Cercariosis
Cercariosis is an acute parasitic disease that develops as a result of damage to the body by trematodes (cercariae). Cercariosis is also known as “bather’s itch”, cutaneous schistosomatosis. Cercariae are the larvae of a single species of flatworms – trematodes. When entering the body through the human skin, cercariae cause severe itching and dermatosis. Infection usually occurs if a person bathes in dirty reservoirs, urban ponds and rivers where bathing is prohibited.
ETIOLOGY AND PATHOGENESIS
The causative agent of the disease is the larvae of trematodes of the genus schistosoma. Adults of these flatworms affect the circulatory system of birds living in reservoirs.
The trematode cycle proceeds with a change of host. Intermediate is a gastropod mollusk, which just lives in reservoirs. After passing part of their life cycle, cercaria larvae leave the body of the mollusk and spread in the water column in search of their main host. Therefore, in hot weather, instead of a bird, cercaria can penetrate into human skin. However, human skin is considered too strong for a parasite larva, so cercaria dies without causing disease. However, in those places where the parasite tried to penetrate through the skin, under the influence of active substances of cercaria, the strongest local allergic reactions occur.
SYMPTOMS OF CERCARIOSIS
Skin itching appears, as a rule, 15-20 minutes after the penetration attempt. After a while (usually 1-2 hours), a rash of spots appears around the injection site, very pronounced itching, swelling is noted.
Mechanical damage to human skin by cercariae and other effects on the body have an active sensitization of the body, toxic effects – with repeated infections, symptoms appear much brighter until the appearance of papules, blisters, hemorrhages. Especially difficult are the processes in children.
Upon penetration of cercariae, lysis (destruction) of epidermal cells occurs. This can provoke the addition of a secondary infection, as well as the formation of infiltrates of leukocytes and lymphocytes.
The rash appears in places characteristic of cercaria – the lower part of the legs – on the shins, thighs, occasionally on the chest and back. Patients note that at the sites of penetration of the parasite they feel some tingling, burning. Children are more sensitive – that’s why they complain of pain, burning.
Since the disease is very severe in children, most often with the development of urticaria rash (acute urticaria). Since children cannot help scratching itchy skin, group elements often appear near the site of insertion – papules and pustules filled with serous-purulent fluid.
In a person with a normally functioning immune system, cercariae die when trying to penetrate human skin. However, doctors have registered cases of the disease with damage to internal organs – in children with weakened immunity, cercariae with blood flow spread throughout the body – so they were found in the lungs. Penetrating into the internal organs, parasites provoke the development of inflammation, hemorrhage.
DIAGNOSIS OF CERCARIOSIS
The disease is easily diagnosed in the presence of a concomitant anamnesis – the fact of bathing in a pond for some time before the symptoms appear. If the cercariae were still able to penetrate into the human body, they can be detected with the help of serological reactions. With the development of an unexplained pronounced allergic reaction in the hot season, the development of cercariosis should also be suspected.
TREATMENT OF CERCARIOSIS
Since the main symptom of cercariosis is skin itching and an allergic reaction, first of all it is necessary to deal with this symptom. The patient is prescribed antihistamines of the latest generations. To prevent the addition of secondary infection, thorough disinfection of the skin is carried out.
