Study: 60pc of fish sold in Kisumu is contaminated
A recent study has shown that 60 per cent of market-ready fish in Kisumu are contaminated with the E.coli bacteria.
Several months ago, while having a meal of fish with fellow researchers on one of Kisumu’s beaches, Dr Silas Onyango Awuor felt compelled to study the safety of the dish he was consuming.
Despite enjoying the delicious fish, the environment where it was served was unappealing—the lake shore was littered with diapers— which prompted him to investigate whether the fish could be contaminated with Escherichia coli (E. coli), a common bacteria rapidly developing resistance to antibiotics.
“I wondered how safe our fish is. Those who use diapers are children under five. For the under-fives, E. coli is normal foecal flora, but for adults, it can be a pathogen,” he said.
The clinical microbiologist at Jaramogi Oginga Odinga Teaching and Referral Hospital sampled 256 tilapia and mudfish for the study. His fears were confirmed.
The study revealed that 60 percent of market-ready fish in Kisumu are contaminated with E. coli. Among the 256 fish samples tested, 153 were positive for E. coli.
According to Dr Awuor—the lead researcher in the team that also included Eric Omwenga, Zipporah Gichana, Grace Ndeda, Jamie Reedy and Theekshana Fernando—while E. coli is typically harmless in the gut, pathogenic strains are a leading cause of severe human infections, including urinary tract infections, bloodstream infections, and meningitis. He noted that these strains acquire resistance genes, complicating treatment and leading to failures.
“The high prevalence highlights a significant risk of bacterial contamination, likely linked to improper waste disposal and inadequate hygiene along the supply chain,” said Dr Awuor. “Diapers disposed of along the road eventually find their way to the lake and are a main reason the fish tested positive for E. coli.”
The study's findings reinforce the critical link between the aquaculture ecosystem and the global fight against antimicrobial resistance (AMR).
“These findings prove that aquaculture is one source of AMR among our community members,” the researchers noted.
Inappropriate use of antimicrobials in fish farming, combined with environmental residues from poor disposal, contributes to the emergence of zoonotic antibiotic-resistant bacteria, which can then be transmitted to humans through food consumption, they said.
“Recently, AMR has become a significant public health concern in aquaculture and fisheries. AMR in aquaculture systems has also been enhanced by antimicrobial residues from poor disposal and usage, which reach fish farming systems,” he said.
Dr Awuor encouraged handwashing while handling fish to avoid contamination.
“If the fish is properly cooked, bacterial infections will not be transmitted. This should not deter us from eating fish, but it should encourage those handling fish to incorporate handwashing. By the time you are handling the fish, practice handwashing in between and after you are done in your kitchen,”he said
Dr Awuor urged the national government to enforce policies for the proper disposal of diapers.
“We are not happy when patients die due to developing drug resistance. There’s a need to involve the agricultural sector and aquaculture in reducing the risk of AMR,” he said.
He also called on diaper manufacturers to innovate ways to kill pathogens after diaper use.
The findings, shared during a recent World Fisheries Day event, prompted immediate responses from county leadership.
Kisumu County Deputy Governor Dr Mathews Owili called for a follow-up study at landing sites to trace contamination to its ultimate source.
The study findings serve as a call to action for the government to strengthen regulations and enforcement mechanisms to monitor antibiotic usage in aquaculture and provide updated guidelines for prudent use.
The Jaramogi Oginga Odinga Teaching and Referral Hospital Anti-Microbial Resistance Committee has since developed a charter incorporating One Health—recognising the link between human, animal and environmental health—into its updated 2025 strategy.
It emphasises the need for cross-sectoral collaboration, engaging the county government, beach management units, fisheries department, and public health teams. It also highlights the importance of surveillance and data strengthening through structured sampling from lake water and fish for continuous microbiological analysis.
The committee used the World Fisheries Day event to sensitise fisherfolk about AMR, safe fish handling, and hygiene practices, demonstrating that the fight against AMR extends beyond hospitals to communities, ecosystems, agriculture and food systems.
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