Schistosomiasis: Snail Fever a Common Type of Parasitic Disease
Author: Thomas C. Weiss : Contact: Disabled World
Published: 2014-06-30 : (Rev. 2015-10-14)
Synopsis and Key Points:
Information regarding Snail fever a common type of parasitic disease found in contaminated fresh water.
Schistosomiasis, is a type of infectious disease that is caused by parasitic worms found in fresh water. Fresh water snails are also infected by this parasite during its life-cycle and people who come into contact with fresh water containing these snails are at risk for infection.
An infection caused mainly by three schistosome species; Schistosoma mansoni, Schistosoma japonicum and Schistosoma haematobium. S. japonicum being the most infectious of the three species. Once the parasite has entered the body and begun to produce eggs, it uses the hosts' immune system (granulomas) for transportation of eggs into the gut. Individuals at risk to infection from S. japonicum are farmers who often wade in their irrigation water, fisherman that wade in streams and lakes, children that play in water, and people who wash clothes in streams.
The statistics related to snail fever are stunning:
- 700,000,000 people at risk
- 74 countries where snail fever is found
- 240,000,000 people are already infected
Snail fever ranks second only to malaria as the most common type of parasitic disease and is the most deadly NTD. It kills an estimated 280,000 people every single year in the African region alone.
The disease may begin with blood in a person's urine or still, as well as anemia and issues with growth and development in children. The disease eventually may become life-threatening because of health effects such as kidney and liver issues and bladder cancer. Children with long-term or repeated infections may experience anemia and malnutrition, which can contribute to lost days at school as well as serious learning disabilities. Attempts to control snail fever include treatment of those who are infected with a medication called, 'praziquantel,' as well as appropriate disposal of urine and feces.
Risk Factors for Snail Fever
Snail fever is an important cause of disease in a number of parts of the world, usually in places with poor sanitation practices. Children who are school age living in these areas are often times most at risk because they tend to spend time bathing or swimming in water that contains infectious cercariae. If you live in or travel to areas where snail fever is found and become exposed to contaminated fresh water - you are at risk.
Areas Where Types of Snail Fever may be Found Include:
- S. intercalatum - Found in parts of West and Central Africa.
- S. mekongi - A type of snail fever found in Laos and Cambodia.
- S. japonicum - A type of snail fever found in parts of China, Southeast Asia, as well as Indonesia.
- S. haematobium - Distributed throughout Africa. Fresh water presents a risk of infection in both southern and sub-Saharan Africa, to include the rivers and great lakes and smaller bodies of water. Transmission also happens in the Nile River valley in Egypt and the Mahgreb region of North Africa. This type of snail fever is found in areas of the Middle East too.
- Schistosoma mansoni - Distributed throughout Africa. There is risk of infection in fresh water in souther and sub-Saharan Africa, to include the rivers and great lakes, as well as smaller bodies of water. Transmission also happens in the Nile River valley in Egypt and Sudan. This particular type of snail fever is also found in South America, to include Brazil, Venezuela, and Suriname. The Caribbean has a low risk of this type of snail fever; Guadeloupe, Dominican Republic, Saint Lucia and Martinique also have this type of snail fever.
A person becomes infected when their skin comes into contact with fresh water that is contaminated and in which certain types of snails that carry the parasite are living. Fresh water becomes contaminated with snail fever eggs when people who are infected urinate or defecate in the water. The eggs hatch and if the the appropriate species of snails are in the water - the parasites infect, develop and then multiply inside the snails.
The parasite ends up leaving the snail and entering the water, where it has the ability to survive for around 48 hours. Snail fever parasites can penetrate a person's skin who has come into contact with contaminated fresh water, usually as they swim, wade, wash or bathe. Over a number of weeks, the parasites migrate through host tissue and develop into adult worms inside the blood vessels of a person's body. Once they have matured, the worms mate and females produce eggs. Some of the eggs travel to a person's bladder or intestine and are passed into the person's urine or stool.
Common Symptoms of Snail Fever
Symptoms of snail fever are caused not by the worms themselves, but by a person's body's reaction to the eggs. Eggs shed by the adult worms that do not pass out of an infected person's body may become lodged in the person's bladder or intestine, causing inflammation or scarring. Children who are repeatedly infected may develop anemia, malnutrition, as well as learning difficulties. After being infected for years, the parasite may also damage a person's intestine, liver, lungs, spleen and bladder.
The majority of people do not experience any symptoms when they first become infected. Within a few days of becoming infected; however, they may develop itchy skin or a rash. Within 1-2 months of becoming infected, symptoms such as chills, fever, a cough and muscle aches can develop.
Diagnosing and Treating Snail Fever
To achieve a diagnosis of snail fever, a person's urine or stool may be examined under a microscope for parasite eggs. The eggs are often times passed intermittently and in small amounts and might not be detected, meaning it may be necessary to perform a blood test.
Chart showing signs and symptoms of chronic snail fever
A safe and effective medication is available to treat both urinary and intestinal snail fever, fortunately. Praziquantel is a prescription medication that is taken for 1-2 days to treat infections caused by snail fever. Without treatment, snail fever may persist for years. The signs and symptoms of chronic snail fever can include:
- Enlarged liver
- Abdominal pain
- Problems passing urine
- Increased risk of bladder cancer
- Blood in a person's urine or stool
Rarely, eggs might be found in a person's spinal cord or brain and may cause seizures, paralysis, or inflammation of the spinal cord.
Preventing Snail Fever
Sadly, no vaccine for snail fever is available. The best way to prevent snail fever is to pursue the following steps if you live in or are visiting an area where snail fever is transmitted.
- Avoid wading or swimming in fresh water when you are in countries in which snail fever occurs.
- Bathing water should be brought to a rolling boil for 1 minute to kill any cercariae and then cooled before bathing to avoid scalding. Water held in a storage tank for at least 1-2 days should be safe for bathing.
- Vigorous towel drying after an accidental or very brief exposure to water might help to prevent the snail fever parasite from penetrating a person's skin. Do not; however, rely on vigorous towel drying alone to prevent snail fever.
- Drink safe water. While snail fever is not transmitted by swallowing contaminated water, if your lips or mouth come into contact with water containing the parasites you might become infected. Because water coming directly from lakes, canals, streams, rivers or springs might be contaminated with a variety of infectious organisms, you should either bring your water to a rolling boil for 1 minute, or filter your water prior to drinking it. Boiling your water for at least a minute will kill any harmful bacteria, parasites, or viruses in the water. Iodine treatment alone Does Not Guarantee the water is safe and free of all parasites.
People who have had contact with potentially contaminated water should visit their health care provider to discuss testing for the snail fever parasite.
Controlling Snail Fever
In countries where snail fever causes significant disease, efforts to control it usually focus on some different things. Reducing the number of infections in people and eliminating the snails that are required to maintain the parasite's life cycle are at the top of the list. For all species that cause snail fever, improving sanitation may reduce or eliminate transmission of the disease. In some areas with lower transmission levels, elimination snail fever is considered to be a battle that can be won by public health officials.
Control measures might even include mass drug treatment of entire communities as well as targeted treatment of school age children. Chemicals used to eliminate snails in fresh water sources may harm other species of animals in the water unfortunately, and if treatment is not sustained - the snails may return to the sites afterwards. For certain species of the parasite, animals such as water buffalo or cows can also become infected. Runoff from pastures, if cows become infected, may contaminate sources of fresh water.
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