The Annie E. Casey Foundation, a Baltimore-based philanthropy for at-risk children and families, said Friday it had named a 16-year veteran of the organization as its new president and chief executive officer. Patrick T. McCarthy, who has served as senior vice president, will take over at the foundation April 4. McCarthy will succeed Douglas W. Nelson, who is retiring after 20 years of leadership. McCarthy joined the foundation in 1994 and has more than 25 years of experience in child welfare. He began his career as a psychiatric social worker at the Camden County Mental Health Center in New Jersey in the 1970s and later worked for the state of Delaware and for a nonprofit advisory group in Pennsylvania. He holds a doctoral degree from Bryn Mawr College's Graduate School of Social Work and Social Research.