Dr. Castillo's work focuses on the development and application of innovative epidemiological methods to understand, control, and eliminate infectious diseases. He conducts research on zoonotic diseases in Latin America where he partners with public health authorities to respond to urban disease outbreaks and prevent zoonoses from re-emerging. Inherently transdisciplinary in his approaches, Dr. Castillo collaborates with colleagues from the Wharton School, Penn Vet, Penn Economics, and Penn Nursing. 

To understand the animal component of zoonotic diseases, Dr. Castillo studies animal population dynamics and fine-scale animal movement to examine their role in pathogen transmission. Also, by combining qualitative and quantitative approaches, he has identified and quantified structural, social, and spatial barriers that reduce access to healthcare and hinder appropriate immunization levels for vaccine-preventable diseases in humans and animals. Using community-based longitudinal studies, he develops algorithms to improve vaccination programs. 

Dr. Castillo has published more than 40 peer-reviewed papers in leading journals of tropical diseases. His published work embodies the “One Health” approach and illustrates pathways for other research on the intersection between human, animal, and environmental health. In addition to garnering press coverage in Latin America, Dr. Castillo's research has been cited in national bills for the control of zoonotic diseases in Peru.