Ethiopia's schistosomiasis map shows a sharp fall after a decade of mass treatment

A decade after Ethiopia began treating schistosomiasis at scale, a national survey has drawn the first high-resolution map of where the parasite remains — and it reports marked progress toward eliminating the disease as a public health problem [s1].

The survey, published in The Lancet Global Health on September 24, is the kind of arithmetic that control programmes are meant to produce but rarely measure this precisely [s1]. These are the numbers to hold, and what they can and cannot be taken to mean.

What was measured

Between June 20, 2021, and October 22, 2024, researchers enrolled 121,593 children at 4,258 sites across ten regions of Ethiopia [s1]. Children aged 9 to 14 were sampled from schools or communities [s1]. Stool was tested for Schistosoma mansoni by the Kato-Katz thick smear in all ten regions; urine was tested for Schistosoma haematobium by filtration and dipstick in three endemic regions [s1].

Complete datasets for the S mansoni analysis were available from 119,559 children at 4,100 sites, of whom 26,885 were also assessed for S haematobium [s1]. The mean age was 11.4 years, and the sample was close to balanced — 47.7% female and 52.3% male [s1].

The headline finding

The combined survey prevalence of both species was 5.4% (95% CI 5.0–5.9): 5.2% (4.8–5.7) for S mansoni and 1.0% (0.8–1.3) for S haematobium [s1]. Those are the two figures the map turns on.

More consequential for the elimination goal is the intensity of infection, not merely its presence. The prevalence of heavy-intensity infection across the survey population was 0.2% (95% CI 0.2–0.3) overall — 0.2% (0.2–0.3) for S mansoni and below 0.1% for S haematobium [s1]. That sits under the WHO target of 1% for eliminating schistosomiasis as a public health problem [s1].

Elimination "as a public health problem" is a specific, threshold-based claim about heavy infection, not a declaration that transmission has stopped. The distinction matters: light infections persist, and they can rebuild intensity if treatment lapses.

Why a map, not just a number

The point of the survey was resolution. The team fitted geostatistical models using environmental covariates and generated prevalence estimates at the kebele — subdistrict — level [s1]. Of 14,763 kebeles assessed, 1,622 (11.0%) were above the threshold that calls for annual preventive chemotherapy, and the model classified 11,600 (78.6%) of them with a predicted probability of at least 70% [s1].

The programmatic payoff is in what shrank. Compared with baseline district-level categories, areas with prevalence of at least 10% have declined, cutting the number of people above the threshold for annual preventive chemotherapy from 25.6 million to 10.8 million [s1]. A map at this grain lets a programme send praziquantel where transmission actually concentrates rather than blanketing whole districts — cheaper, and easier to sustain as budgets tighten.

The global backdrop

Ethiopia's progress runs against a large and stubborn global burden. WHO estimates that at least 253.7 million people required preventive treatment for schistosomiasis in 2024, of whom more than 100.5 million were reported treated [s2]. Preventive chemotherapy is required in 50 endemic countries with moderate-to-high transmission, and at least 93.9% of those needing treatment live in Africa [s2].

Coverage remains the weak link. WHO data for 2024 show that 39.6% of people requiring treatment were reached globally, with 61.7% of school-aged children needing preventive chemotherapy actually treated [s2]. Deaths from schistosomiasis are currently estimated at 14,353 globally per year [s2]. Against those figures, a national programme reaching elimination thresholds is an outlier worth reading closely.

The caveats the authors flag

This is a cross-sectional survey, a snapshot rather than a trend line, and the comparison with baseline uses categories defined at a coarser geographic level than the new map [s1]. Prevalence measured in children aged 9 to 14 is the standard sentinel for programme monitoring, but it is a proxy for community transmission, not a full census of it.

And the gains are conditional. The decline the survey records is the product of sustained preventive chemotherapy; the same mechanism that produced it has to keep running to hold it. The study was funded through the END Fund's Deworming Innovation Fund, which pools philanthropic financing — a reminder that neglected-tropical-disease control leans heavily on donor money that is neither guaranteed nor immune to the wider squeeze on global health budgets [s1].

What to watch

Whether Ethiopia can move from "elimination as a public health problem" toward interrupting transmission, which demands more than mass drug administration — water, sanitation and snail control among them [s2].

Whether the fine-scale map actually changes where treatment goes, or whether programmes keep treating at the district level out of habit and logistics.

And whether coverage holds. A prevalence of 5.4% in a survey population is a floor built on a decade of treatment; light infections are exactly the reservoir that a funding gap would let regrow.

This article is informational and is not medical advice.