This special issue about selected diseases of nonhuman primates is created in honor to Prof. Dr. Franz-Josef Kaup, who has worked as a primate pathologist at the German Primate Center (DPZ) for 25 years. In 1993, Franz-Josef Kaup started his career at the German Primate Center as head of the working group Experimental Pathology. Prior to that he worked as a research assistant in the electron microscopy division at the Institute of Pathology of the University of Veterinary Medicine in Hanover. When he began, he was already very experienced in the field of electron microscopy and used this expertise to establish a centralized electron microscopy laboratory at the DPZ. In the beginning, the research of the Experimental Pathology group was focused on gastrointestinal and respiratory infections and was closely related to projects of the Department of Virology. At that time, experimental infections of rhesus macaques with simian immunodeficiency virus (SIV) and associated opportunistic infections became the main subject of research. The contribution of Christiane Stahl-Hennig and Nicole Stolte-Leeb provides an overview of SIV-induced diseases and reflects the still ongoing collaboration. After merging of the Experimental Pathology and Primate Husbandry groups in 1996, Franz-Josef Kaup headed the newly created Department of Veterinary Medicine and Primate Husbandry. After the retirement of Manfred Brack in 1999, this department became the central service unit of the DPZ and offered a broad spectrum of services, including veterinary diagnostics, primate husbandry, and animal welfare, which were intensively used by many internal and external scientists. In 2001, Walter Bodemer joined the group and the scientific spectrum expanded, with a new focus on the pathogenies of prion diseases. Some important aspects of this era are summarized by the contribution of Walter Bodemer.

Several animal models were successfully established under the leadership of Franz-Josef Kaup, including an animal model for Helicobacter pylori infections. Currently, the main focus of research focus is on the pathogenesis of orthopoxvirus infections. Kerstin Mätz-Rensing and colleagues established a new animal model for orthopox virus infections, which is based on a natural outbreak of the disease in a private New World monkey husbandry facility. During this outbreak, a new orthopox virus was discovered, which was named calpox after its host species. This animal model was used for pathogenetic and vaccination studies in orthopox virus research. Over the years, close cooperation arose with several working groups working in this important field of virus research. The chapter of Claus-Peter Czerny provides an overview of the monkeypox virus disease, another important orthopox virus representative of this important period. In 2004, the Department of Veterinary Medicine and Primate Husbandry was reorganized into the Pathology Unit and the Cost Center Primate Husbandry, both headed by Franz-Josef Kaup. The Pathology Unit was composed of the Primate Pathology group headed by Kerstin Mätz-Rensing, the Dermatopathology group headed by Bärbel Löblich-Beardi and the Herpes virus group headed by Dieter Jentsch. The research spectrum was further extended through dermatopathology and herpes-virus-related research. As head of the Primate Husbandry group, Franz-Josef Kaup focused on the problem of herpes B in macaques and supported the herpes B diagnostics at the DPZ. Herpes B is of special interest for handling of macaques in research projects and breeding colonies. The development of an efficient herpes B screening test and the current state of the art at the DPZ is described in the contribution of Artur Kaul. Another important disease which can be problematic for breeding colonies is endometriosis. The contributions of Eva Gruber–Dujardin and Ivanela Kondova address this disease and its related research and lead over to spontaneous diseases of nonhuman primates, which have been in the focus of the pathology group for many years.

Over the years, several important cases of emerging diseases, rarely occurring neoplasia or unique disease entities in nonhuman primates have been described by this group. The work by Karen Lampe about a unique T-cell lymphoma in a patas monkey and by Kerstin Mätz-Rensing about amoebiasis are examples of spontaneous diseases observed during routine pathomorphologic diagnostics. The possibility to work on such extraordinary cases emerged from close contact with several German zoos drawing on the expertise of Franz-Josef Kaup’s group in the field of primate diseases and pathology. Other interesting case reports resulted from the routine clinical and diagnostic work at the DPZ, such as the contribution of Tamara Becker about Guillain–Barré syndrome in a rhesus monkey.

Over the years, Franz-Josef Kaup has supported the work of colleagues from the Department of Behavioral Ecology and Sociobiology and other colleagues predominantly working in the field in the natural habitats of nonhuman primates. A major health problem among natural primate colonies is parasites, and the articles contributed by Peter Kapeller, Eckhard Heymann and Fabian Leendertz reflect this problem.

Cooperation with the working group of the Fraunhofer Institute for Toxicology and Experimental Medicine (ITEM) Hanover headed by Fransiska Dahlmann again strengthened the Pathology Unit. The ITEM group works on primate models for COPD and asthma and is supported by the working group Anatomy/Pathology of the Respiratory Tract headed by Martina Bleyer. The contribution of Dahlmann and Bleyer in this issue will highlight aspects of their work.

Over the years, Franz-Josef Kaup’s main research focus has been lung diseases, starting with the work in Hanover on COPD in horses. With the new project on an asthma model in nonhuman primates, his life's work has come full circle.