First report of <italic>Leishmania infantum</italic> infection in the endangered orangutan (<italic>Pongo pygmaeus pygmaeus</italic>) in Madrid, Spain.

Background: Some wild animals have been recognized as potential reservoirs of <italic>Leishmania infantum</italic> infection (e.g. carnivores, lagomorphs, rodents, etc.). <italic>Leishmania infantum</italic> was also identified infecting humans and lagomorphs (i.e. hares and rabbits) over the period of 2009–2016, with the latter acting as the main reservoirs involved in the human leishmaniosis outbreak in Madrid. Results: Two cases of clinical leishmaniosis are reported in orangutans (<italic>Pongo pygmaeus pygmaeus</italic>) housed at two different centres in Madrid. The first is the case of a 36-year-old male orangutan with severe weight loss and apathy. A complete blood count and biochemical profile revealed anaemia, neutropenia, hypoalbuminaemia and elevated transaminases. Hepato-splenomegaly was also observed. Four months later, due to worsening of clinical signs (mainly bilateral epistaxis), blood and bone marrow samples were collected. Amastigotes of <italic>L. infantum</italic> were detected in macrophages from a bone marrow aspirate and by specific polymerase chain reaction. The second case was a 34-year-old female orangutan with severe weight loss and apathy and no other apparent clinical signs. A complete blood count and biochemical profile revealed anaemia, pancytopenia and hypoalbuminaemia. Splenomegaly and pericardial effusion were also observed. As leishmaniosis was included in the differential diagnosis, both blood and bone marrow samples were collected. <italic>Leishmania infantum</italic> infection was confirmed by microscopy, molecular diagnosis and serology (immunofluorescence antibody test). Both animals were treated daily with oral miltefosine for 28 days; allopurinol was also given uninterruptedly in Case 2 for at least 6 months. During follow-up, though good clinical recovery was clear, a lack of parasitological cure was confirmed molecularly in both blood and bone marrow samples from the two orangutans. In both habitats, the presence of the sand fly vector identified as <italic>Phlebotomus perniciosus</italic> was confirmed. Conclusions: To our knowledge, this is the first report of <italic>L. infantum</italic> infection in great apes and in the endangered species <italic>P. p. pygmaeus</italic>. We are presently looking for <italic>L. infantum</italic> in other non-human primates living in the same peri-urban areas. If detected, we will examine the impacts of this serious disease on these critically endangered species. [ABSTRACT FROM AUTHOR]