Stop blanket mass drug administration drives, Scientists tell state

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

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

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

However, 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.

The study, published in the International Journal of Infectious Diseases, mapped the distribution of three main intestinal worms in Kenya, collectively known as soil-transmitted helminths. These are hookworm, whipworm and roundworm.

It analysed data from 146,668 school-going children sampled in 3,752 schools across 207 subcounties between 2021 and 2024.

Using geostatistical modelling, the researchers found that infection burdens vary 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 subcounties, mainly in coastal areas, exceeded the two per cent threshold used to guide treatment decisions.

Whipworm infections were higher, with increased risk in south-western and coastal regions. Roundworm had the highest prevalence of the three, clustering mainly in western Kenya, where some subcounties were estimated to have prevalence above 10 per cent.

According to the study, continuing to treat all regions in the same way risks wasting scarce resources while missing hotspots that require more intensive intervention.

“Intestinal worms primarily affect people living in poor, rural communities and contribute to school absenteeism, malnutrition and delayed developmental milestones in children,” said Dr Nyamai Mutono, the study’s lead author.

“With Kenya’s healthcare system now devolved, tailoring intervention strategies at subcounty level is essential to optimising partner resources and achieving elimination of each STH species. Targeted approaches would allow Kenya to move away from the blanket application of a single treatment strategy across all subcounties,” she said.

Dr Nyamai is a senior research fellow at the Centre for Epidemiological Modelling and Analysis 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.

Kenya has set a national goal of reducing STH prevalence to below two per cent by 2027, signalling a shift towards breaking transmission.

The study estimates the probability of regions exceeding prevalence thresholds of two, 10 and 20 per cent. Across all three worm species, the probability of exceeding 20 per cent remained below 0.5 per cent nationally.

However, for roundworm and whipworm, several western, south-western and coastal subcounties showed a high likelihood of exceeding lower thresholds that trigger more frequent or alternative treatment regimens.

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

“Such precision allows resources to be reallocated to areas with high-prevalence infections, while reducing treatment intensity where the likelihood of exceeding disease thresholds is low,” Dr Nyamai said.

“This promotes more efficient use of limited resources and aligns with the global move towards precision public health,” she added.

She said smarter targeting was also key to cost-effectiveness.

“Resource targeting ensures 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 programmes,” she said.

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

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

However, the study notes that blanket deworming does not account for differences in drug effectiveness across worm species. For instance, commonly used benzimidazole drugs are less effective against whipworm, meaning some high-burden areas may require 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, particularly in regions where roundworm and whipworm persist. Without these complementary measures, reinfection is likely even after repeated treatment rounds.

The findings come as Kenya works towards its 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 Kenya’s diverse epidemiological landscape.