What Is Lymphatic Filariasis?

Lymphatic filariasis is caused by Bannella, Malay, and Timorian filariasis. Its clinical features are mainly acute tuberculitis and lymphadenitis, and chronic tuberculosis and a series of symptoms. There are also those who have no obvious symptoms and only have microfilariae in their blood, which is called "filariasis infection". The microfilaria of these types of filamentous worms all have stricter characteristics of appearing in the peripheral blood flow at night.

Basic Information

Visiting department

Internal medicine

Common causes

Caused by Bann, Malay and Timorian filariasis

Common symptoms

Lymphadenitis and lymphangitis, erysipelasoid dermatitis, filariasis fever periodic fever, spermatic cord inflammation, epididymitis, orchitis

Causes of lymphatic filariasis

Adult

Milky white slender as a thread, slightly pointed at both ends, smooth surface, androgynous, but often tangled together. The body length of the male F. banneri is 28-42 mm, and the width is about 0.1 mm. The length and width of the female is about twice that of the male. Malayan filariasis is shorter. The morphology and internal structure of the females of F. banneri and M. filaria are almost identical, and the differences between males are also very small. The main difference is that there are 8 to 10 pairs of papillae on both sides of the anal fora of Ban males, and one or two pairs of papillae are sometimes seen between the anal foramen and the tail end. There are only four pairs of papillae on the side, one pair behind the anal foramen, and no mastoid between the ends of the anal foramen. There are many similarities in the ultrastructure of various filamentous worms. The corneal cortex, cord and cord mesothelial layer, body wall muscle layer, etc. can be seen in the ultrastructure of the body wall of the adult worms of Malay and Banelliella. The worm has an extensive basement membrane system that separates all structures from the prosthetic cavity. Adult life expectancy is estimated to be 10 to 15 years.

2. Microfilament

Viviparous, mainly in the peripheral blood, swimming like a snake. Banfil microfilariae is about 280m long and 7µm wide. Malay microfilaments are shorter and thinner than Banfil microfilaments. Under the light microscope, it can be seen that the microfilament is slender, the head is blunt, the tail is sharp, the outer sheath is sheathed, and the body has a round body nucleus. The nerve ring is located 1/5 of the front of the worm, followed by excretory holes, excretory cells. There are four cells in the back of the worm, G, R2, R3 and R4. There is an anal fora on the ventral side, and the tail nucleus is located at the tail. The morphology of Bansley and Malayan silkworms are significantly different. The ultrastructure of microfilariae is basically the same as that seen under light microscopy, and the body wall is similar to that of adult worms, including multi-membrane keratoderma, dorsal, ventral and lateral cords, subcutaneous layer and muscle cells, etc. Undifferentiated prosthetic cavity. The life span of microfilariae can live in the human body for 2 to 3 months, even up to 3 years. Microfilariae filariae can live in laboratory animals for more than 9 months.

3. Life history

The life history of Bann and Malaria includes two different stages: one stage occurs in the insect (mosquito) host body, the intermediate host, and the other stage in the human body, the final host.

(1) When a mosquito bites a microfilariae-positive patient in the mosquito , the microfilariae in the blood is sucked into the mosquito stomach for about 2 to 7 hours. The molting sheath passes through the stomach wall through the abdominal cavity and enters the pectoral muscles. After reaching the pectoral muscles, development can begin After 6 to 14 days of peeling, it becomes the third stage or infectious stage larva. After mature, it leaves the pectoral muscle and migrates to the lower lip of the mosquito kiss. It enters the human body when the mosquito sucks blood.

(2) After the larvae invaded the human body, some larvae die or are destroyed during migration and development in the tissues. Some larvae reach the lymphatic vessels or lymph nodes and develop into adults. Adults of B. banneri usually reside in the deep and superficial lymphatic system of the abdominal cavity, spermatic cord, and lower limbs; adult Malays often reside in the superficial lymphatic system of lower extremities. It takes 8 to 12 months for the filamentous worm to infiltrate the human body until the microfilariae appear in the peripheral blood. Malafilariasis takes 3 to 4 months.

Clinical manifestations of lymphatic filariasis

The incubation period of this disease is about one year from the invasion of larvae to the body and the discovery of microfilariae in the blood, but it can be as early as 4 months or as late as 1.5 years. Timorian filariasis incubation period is 3 months. From the early examination of human lymph nodes, it was found that the adults of F. banqueeri were 3 months after infection. The clinical manifestations of filariasis vary, with 50% to 75% of "asymptomatic" infections in endemic areas. Malaria filariasis is mainly parasitic in the superficial lymphatic system, so lymphangiitis and elephantiasis of the limbs are most obvious. Fimbria banseri is not only parasitic in the lymphatics of the extremities, but also in the urinary and reproductive organs of the deep lymphatic system, causing inflammation and nodules of the spermatic cord, epididymis testis, and scrotum. Reproductive system lesions have not been proven in patients with simple male filariasis. Timor's filariasis is similar to the clinical manifestations of male filariasis. The acute phase is recurrent lymphangitis, lymphadenitis, and fever; the chronic phase is lymphedema and elephantiasis.

Acute phase

The prominent symptoms of this period are lymphadenitis, lymphangitis, filariasis, and spermatitis, which are characterized by periodic attacks, occurring every 2 to 4 weeks or once every few months. Each episode is usually after exercise or fatigue. Occasionally, occasional seizures are also seen. There are more attacks in summer and autumn than in other seasons.

(1) Lymphadenitis and lymphangitis can occur independently, but often occur simultaneously with lymphangitis, and the common parts are the groin, femur, posterior elbow, and underarms. However, deep areas such as the abdominal cavity and pelvic cavity can also be invaded, and clinically common cases are limb lymphadenitis, especially the lower extremity inguinal and femoral areas with the most frequent recurrent episodes and accompanied by retrograde lymphangitis as its characteristics. In addition, the local lymph nodes are swollen and painful, and the degree of swelling is related to the severity of the infection.

Lymphangiitis is a common symptom of filariasis. It is more common in Malay than Bann s, and it is more common in the limbs. The lower limbs are far more than the upper limbs. They can be accompanied by fever at each episode, mostly between 38 and 39 ° C. Retreat within 1 to 3 days, a few can reach more than 10 days. Concomitant symptoms include headache, muscle and joint pain, and chills. Top-down, centrifugal "red lines", which are often referred to as retrograde lymphangitis, are often found in the skin of the affected area. They generally have pain, tenderness, and localized heat, but they are not as severe as those with bacterial properties. The most prominent feature of Timor's filariasis is the scarring of the skin after acute lymphadenitis suppuration.

(2) Erysipelas dermatitis is caused by intradermal microlymphangiitis, which is often secondary to lymphadenitis and lymphangitis, and can also occur separately. Because the skin was red and swollen at the time of the onset, it looked like erysipelas, so it was called erysipelas-like dermatitis, commonly known as "liuhuo", often accompanied by fever, and its heat was related to the severity of the attack. The duration of each episode is generally longer than that of lymphadenitis and lymphangitis.

(3) Periodic fever of filamentous worms sometimes starts with chills, body temperature can reach 40 ° C, and retreats after 2 to 3 days, which can also last up to 1 week. Some only have low fever, no chills, no local lymphangiitis or lymphadenitis visible, and sometimes with abdominal pain. Such attacks may be caused by deep lymphadenitis and lymphangitis.

(4) Spermatiditis, epididymitis, and orchitis are adult worms living in spermatic cord, epididymis, and testis adjacent to the lymph vessels, causing lymphangiitis and interstitial inflammation. Presented with fever, pain in one side of the scrotum, which can spread from the groin down into the scrotum, and can radiate to the inner thigh, and some cases show colic. In addition to local epididymitis and testicular enlargement, the main examination is a nodular mass of spermatic cord, which has obvious tenderness. After a few days, the local inflammation subsided, the mass became smaller and harder, and it could be recurred. The local mass also appeared. It gradually increases with each attack. Because filariasis rarely causes lesions in the vas deferens and sperm are still present in the semen, filariasis in the scrotum rarely causes infertility.

(5) Pulmonary eosinophilic infiltration is mainly manifested by chills, fever, cough, asthma, and migratory cell infiltration in the lungs; eosinophils and Charco-Lyden crystals are mostly present in the sputum, and in peripheral blood The total number of white blood cells can be as high as 40 × 10 / L, and eosinophils increase, ranging from 20% to 30%. Most microfilariae in the blood were negative, anti-microfilament antibody titers were high, and IgE levels were high. Treatment with ethiazine is effective, not only the symptoms are relieved, but also nodules caused by the death of adults; other symptoms include urticaria and angioedema. Some people think that this disease is a kind of "hidden filariasis". The host's immune system can quickly clear the blood microfilariae, so it is difficult to find the pathogen in the blood, but the lungs can often find the microfilament accumulation of eosinophilic acid. Granulocyte foci. It is speculated that the pathogen of this disease is mainly caused by non-human filariasis.

Chronic phase

Due to repeated inflammation, the lymph nodes and lymphatic vessels are eventually blocked by the proliferating granulation tissue and fibrous tissue, resulting in clinical symptoms and signs.

(1) Lymph nodes and varicose veins Lymph node varicose veins refer to concentric lymphatic varicose veins and lymphatic sinus dilatation of lymph nodes, which are common in the groin and femoral side, on one or both sides. When palpated, there is stiffness Nuclear sensation. Lymphatic varicose veins are common in the spermatic cord, scrotum, and inner thighs, and occasionally in the upper limbs. Varicocele can have varicose veins, and scrotal lymphatics can coexist with lymphatic scrotum. Lymphatic varicose veins can also occur in the deep, and it has been reported that angulated thoracic ducts are 1.5 cm in diameter.

(2) Hydrocele, lymphuria, and lymphatic ascites are caused by obstruction of spermatic cord and testicular lymphatics, and lymph fluid flows into the sheath cavity. The scrotum skin and subcutaneous tissue often edema due to obstruction of lymphatic fluid return, forming scrotal lymphatic fluid. Those with mild hydrothorax are asymptomatic, and those with more hydrophlegm have severe drooping or even difficulty walking. The volume of the scrotum was increased during the examination. The mass was often pear-shaped, the scrotal skin was tense, the wrinkles disappeared, the penis contracted, and the light transmission test was often positive. If the sheath is extremely thick and accompanied by a scrotal elephantia, the light transmission test is negative.

(3) Chyluria, chylous effusion, chylous ascites, chylous diarrhea, chyluria is one of the common symptoms of advanced filariasis, and its incidence is about 2%. The incidence of young adults accounts for 78.3% ; The shortest course of several days can be up to 54 years, the most 25 years. Lymphatic rupture sites in patients with chyluria are common in the calyx and ureter, but not in the bladder.

(4) Elephantiasis Elephantiasis is the most common symptom of two types of filariasis in the late stages, which occurs about 10 years after infection. The site of occurrence varies depending on the site of lymphatic obstruction. Occurrence sites are limbs, scrotum, penis, labia, clitoris and breast. The most common site is the lower extremity.

(5) Other ocular filariasis is extremely rare, and can cause microfilariae in the eye, which can cause iridocyclitis, keratitis, retinal hemorrhage, optic nerve atrophy, increased intraocular pressure, and turbid aqueous humor.

Lymphatic filariasis examination

1. White blood cell count and classification

Patients with early allergic reactions increased the total number of white blood cells and eosinophils. The former was mostly between (10-20) × 10 / L, and the latter was above 20%. If there are secondary infections of bacteria, in addition to the increase in the total number of white blood cells, neutrophils also increase significantly.

2. The discovery of blood microfilaria

The diagnosis of filariasis relies on the discovery of microfilariae. Peripheral blood tests are usually used. Most of them are most easily found from 10 am to 2 am. If the blood is more than 150/60 l at night, it can be found during the day. turn up.

(1) Fresh blood method: Use a hemoglobin meter pipette to draw 20 l of earlobe blood, and look for microfilariae under a low-power microscope. Positive people can see the microfilariae swing freely, curl back and forth, and are quite active.

(2) Smear method: Three large drops of blood (approximately 60 l) are collected from the earlobe and placed in the center of the slide. They are coated with rectangular or oval thick blood slices with uniform thickness and uniform edges. It is specified as 120 l, which is a six-drop large two-plate method. Dyeing can use blue or borax methylene blue dyeing methods such as identification of insect species can be used with Giemsa or hematoxylin staining. The fluorescent acridine orange staining method can also improve the detection rate of microfilariae.

(3) Concentration method Many microfilariae are concentrated by dissolving red blood cells in the blood, and centrifuging the sediment to suck up the sediment to find the microfilament concentrated in the sediment. A commonly used hemolytic agent is distilled water.

(4) Microporous membrane filtration method Use a 10ml syringe containing 5% sodium citrate 0.1ml to draw 1m1 of blood and mix thoroughly, and then suck 9ml of 10% teepol solution (or 2% Tween 80 solution or 0.1% sodium bicarbonate solution) Mix the hemolysis, connect the syringe to a 25mm diameter 5m pore size microporous membrane filter, filter the hemolyzed blood through the membrane, and retain the microfilaments on the membrane. Remove the membrane and stain with 0.1% hematoxylin or 0.1% methylene blue. Microscopy.

(5) Microfilariae daytime induction method Microfilariae can be found in the peripheral blood within 1 hour after oral administration of 100 mg of acetazine during the day . This method should not be used as a method for census of filariasis. Examination in the clinic can be used as a reference.

3. Examination of various body fluid microfilaments

Examination of microfilariae in fluids such as hydrocele, chyluria, lymph or chyloascites, pericardial effusion, anterior aqueous humor, etc., can be performed by direct smear, staining microscopy, or centrifugal concentration method

4. Immunological diagnosis

Common immunological diagnostic methods at home and abroad are:

(1) Intradermal test: 0.05ml of Candida filariae antigen was injected into the skin of the subject's forearm, and the papules exceeding 0.9cm were positive after 15min. The rate of coincidence with the signs of filariasis patients in this test was 73.6% to 96.6%, and the rate of coincidence with microfilariae in the blood was 86.2% to 94.1%. However, mild cross-reactions with schistosomiasis can occur. And the value of auxiliary diagnosis should not be used for monitoring in the later stage of prevention and control.

(2) Indirect immunofluorescent antibody test The adult and microfilariae collected from animal models such as gerbils are used as antigens. The fluorescent antibody uses goat anti-human IgG fluorescent antibody conjugate, which is highly sensitive and specific. Adult worm sections were used as antigens with a sensitivity of 92% to 98% and specificity was 95%; using microfilariae sections as antigens had a sensitivity of 92% to 96% and specificity of 98%. This method can be used as auxiliary diagnosis of filariasis and seroepidemiological investigation and on-site monitoring. Disadvantages are still that they cannot be used for efficacy evaluation and distinguish patients from previous infections or active infections.

(3) Enzyme-linked immunosorbent assay (ELISA) uses soluble antigens such as Malaria filariasis, F. canis, finger-shaped abdominal worms, and microfilariae, and ELISA measures antibodies. The positive agreement rate with filariasis patients is 85. % To 100%, false positive response was 1.5% to 8.2%. The positive coincidence rate of microfilariae or adult ES antigens against microfilariae was 93% to 95%, and healthy people in non-endemic areas and those infected with intestinal nematodes were negative. This method is used to detect human filariasis antibodies and has high specificity and sensitivity. It is suitable for on-site investigations. This method cannot be used to evaluate the efficacy and distinguish whether patients are active infections.

(4) Detection of circulating antigens WHO recommends the use of immunochromatographic technology (ICT) test cards to detect B. filariasis antigens. It has been reported that the sensitivity is 90% to 98% and the specificity is 99% to 100%.

Monoclonal antibody enzyme-linked immunosorbent assay (McAbELISA) and dot enzyme-linked assay (Dot-ELISA) were used to detect antigens in sera of patients with filariasis, with specificities of 94% and 96%, respectively. L antigen, while McAbELISA can only detect 10 g / L antigen. Both can detect active infections as a late surveillance of filariasis control, search for residual infection sources, and evaluate control effects.

5.Molecular hybridization and DNA recombination technology

Gene cloning and DNA technology are currently used in the diagnosis of filariasis, with high sensitivity and specificity.

6. Chyluria and Lymphuria

Chyluria and lymphuria, the former is milky white, can be extracted with ether, stained with Sudan III, and the macroscopic examination of red-yellow oil-spot lymphatic urine under normal microscope is no different from normal urine. Its content is mainly protein and there are a few red blood cells. Tubeless. The chylous fluid and lymph fluid obtained from the puncture of the sheath fluid are approximately the same as chyluria and lymphatic urine, and active microfilariae can be found in the sediment.

7. Biopsy

The suspected diseased tissues, such as the superficial lymph nodes and epididymal nodules of the lower limbs, are cut into small pieces for pathological examination, and adult and visible pathological changes can be found.

8. Other auxiliary inspections

Lymphangiography: Patients with filariasis often show dilated input lymphatics and narrow output lymphatics, and the parenchymal lymph nodes have defects.

Lymphatic filariasis diagnosis

1. Epidemiology and clinical diagnosis

Filariasis must be combined with an epidemiological history. The majority of patients in endemic areas in China are farmers. Lymphangiitis, lymphadenitis, and dermatose-based disease are characterized by people from endemic areas who suffer from spermatic corditis, orchitis, and chyluria, mostly filariasis.

2. Laboratory diagnosis

Mainly look for microfilariae in peripheral blood. A diagnosis of microfilariae can be established in the blood.

3. Therapeutic diagnosis

The purpose of this method is to diagnose patients with suspicious filariasis symptoms and signs, but no microfilariae in the blood. After taking ethamazine, some patients can develop lymphatic reactions and lymphatic nodules within 2 to 14 days. This is evidence that the drug is acting on adult worms. If necessary, the nodules can be removed to look for worms.

4. Lymphangiography

Patients with filariasis often show dilated input lymphatic vessels and narrow output lymphatic vessels, and the parenchymal lymph nodes have defects.

Lymphatic filariasis treatment

Pathogen treatment

(1) Ethylazine is ethanazine citrate (hetrazan). This product has no direct killing effect on microfilariae in vitro, but it can quickly clear the blood of people or animals infected with filariasis. Microfilament. The effect on Malayalam is faster than that of Bancella, and it can also kill adult worms when using larger doses or longer courses. After three courses of intermittent medication, the conversion rate of microfilament yin and yin can reach 90% -99.8%, and Malayan 96.3% -100%. The incidence of nodules is 30% -40%, and above 50.

(2) Furanone synthesized in China in 1979 against filariasis. It has a significant killing effect on adult worms and microfilariae, with side effects similar to those of ethamazine. This product is an enteric-coated tablet, and it can be taken for 7 days as a course of treatment.

(3) Ivermectin can effectively remove Bancroft's microfilariae, single-dose or two-day oral administration has a better effect on removing Bancroft's microfilariae than ethamizine, but the duration of the effect varies according to different reports. It has a poor effect on Malay microfilariae, with adverse reactions such as headache, fever and anorexia.

Symptomatic treatment

(1) The treatment of lymphangitis, lymphadenitis, spermatic corditis, and orchitis can refer to the local reactions during the treatment of ketamine. Patients with severe symptoms should rest in bed and raise lower limb prednisone or compound acetylsalicylic acid (Compound Aspirin) can also be applied. If there is a secondary infection of bacteria, antibacterial drugs should be applied.

(2) Treatment of elephantiasis The treatment of elephantiasis of the lower limbs can be treated by drying and bundling. The affected limb is radiated with heat or microwave. Bandaged with elastic bandages after drying, 1 time / day, the former 1 hour / time, 20 times as a course, rest for half a month, and the next course; the latter 30 minutes / time, 15 times as a course, rest 2 Month, proceed to the next course. During the day of bake therapy and rest, the affected limb should be continuously bandaged with elastic bandages for 2 to 3 courses of treatment. Patients with tinea pedis are treated with antifungals to control infection. Combined with the low-dose long-term course of acetazine treatment while curing the bundling therapy, the outbreak of fire can be stopped. For a small number of giant lower extremity elephantiasis, a large-scale full skin graft can be used and pressure bandaging.

(3) Treatment of chyluria. When chyluria is first developed, supine rest, abdominal pressure bands, and elevation of the pelvis to reduce lymphatic pressure may cause the closed channels to be formed. Patients need to drink more water or light tea to limit fat and Protein diet. Medium chain oil (medium carbon chain triglyceride, MCT) can be used to replace common edible oils. Those who still have chyluria after a long period of rest or medical treatment can consider 1% to 2% silver nitrate infusion or surgical treatment. If there is chyluria, hemostatic drugs can be used.

(4) At present , the treatment of hydrocele is mostly surgical, with satisfactory results. Generally, 1 to 2 courses of 3 g of ethamazine should be given as a pathogen treatment.