Professor Jeggo qualified as veterinary surgeon in the UK in 1972 and after a short four-year spell in general practice has worked in research and research management of infectious diseases. This included spells in a number of developing countries, at the UK high containment laboratory and within the United Nations. During this period of 18 years at the UN, he managed programs of support for animal health in the developing world with research related projects in some 150 countries. One such program involved support to laboratories in 40 countries assisting the global eradication of rinderpest.

In 2002 he became Director of the Australian Animal Health Laboratory and as such was a member of the Australian Animal Health Committee and Chair of SCHALS. In 2013 he retired from AAHL and works on a part time basis within the framework of the Geelong Centre for Emerging Infectious Diseases – a One Health consortium.  He is Chair of the Governing Board of AUSGEM (a research partnership between UTS and EMAI, NSW), on the Board of the International Livestock Research Institute (ILRI) the Advisory Board of GALMED and the International Advisory Board of SACIDS.