and pig hookworm A. carinum but is is highly unsual.

Image of adult worms taken from Parasite Images List from Queensland University of Technology.