Filariasis

Introduction to filariasis The disease is caused by filarial (a parasitic nematode transmitted by blood-sucking arthropods) in the lymphatic system of the vertebrate terminal host, subcutaneous tissue, abdominal cavity, chest cavity, etc., and the clinical manifestations of filariasis caused by two filamentous diseases Very similar, the acute phase is recurrent lymphangitis, lymphadenitis and fever, and the chronic phase is lymphedema and elephantiasis, which seriously endangers the health and economic development of residents in endemic areas. basic knowledge The proportion of illness: 0.003% Susceptible people: no special people Mode of transmission: insect vector transmission Complications: chyluria

Cause of filariasis

There are currently 8 species of silkworms that are known to be parasitic in humans. However, only Wuchereria bancrofti and brugia malayi are popular in China. The former is mainly transmitted by Culex pipiens. The spread of Anopheles mosquitoes is basically similar.

The pathogenesis of filariasis has not yet been fully elucidated. The occurrence and development of filariasis depends on various factors, the host's reactivity, the infected species, the degree and frequency, and the developmental stage of the worm, the habitat and Some factors have been shown to be related to the survival condition. Some experiments have shown that the larvae, adult and microfilariae and their metabolites of the silkworm are antigenic, and the body can produce specific antibodies against filarial worms. Both IgG and IgE levels are elevated. Experiments have also shown that in addition to humoral immunity, fibroin infection may involve cellular immunity. For example, sensitized animals may also develop delayed onset allergic reactions and macrophage movement in the sensitized animals. Suppress the phenomenon.

In addition, mice with excised thymus were observed to have increased susceptibility to filamentous worms, and microfilaremia appeared. It is generally believed that the acute phase of filariasis plays an important role in the metamorphosis of worms and adult worms, especially It is the secretion of larvae during infection, the female uterus secretion and the dead insects and their decomposition products can cause local and systemic allergic reactions. Late filariasis has an important relationship with the obstruction of lymphatic flow by adult filariasis, but advanced patients When a progressive elephantiasis occurs, it is often impossible to prove that there are live filaments in the host, and it is difficult to find microfilaria in the blood. The serum IgG is elevated in the patient, so whether there is any self in the pathogenesis of advanced filariasis. The existence of immune factors remains to be confirmed. The acquired immunity of the human body to the infection of the filaria can neither completely eliminate the infected worms nor prevent reinfection.

Filariasis prevention

(1) Anti-mosquito and mosquito killing

Cut off the means of transmission and eliminate mosquito breeding grounds. It is best to use mosquito nets during the mosquito season; when working outdoors, pay attention to the skin on the exposed parts such as anti-mosquito oil, mosquito repellent and other repellents. The head can be impregnated with 701 anti-mosquito net made of cotton. .

(2) census

In the summer, a census of people over 1 year old in the epidemic area requires more than 95% of the residents to receive blood collection; early detection of patients and worms, timely cure, not only to ensure the health of the people, but also to reduce and eliminate the source of infection. In the winter, the microfilariae-positive or microfilaria-negative but with a history and signs of filariasis were treated.

(3) Epidemiological surveillance

Strengthen epidemiological surveillance of areas where basic filariasis indicators have been eliminated. In the monitoring work, it should be noted that: 1 the original positive patients should be reviewed and re-examined; those who have not been tested in the past should be supplemented and supplemented; at the same time, the management of the floating population should be strengthened, and the patients should be treated promptly until they turn negative.

2 Strengthen the mosquito-borne surveillance of blood-positive households and find that infected mosquitoes, that is, focus on infected mosquitoes, expand blood tests and kill mosquitoes to surrounding people to remove epidemic spots and prevent further spread.

(4) Protect susceptible populations

In the endemic areas, the sea group raw salt therapy is used. Each kilogram of salt is mixed with seaweed 3g, with an average of 16.7g of salt per person per day, containing 50mg of sea group, which can reduce the positive rate of microfilaria in the population.

Filariasis complications Complications

The acute phase is recurrent lymphangitis, lymphadenitis and fever. The chronic phase is lymphedema and elephantiasis. In severe cases, myocarditis, lower extremity or scrotal edema, mental symptoms and even exhaustion may occur.

Symptoms of Filariasis Common Symptoms Inflammatory joints, soreness, granuloma, repeated infection, fatigue, white urine, ascites, epidermal keratinization, erysipelas, hypothermia

(1) Acute phase

1. Lymphadenitis and lymphangitis

Unscheduled periodic episodes may occur once a month or months. At the time of the attack, the patient was chilly and feverish, and the body was weak. Lymphadenitis can occur alone, and lymphangitis is usually associated with lymphadenitis. Local lymphadenopathy is painful and tender, and it disappears after 3 to 5 days. Secondary infection can form abscesses, lymphangiitis is more common in the lower limbs, often occurs on one side, or both legs can occur simultaneously or sequentially. The symptom is that there is a red line along the inner lymphatics of the thigh, which spreads from top to bottom. "Cypressive lymphangitis." When the inflammation spreads to the lymphatic vessels, the local skin appears diffuse redness and radiance, burning and burning. It is similar to erysipelas. It is called dan-like dermatitis and is commonly known as smoldering. It lasts for 2 to 3 days.

2. Filaria fever

Periodic chills, high fever, lasting 2 days to 1 week subsided. Some patients only had low fever but no chills. After repeated episodes, local symptoms gradually appeared, and those with abdominal pain were mostly caused by retroperitoneal lymphadenitis.

3. Seminal vesiculitis, epididymitis, orchitis

Common in filariasis. The patient consciously scrotum pain that spreads downward from the groin and can be radiated to the inside of the thigh. The testis and epididymis are swollen, the scrotum is red and swollen, and one or two spermatic cords can touch one or several nodular masses, which have tenderness, and the inflammation shrinks and shrinks and becomes hard. Can be accompanied by hydrocele and inguinal lymphadenopathy.

4. Pulmonary eosinophilic infiltration syndrome (pulmonary filariasis)

Caused by an allergic reaction caused by developmental immature larvae. Performance of chills, fever, cough, asthma, inflammation of the lungs, eosinophils and Charcot-Derden crystals, peripheral blood; elevated white blood cells, eosinophils (20 to 80%) ), the microfilaria in the blood is more negative. A small number of urticaria and angioedema can still occur.

(2) Chronic period

Lymph node enlargement

Lymph node enlargement is caused by inflammation and lymphatic sinus expansion in the lymph nodes, and often accompanied by centripetal lymphatic varices around the lymph nodes. Found on one or both sides of the groin and thigh, a local cystic mass, the central hard, puncture can extract lymph, sometimes can be found microfilaria, easily misdiagnosed as sputum.

2. Lymphatic varices

Lymphatic varices are common in the spermatic cord, scrotum, and inner thigh. Lymphatic varices can adhere to each other in a strip shape, which is easily confused with varicose veins. Scrotal lymphatic varices can be present in conjunction with scrotal lymph nodes.

3. Scrotal lymphoma

Due to superficial lymph nodes and lymphatic obstruction in the inguinal region, the scrotum is swollen and the epidermis is thickened like orange citrus skin. There are clear or milky white blisters. After rupture, there is lymphatic exudation or chyle leakage. Sometimes microfilaments can be found. larva.

4. Collateral effusion

More common in filariasis. One or both sides can occur. There is no obvious symptom in the light, when the effusion is long, the volume of the scrotum is increased, the shape of the scrotum is oval, the wrinkles of the skin disappear, the light transmission test is positive, and the microfilaria can be found by centrifugation of the puncture liquid.

5. chyluria

This symptom is a common symptom of plague filariasis. The location of the patient's lymphatic rupture is mostly in the kidney and the ureter. Clinically intermittent, recurrent in weeks, months or years. Before the onset, there may be asymptomatic or chills, fever, lumbar, pelvic and abdominal pain in the groin, followed by chyluria. Chyluria is easy to coagulate, can block the urethra, cause dysuria, and even have renal colic.

6. Elephant cutaneous swelling

More common in the late Malay and filariasis. It occurs about 10 years after infection. Often occurs in the lower extremities, a few found in the scrotum, penis, labia, upper limbs and breasts. Beginning with a confined solid edema, the skin becomes thicker and thicker, the skin wrinkles deepen, the skin has mossy changes, and the sacral protrusions change, which is easy to cause bacterial infection to form chronic ulcers.

Filariasis examination

(1) Laboratory inspection

1. Total number and classification of white blood cells

The total number of white blood cells is between 10 and 20 x 109 / L, and eosinophils are significantly increased.

2. Pathogen diagnosis refers to the detection of microfilariae and adults from peripheral blood, chyluria, and extract.

(1) Blood test microfilaria: the main basis for the diagnosis of filariasis. Since the microfilariae has a nighttime periodicity, the blood collection time is preferably from 9:00 pm to 2:00 am, and the positive rate is higher.

1) Smear method: take 3 drops of earlobe blood, place it on a clean glass slide, and use a corner of another slide to coat a rectangular thick blood film about 2cm long and 1.5cm wide. In the afternoon, hemolyze in water. 5~10 Minutes, to be dried, fixed staining microscopy.

2) Blood film method: Take 1 drop of earlobe blood on the slide, add a few drops of water to hemolyze, and cover the slide with low magnification. When positive, the microfilaria can be seen to swing freely, flexing and stretching.

3) Concentration method: take 2ml of venous blood, inject a 0.4ml anticoagulant test tube, add distilled water 8~10ml, hemolyze and then centrifuge to precipitate, pour the liquid, add N/20 sodium oxychloride 8~10ml, mix Place it for 5 to 10 minutes, centrifuge, discard the liquid, and take a sedimentation microscopy. The positive rate of this method is high.

4) Daytime trapping method: 100mg of oral sea group was taken during the day, and blood was taken at 15, 30, 60 minutes.

(2) chyluria and lymphatic urine examination: chyluria should be added with ether (5ml urine + 2ml ether) in a test tube, the fat is dissolved, the ether is discarded, diluted with water and centrifuged. Lymphatic urine is easy to coagulate, anticoagulant should be added first, then directly smear or diluted with water 10 times centrifugal microscopy.

(3) Body fluid and urine examination Microfilaria: Microfilariae can also be found in various body fluids and urine, so microfilaria can be found in hydrocele, lymph, ascites, chyluria and urine. Direct smear of the above body fluids may be taken, staining microscopic examination; or by centrifugation concentration method, membrane filtration concentration method and the like. The liquid containing chyle can be added with ether to fully dissolve the fat, remove the fat layer above, dilute with water 10 times, centrifuge at 1500-2000 rpm for 3 to 5 minutes, and take a sediment microscopy.

(4) biopsy blood microfilaria examination negative patients may take subcutaneous nodules, superficial lymph nodes, epididymal nodules and other disease tissue biopsy to determine the diagnosis.

(2) Immunodiagnosis can be used as an auxiliary diagnosis for the detection of filarial antibodies and antigens in serum, including intradermal tests, indirect immunofluorescent antibody tests, complement fixation tests, enzyme-linked immunosorbent assays, and the like. Specificity is limited due to cross-reactivity with other nematodes.

Diagnosis and identification of filariasis

(1) Filaria chyluria is a lesion caused by urinary and abdominal lymphatic obstruction in patients with filariasis. Need to be identified with tuberculosis and tumor-causing.

(2) Lymphadenitis and lymphadenitis of filariasis are usually caused by adult colonies in the lymph nodes, and are more common in the groin, axillary fossa and axillary fossa. Should be identified with bacterial lymphangitis.

(3) Filaria epididymitis and orchitis are mainly found in filariasis. The patient consciously scrotum pain that spreads downward from the groin and can be radiated to the inside of the thigh. The testis and epididymis are enlarged. The hydrocele refers to an increase in the size of the scrotum, which is oval-shaped and the skin wrinkles disappear. Both should be differentiated from tuberculosis.

(4) The elephantiasis begins to have a confined solid edema. The skin becomes thicker and thicker, the skin wrinkles deepen, the skin has mossy changes, and the verrucous changes. It is easy to cause bacterial infection to form chronic ulcers. It should be differentiated from local lesions, tumor compression, and elephantiasis caused by surgical removal of lymphoid tissue.

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