Zoonotic pathogens in bonobos and implications of One Health

Researchers report PCR screening for potentially zoonotic pathogens detected in fecal samples from wild and semi-captive bonobos. This has raised some interesting questions for One Health and wildlife conservation.

Bonobo screening and fecal PCR.

Our closest relative, the endangered bonobo, Pan paniscus, is only found in the Congo Basin in the Democratic Republic of Congo (DRC). Their population is estimated between 10,000 and 50,000 individuals and they are listed as endangered with a declining population by the International Union for the Conservation of Nature. The biggest threats to bonobo populations are deforestation and poaching, which have increased due to civil unrest and growing poverty in surrounding areas. With increased overlap and interaction between humans and bonobos, whether through negative aspects such as deforestation, but also through conservation, rescue and rehabilitation efforts, infectious diseases must be avoided from both sides. humans to bonobos and bonobos to humans, to protect everyone.

Bonobos are difficult to study. In addition to the aforementioned population decline, forest habitat, civil unrest, etc., it is very difficult to obtain permits to conduct invasive sampling of these highly protected animals. So, in this study, the researchers used PCR screening of fecal samples to test a wide range of potential pathogens in bonobos. This method is non-invasive and therefore can be approved for research on non-human primates (NHPs). It can identify intestinal parasites, but also by PCR can detect pathogens of the blood system and urogenital system.

Bonobo stool samples were collected from two locations: one was Lola Ya Bonobo, a sanctuary in Kinshasa where rescued and orphaned bonobos are cared for and rehabilitated to be released into the wild, and the other at Ekolo Ya Bonobo. , the only bonobo reintroduction site in the world, located in the Equator region of the DRC.

What’s in a poo?

Researchers collected 91 fecal samples from two sites in DRC: 75 samples were from Lola Ya Bonobo (semi-captive bonobos) and 16 samples from Ekolo Ya Bonobo (wild bonobos).

After DNA / RNA extraction from diluted fecal samples, reverse transcription (cDNA), quantitative real-time PCR (qPCR), and standard PCR and sequencing were used to amplify genetic material using primers for the following microorganisms:

Table of pathogens for which tests have been carried out, pathogens detected in bold. Modified from Medkour, H., Castaneda, S., Amona, I. et al. Potential zoonotic pathogens harbored by endangered bonobos. Sci Rep 11, 6331 (2021). https://doi.org/10.1038/s41598-021-85849-4

Results:

  • Viruses – three viral groups were identified in fecal samples: astroviruses, encephalomyocarditis virus (ECMV) and adenoviruses (AdVs). Adenoviruses were the most common group in the Lola (semi-captive) and Ekolo (wild) samples. Astroviruses were only found in Lola’s sample and ECMV was found in samples from both sites.
  • Bacteria – 6 groups of bacteria were detected in fecal samples. Pathogenic Leptospira spp; Mycobacterium (no-tuberculosis); Treponema spp. (no-pallidum), Acinetobacter spp. (no-baumanii), Salmonella spp. (no-typhi / paratyphi) and Mycoplasma spp. With the exception of Acinetobacter spp. (no-baumanii), these bacterial groups were more frequent in Lola’s samples (semi-captive).
  • Parasites – faecal samples from Ekolo (wild) had more parasites than those from Lola (semi-captive), except for Giardia lamblia which was only detected in Lola Bonobos samples. Strongyloides stercoralis, Taenia solium, were only detected in stool samples from Ekolo (wild) Bonobo. Nematode spp, Kinetoplastida spp where detected in semi-captive and wild Bonobo fecal samples.

The sequences were compared to those found in the GenBank BLAST database and the phylogenetic analysis of the microorganisms was presented in the research document. For example, using phylogenetic analysis, researchers found that adenoviruses clustered tightly to Human mastadenovirus (HAdVs), as the name suggests, a human virus. Nematode species have been identified as being Esophagostomum spp and some Kinetoplastida spp in Lola’s samples were identified as Trypanosoma theleiri.

Health and Wildlife

This post raised many questions pertaining to the One Health concept:

  1. Health in wild bonobos Ekolo (small human contact) vs semi-captive Lola, human environment, bonobos.

The authors discuss the challenges of zoonotic transmission, particularly with regard to semi-captive bonobos. Could human interaction or captive conditions lead to an increased incidence of infection in bonobos? Researchers are highlighting how ECMV can lead to a high death rate from viral encephalomyocarditis in monkeys and great apes, and how rodents can be reservoirs potentially explaining outbreaks in bonobo dormitories in Lola.

  1. Conservation efforts and reintroduction of bonobos recued.

What about when these bonobos are released into the wild during reintroduction events? What pathogens can be introduced into the fragile population of wild bonobos? And what could be its impact? Researchers highlight a disturbing discovery of Human mastadenovirus in the reintroduced Bonobos.

  1. Deforestation, poaching and contact with the Bonobos.

How could deforestation and poaching increase zoonotic transmission between humans and bonobos? T. solium can cause cysticercosis and neurocysticercosis, one of the main causes of seizures in humans and is contracted when people eat undercooked or contaminated meat. Could bonobo bushmeat or the overlap of humans and bonobos, for example through deforestation or even conservation efforts, pose a threat to humans? An article by Inogwabini and Leader-Williams in 2012 suggested that trypanosomiasis may be a factor limiting the range of occupancy of bonobos. Trypanosoma theileri found in Lola’s samples in this study, normally infects cattle and is widespread in cattle. If deforestation leads to an increase in livestock grazing, could Bonobo numbers be decimated by both deforestation and disease?

To be human

Finally, what about the behavior of Bonobo animals and infections / diseases? A few years ago I attended a Linnean Society talk given by Dr Zanna Clay, a primatologist, on what we can learn about human evolution from our closest relatives, the great apes, the bonobos and chimps, I highly recommend watching the recording! This lecture focused on behavioral traits such as communication, empathy and social structures. So, I wonder what our closest relatives are telling us about the evolution of human behavior when it comes to health, infection and disease?


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