Schistosomiasis: symptoms, cycle and treatment

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 water from rivers and lakes and can penetrate people's skin and initially cause redness. and itchy skin, muscle weakness and pain, for example.

Schistosomiasis is more frequent in tropical environments where there is no basic sanitation and there is a large amount of snails, since these animals are considered intermediate hosts of Schistosoma , that is, the parasite needs to spend time in the snail to develop and reach the infective stage for people.

Signs and symptoms of schistosomiasis

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, the main ones being:

• Redness and itching where the parasite has penetrated; Fever; Weakness; Cough; Muscle pain; Lack of appetite; Diarrhea or constipation; Sickness and vomiting; Chills.

As the parasite develops in the body and moves to the portal circulation, which is a system of veins that takes blood from the abdominal organs to the liver, more serious signs and symptoms may appear, characterizing the second stage of the disease, also called the chronic phase, which is characterized by:

• Presence of blood in the stools; Cramps; Abdominal pain; Dizziness, Weight loss; Ascites, also called water barrage; Palpitations; Hardening and enlarged liver; Enlarged spleen; Cirrhosis; Hemorrhage due to rupture of the esophageal veins.

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. The diagnosis is made through a 3-day stool exam, in which Schistosoma mansoni eggs are searched . In addition, a complete blood count and measurement of liver enzymes, such as ALT and AST, which are usually altered, can be requested, in addition to imaging tests, such as abdominal ultrasound, for example, in order to verify the increase and functioning of the liver and spleen.

Schistosoma mansoni cycle

Infection by Schistosoma mansoni happens from contact with contaminated water, that is, as places where there are large amounts of snails, favoring the release of evolutionary forms that can move in water to people and penetrate the skin. Therefore, farmers, fishermen, women and children are more vulnerable to having this disease after fishing, washing clothes or bathing in polluted water.

The life cycle of schistosomiasis is complex and occurs as follows:

1. Schistosoma mansoni eggs are released into the feces of infected people and have a life expectancy of 24 hours in the case of liquid stools and 5 days in the case of solid stools; The eggs, upon reaching the water, hatch due to the temperature elevated, intense light and quantity of oxygen from the water, and release the miracide, which is one of the evolutionary forms of Schistosoma mansoni ; the miracidia present in the water are attracted to the snails due to substances released by these molluscs; miracidia lose some of their structures, develop to the cercaria stage and are released into the water; the cercariae are released into the water, penetrate people's skin; at the moment of penetration, the cercariae lose their tail and become schistosomules, which reach the blood circulation; Schistosomules migrate to the portal circulation, where they mature until adulthood; Adult worms, males and females, migrate ram up to the intestine, where the eggs are laid by the females; the eggs take about 1 week to be ripe, that is, for the miracide to form; the ripe egg is then released in the feces and, when in contact with water, breaks out, giving rise to a new cycle.

Therefore, in places where there is no basic sanitation, it is common for several people in the same community to be contaminated with schistosomiasis, especially if there are large numbers of snails in the region, as this animal has a fundamental role in the parasite's life cycle. Thus, to break this cycle and prevent other people from becoming contaminated, one must avoid contact with polluted water and eliminate snails.

How the treatment is done

Treatment is usually done with antiparasitic remedies like Praziquantel or Oxamniquina for 1 or 2 days, which kills and eliminates the parasite. In addition, the doctor may recommend the use of corticosteroid ointments to relieve itchy skin, and it is also indicated to rest, maintain good hydration by drinking water and analgesic remedies and to lower fever and cramps.

These remedies should not be used during pregnancy and if the woman is breastfeeding she should not breastfeed for 3 days after taking these drugs because they pass through breast milk.

In people who develop the chronic phase when the liver, spleen and intestines are severely affected due to the presence of the parasite, medicines can be used to control diarrhea and sclerotherapy of esophageal varices and the use of beta-blockers is important.

Schistosomiasis has a cure

Schistosomiasis can be cured 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, the 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

Prevention 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 carried out mainly in places where there is no adequate sanitation and the sewage runs in the open.