Schistosoma cercariae dermatitis

Introduction to Schistosoma cercariae dermatitis Schistosomiasis cercaria dermatitis refers to an allergic inflammation caused by the intrusion of the cercariae of poultry and animal schistosomiasis into human skin. Because it often occurs during rice planting, it is also called rice dermatitis. In many countries, it often occurs after swimming in a freshwater lake or a brackish sea, so it is called itchy, and the Japanese call it a lakeshore disease. In China, from the northeast to Guangdong, from the eastern coast to the southwest, the disease is seen in rice growing areas. There are many types of schistosomiasis that can cause this disease, but in China, it is mainly parasitic worms of the genus Diptera in the ducks and the cercariae of the worms of the genus Dioscorea in the cattle and sheep. Since humans are not suitable hosts for these schistosomiasis, the cercaria can be killed in local tissues after drilling into the skin, and cannot survive even if it enters the bloodstream to the lungs. The proteases secreted by the cercariae and the proteins and polysaccharides released after the death of the cercariae are antigenic, which can cause allergic reactions and cause dermatitis. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific population Mode of infection: non-infectious Complications: acute lymphadenitis

The cause of cercariae cercariae dermatitis

[cause]

Schistosomiasis cercaria dermatitis is caused by the cercariae of Schistosoma japonicum that is parasitic on mammals, birds and birds.

[Pathogenesis]

The cercaria cercariae invade the epidermis for the first time, and can also enter the dermis. The secreted products of the cercariae and the cleavage products of the cercariae have strong antigenicity, causing immediate allergic reactions, causing cell growth, cell infiltration, hair follicles, and edema around the sebaceous glands. There are small blisters in the epidermis, lymphocytes in the cells, infiltration of eosinophils, necrosis of the epidermis of the blisters, such as secondary infection can form epidermal abscess, such as repeated infection, immune response is more intense, local lesions appear earlier and more intense.

Schistosomiasis cercaria dermatitis prevention

How to prevent schistosomiasis cercaria dermatitis after flood

After the flood, the water source in the infected area is polluted, and the cercaria cercariae are flooded. Once these tail scorpions are drilled into the human body, the skin will cause local inflammation. Generally, it can be ill 10 to 30 minutes after the water is launched. The part is immersed in the water, the calf, the tread, the forearm. More common, more itch, followed by miliary papules, erythema, developed into mung beans up to a large red papule or pityriasis after a few hours, surrounded by red faint, top insect bites, very itchy.

Prevention of this disease is mainly for personal protection, before the water, local can be rubbed dibutyl phthalate emulsion, 20% rosin alcohol, etc., treatment to relieve itching, anti-inflammatory, prevention of secondary infections, can be used externally Stone powder lotion, 1% - 3% camphor alcohol, systemic treatment can be taken orally anti-allergic drugs.

Schistosomiasis cerebral dermatitis complications Complications acute lymphadenitis

After itching, every infection caused by skin rupture and erosion, a few people have fever, swollen lymph nodes.

Schistosomiasis cercaria dermatitis symptoms common symptoms skin bleeding spots fever skin atrophy and pigmentation

The disease mostly occurs in the skin area that is in contact with the water surface, and is related to the habit of the tail owl often on the water surface. The dermatitis that occurs in the rice field labor mainly occurs in the two calves, the two forearms, the back of the hand, and the back of the foot. After the skin is in contact with the effluent containing cercaria, itching occurs within a few minutes or hours, followed by erythema and harder and harder pimples, with obvious redness around it; in severe cases, the papules expand and merge into a mass of blisters, even forming blisters. . Then, the symptoms gradually subsided and dislocated. If the affected part is smashed, it may be infected or eroded. If repeated exposure to the infected water is infected by the cercaria, the symptoms of dermatitis become more serious. In general, the symptoms of dermatitis caused by Schistosoma japonicum cercariae are more pronounced and more severe than those caused by Schistosoma japonicum.

Examination of cercariae cercaria dermatitis

Immunological examination: the value of auxiliary diagnosis, the intradermal test, the cerebral aponeurosis test, the ring egg precipitation test is more specific and more applied. Generally, such methods are not based on the diagnosis.

(1) Intradermal test: Intraperior arm intradermal injection of 0.03 ml of liver egg antigen adult antigen as a papule with a diameter of about 0.5 cm. After 15 minutes, the diameter of the wheal group is 0.8 cm or more, and a few patients can be in the latent period and the early stage of the disease. Positive, most patients were positive at 8 weeks after infection, the positive rate was generally above 95%, occasionally false positive reaction, skin test has reference value for diagnosis, can not be used as a standard of efficacy evaluation.

(2) cerebral palpebral membrane test: take 1 to 2 drops of patient serum on the slide, add 5 to 10 live or freeze-dried cercariae cercariae, add 2 to 3 drops of normal saline, mix, set 37 ° C incubator, 3 After ~4 hours, microscopic examination showed that there was a membrane formation around the cercariae, the positive rate was 95%, and there was a positive reaction 7 to 12 days after infection. There were few false positive reactions, which had early diagnostic value due to paragonimiasis and The Chinese clonorchiasis has a cross-reaction, and because of the difficulty in supplying the cercaria, it is not easy to promote.

(3) Ring egg sedimentation test: Take a drop of live egg suspension on a sterile glass slide, add the patient's serum to the same amount, add a cover glass paraffin seal, and incubate at 37 ° C for 24 to 48 hours, observe under low magnification microscope. It can be seen that there are spherical, finger-like, filamentous, chrysanthemum-like precipitates around the eggs, and 100 mature eggs are observed. The percentage of eggs with a sediment greater than 10um is calculated. Positive, 7 to 12 days after infection, the positive rate is over 95%, with early diagnosis value.

(4) Indirect hemagglutination test: The sera of sputum egg antigen-sensitized red blood cells are used to determine the antibody in the serum of patients, and the agglutination is positive, the specificity and sensitivity are high, the positive rate is above 90%, the observation result is fast, and the blood volume is small. And easy to operate, this test has a cross-reaction with paragonimiasis.

(5) Enzyme-linked immunosorbent assay (ELISA): the combination of purified adult or egg antigen with peroxidase or alkaline phosphatase, determination of serogroup antibodies in serum or urine of patients, high sensitivity and specificity, positive rate More than 95%, easy to operate, suitable for large-scale field use.

(6) Enzyme-linked immunosorbent assay: After peroxidase labeling and purification of egg antigen, convective immunoelectrophoresis was performed to detect serum-specific antibodies, which were reported in 1/2 to 1 hour, and the positive rate was over 80%.

(7) Determination of circulating antigen: Circulating antigen is a specific antigenic substance present in the blood and urine of patients, and circulating antigen is positive, indicating that there is live schistosomiasis infection in the host, which has the value of evaluating the efficacy of the drug.

Diagnosis and identification of cercariae cercaria dermatitis

Otitis dermatitis needs to be differentiated from rice dermatitis. Rice dermatitis is caused by the parasitic cercariae of the animal in the portal vein of animals such as cattle, sheep and ducks. It is more common in the southeast, northeast and southwestern provinces of China. The host ovulates into the water and hatches the edulis. Into the cone, the snail enters the snail, and the snail escapes immediately after the human touches the cercaria, causing dermatitis. The dermatitis is red at the beginning, gradually expanding into a red papule. The rash subsides after one week, and the cercaria is eliminated. Develop again.

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