The widespread overuse of antibiotics for growth promotion in poultry in India is leading to development of drug resistance in humans, scientists have warned.
Researchers from the Center for Disease Dynamics, Economics and Policy (CDDEP), based in Washington and Delhi, collected samples from 530 birds in 18 poultry farms in Punjab, a major poultry state, and tested them for resistance to a range of antibiotic medications critical to human medicine.
Veterinary scientists from the Guru Angad Dev Veterinary and Animal Sciences University in Ludhiana were among researchers who collaborated in the study.
The researchers detected widespread and indiscriminate use of antibiotics on farms and drug-resistant superbugs in chicken that they say could threaten human health.
Their study, based on 1,500 samples of bacteria from 18 farms, has found that over two-thirds of farms used antibiotics as growth promoters and broiler (chicken meat) farms had twice the antibiotic resistance as layer (egg) farms.
While earlier studies in India have noted drug-resistant microbes in poultry samples, the new investigation is being described as the largest to date to systematically survey broiler and layer farms across organized and unorganised sectors to determine antibiotic use patterns.
"We saw an abundance of overuse of antibiotics in the farms we surveyed," said Ramanan Laxminarayan, director of the CDDEP). "The use of antibiotics for growth promotion can turn poultry farms into reservoirs of drug-resistant bacteria that could pose a threat to human health."
The study, published on Thursday in the journal Environmental Health Perspectives, found samples of bacteria resistant to several antibiotics, including 39 per cent resistance to ciprofloxacin, a drug used to treat respiratory infections to 86 per cent resistance to nalidixic acid, an antibiotic used to treat urinary tract infections.
Additional testing revealed the presence of certain enzymes that confer drug resistance to medications used to treat E coli, bacterial pneumonia, and other infections. Almost 60 per cent of E coli isolates analysed contained these enzymes, the researchers said.
Most of the farms surveyed in the study had on average about 50,000 birds, and all reported using antibiotics. Among 16 farms that agreed to respond to the survey, 12 reported using antibiotics for growth promotion.
"Given the size and reach of poultry farms in the retail market, the risk of exposure to resistant bacteria to humans is a significant concern," the CDDEP researcher and collaborating institutions in India and the US said in their report. Drug-resistant infections in humans are more expensive to treat and harder to eliminate.
The scientists said poultry farm workers in direct contact with the birds are at high risk of picking up drug resistant bacteria and spreading them into the community. Two-thirds of the farm workers questioned in this survey indicated they do not wear closed-toe shoes or take other precautions when entering poultry sheds.
A survey by the New Delhi-based non-government Centre for Science and Environment had in 2014 reported that 40 per cent of 70 chicken meat samples picked up from retail shops in Delhi contained antibiotic residues relating to several antibiotics, including a class of antibiotics called fluoroquinolones, The Telegraph reports.
The US banned the use of fluoroquinolones for veterinary use in poultry in 2005 after studies indicated that using the drugs to treat respiratory diseases in poultry contributed to the emergence of drug-resistant bacteria in humans and animals. And Europe has banned the use of antibiotics for growth promotion in response to evidence that growth promoting antibiotics drive the spread of resistance.
"It is critical that India also takes similar steps to end the use of antibiotics for growth promotion in animal breeding practices," Laxminarayan said.
Previous studies have projected that antibiotic consumption in food animal production will rise globally by 67 per cent by 2030, including more than a tripling of use in India.
The Union health ministry had in April this year announced a national multi-ministerial action plan to curb antibiotic resistance that calls on the Union agriculture ministry and animal husbandry departments to take measures to stop the indiscriminate use of antibiotics on farms.