Parasitic worm infection of the Trematoda class. It occurs in various parts of the world in an uncontrolled (endemic) manner. In these places the number of people with this parasitosis remains more or less constant.
The parasites of this class are five, and vary as the causative agent of infection according to the region of the world. In our country schistosomiasis is caused by Schistosome mansoni. O main host and reservoir of the parasite is manIt is from their excreta (feces and urine) that eggs are spread in the wild.
It also has a intermediate host which are snails, snails or slugswhere the eggs pass the larval (cercaria) form. The latter disperses mainly in untreated waters, such as lakes, infects man through the skin causing inflammation of the same.
Already in man the parasite develops and lodges in the veins of the intestine and liver causing obstruction, which is the cause of most symptoms of the disease that can be chronic and lead to death.
The feces of infected people contaminate rivers and lakes with the eggs of the Schistosome mansoni.
The sexes of Schistosome mansoni are separated. The male measures from 6 to 10 mm in length. is robust and has a ventral groove, the gynecophore channel, which houses the female during mating. The female is longer and slender than the male. Both have fixation cups, located at the anterior end of the body, which facilitate the adhesion of worms to the blood vessel walls.
How do you get it?
The eggs eliminated by the urine and feces of contaminated men evolve into larvae in the water, these lodge and develop into snails. The latter release the adult larva, which while in the water contaminate man. In the human venous system the parasites develop to reach 1 to 2 cm in length, reproduce and eliminate eggs.
The development of the parasite in humans takes approximately 6 weeks (incubation period), when it reaches the adult and reproductive form already in its final habitat, the venous system. The release of eggs by man can remain for many years. (See cycle details)
What do you feel?
At the time of contamination an allergic skin reaction with itching and redness may occur, triggered by parasite penetration. This reaction occurs approximately 24 hours after contamination. After 4 to 8 weeks, fever, chills, headache, abdominal pain, inappetence, nausea, vomiting and dry cough appear.
The doctor examining the parasitic carrier at this stage may find the liver and spleen enlarged and lingering throughout the body (enlarged lymph nodes or lymphadenomegaly).
These signs and symptoms usually disappear within a few weeks. Depending on the amount of worms, the person may become a carrier of the parasite without any symptoms, or over the months may present symptoms of the chronic form of the disease: fatigue, colic abdominal pain with intermittent diarrhea or dysentery.
Other symptoms are due to obstruction of the spleen and liver veins with consequent enlargement of these organs and deviation of blood flow that can cause from discomfort or pain in the upper left quadrant of the abdomen to vomiting with blood by varicose veins that form in the esophagus.
How is the diagnosis made?
In order to diagnose schistosomiasis, the information that the suspect of being infected has been in an area where there are many cases of disease (endemic zone) is very important, besides the symptoms and signs described above (clinical picture). Stool and urine tests with parasite eggs or even small tissue samples from some organs (end-intestinal mucosa biopsies) are definitive. More recently, tests are available to detect the presence of antibodies against the parasite in the blood which are useful in cases of mild or no symptoms.
How is it?
The treatment of choice with antiparasitics, chemicals that are toxic to the parasite.
There are currently three groups of substances that eliminate the parasite, but the medication of choice is Oxaminiquin or Praziquantel or, which is usually taken as tablets for a day.
This is sufficient to eliminate the parasite, which also eliminates the spread of eggs in the environment. In those cases of chronic disease, complications require specific treatment.
Because it is a disease of worldwide and endemic disease in several places (Arabian Peninsula, Africa, South America and the Caribbean), public health agencies (WHO - World Health Organization - and Ministry of Health) have their own programs to control the disease. . Basically the strategies for disease control are based on:
- Identification and treatment of carriers.
- Basic sanitation (sewage and water treatment) in addition to combating the intermediate host clam
- Health education.
Do not evacuate near ponds, rivers or dams.
Use a toilet with sewerage
Health begins in the classroom