Researchers entering sampling data (photo credit: Zoonoses and Emerging Diseases).

In the cities of developing nations, where unregulated antibiotic use is common and livestock jostle with people amid often unsanitary conditions, scientists have found a potentially troubling vector for the dissemination of antimicrobial resistant bacteria: wildlife.

The epidemiological study published in the June 2019 issue of the journal Lancet Planetary Health shows that urban wildlife in Nairobi carry a high burden of clinically relevant antimicrobial resistant bacteria. The research team included scientists from the International Livestock Research Institute (ILRI), the University of Liverpool and the Kenya Medical Research Institute, among other research institutions.

Antimicrobial resistance is an increasingly serious threat to public health. Through misuse and overuse of antibacterial medication, more and more of the bacterial diseases that were once easily treated with antibiotics have become drug-resistant; these new strains of old germs require expensive and prolonged treatment at best and at worst can be lethal.

The 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 antimicrobial resistance 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 antimicrobial resistance is a serious issue. This is not just specific to Nairobi but findings can be extrapolated to other cities in Africa,” said Eric Fèvre, a joint appointed scientist at ILRI and professor of veterinary infectious diseases at the University of Liverpool.

“We tend to think of antimicrobial resistance 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, better livestock husbandry practices. This can go far toward disrupting antimicrobial resistance exchange between wildlife, livestock and humans,” said Fèvre.

The lead author of the study, James Hassell, said, “Although we found no evidence to suggest that antimicrobial resistance 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 antimicrobial resistance is in urban environments. Species that move freely across cities and further afield could disseminate resistance acquired in urban areas more widely.”

“We cannot address the rise of antimicrobial resistance without focusing on the environmental, ecological and social settings in which humans exist,” said Hassell.

Citation

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.J. and Fèvre, E.M. 2019. Clinically relevant antimicrobial resistance at the wildlife–livestock–human interface in Nairobi: An epidemiological study. Lancet Planetary Health 3(6): e259–e269.

Sheep market in Doyogena, Ethiopia (photo credit: ILRI/Zerihun Sewunet).

To tackle a growing problem of rising antimicrobial resistance in low- and middle-income countries, CGIAR, a global research partnership for a food-secure future, is forming an international hub to help integrate and channel research and development efforts.

The hub, launched on 21–22 February 2019, in Nairobi, Kenya, will be led and hosted by the International Livestock Research Institute (ILRI).

Antibiotics and other antimicrobial drugs are among the most important tools available to medical and veterinary professionals for curing human and animal diseases and improving their welfare, yet these drugs are increasingly failing. Development of resistance to these drugs in disease-causing bacteria and other microbes poses a major threat to global development; the World Bank estimates that annual global gross domestic product could fall by more than 1 trillion United States dollars (USD) by 2030 because of it.

While the World Bank also estimates that investments of USD 6 to 8 billion annually could mitigate this loss, at present, it seems the antimicrobial resistance problem will get rapidly worse before it gets better. Large quantities of antimicrobial drugs are used to cure human illness and provide healthy livestock and fish for food.

Though specifics are unknown, use of antimicrobials for livestock and in aquaculture, is rising, particularly in low- and middle-income countries. These antimicrobials are often used in suboptimal ways, such as applying dosages too little to be effective or over too long a time period to be environmentally healthy, or the wrong drugs are used, or antibiotics are used for diseases not caused by bacteria. Humans, livestock and fish excrete these drugs, which leads to environmental contamination, including that of water systems.

Globally, the main driver of the growing incidence of antimicrobial resistance in humans is overuse and misuse of antibiotics in human medicine, which applies selective pressure for resistant pathogens. But antimicrobial use in agriculture to control animal and plant diseases also contributes to this growing drug resistance problem, although experts don’t know the contribution of agriculture to the problem in humans.

The greatest challenges and burdens of antimicrobial resistance will be felt by the poorest in poorer countries. While these countries with their rapidly growing populations face the greatest and rising demand for increased food production, their populations also tend to have poorer access to relevant knowledge, veterinary and health services. The countries face challenges in enforcing regulations and understanding and implementing effective antimicrobial resistance surveillance.

With its mandate to improve the livelihoods of poor people, improve food and nutrition security and improve natural resource management through agriculture and food research, CGIAR is ideally positioned to tackle agriculture-related antimicrobial risks in developing countries and to develop, test and promote solutions to mitigate these risks together with its partners.

Like climate change and malnutrition, two other global challenges CGIAR works to address, antimicrobial resistance challenges us to use evidence and find ways to change the knowledge, attitudes and behaviors of people. Any solutions will require combining technical, institutional and policy innovations and leveraging the contributions of different sectors and disciplines, and both public and private actors.

The new CGIAR Antimicrobial Resistance Hub will work to foster learning from past experiences, support research excellence in the global south and ensure a critical mass of coordinated research to find suitable and sustainable solutions. ILRI will be joined in this effort by three CGIAR research programs—Agriculture for Nutrition and Health, FISH and LIVESTOCK—along with three CGIAR centers—the International Food Policy Research Institute, the International Water Management Institute and WorldFish. Together, these seven research programs and institutions with their national partners and partner research organizations outside CGIAR, will support global research efforts among experts the world over—from low- to middle- to high-income countries.

For more information about the CGIAR Antimicrobial Resistance Hub, contact Barbara Wieland at b.wieland@cgiar.org or Delia Grace Randolph at d.randolph@cgiar.org.