Schistosomiasis mansoni remains a major public health burden in endemic regions of Brazil and other parts of the world where the parasite’s larvae, released from freshwater snails, penetrate human skin during contact with contaminated water. While the acute phase of infection often produces only vague symptoms, the long-term consequences can be severe. Eggs deposited by adult worms in the mesenteric veins trigger a chronic inflammatory reaction in the liver, leading over years to periportal fibrosis, a fibrotic thickening around the portal tracts that distorts the organ’s vascular architecture. Unlike the cirrhosis produced by alcohol or viral hepatitis, schistosomal liver damage typically spares the hepatocytes themselves, but the fibrotic obstruction of portal blood flow drives the pressure inside the portal vein dangerously upward.

The clinical stakes of this process are considerable. Portal hypertension in schistosomiasis manifests as splenomegaly, the development of collateral blood vessels, and ultimately esophageal varices that can rupture and cause life-threatening upper gastrointestinal bleeding. Detecting periportal fibrosis early, and gauging how far it has advanced, is therefore essential for deciding which patients need closer surveillance or intervention. The reference standard for assessing this fibrosis in the field is abdominal ultrasound interpreted according to the Niamey classification, a scoring system that grades the periportal thickening from pattern A, essentially normal, through patterns B and C for mild involvement, to patterns D and E for moderate and advanced disease, and pattern F for the most severe fibrotic distortion. Ultrasound, however, requires trained examiners and equipment that are not always available in the rural areas where the disease is most prevalent.

The ELF test was developed as a noninvasive alternative for quantifying liver fibrosis in conditions such as chronic hepatitis C and nonalcoholic fatty liver disease. It combines the serum concentrations of three markers of fibrotic remodeling: hyaluronic acid, a component of the extracellular matrix that accumulates as fibrosis progresses; tissue inhibitor of metalloproteinases 1, or TIMP-1, which reflects the inhibition of matrix-degrading enzymes; and procollagen III amino-terminal peptide, known as PIIINP, a byproduct of new collagen synthesis. An algorithm converts the three measurements into a single ELF score, with higher values indicating more extensive fibrosis. Because the test uses a standard blood sample and a validated analytical platform, it could in principle be deployed in settings where imaging expertise is scarce.

Despite this potential, few studies had examined whether the ELF score performs meaningfully in schistosomiasis mansoni, whose fibrotic pattern differs fundamentally from the cirrhotic scarring for which the test was calibrated. The new study, led by Rebecca Dantas Thorp and colleagues at institutions in Pernambuco, Brazil, set out to determine whether serum ELF values correlate with the periportal fibrosis pattern established by the Niamey ultrasound classification, and whether the score relates to a history of upper gastrointestinal bleeding, the most feared complication of advanced disease.

The researchers conducted a cross-sectional, bidirectional analytical study enrolling patients from an endemic area and from a reference outpatient clinic dedicated to schistosomiasis care. In total, 196 patients were evaluated, 58 percent of them women, with a mean age of 45.04 years and a standard deviation of 15.30 years. Each participant completed a structured questionnaire capturing sociodemographic and clinical information, including any prior episodes of upper gastrointestinal bleeding, and provided blood samples for ELF determination. A single examiner performed all ultrasound examinations, an approach that eliminated interobserver variability and ensured that the Niamey patterns were assigned consistently across the cohort.

The distribution of fibrosis severity in the study population spanned the full range of the Niamey scale. Eighteen patients showed pattern A plus B, indicating no or minimal periportal thickening, while 64 fell into pattern C, 56 into pattern D, 49 into pattern E, and 9 into pattern F, the most advanced category. When the researchers compared median ELF values across these groups, a clear gradient emerged: the median score rose from 8.36 in patients with pattern A plus B, to 8.40 in pattern C, 8.64 in pattern D, 8.99 in pattern E, and 9.75 in pattern F. This monotonic increase was statistically significant, with a p value of 0.0021, indicating that the probability of observing such a pattern by chance alone was low.

The team then tested whether the ELF score could discriminate between broader categories of fibrosis severity. It could. The test differentiated patients without periportal fibrosis from those with mild, moderate, and advanced disease when the Niamey patterns were grouped as A plus B versus C versus D versus E plus F, with a p value of 0.0024. It also distinguished patients with advanced fibrosis from those without fibrosis or with moderate fibrosis: the comparison of A plus B versus E plus F yielded a p value of 0.0464, and the comparison of C plus D versus E plus F was even stronger, at p equal to 0.0007. In practical terms, this means the blood test reliably flagged the patients whose livers had reached the stage of fibrosis most likely to produce clinically significant portal hypertension.

One result, however, tempered the enthusiasm. When the researchers compared mean ELF values between patients with and without a history of upper gastrointestinal bleeding, they found no statistically significant difference. This suggests that while the ELF score tracks the structural progression of periportal fibrosis as seen on ultrasound, it does not by itself identify which patients have already experienced variceal hemorrhage. Bleeding risk in schistosomiasis depends not only on the degree of fibrosis but also on the size and wall tension of the collateral vessels, factors that a fibrosis marker measured in serum cannot directly capture. The authors therefore position the ELF test as a complement to, rather than a replacement for, clinical assessment and endoscopic or imaging surveillance of varices.

Nevertheless, the study’s conclusion is significant for a disease that continues to affect millions of people in poverty-stricken rural communities. The ELF test demonstrated potential as a tool for assessing periportal fibrosis in patients with schistosomiasis mansoni, because it could differentiate those with minimal fibrosis from those with moderate or advanced fibrosis using nothing more than a blood sample. As a pilot study with a modest sample size and a cross-sectional design, it cannot yet establish whether serial ELF measurements can monitor fibrosis progression in individual patients over time, or whether the score predicts future decompensation. Those questions will require longitudinal cohorts and validation in other endemic regions. But if larger studies confirm these findings, the ELF score could become a practical, scalable screening instrument, allowing health systems in endemic areas to reserve scarce ultrasound resources for patients whose blood tests signal advancing disease, and to intervene before portal hypertension claims another life.

Subject of Research: Use of the Enhanced Liver Fibrosis serum score to assess periportal fibrosis severity in schistosomiasis mansoni

Article Title: Evaluating periportal fibrosis in schistosomiasis mansoni using the ELF [Enhanced Liver Fibrosis] score: A pilot study

Article References: Thorp, R. D., Batista, A. D., Mariz, C. A., de Araújo, L. R. M. G., Diniz, G. T. N., Barreto, A. V. M. S., de Morais, C. N. L., Silva, P. C. V., Domingues, A. L. C., & Lopes, E. P. (2026). Evaluating periportal fibrosis in schistosomiasis mansoni using the ELF [Enhanced Liver Fibrosis] score: A pilot study. PLOS Neglected Tropical Diseases, 20(10), e0014775. https://doi.org/10.1371/journal.pntd.0014775

Image Credits: AI Generated

DOI: 10.1371/journal.pntd.0014775

Keywords: schistosomiasis mansoni, periportal fibrosis, ELF score, liver fibrosis, Niamey classification, portal hypertension, ultrasound, biomarkers, neglected tropical diseases, Brazil, noninvasive diagnostics, PLOS Neglected Tropical Diseases

The numbers are striking. Using the Kato-Katz technique, the standard coproscopic method recommended by the World Health Organization, researchers found a positivity rate of 23.68 percent among 266 residents who provided stool samples. When the team added the Hoffman, Pons and Janer sedimentation technique, six additional infections emerged. Crucially, they then applied real-time polymerase chain reaction to a subset of samples that had tested negative by both microscopic methods, and nearly 16.5 percent of those came back positive for parasite DNA. That molecular layer pushed the overall estimated prevalence to 28.94 percent, a figure the authors caution is likely still an underestimate, because qPCR was not applied to every negative sample and its greater sensitivity relative to parasitological techniques is well established.

This diagnostic gap matters far beyond academic precision. Under Brazilian Ministry of Health guidelines, the recommended response to schistosomiasis depends directly on the measured local positivity rate. In areas with rates between 15 and 25 percent, all positive cases and their household contacts should be treated with praziquantel. Above 25 percent, the guidance escalates to treating entire communities and prioritizing those areas for intensified control. A neighborhood that crosses that threshold on paper therefore triggers a fundamentally different public health strategy than one that appears quiet because insensitive tests missed low-burden infections. The Kato-Katz method, while practical and inexpensive, is known to perform poorly in individuals carrying few eggs, precisely the profile that dominates in low-transmission settings where control programs believe they are winning.

The study’s clinical findings add urgency. Of 55 infected residents who underwent upper abdominal ultrasound, 31 showed periportal fibrosis, the scarring around the liver’s portal veins that develops as the immune system walls off parasite eggs deposited in hepatic tissue. Fibrosis graded by the Niamey protocol ranged from peripheral ring echoes to advanced patterns. Consistent with the disease’s pathophysiology, individuals with fibrosis were significantly older, with a mean age of about 41 years compared with 21 among infected people without fibrosis, and they carried heavier parasite loads, averaging around 330 eggs per gram of stool. Fibrosis was also far more common in males, who made up roughly three quarters of the fibrosis group, echoing sex-related patterns reported across schistosomiasis research.

Perhaps most telling was the state of the portal vein. Infected residents with periportal fibrosis had a significantly larger portal vein diameter than those without, a measurement associated with progressing disease severity and, in advanced hepatosplenic cases, with the risk of life-threatening esophageal variceal bleeding. In this community-based sample the diameters remained within normal reference limits, and the researchers found no significant differences in spleen size or liver lobe measurements between groups, likely because only one participant showed the most advanced fibrosis pattern. That scarcity of severe disease is itself informative: it captures the pathology at a compensated, earlier stage, before the decompensated forms that fill referral hospitals, and it underlines why population-based surveys rather than hospital records are essential for understanding where transmission is heading.

One result stood out as a warning about early exposure. Although hepatic fibrosis typically requires years of chronic infection, and the relationship between age and fibrosis is generally treated as roughly linear, the team documented children and adolescents under 18 who already displayed pattern C peripheral fibrosis. The questionnaire data explain why. Residents described routine, involuntary contact with floodwater: roughly 98 percent of both infected and uninfected participants reported water accumulating on their streets, and almost no one had a practical means of avoiding exposure. In Novo Horizonte, infection risk is not tied to occupational fishing or farming but to simply walking through inundated streets during the rainy season, a hallmark of urban schistosomiasis.

The socioenvironmental picture is bleak in ways that map directly onto transmission. Fewer than 11 percent of infected residents lived on paved streets. About three quarters reported open septic tanks leaking sewage onto their roads, and more than 95 percent described standing water and flooding near their homes. Most infected individuals had lived in the area for at least five years, and duration of residence was one of the few socioenvironmental factors showing a statistically significant association with infection. Nearby water bodies harbor the Biomphalaria snails that serve as intermediate hosts, releasing the cercariae that penetrate human skin in a matter of minutes. In such an environment, every heavy rainfall converts streets into transmission sites.

History shows how hard this cycle is to break. An epidemiological assessment from 2011 recorded a 15.7 percent positivity rate in Novo Horizonte, which fell after collective treatment with praziquantel. More than two decades later, the parasite is back at roughly twice that level, demonstrating that mass drug administration alone, without durable sanitation infrastructure, produces only temporary suppression. Notably, among residents who tested negative by all three diagnostic methods, a full third nonetheless showed periportal fibrosis on ultrasound. The researchers suggest many were treated in earlier campaigns for infections that were never formally diagnosed, leaving behind fibrotic scars from cleared or subclinical infections, a hidden reservoir of morbidity that standard surveillance cannot see.

The broader Brazilian context makes these findings more consequential. National control program activity has been declining, and Pernambuco illustrates the trend: in 2024, of 240,436 coproscopic examinations scheduled across endemic municipalities, fewer than 43 percent were completed. Jaboatão dos Guararapes reached only about 30 percent of its scheduled exams, yielding an official municipal positivity of 3.2 percent, which qualifies it as low endemicity even as this study documents a moderately positive hotspot within its borders. Meanwhile the state recorded 1,528 deaths from schistosomiasis between 2015 and 2024, including 111 in the final year, and it carries the country’s highest hospitalization rates for the disease. Where screening coverage falls, deaths rise, and low official positivity rates may simply reflect too few tests rather than genuinely low transmission.

The study team, led by researchers at the Federal University of Pernambuco and the Oswaldo Cruz Foundation’s Aggeu Magalhães Institute, argues that frequent parasitological surveys, strengthened active case finding, and adoption of more sensitive molecular diagnostics are needed to interrupt transmission before severe hepatic disease takes hold. All infected participants received their results and referrals for praziquantel treatment under Brazilian program guidelines, and all participants or their guardians provided written informed consent, with ethical approval from the university’s research committee. The researchers also acknowledge limitations: younger residents were less likely to submit stool samples, and infrastructure constraints meant not every negative sample could undergo qPCR or ultrasound. Even so, the message from Novo Horizonte is difficult to ignore. In Brazil’s urbanizing coastal Northeast, a neglected tropical disease is quietly rewriting the maps that guide its control, and the communities most exposed to flooded, unsanitized streets are paying the price while official statistics lag behind the worms.

Subject of Research: Urban transmission and clinical burden of Schistosoma mansoni infection in Pernambuco, Brazil

Article Title: Epidemiological and Clinical-Laboratorial Profile of Schistosomiasis in an Endemic Urban Area in Pernambuco, Brazil

Article References: da Silva Pereira, M. E., Júnior, W. L. B., da Silva Fernandes, D. L. R., Domingues, A. L. C., de Lorena, V. M. B., & de Souza Gomes, E. C. (2026). Epidemiological and Clinical-Laboratorial Profile of Schistosomiasis in an Endemic Urban Area in Pernambuco, Brazil. Acta Parasitologica, 71(5), Article 206. https://doi.org/10.1007/s11686-026-01384-0

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01384-0

Keywords: schistosomiasis, Schistosoma mansoni, neglected tropical diseases, Brazil, urban transmission, Pernambuco, periportal fibrosis, Kato-Katz, qPCR diagnosis, ultrasound, public health, praziquantel