Fresh Water Snail Spreads Fever Across Africa


Studies have discovered a new cause of fever in Africa. Fresh water snail is being accused of harboring parasitic worms and transferring an ailment, characterized by fever, to humans who eat it. Once a victim is infected, the disease, which is also fatal, can persist in the body for decades.

The worms live in snails and once they are released from the snails, burrow into the skin and deep inside the body of whoever they get in contact with in water. This results into a disease called Schistosomiasis, also known as Bilharzia. This chronic infection is caused by parasitic Schistomosa worms, which have the ability can live inside blood vessels for years, thereby causing fever, chills and inflammation.

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Any freshwater which has these snails in them could be the cause of infection,” says Alan Fenwick, Professor of Tropical Parasitology at Imperial College London.

Unfortunately, most of the infected waters are found in Africa, particularly Lace Victoria, the continent’s largest lake. The risk of getting infected in Lake Victoria is higher than in any other water body. The negative side of this disease is that people don’t often develop symptoms for years, but can continue to transmit the infection. This is also a major challenge in controlling the disease.

Cycle of Transmission

Inside the human body, female worms grow into adults and lay eggs that migrate through the body for release in faeces. If released into freshwater, through defecation in the water, they hatch and become ready to infect any freshwater snails on their path. Once inside the snails, the young worms transform into versions of themselves now capable of burrowing back into human skin.

On release back into the water they swim ready to, again, infect humans in their vicinity. It’s a perpetual cycle in which the parasites use both snails and humans to their advantage, manipulating both, to ensure the survival of their species.The eggs of the parasites travel primarily to the intestine when inside humans, for release, but along this journey can become trapped in organs and intestinal lining to cause inflammation. The characteristic symptom of the disease is a swollen abdomen.

The size of the burden is immense,” says Fenwick who is also Director of the Schistosomiasis Control Initiative(SCI), a charity working to tackle the disease in sub-Saharan Africa.

In 2014, more than 61 million people were treated for schistosomiasis, according to the World Health Organization (WHO), and more than 258 million required preventive treatment. The majority of cases are in Africa and outweigh the numbers affected by other diseases in the region.

There are 25 to 35 million people infected in sub Saharan Africa with HIV [and] ten times that number of people after affected by schistosomiasis,” says Fenwick.

water snail

According to WHO, the number of deaths caused by the disease, although difficult to record, is estimated to be between 20,000 to 200,000 deaths per year. WHO also says 90% of people who need treatment for schistosomiasis live in Africa, especially the ones whose houses are around lakes and rivers. However, this deadly disease can be managed in such areas with the help of enhanced sanitation systems.

The problem that sub Saharan Africa has is a lack of fresh water, safe water, and adequate sanitation,” says Fenwick. “People who need to urinate and defecate tend to do so on the open ground, and their excreta can be washed into water where the eggs will then infect snails.”

The infections primarily affect young children, but symptoms can take years to appear, thereby making it difficult to trace the place of contraction as well as method of treating.

We have to proactively go out and find children who are infected and treat them so that we protect them from an early grave,” says Fenwick.

The district of Wakiso, Uganda located on the Northern shores of Lake Victoria is one location that encourages the spread of this virus. The cause here, remains poor sanitation.

People are still using the lake… they defecate there,” says Juma Mpima, Vector control officer with Uganda’s Ministry of health who focuses on controlling infections in lakeside districts, like Wakiso.

Mpima regularly visits the shore of Busabaala, which is popular with locals for the fresh fish sold in the market each day. More than 800 people visit the shore every day, with only one toilet to share among them.

With one facility, and over 800 people to use one facility…people resort to using other waters,” he says.

Increasing the number of latrines in lakeside communities, and administering treatments to everyone there will go a long way to reduce the risk of getting Schistosomiasis. Large scale control programs, improved environments and greater sanitation facilities will also help control the disease.

In those fishing villages, people have to have contact with the lake for their survival and for their living and some of these lakes have the highest transmissions in the world, ” says Fenwick.

We give the treatment to all the people in the area irrespective of whether they’re infected or not infected,” says Mpima. This strategy is known as mass drug administration and is an approach used to control a range of infectious diseases including hookworm and elephantiasis.

The idea is to treat everyone who is at risk, although most people don’t know they’re infected. Despite the annual delivery of drugs, hotspots of the disease remain making reinfection inevitable. And so, the World Health Organization has set a goal to control morbidity from schistosomiasis by the year 2020 and also eliminate it as a public health problem by 2025.

Progress has been made to date in other African countries, such as Zanzibar and Burundi, but when it comes to these hotspots, there’s a long In the hotspots at the moment I think that we’ll be treating for ten years to come,” says Fenwick. We are not 100% sure that we’ll be able to eliminate,” he says. “But we believe that we can certainly get quite close.”

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