Fatal Amoebic Meningoencephalitis Caused by Balamuthia mandrillaris in Pongo pygmaeus and First Case Report in Pan troglodytes verus

Rubén L. Rodríguez-Expósito ^1,2,3 Loles Carbonell ⁴ Jesús Recuero-Gil ⁵ Javier Martinez ⁴ Rosa Martinez ⁵ Carmen Martinez-Fernandez ⁶ Joaquin Ortega ⁷ Agustín Barragán Hernández ⁷ Juan M Corpa ⁷ Estefanía Montero Cortijo ⁷ Jesús Sánchez-Nicolás ⁵ Sergio Moya ⁵ Patricia Perez-Perez ^1,2 María Reyes-Batlle ^1,2,3 Angélica Domíngez-De-Barros ^1,3 Omar García-Pérez ^1,3 Angela Magnet ⁶ Fernando Izquierdo Arias ⁶ Soledad Fenoy Rodríguez ⁶ Carmen Del Aguila ⁶ Elizabeth Córdoba-Lanús ^1,3* Francisco De Asis García-González ⁵ Miguel Casares ^4* Jose Piñero ^1,2,3* Jacob Lorenzo-Morales ^1,2,3*

• ¹ Institute of Tropical Diseases and Public Health of the Canary Islands, University of La Laguna, San Cristóbal de La Laguna, Spain
• ² Departamento de Obstetricia y Ginecología, Pediatría y Medicina Preventiva y Salud Pública, Facultad de Ciencias de la Salud, Universidad de La Laguna, Tenerife, Spain
• ³ Centro de Investigación Biomédica en Red de Enfermedades Infecciosas (CIBERINFEC), Madrid, Asturias, Spain
• ⁴ Bioparc Valencia, Valencia, Spain
• ⁵ Bioparc Fuengirola, Málaga, Spain
• ⁶ CEU San Pablo University, Madrid, Madrid, Spain
• ⁷ Faculty of Veterinary Science, CEU Cardenal Herrera University, Valencia, Spain

Balamuthia mandrillaris is a leptomyxid amoeba that can cause granulomatous amoebic encephalitis (GAE) as well as lung and skin infections in both humans and animals. Studies on B. mandrillaris-related GAE cases have increased in recent years. This amoeba has been identified as a cause of encephalitis and death in several non-human primates. In this study, we report a case of a 4-year-old female Bornean orangutan (Pongo pygmaeus) in a zoological centre that exhibited neurological symptoms for several days. After unsuccessful treatments and a worsening in her condition, euthanasia was deemed necessaryrequired. Additionally, we describe the case of a 4-year-old male chimpanzee (Pan troglodytes verus) who died suddenly in a different zoo at the centre. Postmortem analysis revealed brain lesions with multiple haemorrhages, oedema, and inflammation in various organs in both cases. Histology showed the presence of B. mandrillaris trophozoites in necrotic and inflamed brain tissues, consistent with granulomatous amoebic meningoencephalitis. The diagnosis was confirmed using a multiplex qPCR assay on brain tissue samples from both animals. Water and soil samples from the chimpanzee's enclosure and soil from the orangutan's enclosure tested positive for B. mandrillaris DNA, confirming environmental exposure. An immunofluorescent antibody (IFA) assay detected B. mandrillaris in chimpanzee brain slices. According to the authors' knowledge, this report documents the first known cases of Balamuthia amoebic encephalitis in non-human primates in Spain and the first case in Pan troglodytes verus.