The World Health Organization (WHO) considers schistosomiasis “a disease of poverty.” Schistosomiasis is categorized as a neglected tropical disease (NTD) as it primarily affects tropical locations “where people do not have access to clean water or safe ways to dispose of human waste.” Schistosomiasis is “highly endemic” in Tanzania — it has the second highest number of cases in sub-Saharan Africa behind Nigeria. As a result, efforts are underway to help counter the spread of this disease.

The Background

Schistosomiasis, more commonly known as bilharzia, is an infectious disease that affects around 240 million individuals globally, according to WHO. After malaria, bilharzia is the second most devastating illness that parasites cause, the Centers for Disease Control and Prevention (CDC) says. WHO says “infection is prevalent in tropical and sub-tropical areas, in poor communities without potable water and adequate sanitation.”

A person can become infected when the skin comes into contact with freshwater contaminated with Schistosoma parasites. More significant signs of infection, such as fever and muscle aches, begin within one or two months. “Symptoms of schistosomiasis are caused by the body’s reaction to the eggs produced by worms, not by the worms themselves,” the CDC says. This immune reaction can cause damage to the organs and bring about other health issues.

There are two main forms of the disease: intestinal and urogenital. Children who become infected with these parasites several times “can develop anemia, malnutrition and learning difficulties.” Furthermore, “after years of infection, the parasite can also damage the liver, intestine, lungs and bladder,” according to the CDC.

Chronic schistosomiasis arises when the parasites remain in the body for a long time and the body produces immune responses against the parasitic eggs once they reach body tissue. Cases of chronic schistosomiasis in Tanzania are common and may limit people’s capacity to work.

Past and Current Epidemiology

During the 70s and 80s, Tanzania noted a pressing need to build new irrigation systems and dams to provide clean water for the growing population. However, these innovations had a negative effect on the expansion of the disease since schistosome parasites that live inside snails grow optimally in fresh water. Furthermore, the prevalence of the disease seems to rise as the country’s population size expands. In Tanzania, in 1977, the prevalence rate stood at 19% but swelled to 51.5% (more than 23 million people) by 2012. In 2019, around 15 million people in Tanzania required treatment for schistosomiasis in Tanzania.

Efforts to Tackle Schistosomiasis in Tanzania

WHO recommends “large-scale treatment of at-risk population groups, access to safe water, improved sanitation, hygiene education and snail control” to adequately address schistosomiasis. WHO endorsed treatment for the disease involves the administration of an anti-parasite drug known as praziquantel. In Tanzania, praziquantel is distributed on a large scale to schools and communities.

According to WHO, Tanzania received approximately 33 million praziquantel treatments for mass administration from 2009 to 2018, with a focus on school children.

Thanks to the Zanzibar Elimination of Schistosomiasis Transmission (ZEST) program, which took place from 2011 to 2017, the prevalence of the disease was reduced. Among children aged 9-12, prevalence decreased from 6.1% to 1.7%, while among adults aged 20-55, prevalence decreased from 3.9% to 1.5% by 2017. This successful project, launched by the Zanzibar government, mainly focused on the distribution of praziquantel twice a year, snail control measures and behavioral adjustments among the populace.

However, knowledge about the disease and how to prevent or treat it is integral for reducing future cases. Many people still do not have access to treatment and others prefer not to take the treatment due to a lack of information. This, added to the fact that one can become reinfected, shows why control is difficult. For example, in Mtama, a city that belongs to the Lindi region in Tanzania, the prevalence of the disease is still more than 50%. This is due to a lack of knowledge, interrupted access to praziquantel and unhygienic water practices, among other reasons.

WHO Guideline

In February 2022, WHO released a guideline for the control of schistosomiasis in affected nations. The guideline covers several evidence-based recommendations, including:

• Snail control measures to decrease transmission risks.
• Water, sanitation and hygiene efforts in approaches to control the disease.
• The “expansion of preventive chemotherapy to all in need, including adults and preschool-aged children.”

Schistosomiasis in Tanzania is still a problem that affects a large part of the population, despite the control systems implemented throughout the years. In a country with a population of about 58 million in 2019, 15 million people required treatment for this disease. Implementing comprehensive measures will safeguard the well-being of citizens in an endemic country.

– Carla Tomas
Photo: Flickr