SAN FRANCISCO, Agusan del Sur (MindaNews / 29 March) — When Rogelio Timbal tends his one-hectare rice field in Barangay Caimpugan in this municipality, the thick, knee-deep mud makes every step a struggle. His boots, meant to protect him, only slow him down, making him sink deeper into the sludge with each step.
A barefoot farmer steers his carabao through rice paddies as he hauls the harvested rice grains in San Francisco, Agusan del Sur. Mindanews Photo by IVY MARIE MANGADLAO
“Hubuon ko na lang ang botas kay malangan ang trabaho. Makabug-at sa akong tikang,” he lamented. (I just have to take off my boots because they slow me down; they just make each step heavier.)
For 11 years, this has been his routine, wading barefoot through the waterlogged paddies, his feet constantly soaked in mud.
“It’s just part of the job,” he said.
But in 2023, the exposure took its toll.
At first, it was just dizziness, a headache here and there. Then, the left side of his body started feeling numb. He ignored it, thinking it was just exhaustion from long hours in the field.
But when the symptoms worsened, he had no choice but to go to a clinic. That was when he found out he had schistosomiasis.
A disease long associated with poverty, schistosomiasis remains a constant threat to farmers like Timbal, whose livelihoods depend on the very conditions that put them at risk.
According to the World Health Organization (WHO), schistosomiasis is an acute and chronic disease caused by parasitic blood flukes of the genus Schistosoma.
Classified by WHO as a neglected tropical disease (NTD), it mostly affects poor rural communities in Asia, the Middle East, Africa, and South America.
The article Management and Control of Schistosomiasis in Agusan del Sur, Philippines: A Modeling Study by scientists from the University of the Philippines and from Bicol University posted online in March 2022 highlighted that schistosomes require both a mammalian definitive host and a freshwater snail intermediate host to complete their life cycle.
Schistosomiasis, first reported in the Philippines in 1906, is caused by Schistosoma japonicum, a zoonotic parasite that infects humans and over 40 mammalian species, including carabaos, dogs, pigs, cats, rats, and goats. The Oncomelania snail serves as the parasite’s intermediate host.
Definitive hosts become infected when the larval form of the parasite, known as cercariae, penetrates the skin during direct contact with infested water.
Once inside, the cercariae shed their tails and transform into schistosomulae, which travel through the bloodstream before settling in the hepatic portal vein leading to the liver.
There, they mature into adult worms and begin laying eggs, which are excreted in the host’s stool.
Upon exposure to freshwater, the eggs hatch into miracidia, which infect snails. Inside the snails, the miracidia multiply asexually into sporocysts and later develop into cercariae.
The cycle continues when these newly developed cercariae penetrate the skin of another mammalian host.
An aerial view of vast rice paddies in Barangay Caimpugan, San Francisco, Agusan del Sur. Photo courtesy ERWIN MASCARIÑAS
The rice paddies where Timbal works daily are in schistosomiasis-endemic areas, farmlands that were once natural habitats for snails carrying schistosomiasis, according to the Department of Health Caraga.
In the Philippines, these snails originally thrived in floodplain forests and swamps, many of which have been converted into agricultural lands.
While farming has altered these environments, the snails have adapted, finding new homes in irrigation canals, abandoned or minimally farmed rice fields, and even roadside ditches.
This has allowed them to persist and continue the cycle of schistosomiasis transmission, putting farmers like Timbal at constant risk. The result: more and more people are getting infected with the disease.
The still unpublished study “Prevalence, Clinical Profile, and Outcomes of Admitted Cases of Schistosomiasis Japonicum in Agusan del Sur from 2012 to 2022” conducted by Dr. Annie Abordo-Dioso, a 2024 graduate of the Infectious Diseases Fellowship Program at the Research Institute for Tropical Medicine (RITM), initially recorded a total of 620 cases after analyzing analyzed admissions in nine hospitals across the province, But after filtering out non-residents and those with incomplete records, only 449 cases remained.
Dr. Annie Abordo-Dioso presents the findings of her study, “Prevalence, Clinical Profile, and Outcomes of Admitted Cases of Schistosomiasis japonicum in Agusan del Sur from 2012 to 2022,” during a research forum at the Research Institute for Tropical Medicine on April 24, 2024. Photo courtesy of the RITM
Now an Adult Infectious Disease Specialist practicing at the Democrito O. Plaza Memorial Hospital in Prosperidad in Agusan del Sur and at the Manuel J. Santos Hospital in Butuan City, Dioso told MindaNews that many of the cases were already in the late stages of the disease by the time they were admitted. Most of those affected were men, particularly farmers like Timbal.
“Many had only reached grade school education, and while farmers were the most at risk, the disease was so prevalent that even non-farmers became infected,” Dioso said.
The study Schistosomiasis in the Philippines: A Comprehensive Review of Epidemiology and Current Control by Emmanuel John Tabilin et al., published in the Tropical Medicine and Infectious Disease journal in January 2025 also stated that the most susceptible groups in these agricultural transmission hotspots are farmers and irrigation workers, as they labor in contaminated fields and irrigation canals, exposing themselves to infectious cercariae.
“People who did not work on rice farms were shown to have lower odds of infection than those working full-time on rice farms,” the study showed.
The review further stated that farming is a male-dominated occupation and has been identified as a high-risk cohort due to greater exposure, which explains the higher prevalence of schistosomiasis among men compared to women.
The highest number of cases came from municipalities near the Agusan River, including San Francisco, Talacogon, Prosperidad, San Luis, and Bunawan.
Dioso noted that Sibagat, a town at a higher elevation with fewer bodies of water and fewer rice paddies, had no recorded hospital admissions for schistosomiasis.
“Despite the presence of the disease, it remains underreported. The number of hospital admissions for schistosomiasis has increased over the years, even during the COVID-19 pandemic when hospitals were prioritizing coronavirus patients,” Dioso added.
She noted that the most common form of schistosomiasis found among admitted patients was hepatosplenic schistosomiasis, affecting the liver.
“Symptoms ranged from liver cysts and vomiting to severe cases of abdominal swelling (ascites) and internal bleeding due to liver damage. Some patients also suffered from neuroschistosomiasis, a rarer but severe form of the disease that leads to seizures,” Dioso said.
‘Tip of the iceberg’
But Dioso said these numbers likely represent only the tip of the iceberg as they account only for patients who managed to reach a hospital.
“Many residents have accepted schistosomiasis as a ‘normal’ disease. As a doctor, I noticed that many patients no longer fear schistosomiasis because they see it as an unavoidable part of life. But we know that schistosomiasis is preventable,” Dioso said.
She pointed out that one reason for this is patients’ reluctance to take medication, as many fear side effects such as dizziness and nausea, which are common after schistosomiasis treatment.
“This fear prevents them from seeking treatment, which is why patient education and encouragement are critical,” she added.
Dioso also emphasized that her study included only hospitalized patients, not outpatient cases from clinics.
“If I included OPD cases from clinics, the numbers would be much higher. For example, when I checked San Francisco Doctors’ computerized records and simply typed ‘schistosomiasis’ in the diagnosis search—including both admitted and OPD cases—there were over 1,000 cases in San Francisco Doctors alone. But if you look at the admitted cases from San Francisco Doctors, there were only 96. So, you can see the gap—1,000+ OPD cases versus only 96 admitted cases,” Dioso said.
Dioso explained that symptoms can vary based on the severity and duration of the disease.
Acute schistosomiasis is more commonly seen in individuals who are newly exposed to the parasite.
“Symptoms include swimmer’s itch or rashes, fever, chills, body pain, abdominal pain, diarrhea, cough, and difficulty breathing,” Dioso stated.
Chronic schistosomiasis, on the other hand, is more prevalent among residents of endemic areas such as Agusan del Sur, who experience repeated exposure.
“Over time, the infection can cause hepatosplenic complications, leading to liver cirrhosis. This stage is marked by severe symptoms such as gastrointestinal bleeding due to varices, abdominal swelling, jaundice, anemia, and malnutrition. In some cases, the infection may also affect the nervous system, leading to seizures (a condition known as neuroschistosomiasis) or even lung manifestations such as pneumonia,” Dioso added.
Data from the Field Health Services and Information System of the Department of Health (DOH) for the period 2013–2023, except for 2016, on schistosomiasis-positive cases in Agusan del Sur were consolidated by MindaNews.
From 2019 to 2023, the DOH categorized cases separately, distinguishing acute schistosomiasis (recent infections presenting with systemic symptoms) from chronic schistosomiasis (long-term cases with organ involvement).
Meanwhile, data from 2013 to 2016 report only the total number of positive cases without differentiation between acute and chronic cases.
Low productivity
Timbal, like many others, had no idea he was carrying the parasite until his body began to fail him.
He said he never imagined that something as routine as stepping into the fields each day could put his life at risk.
Yet, for many farmers in Agusan del Sur, the choice is clear—endure the danger or give up their only source of livelihood.
Timbal recalled that before his diagnosis, when he was feeling weak and dizzy, he couldn’t work.
“Half of my body lost strength—it was like I was paralyzed. When I walked, my leg kept dragging. It was always my left leg. I’m left-handed, so that’s my dominant side, but I couldn’t even move it,” he said.
The same DOH data highlighted the significant economic impact of schistosomiasis, citing its public health burden and the associated loss of productivity.
The disability-adjusted life year (DALY), which estimates disease burden in terms of healthy years lost due to premature mortality or disability, can be used as a measure of lost productivity.
In the Philippines, the estimated DALY for schistosomiasis in 2021 was 22,300, according to the WHO’s World Health Observatory.
While no documentation is available yet for Agusan del Sur, Tabilin et al. said that endemic communities in Leyte estimate that illness due to schistosomiasis results in the loss of 45.4 productive days per infected person per year. However, this loss is reduced to just four days after treatment.
Animal transmission
For farmers, the risks extend beyond direct exposure to infected waters. The carabaos they rely on as draught animals in rice farms are another source of infection.
Timbal said that when the rice paddies are not in use for planting, farmers often let their carabaos wallow in the water.
A farmer and his carabao in Barangay Caimpugan, San Francisco, Agusan del Sur. MindaNews hoto by IVY MARIE MANGADLAO
Tabilin et al. noted that animal infections significantly contribute to transmission, as infected carabaos contaminate the environment with parasite eggs in their stool, sustaining the parasite life cycle even in the absence of human infections.
These freshwater areas, where farmers wade daily, are also common wallowing places for carabaos, increasing the risk of exposure for both humans and animals.
“Carabaos have been established as crucial in maintaining the parasite life cycle in China and the Philippines. Each infected carabao can sustain large numbers of schistosome parasites, releasing hundreds of thousands of eggs into the environment, accounting for up to 90% of the total egg contamination,” the review stated.
In the Philippines, carabaos remain essential agricultural aides, with 2.7 million working on farms across the country as of September 2023, according to the Philippine Statistics Authority’s Carabao Inventory.
“Approximately 99.3 percent of the country’s carabao population comes from smallhold farms, while the remaining 0.5 percent and 0.2 percent are from semi-commercial and commercial farms, respectively,” the PSA stated.
Flooding increases risk
Naelyn Bayogbog, a nurse assigned to the health center in Barangay Caimpugan, told MindaNews that aside from farmers who come into contact with rice paddies, schistosomiasis cases are also high due to flooding.
Nurse Naelyn Bayogbog unpacks praziquantel tablets at the barangay health center in Caimpugan, San Francisco, Agusan del Sur. MindaNews photo by IVY MARIE MANGADLAO
“Even if you tell farmers to wear boots or ask people not to go to schistosomiasis- infected streams or rivers, the floodwaters still expose them to schistosomiasis,” she said.
Timbal added that it’s not just farmers who are affected.
“Even if you don’t go to the rice fields, you still can’t avoid it. When the floods come, the water rises, and you have to wade through it,” he said.
The most recent major flood in Caimpugan occurred in February 2024, taking almost a month to fully subside. The floodwaters reached the first floor of houses after the Gibong River overflowed, inundating rice paddies and communities.
A review by Guo et al., published in the Pathogens journal in November 2021 (From the One Health Perspective: Schistosomiasis Japonica and Flooding), examined cases in China and the Philippines, noting that flooding damages water conservancy infrastructure such as dams, rivers, and embankments and sanitation facilities, leading to fecal contamination and increased water contact for both humans and animals, which further raises the risk of schistosomiasis infection.
An aerial view of Barangay Caimpugan, showing the rice paddies and the Gibong River. Photo courtesy ERWIN MASCARIÑAS
“Flooding may carry snails to previously snail-free areas and lead to both active and passive diffusion of the snails. As a result, the density of snails will significantly increase by the third year after flooding, and their habitats may expand,” the article stated.
The review noted that with increased human and animal contact with water, as well as larger snail habitats with a higher density of living snails, the transmission risk of schistosomiasis rises, especially following catastrophic flooding.
Challenges in treatment
Dianne Antonette G. Li, Health Program Officer II for Schistosomiasis of the DOH Center for Health Development in the Caraga Region, told MindaNews that one of the agency’s interventions is the Mass Drug Administration (MDA), which involves the use of praziquantel. It is primarily used for morbidity control of schistosomiasis in the Philippines.
Dianne Antonette G. Li, Health Program Officer II of the Schistosomiasis program at the DOH Center for Health Development in the Caraga region (in blue shirt), assists with the field laboratory operations and stool examinations in Brgy. Libertad, Bunawan municipality. Photo courtesy of PHO Agusan del Sur
“Because we really can’t prevent farmers from stepping on the soil as they go to their farmlands for their livelihood. So if they live in an endemic area, they should take praziquantel yearly since it’s completely free. It’s always available at the Rural Health Unit, so they should take it every year,” Li said.
However, Li noted that there are still challenges in the implementation of the MDA, particularly MDA fatigue.
“Some people in Agusan del Sur, especially those who have been taking praziquantel for several years, are experiencing MDA fatigue. I have personally experienced taking praziquantel, and it has side effects. But that’s normal. That’s why you should take it on a full stomach to reduce the side effects,” Li added.
Praziquantel is currently the drug of choice for treating schistosomiasis under the Mass Drug Administration (MDA) program in the Philippines. The Department of Health, through the Schistosomiasis Control and Elimination Program, conducts MDA for schistosomiasis every January. MindaNews photo by IVY MARIE MANGADLAO
Timbal has been following the health center’s advice to take praziquantel on a full stomach, and has been feeling well after receiving three doses of praziquantel since 2023. By 2024, he reported no more symptoms but decided to take mass drug administration treatment once a year as a precaution. He has already taken his 2025 dose last January.
Despite health center recommendations to wear protective boots, Timbal refuses, saying they are an added burden.
“I’ll just take the medication along with my family to prevent schistosomiasis. Exposure is unavoidable since I work in the rice fields, and I can’t stop farming because it’s our livelihood,” he said.
One Health approach
A review entitled “The Status of Schistosomiasis Japonica Control in the Philippines: The Need for an Integrated Approach to Address a Multidimensional Problem” published by Vicente Y. Belizario, Jr. et al. of the University of the Philippines Manila in February 2022 in the International Journal of OneHealth cited schistosomiasis as a public health concern across the country despite ongoing control efforts.
According to the review, the One Health approach is particularly suitable for schistosomiasis control, as it involves designing and implementing programs, policies, legislation, and research through multi-sectoral collaboration to achieve better health outcomes.
“Examples of areas where a One Health approach can be applied include the development of more sensitive and cost-effective diagnostics for schistosomiasis, integration of surveillance systems, strengthening of animal and public health activities, improving access to safe WASH (Water, Sanitation, and Hygiene), and empowering local governments,” the review stated.
Li said that aside from the MDA, the One Health approach has also been integrated by the DOH to reduce cases of schistosomiasis, in line with the WHO’s road map for 2021-2030 that aims to end the suffering from neglected tropical diseases by 2030, which specifically targets the elimination of schistosomiasis as a public health problem globally.
With only five years remaining until 2030, Li said that achieving this goal is challenging.
“What we need to do now is to focus on our other partners and government agencies to fully implement the One Health approach. The Department of Health, Provincial Health Office and Rural Health Unit cannot combat this alone, so we really need to strengthen our partnership with the Department of Agriculture and Veterinary Offices, especially when dealing with carabaos and snails,” Li stated.
The Provincial Health Office of Agusan del Sur distributes water-sealed toilet bowls to the Rural Health Unit of San Francisco. Photo courtesy of PHO Agusan del Sur
Li also noted that the implementation of Zero Open Defecation (ZOD) in all municipalities and cities is important in Agusan del Sur. For this to be successful, she said they need the help of local government units and communities.
DOH Caraga data stated that out of 314 barangays in Agusan del Sur, 207 have already achieved ZOD status, including Barangay Caimpugan.
Bayogbog said they achieved ZOD in 2024 after consistently convening residents through Family Development Sessions or general assemblies.
“We put in a lot of effort to explain and educate them during family sessions, emphasizing the benefits of having their own toilet and the affordable options available to households,” Bayogbog added. (Ivy Marie Mangadlao / MindaNews)
This story is published with the support of Canal France International under the Media for One Health program.
Dr. Annie Abordo-Dioso (right) presents the findings of her study, “Prevalence, Clinical Profile, and Outcomes of Admitted Cases of Schistosomiasis japonicum in Agusan del Sur from 2012 to 2022,” to MindaNews’ Ivy Marie Mangadlao in Butuan City. Photo courtesy ERWIN MASCARIÑAS
