During the Sui and Tang Dynasties in China (AD 58 1-907), ancient books recorded that "gaskin's feet were red and swollen, with cold and heat like typhoid fever, once every two months from now on or January". The spread of "Filariasis" and "Bigfoot Wind" among the people shows that this disease has been prevalent in China for a long time.
The clinical features are mainly lymphangitis and lymphadenitis in the early stage, and lymphatic obstruction and its series of symptoms in the late stage.
[etiology]
There are 8 species of filariasis parasitic on human body in the world, and only spotted filariasis and Malay filariasis are prevalent in China. The adults of Banji and Filaria malayi are similar in morphology, slender as a line, milky white, smooth in surface and hermaphrodite. The male body length is 28.2 ~ 42 mm, the male body length is 20 ~ 28 mm, and the two females are about twice as long as the males. Male and female adults are often intertwined and parasitic in lymphatic vessels and lymph nodes. The service life can be as long as 12 years or longer. Female viviparous larvae are filamentous and called microfilaria. Microfilaria punctata is about 280μm long and 7 μ m wide. Microfilaria malayi is shorter and thinner than microfilaria banji. After microfilaria enters the blood circulation from the lymphatic system, it mostly hides in the microvascular system of the lung during the day and enters the surrounding blood circulation at night, which has obvious nighttime periodicity. Usually microfilaria malayi is from 8 pm to 4 am, and microfilaria bancrofti is from 10 pm to 2 am. The mechanism of microfilaria periodicity is not completely clear, and there are several explanations: ① When people sleep, the vagus nerve is excited, the pulmonary microvascular dilates, and microfilaria enters the surrounding blood in large quantities from the lungs; ② Changes of partial pressure of oxygen in lung and peripheral blood can change the periodicity of microfilaria. Inhale O2 to patients at night, increase the oxygen partial pressure of blood, and the number of microfilaria in peripheral blood will decrease. ③ It is related to the autofluorescence particles in microfilaria. Where microfilaria contains many fluorescent particles, its periodicity at night is obvious, and vice versa.
The life history of filaria malayi and banyan trees can be divided into two stages: one stage is in mosquitoes (intermediate hosts); The other stage is in humans (the ultimate host).
(1) When a female mosquito bites a patient with microfilaria positive in the mosquito, microfilaria is inhaled into the mosquito's stomach. 1 ~ 7 hours later, it comes out of the sheath, passes through the stomach wall and enters the pectoral muscle through the abdominal cavity. After about 1 ~ 3 weeks, it develops into an infectious larva, leaves the pectoral muscle, moves to the mosquito's lower lip, and then invades the human body when biting people.
(2) After the larvae invaded the human body during the infection period, some larvae died during the migration and development in the tissue, some larvae reached lymphatic vessels or lymph nodes, developed into adults after 8 ~ 12 months, and produced microfilaria after mating.
Pathogenesis principle
The incidence and pathological changes of filariasis are mainly caused by adults and infected larvae. Infected larvae invade the human body through mosquito bites, and develop into adults, larvae and adult metabolites and female uterine secretions in the lymphatic system, causing systemic allergic reactions and local lymphatic system tissue reactions. It is characterized by acute filariasis, lymphadenitis and lymphangitis. Repeated inflammation of the lymphatic system leads to chronic lymphatic obstruction, lymphatic varicose veins, chyluria, elephantiasis and other symptoms.
[epidemiology]
Spotted filariasis is widely distributed, but mainly in Asia. Malayan filariasis is endemic only in Asia. It is distributed in Shandong, Henan, Jiangsu, Shanghai, Zhejiang, Anhui, Hubei, Hunan, Jiangxi, Fujian, Taiwan Province, Guizhou, Sichuan, Guangdong and Guangxi. Bancroftian filariasis is endemic in Shandong, Guangdong and Taiwan Province provinces, but it is found in other provinces (cities, autonomous regions). After liberation, due to the general survey and treatment, the infection rate of this disease decreased obviously.
(1) microfilaria patients are the main source of infection. Filariasis malayi can also parasitize cats, dogs, monkeys and other mammals, and may become the source of animal infection.
(2) The route of transmission is through female mosquito bites. The main vectors of spotted filariasis are Culex pipiens pallens and Culex pipiens quinquefasciatus, while Anopheles sinensis is the main vector of Malay filariasis.
(3) Susceptible people are generally susceptible. There is no significant difference in incidence between men and women. 20-25 years old has the highest infection rate and incidence rate, and there are very few people under 1 year old. After illness, the immunity is low, and the infection is often repeated.
(4) The epidemic season of filariasis is from May to 10. In the warm south, it can be infected all year round.
[Pathogenesis and pathological changes]
The incidence and pathological changes of filariasis are mainly caused by adults and infected larvae. Infected larvae invade the human body through mosquito bites, and develop into adults, larvae and adult metabolites and female uterine secretions in the lymphatic system, causing systemic allergic reactions and local lymphatic system tissue reactions. It is characterized by acute filariasis, lymphadenitis and lymphangitis. Due to the repeated inflammation of lymphatic system, the occurrence and development of filariasis, such as chronic lymphatic obstruction, lymphatic varicose veins, chyluria and elephantiasis, depend on the species of filariasis, parasitic parts, the number of larvae invading and the reactivity of the body. Filariasis malayi mainly lives in the superficial lymphatic system of limbs, so the symptoms of limbs are more common; Filariasis mainly occurs in abdominal cavity, spermatic cord and deep lymphatic system of lower limbs, which often leads to urinary system symptoms. The pathological changes of filariasis are in lymphatic vessels and lymph nodes, which are caused by mechanical stimulation of adults or chemical stimulation of decomposition products of worms after death. The acute stage showed exudative inflammation, congestion of lymph nodes, edema of lymph wall, eosinophil infiltration and fibrin deposition. Lymphatic vessels and lymph nodes gradually developed proliferative granuloma reaction. The center of granulation is denatured adults and eosinophils, surrounded by fibrous tissue and epithelioid cells, and a large number of lymphocytes and plasma cells gather to form tuberculous nodules. The chronic stage is characterized by a large number of fibrous tissue hyperplasia, worm calcification, lymph node sclerosis, lymphatic fibrosis and occlusive lymphangitis. Obstruction of lymphatic vessels can increase the internal pressure of distal lymphatic vessels, leading to expansion and rupture of lymphatic vessels, lymphatic stagnation and increase of protein components in lymphatic vessels. The blockage is located under the skin, and lymph constantly stimulates the tissue, which makes a large number of fibrous tissues proliferate, and the subcutaneous tissue thickens, thickens, wrinkles and hardens to form elephantiasis. If the obstruction is located in the deep lymphatic system, there will be scrotal elephantiasis, lymphatic ascites, chylous diarrhea and chyluria. Because of local blood circulation disorder, it is easy to cause secondary infection, aggravate elephantiasis and even form ulcers.
[Clinical manifestations]
After being infected with filariasis, it usually takes 5 months to 1 year to get sick. At the initial stage of the disease, the main manifestations are local lymphadenopathy, pain and lymphangitis, and there is a local red line extending from the proximal end to the distal end of the limb, especially in the thigh. At the same time, it may be accompanied by systemic symptoms, such as chills, fever, loss of appetite, muscle and joint pain. When abdominal lymphangitis occurs, acute abdominal pain accompanied by deep tenderness may occur. In addition, symptoms such as swelling of spermatic cord and bone pill and scrotal pain may occur. The recurrence of the above symptoms will aggravate the condition. Pain often occurs in the waist, pelvis and groin; The urine is milky white, that is, "chyluria". The skin of lower limbs and scrotum is constantly thickened, and then thickened and hardened, and the skin is rough, with rice furrows and warty nodules, commonly known as "elephantiasis". If microfilaria is found in the blood, the disease can be diagnosed.
[therapy]
(1) Symptomatic treatment
1. Acute lymphangitis and lymphadenitis can be treated with prednisone, prednisone and aspirin orally for 2 ~ 3 days. Patients with bacterial infection should be given antibiotics.
2. Bed rest for chyluria, raising pelvis, drinking more boiled water, eating more mussels, limiting fat and protein diet, and treating with traditional Chinese medicine. Patients with chyluria can take VitC and VitK4, or intramuscular injection of Roan blood and hemostatics. If it is ineffective, 1% silver nitrate 10ml or 12.5% sodium iodide solution can be used for renal pelvis irrigation or surgical treatment.
3. elephantiasis ① Keep the skin of the affected limb clean to avoid squeezing friction and trauma. ② Radiation heat binding therapy: put the affected limb into a brick leg furnace or electric oven at 60 ~ 100℃, 1 time/day or once every other day, each time for 30 minutes, 1 month is a course of treatment, and 2 ~ 3 courses of treatment are feasible in one year. ③ Surgical treatment; Skin transplantation can be done for severe lower limbs, and plastic surgery can be done for elephantiasis of scrotum.
(2) pathogen treatment
1. Haiqunsheng (also known as pyrimethamine and Yiqunsheng) can kill both microfilaria and adults. The curative effect of marine colony on Malay filariasis is faster and more thorough than that of banyan filariasis. (1) Short-term therapy: It is suitable for malayan filariasis patients with good health. Adults take 1.5g once in the evening or 0.75g twice a day for 2 days. This therapy has a great response. (2) Medium-range therapy: used for more and heavier microfilaria infections and blood filariasis. 0.3g, twice a day, 7 days as a course of treatment. (3) Intermittent therapy: 0.5g for adults, once a week/kloc-0, for 7 weeks. This method has high negative conversion rate, reliable curative effect and few side effects. Side effects: mainly allergic reaction caused by the death of microfilaria or adults, causing local symptoms in adults. Generally, filariasis in Malaya is more serious than filariasis in banyan. For serious heart, liver and kidney diseases, active pulmonary tuberculosis, acute infectious diseases, and those who are pregnant for 3 months or more than 8 months, menstrual women should be treated slowly or contraindicated.
2. Levamisole: It has a good effect on microfilaria. The dosage is 4 ~ 5mg/kg/ day, taken twice, and the course of treatment is 5 days. Combined with marine bacteria can improve the curative effect. The side effects are similar to those of marine bacteria, but lighter than the latter.
3. Furazolidone: It can kill both adult filariasis and microfilaria. 20mg/kg/ day, divided into 2 ~ 3 times, for 7 days. The side effects are similar to those of marine colonies.
[prevention]
(1) general survey and universal treatment
In summer, people over 0/year old in epidemic areas were investigated, and people with microfilaria positive or microfilaria negative but with filariasis history and signs were treated in winter.
(2) Mosquito control
Vigorously carry out patriotic health campaigns to eliminate mosquito breeding grounds. Correct use of mosquito nets in mosquito season; When working outdoors, use insect repellent such as mosquito repellent oil and mosquito repellent to coat the exposed skin, and the head can be made of mosquito net (cotton thread soaked with 70 1 mosquito repellent oil).
(3) Protecting vulnerable groups
In the epidemic area, the salt-producing therapy of sea colony was adopted, and 3g sea colony was mixed into each kilogram of salt, with an average of 65438 06.7 g salt per person per day, including 50mg sea colony, which could reduce the positive rate of microfilaria in the population for half a year.