Central India is the new hotspot for antimicrobial resistance (AMR), according to a new study published in Science. The report also finds that the risk of antibiotic resistance in food animals raised in low- and middle-income countries has nearly tripled in less than a decade. The study is the first of its kind to map rates of antibiotic resistanceÂrather than useÂin food animals in low- and middle-income countries, where this kind of monitoring is nascent.

The study, led by the Center for Disease Dynamics, Economics & Policy (CDDEP), has serious implications not only for animal and human health but also for global food agriculture and the supply of meat in low- and middle-income countries, where demand is growing.

Regions affected by the highest levels of AMR should take immediate actions to preserve the efficacy of antimicrobials that are essential in human medicine, by restricting their use in animal production, the study recommends. In some middle-income countries, in particular, in South America, surveillance must be scaled up to match low-income African countries that are currently outperforming them despite more limited resources. In regions where resistance is starting to emerge, there may be a window of opportunity to limit the rise of resistance, by encouraging a transition to sustainable animal farming practices.

The largest hotspots of AMR in animals were in Asia, which is home to 56% of the worldÂs pigs and 54% of the chickens. In Asia, targeted interventions such as legislative action and subsidies to improve farm hygiene could reduce the need for antimicrobials in animal production, thereby preserving important drugs for human medicine, and the treatment of sick animals. It identified hotspots for the emergence of AMR including central India and Kenya, where resistance to multiple drugs has appeared but not yet reached 50%. In these regions, meat consumption is still low, and animal production is gradually intensifying. Here, there may be a window of opportunity to contain AMR by imposing strict hygiene standards in newly built farms. This approach could reduce the risk of spread of resistant pathogens such as mcr-1-carrying E. coli that have emerged in regions where intensive meat production has been facilitated by enormous quantities of veterinary antimicrobials. 

In Africa, resistance maps reveal the absence of major AMR hotspots, except for the Johannesburg metropolitan area. This suggests Âbased on the regions surveyed that Africa probably bears proportionately less of the current global burden of AMR than high- and upper-middle-income countries. Policymakers coordinating an international response to AMR might therefore spare Africa from the most aggressive measures, which may undermine livestock-based economic development, and rightfully be perceived as unfair. 

In the Americas, where the number of surveys was limited, the observed low AMR levels could reflect either good farming practices (low antimicrobial use) or the absence of surveys conducted in areas most affected by AMR. Considering that Uruguay, Paraguay, Argentina and Brazil are net meat exporters, it is of concern that little epidemiological surveillance of AMR is publicly available for these countries. Many low-income African countries have more point prevalence surveys per capita than middle-income countries in South America. Globally, the number of surveys per capita was not correlated with GDP per capita, suggesting that surveillance capacities are not solely driven by financial resources.

Antimicrobial consumption in animals is three-fold that of humans, and has enabled large-scale animal protein production. The consequences for the development of antimicrobial resistance has received comparatively less attention than in humans. The study analyzed 901-point prevalence surveys of pathogens in developing countries to map resistance in animals. China and India represented the largest hotspots of resistance with new hotspots emerging in Brazil, and Kenya. From 2000 to 2018, the proportion of antimicrobials showing resistance above 50% increased from 0.15 to 0.41 in chickens, and from 0.13 to 0.34 in pigs. Escalating resistance in animals is anticipated to have important consequences for animal health, and eventually for human health, it says.

The study `Global Trends in Antimicrobial Resistance in Animals in Low- and Middle-Income Countries was conducted by Institute for Environmental Decisions, ETH Zurich, Zurich, Switzerland; Center for Disease Dynamics, Economics & Policy, New Delhi, India; Department of Ecology and Evolutionary Biology, Princeton University, NJ, USA;  Princeton Environmental Institute, Princeton University, NJ, USA; Université Libre de Bruxelles (ULB), Brussels, Belgium; and Institute for Integrative Biology, ETH Zurich, Zurich, Switzerland. 

The analysis focused on resistance in E. coli, Campylobacter spp., non-typhoidal Salmonella and S. aureus. The number of published surveys on resistance to those pathogens in Low and Middle Income Countries (LMICs) increased from three in 2000 to 121 in 2018 and peaked at 156 per year in 2017. However, the number of surveys conducted during that period was uneven across regions: surveys from Asia exceeded the total for Africa and the Americas. The number of surveys per country was not correlated with gross domestic product (GDP) per capita. 

In LMICs, from 2000 to 2018, the proportion of antimicrobial compounds with resistance higher than 50% (P50) increased from 0.15 to 0.41 in chickens, from 0.13 to 0.34 in pigs, and plateaued between 0.12 to 0.23 in cattle. Those trends were inferred from average yearly increase in P50, (1.5%/year for chickens, and 1.3%/year for pigs), weighted by the number of studies published each year. 

In LMICs, resistance levels showed considerable geographic variations. Regional hotspots (P50 > 0.4) of multidrug resistance were predicted in south and northeast India, northeast China, north Pakistan, Iran, Turkey, the south coast of Brazil, the Nile River delta, the Red River delta in Vietnam and the areas surrounding Mexico City and Johannesburg. Low P50 values were predicted in the rest of Africa, Mongolia and western China. Based on maps of animal densities, we estimate that across LMICs, 9% of cattle, 18% of pigs and 21% of chickens were raised in hotspots of AMR in 2013. For chickens, the percentage of birds raised in hotspots of resistance in each country exceeded global average in China (38%), Egypt (38%) and Turkey (72% ). We also identified regions where AMR is starting to emerge by subtracting P50 from P10 (the proportion of antimicrobial compounds with resistance higher than 10%). In Kenya, Morocco, Uruguay, southern and eastern Brazil, central India, Iran, Chile, and southern China, the difference between P10 and P50 was high (>0.5), indicating that those regions are emerging AMR hotspots. Conversely, established hotspots of AMR, where the difference between P10 and P50 was low (<0.1) included north-eastern China, West Bengal and Turkey, the study says. 

The highest resistance rates were observed in the most commonly used classes of antimicrobials in animal production: tetracyclines, sulfonamides and penicillins. Among antimicrobials considered critical to human medicine, the highest resistance rates were for ciprofloxacin and erythromycin (20Â60%) and moderate rates for third and fourth generation cephalosporins (10Â40%). Other critically important antimicrobials, such as linezolid and gentamicin, were associated with lower resistance rates (< 20%). AMR trends in LMICs were in agreement with the trends reported in Europe and the United States for tetracyclines, sulfonamides, and third and fourth generation cephalosporins, but differences also exist for quinolones and aminoglycosides.