Conventional disciplinary research approach is losing momentum in the face of dynamic health challenges of the 21st century. There is a need for a new, suitable approach, to tackle these emerging and re-emerging human and animal diseases through integrating livestock and human health research in a cross-disciplinary approach for greater impact. This is particularly important for the developing world owing to the closer contact of humans with animals as well as the consumption of raw animal products, worsened by low levels of literacy. Animals are the major source of today’s emerging and re-emerging infectious diseases that threaten both human and animal populations of the world. Among recent examples are SARS (severe acute respiratory syndrome), the Hendra and Nipah virus infections, BSE or mad cow disease (bovine spongiform encephalopathy) and now highly pathogenic avian influenza (HPAI), or bird flu. In addition, bovine tuberculosis and rift valley fever (RVF) are some examples of important re-emerging zoonoses. In recent years, bovine tuberculosis has become increasingly important with the HIV and AIDS pandemic in the developing world. This paper highlights the past and current research portfolio of ILRI and its partners, focusing on diseases that are transmissible between human and animals in the context of developing countries.