Scientists question blanket deworming activities in Kenya

Lead author Dr Nyamai Mutono, a senior research fellow at the Centre for Epidemiological Modelling and Analysis (Cema) at the University of Nairobi and the modelling and training lead at the Africa Modelling Network for Neglected Tropical Diseases.

Researchers are urging Kenya to rethink its long-running mass drug administration programme for intestinal worms.

They called for targeted, region-specific interventions to replace the blanket approach that has been widely used for years to control infectious diseases.

Mass drug administration (MDA) has been credited with major public health gains in Kenya, including sharp reductions in diseases such as elephantiasis, trachoma and soil-transmitted helminths.

But scientists behind a new national study say declining funding and clear regional differences in worm infections mean the one-size-fits-all model is no longer efficient.

Their study, published in the International Journal of Infectious Diseases, mapped the distribution of three main intestinal worms in Kenya. These are hookworm, whipworm and roundworm. It analysed data from 146,668 school-going children sampled in 3,752 schools across 207 sub-counties between 2021 and 2024.

Using geostatistical modelling, the researchers found that the burden of infection varies sharply by region and by worm species. Hookworm prevalence was generally low, with a national mean of 0.6 per cent. However, six per cent of sub-counties, mainly in coastal areas, exceeded the two per cent threshold used to guide treatment decisions.

Whipworm infections were higher, with increased risk in southwestern and coastal regions. Roundworm had the highest prevalence of the three, clustering mainly in western Kenya, where some sub-counties were estimated to have a prevalence above ten per cent.

According to the study, these patterns show that continuing to treat all regions in the same way risks wasting scarce resources while missing hotspots that need more intensive action.

“Intestinal worms primarily affect people living in poor, rural communities and are known to contribute to school absenteeism, malnutrition, and delayed developmental milestones in children. Against this realisation, and with Kenya’s healthcare system now devolved, tailoring intervention strategies at the sub-county level is essential to optimising partner resources and achieving the elimination of each STH species. Targeted approaches would enable Kenya to move away from the current blanket application of a single treatment strategy across all sub-counties,” said Dr Nyamai Mutono, the study’s lead author.

Dr Nyamai is a Senior Research Fellow at the Centre for Epidemiological Modelling and Analysis (Cema) at the University of Nairobi and the modelling and training lead at the Africa Modelling Network for Neglected Tropical Diseases.

The study is titled, "Geostatistical modelling of soil-transmitted helminth prevalence in Kenya: Informing targeted interventions to accelerate elimination efforts."

It estimates the probability of different regions exceeding key prevalence thresholds of two, ten and twenty per cent. Across all three worm species, the probability of exceeding twenty per cent remained below 0.5 per cent nationally. But for roundworm and whipworm, several western, southwestern and coastal sub-counties showed a high likelihood of exceeding lower thresholds that trigger more frequent or different treatment regimens.

The researchers argue that this level of detail should guide decisions on which drugs to use, who to treat and how often treatment should be given.

“Such precision also allows for the reallocation of resources to areas with high-prevalence infections, while reducing treatment intensity in regions where the likelihood of exceeding disease thresholds is low. This promotes a more efficient use of limited resources and aligns with the global move toward precision public health,” Dr Nyamai said.

She added that smarter targeting is also about cost-effectiveness. “Ultimately, resource targeting ensures that the most appropriate and cost-effective treatment methods are adopted, minimising wastage on ineffective interventions and maximising the impact of every shilling spent on deworming programs.”

Mass drug administration has been a cornerstone of Kenya’s fight against neglected tropical diseases for over a decade, largely through school-based programmes using donated medicines.

The approach has helped Kenya get close to eliminating some diseases and earn certification for eliminating Guinea worm in 2018.

However, the new study notes that blanket deworming does not account for differences in drug effectiveness across worm species. For example, commonly used benzimidazole drugs are less effective against whipworm, meaning some high-burden areas may need alternative medicines or strategies.

The authors also point to Kenya’s devolved health system as an opportunity to tailor interventions more closely to local conditions, using high-resolution data rather than national averages.

Beyond drugs, the study stresses the importance of investing in water, sanitation and hygiene, especially in regions where roundworm and whipworm persist. Without these complementary measures, reinfection remains likely even after repeated treatment rounds.

The findings come as Kenya works towards its national goal of reducing soil-transmitted helminth prevalence to below two per cent by 2027, in line with the World Health Organization roadmap for neglected tropical diseases.

According to the researchers, achieving that goal will require moving beyond blanket solutions and embracing data-driven, targeted action that reflects the country’s diverse epidemiological landscape.