Antimicrobial resistance at the wildlife-livestock-human interface in Nairobi
In a paper published in The Lancet Planetary Health, scientists from the University of Liverpool and the International Livestock Research Institute (ILRI) show that urban wildlife in Nairobi carry a high burden of clinically relevant antimicrobial resistant (AMR) bacteria, resistant to recently developed drugs that the World Health Organisation deems critically important to human medicine.
The scientists involved in the Nairobi study deployed teams of veterinary, medical, environmental and wildlife personnel to sample 99 households randomly chosen from Nairobi’s socio-economically diverse neighbourhoods.
The study found higher diversity of AMR in livestock and the environment than humans and wildlife. Rodents and birds were significantly more likely to carry resistance to multiple drugs when exposed to human and livestock waste through poor management practices, a common feature of lower-income neighbourhoods.
“This paper shows that contamination of urban environments with AMR is a serious issue. This is not just specific to Nairobi but findings can be extrapolated to other cities in Africa,” said Professor Eric Fèvre, a joint appointee at the University of Liverpool and ILRI. “We tend to think of AMR in primarily medical terms, of developing new drugs and better using old ones. But we need to take an ecological approach to addressing this threat. Urban cities can address this by better urban planning, better waste disposal, and better livestock husbandry practices. This can go far toward disrupting AMR exchange between wildlife, livestock and humans.”
Dr James Hassell, lead author of the study, and now working with the Smithsonian Global Health Program added: “Although we found no evidence to suggest that AMR carried by urban wildlife poses a direct threat to human health, that these animals harbour high levels of resistance to drugs used in human and animal medicine is particularly worrisome. Since wildlife are not treated with antibiotics, this is indicative of how pervasive AMR is in urban environments. Species that move freely across cities and further afield could disseminate resistance acquired in urban areas more widely.”
To gain a better understanding of how urbanisation might affect the diversity and spread of drug-resistant genes amongst wildlife, the team also examined AMR genes in E. coli carried by wild birds sampled from the same 99 households across Nairobi. The research, which has been published separately in Nature Communications, found that as households became more densely populated by humans and their livestock, as is often seen in lower-income neighbourhoods, the diversity of AMR genes in peri-domestic wild birds increased.
“As well as providing further evidence that urban households are important interfaces for AMR to be exchanged between humans, their livestock and wildlife, these results suggest that the structure of our towns and cities can have important, but potentially predictable effects on the underlying determinants of bacterial evolution in wildlife, with implications for human and animal health,” said Dr Hassell.
The research was funded by the Medical Research Council, through the Environmental and Social Ecology of Human Infectious Diseases Initiative (ESEI).
Hassell, J.M., Ward, M.J., Muloi, D., Bettridge, J.M., Robinson, T.P., Kariuki, S., Ogendo, A., Kiiru, J., Imboma, T., Kang’ethe, E.K., Öghren, E.M., Williams, N.J., Begon, M., Woolhouse, M.E., Fèvre, E.M. (2019). Clinically relevant antimicrobial resistance at the wildlife-livestock-human interface in Nairobi: an epidemiological study. The Lancet Planetary Health, 3(6):e259-e269, doi: 10.1016/S2542-5196(19)30083-X
Hassell, J.M., Ward, M.J., Muloi, D., Bettridge, J.M., Phan, H., Robinson, T.P., Ogendo, A., Imboma, T., Kiiru, J., Kariuki, S., Begon, M., Kang’ethe, E.K., Woolhouse, M.E., Fèvre, E.M. (2019). Deterministic processes structure bacterial genetic communities across an urban landscape. Nature Communications, 14;10(1):2643, doi: 10.1038/s41467-019-10595-1
[SOURCE: University of Liverpool]