Zoonotic pathogens in bonobos and the 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 declining population by International Union for 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 the increase in overlap and human-bonobo interaction, either through negative aspects such as deforestation, but also through conservation efforts, rescues and rehabilitation, infectious diseases must be avoided from both humans to bonobos and bonobos to humans, to protect everyone.

Bonobos are difficult to study. In addition to declining population, forest habitat, civil unrest, etc. mentioned above, it is very difficult to obtain permits to conduct invasive sampling of these highly protected animals. So in this study researchers use fecal sample PCR screening to test a broad spectrum 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, it can also detect pathogens of hematogenous and urogenital system.

Bonobo fecal 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 for release into the wild, and the other at Ekolo Ya Bonobo, the only bonobo reintroduction site in the world, located in the Equateur 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 (AdV). 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 prevalent in Lola’s samples (semi-captive).
  • Parasites – faecal samples from Ekolo (wild) contained 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 faecal samples from Ekolo (wild) Bonobo. Nematodes spp, Kinetoplastida spp where they were detected in fecal samples from semi-captive and wild Bonobo.

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

A health and a fauna

This publication has raised many questions that fall within the One health concept:

  1. Health in wild Ekolo bonobos (little 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? The researchers highlight how ECMV can lead to a high death rate from viral encephalomyocarditis in monkeys and monkeys, and how rodents can be reservoirs potentially explaining epidemics in Bonobos’ dormitories in Lola.

  1. Conservation efforts and the reintroduction of recovered bonobos.

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 bonobos.

How could deforestation and poaching increase zoonotic transmission between humans and bonobos? T. solium may cause cysticercosis and neurocysticercosis, a major cause 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 due to deforestation or even conservation efforts, pose a threat to humans? An article by Inogwabini and Leader-Williams in 2012, trypanosomiasis could 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’s workforce be decimated by both deforestation and disease?

To be human

Finally, what about behavior and infection / disease of Bonobo animals? A few years ago I attended a Linnean Society lecture by Dr Zanna Clay, primatologist, on what we can learn about human evolution from our closest relatives, the great apes, bonobos and chimpanzees, I highly recommend watch the recording! This conference focused on behavioral traits such as communication, empathy and social structures. So, I wonder what our closest relatives tell us about the evolution of human behavior regarding health, infection and disease?

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