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Schistosomiasis, popularly known as schistosis, water belly or snail disease, is an infectious disease caused by the parasite Schistosoma mansoni, which can be found in the water of rivers and lakes and which can penetrate the skin, causing redness and itching of the skin, weakness and muscle pain, for example.
Schistosomiasis is more frequent in tropical environments where there is no basic sanitation and where there is a large amount of snails, since these animals are considered hosts of the parasiteSchistosoma, that is, the parasite needs to spend time in the snail to develop and reach the stage where it can infect people.
Main signs and symptoms
In most cases, schistosomiasis is asymptomatic, however the person infected by the parasite may develop initial signs and symptoms that characterize the first phase of the disease, also called the acute phase:
- Redness and itching where the parasite has penetrated;
- Fever;
- Weakness;
- Cough;
- Muscle aches;
- Lack of appetite;
- Diarrhea or constipation;
- Nausea and vomiting;
- Chills.
As the parasite develops in the body and moves to the liver circulation, other more serious signs and symptoms may appear, characterizing the second phase of the disease, also called the chronic phase:
- Presence of blood in the stool;
- Cramps;
- Abdominal pain;
- Dizziness,
- Slimming;
- Swelling of the belly, also called water barrier;
- Palpitations;
- Hardening and enlargement of the liver;
- Enlarged spleen.
To avoid the onset of the most severe symptoms of schistosomiasis, it is important that the diagnosis is made, preferably, still in the acute phase of the disease.
How the diagnosis is made
The diagnosis is made by examining 3-day feces, in which eggs Schistosoma mansoni. In addition, a complete blood count and measurement of liver enzymes, such as ALT and AST, which are usually altered, can be requested, as well as imaging tests, such as abdominal ultrasound, for example, in order to verify the increase and functioning of the liver and spleen.
How is the cycle of schistosomiasis
Infection with Schistosoma mansoni it happens from contact with contaminated water, especially in places where there are large amounts of snails. Thus, farmers, fishermen, women and children are more vulnerable to having this disease after fishing, washing clothes or bathing in polluted waters.
The life cycle of schistosomiasis is complex and occurs as follows:
- Eggs from Schistosoma mansoni they are released into the faeces of infected people;
- Eggs, upon reaching the water, hatch due to the high temperature, intense light and the amount of oxygen in the water, and release the miracide, which is one of the first forms of Schistosoma mansoni;
- The miracids present in the water are attracted to snails due to substances released by these animals;
- Upon reaching the snails, the miracidia lose some of their structures and develop until the cercaria stage, being released again in the water;
- The cercariae that are released into the water can penetrate people's skin;
- At the moment of penetration, the cercariae lose their tails and become schistosomules, which reach the bloodstream;
- Schistosomules migrate to the portal circulation of the liver, where they mature until adulthood;
- Adult worms, male and female, migrate to the intestine, where the eggs are laid by the females;
- Eggs take about 1 week to be ripe;
- The mature egg is then released into the faeces and, when in contact with water, hatches, giving rise to a new cycle.
Therefore, in places where there is no basic sanitation, it is common for several people from the same community to be contaminated with schistosomiasis, especially if the region has a large number of snails, since this animal has a fundamental role in the parasite's life cycle. To break this cycle and prevent other people from becoming contaminated, one must avoid contact with polluted water and eliminate excess snails.
How the treatment is done
Treatment is usually done with antiparasitic drugs such as Praziquantel or Oxamniquina for 1 or 2 days, which kill and eliminate the parasite. In addition, the doctor may recommend the use of corticoid ointments to relieve itchy skin, and it is also indicated to rest, maintain good hydration, and drink water. In addition, pain relievers, for lowering fever and for colic, may also be indicated.
Beta-blockers and drugs to control diarrhea can also be used in people who develop the chronic phase of schistosomiasis, in addition to sclerotherapy of esophageal varices.
Is schistosomiasis curable?
Schistosomiasis is curable when the diagnosis is made early in the disease and treatment is started as soon as possible, as it is possible to eliminate the parasite and prevent the appearance of complications, such as enlarged liver and spleen, anemia and delay in the child's development, for example. Therefore, in case of suspicion that the person has worms, medication should be started as soon as possible.
To find out if the person has actually healed, the doctor may request that a new stool test be done on the 6th and 12th week after starting treatment. In some cases, for the avoidance of doubt, the doctor requests a rectal biopsy 6 months after the start of treatment.
However, even if the cure for schistosomiasis is verified, the person does not acquire immunity, and can be infected again by the parasite if it comes into contact with contaminated water.
How to avoid being contaminated
The prevention of schistosomiasis can be done through basic hygiene measures such as:
- Avoid contact with rain and flood water;
- Do not walk barefoot on the street, on land or in freshwater streams;
- Drink only potable, filtered or boiled water.
These precautions should be done mainly in places where there is no adequate sanitation and the sewage runs in the open.