Detection and characterisation of respiratory pathogens among habituated, wild living chimpanzees (Pan troglodytes verus) of Taï National Park, Côte d’Ivoire

Abstract

Respiratory diseases are one of the most important threats to wild great apes habituated to human presence for research or tourism. However, the aetiological agents of such diseases have not been documented so far. Between 1999 and 2006 five distinct respiratory disease outbreaks hit three communities of habituated chimpanzees at our research site in Tai National Park, Cote d’Ivoire. Three of the outbreaks resulted in high morbiditiy and mortality. Necropsies were performed on seven individuals found shortly after death and histopathologic examination revealed the presence of purulent bronchopneumonia. Based on these examinations, the main objective of the present study was to identify and characterise the causative pathogens and determine possible sources of infection. Lung tissue samples were screened by PCR for a broad range of respiratory viruses. All samples tested were positive for either of two paramyxoviruses, the human respiratory syncytial virus (HRSV) or the human metapneumovirus (HMPV). To establish the origin of the viruses found, phylogenetic analyses were performed and revealed that the strains were closely related to strains circulating in contemporaneous, worldwide human epidemics. This represents the first direct evidence of anthropozoonotic virus transmission to wild great apes, suggesting that the close approach of humans to apes, which is central to both research and tourism programs, represents a serious threat to these animals. Furthermore, isolation of bacteria was performed and revealed that some of the deceased individuals were co-infected with Pasteurella multocida. Isolates were subjected to a detailed phenoand genotypic characterisation providing the first description of P. multocida in wild living chimpanzees. Two different strains were identified, both showing high similarity to previously described strains from different host and geographical locations. This suggests that chimpanzees are involved in the epidemiology of P. multocida. The question of whether this bacterium is carried naturally by chimpanzees or was transmitted by other animals will be investigated in further studies. To systematically evaluate the occurrence of respiratory pathogens without disturbing the chimpanzees’ natural behaviour, the establishment of non-invasive diagnostics was another aim of this work. Therefore, faecal samples which had been collected during and between outbreaks were tested for HRSV and HMPV by PCR. Using this approach it was possible to identify the causative agents of lethal as well as of non-lethal outbreaks, to evaluate the virus prevalence among a larger study group, and to perform phylogenetic analyses of the viruses detected. This demonstrates that the screening of faecal samples is a suitable tool for monitoring acute respiratory diseases in wild living chimpanzees. This is the first systematic study of respiratory diseases in wild great apes. The results presented are of great relevance for future conservation strategies as a deeper knowledge of the involved pathogens may help to prevent or mitigate future disease outbreaks.