Introduction

Wildlife sanctuaries contribute to the conservation of endangered animals by providing treatment, rehabilitation and long-term care [1]. Recently, it has been demonstrated, that drug-resistant human Staphylococcus aureus can be transmitted from care workers and veterinarians to chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla), as shown in two sanctuaries in Uganda and Zambia [2] or in a research center in Gabon [3]. Apart from colonization, it was reported that transmitted S. aureus has led to severe and even lethal infection of one gorilla in the Gabonese center [3] highlighting the threat of this “humanosis” in apes. It has been reported that S. aureus can cause sepsis, skin and soft tissue infection, visceral abscess, air sacculitis and meningitis in monkeys and apes [3–5].

It is likely, that fatal S. aureus infections could not only occur in captive animals but also in wild conspecifics. Most sanctuaries consider reintroduction as an important tool for the conservation of endangered animals [1]. This bears the risk to introduce human adapted pathogens into the wild population where surveillance and infection control measures are hardly feasible [2,6].

A surveillance strategy for pathogens can therefore be used to assess the risk caused by re-introduction of captive wild animals into their natural habitat. Ideally, specimens used for surveillance should be non-invasive to avoid narcotization of wild animals for sampling of mucosal swabs. While the anterior nares are known as principle habitat of S. aureus, the main colonization sites for monkeys and apes are largely unknown.

Recently it has been shown that a number of viruses and bacteria can be monitored in fecal and urine samples, e.g. respiratory viruses, SIV and plasmodium [7,8] or antibodies to simian T-lymphotropic virus [9]. Similarly, fecal samples were used to show that Escherichia coli can be transmitted between humans, gorillas and livestock if their habitats overlap [10]. Recently, we also showed that chewed spit-out remains (fruit wadges) from chimpanzees are suitable to analyze oro-pharyngeal carriage of S. aureus [11].

The objectives of our study were (i) to identify the most suitable anatomical sites or specimens to assess S. aureus colonization among lemurs and apes as exemplified by samples from captive chimpanzees (Uganda), wild chimpanzees (Côte d’Ivoire) and wild lemurs (red fronted lemurs and Verreaux’s sifakas, Madagascar) and (ii) to assess the detection rate of S. aureus from non-invasive samples (stool and fruit wadges) from chimpanzees.

Methods

Results

Discussion

Recent reports on S. aureus infection and colonization in chimpanzees and gorillas fueled the concern of the transmission of human pathogens such as S. aureus or E. coli to great apes [2,3,10]. Screening for potential pathogens prior to reintroduction and the surveillance of these pathogens in wild conspecifics is therefore suggested to combat “humanoses” in endangered animals [6].

In the present study, we analyzed the colonization pattern and genetic structure of S. aureus in lemurs, wild and captive chimpanzees in Africa. Main findings are high oro-pharyngeal colonization in lemurs and captive chimpanzees and frequent vaginal colonization in captive female chimpanzees. Duplicate samples of stool and fruit wadges from wild chimpanzees reliably detect those animals which shed S. aureus. These data are essential tools to monitor the anthropozoonotic acquisition of S. aureus both in the sanctuary setting and in the wild.

Nasal swabs from wild lemurs revealed a nasal carriage rate of 36.7% which is similar to nasal colonization in captive macaques (Macaca mulatta, 39%), although they belong to a different suborder [18]. The high proportion of vaginal colonization in chimpanzees (50.0-80.0%) has been reported in captive female lion tamarins (Leontopithecus sp.) as well (24%) but is in contrast to 5% vaginal carriage in humans [19,20]. Similarly, oro-pharyngeal colonization was more frequent in lemurs (72%) and captive chimpanzees (69.2-100%, table 1) compared to humans (10-20%) [19]. In addition, detection rate of S. aureus in stools from wild chimpanzees was slightly higher than intestinal colonization rates in humans (43.8% vs. 20%) [21]. As oro-pharyngeal swabs and stool samples were not simultaneously taken, we cannot assess the correlation between oro-pharyngeal and intestinal carriage of S. aureus in chimpanzees. However, positive correlation between intestinal and nasal colonization is reported from humans [21]. In general, the feasibility to take mucosal swabs is constricted as aesthesia is usually necessary to be able to take nasal or oro-pharyngeal swabs from monkeys and apes even in the sanctuary setting.

The detection of S. aureus from multiple stool samples and fruit wadges enabled us to calculate the needed number of consecutive samples to reliably detect S. aureus shedding. We showed that two samples (stool or fruit wadge) of each individual are sufficient to identify shedding of S. aureus. An additional third sample did not increase the detection rate. For hospitalized human patients it is known that the detection of nasal S. aureus colonization can be increased from 94% to 100% if a third nasal swab is taken after 24 hours [22].

The predominance of certain S. aureus lineages in Kirindy (ST188), Ngamba (ST2168 and ST80) and Entebbe (ST6) indicates a high transmissibility of these clones. While ST2168 has only been reported from captive chimpanzees so far, ST6, ST80 and ST188 are mainly prevalent in humans in Gabon and Mali [2,23,24]. It is therefore likely that human associated lineages have been transmitted to animal groups. This human to animal transmission has been shown in captive chimpanzees in Zambia and Uganda [2] and most likely occurred in a primate research center in Gabon [3]. However, the S. aureus lineage that caused a fatal infection in a captive gorilla in Gabon was not detected in our collection (ST72, t148) [3]. In general a trend may be visible here in the frequency of detection of likely human strains of S. aureus along a gradient from “no” to “intense” history of human contact (captive primates > primates captured once or every other year to exchange the radio collar> wild and never touched). Although our study provides valuable information to screen for and monitor human S. aureus lineages in sanctuary animals and wild conspecifics, some limitations need to be addressed. First, the small sample size and missing data on other species limit general conclusion. Second, detection rate of S. aureus in multiple samples from stools and fruit wadges was hampered by the high number of missing follow-up samples. It is a challenge to permanently observe wild living chimpanzees in order to collect stool samples from the respective animal in a given period of time.

In conclusion, nasal, oro-pharyngeal and vaginal swabs are useful to screen for S. aureus colonization in animals before reintroduction. Duplicates of non-invasive samples (stool and fruit wadges) reliably detect S. aureus shedding in wild chimpanzees. These data will help to establish screening and surveillance strategies for human-associated bacteria (e. g. E. coli) in African wildlife.

Acknowledgments

We thank the Ivorian authorities (Ministry of Environment and Forests, Ministry of Research, the directorship of the Taï National Park, the “L’ Office Ivoirien des Parcs et Réserves” and the Swiss Research Centre in Abidjan) As well as the assistants of the Tai chimpanzee project for their long-term support. We also thank the “Département de Biologie Animale, Université d’Antananarivo”, the CAFF of the “Direction des Eaux et Forêts” and the CNFEREF Morondava for the authorisation of this study. We thank Grit Schubert, Robert Koch-Institut, Berlin for permanent assistance, organization of shipment and good company.