Thoracic filariasis

　　1. Etiology

　　The definitive hosts of Brugia malayi and Wuchereria bancrofti are humans. Patients with microfilariae in the blood or carriers are the main sources of infection for the disease. However, these two species of filaria have also been found in the lymphatic systems of monkeys, dogs, pigs, and some wild animals, so animal reservoir hosts may also exist. The main mosquitoes that transmit Wuchereria bancrofti are Aedes albopictus and Culex quinquefasciatus, followed by Anopheles sinensis. The main mosquitoes that transmit Brugia malayi are Anopheles sinensis and Anopheles dirus anthropophagus, and Aedes albopictus in coastal areas can also transmit both Wuchereria bancrofti and Brugia malayi disease.

　　2. Pathogenesis

　　The pathogenesis of thoracic filariasis is mainly divided into two stages:

　　1. Early stage

　　It is mostly an allergic reaction and an inflammatory reaction dominated by exudation. Metabolic products and exuvial fluid of microfilariae and adult worms, secretions from the uterus of adult worms, decomposed products of dead worms, and other factors can all cause systemic or local allergic reactions in the body. In the lungs, it can manifest as eosinophilic granulocyte infiltration, and symptoms such as asthma, dry cough, chest pain, hemoptysis, and dyspnea may occur.

　　2. Chronic stage

　　Due to the specificity of the lymphatic circulation, the deep intrathoracic lymphatic system is blocked by eosinophilic granuloma or fibrosis, resulting in obstruction of lymph fluid return. This leads to expansion of the lymphatic vessels below the blockage, increased pressure, and even rupture, thus causing chylous pleural effusion, chylous sputum, and other symptoms.

　　Complications may include bacterial infection. In the lungs, it can manifest as eosinophilic infiltration and symptoms such as asthma, dry cough, chest pain, hemoptysis, and dyspnea. In the chronic stage, about half of the patients have periodic symptoms similar to common cold, such as chills, rigor, fever, known as filarial fever, with body temperature up to 40℃, which subsides spontaneously after 2 to 3 days. It can also be accompanied by low fever without chills, as well as fatigue, malaise, chest tightness, chronic cough, chest pain, hemoptysis, dyspnea, asthma, recurrent rash, and angioneurotic edema, etc.

　　About half of pulmonary filariasis patients have no clinical symptoms, and about half have periodic symptoms similar to common cold, such as chills, rigor, fever, known as filarial fever, with body temperature up to 40℃, which subsides spontaneously after 2 to 3 days. It can also be accompanied by low fever without chills. In addition, there may be fatigue, malaise, chest tightness, chronic cough, chest pain, hemoptysis, dyspnea, asthma, recurrent rash, and angioneurotic edema, etc. Physical examination may show wheezing in the lungs, dry and moist rales. If the filaria (usually Wuchereria bancrofti) is寄生 in the lymphatic ducts of the breast, it can lead to obstructive lymphangitis and eosinophilic granuloma caused by the metabolic products or fragments of the adult worms, so there may be unilateral or bilateral breast nodules or hard lumps, the size of soybeans to broad beans, soft in the early stage and hard in the late stage without tenderness. Nodules are more common in the outer quadrant, and are easily misdiagnosed as breast fibroadenoma, lobular hyperplasia, or breast cancer.

　　1. Praziquantel powder is processed with salt to make 0.3% medicated salt, which is commonly consumed in epidemic areas for 6 months, with an average total dose of praziquantel of about 9g per person.

　　2. In the epidemic areas, praziquantel is taken intermittently by the general population, with an adult dose of 6mg/kg, taken once a week or once a month, a total of 12 times.

　　The above two methods can greatly reduce the infection rate of the population and Aedes albopictus, and the positive rate of microfilariae from 10% before treatment to 1%, with reliable preventive effects. In addition, the principle of 'exterminating mosquitoes early, exterminating mosquitoes in small numbers, and exterminating mosquitoes thoroughly' is very important.

　　One, Early Allergic Reaction

　　The total white blood cell count in peripheral blood increases to (10～20)×109/L, and eosinophils reach more than 20%, but in the chronic stage, the eosinophils are significantly increased in less than 10% of patients. If accompanied by infection, neutrophils can also increase.

　　Two, Blood Examination for Microfilariae

　　It is the only reliable method for early diagnosis of filariasis, usually using peripheral blood, with the best blood collection time from 9 pm to 2 am. If the number of microfilariae in the blood at night exceeds 150 per 60μl, microfilariae can also be detected in the blood during the day. Three large drops of blood from the earlobe (about 60μl) can be used to make a thick blood film, or one large drop of fresh blood (about 20μl) can be used to make a film for examination under a low-power microscope. Microfilariae can also be found in pleural fluid, pericardial fluid, and even chyle sputum occasionally.

　　Three, Chyle Test

　　For specimens suspected of being chyle sputum, chyle pleural effusion, etc., Sudan III staining is commonly used to confirm.

　　Four, Immunological Tests

　　Due to the existence of false positives and other issues, its practical value has always been controversial, but in recent years, there have been certain progresses in the immunological diagnosis of filariasis.

　　1. Antigen skin test

　　Skin tests are performed using antigens made from canine, Bancrofti, or Malay microfilariae, infective larvae, or adult worms. The positive rate reaches over 90%, and the antigen specificity is also high, but there is a slight cross-reaction with schistosomiasis.

　　2. Indirect immunofluorescence assay and enzyme-linked immunosorbent assay

　　Both have a high positive rate, can be used for epidemiological investigation, but due to the long time for turning negative, it cannot be used to evaluate efficacy, nor can it distinguish past infection or active infection.

　　3. Spot enzyme-linked immunosorbent assay and monoclonal antibody enzyme-linked immunosorbent assay

　　Detection of antigens in the serum of filariasis patients, with specificity reaching 96%, 94% respectively, and both can detect active infection patients.

　　Filariasis food therapy recipe
　　Recipe one
　　Medicines: Rhododendron (red azalea) root 30 to 60 grams.
　　Usage: Boil the medicine in water, use 30 to 60 grams of sugar as a guide, once a day.
　　Indications: Used for adjuvant treatment of filariasis.
　　Recipe two
　　Medicines: Fresh lychee root 1000 grams.
　　Usage: Wash the lychee root clean and chop it, boil it for 8 to 10 hours, then filter out the dregs, and concentrate it to 120 grams. Take 30 grams each time, twice a day, for 2 consecutive days.
　　Indications: Used for adjuvant treatment of filariasis.
　　Recipe three
　　Medicines: Fresh hawthorn 1000 grams, areca nut 50 grams.
　　Usage: Wash hawthorn clean and remove the core, start eating it little by little from 8 hours before bedtime, and do not eat dinner. The next morning, take 1 cup of hawthorn decoction with areca nut and take it at one time.
　　Indications: Used for adjuvant treatment of filariasis.
　　Recipe four
　　Medicines: Celery root 30 to 60 grams, sugar 30 grams.
　　Usage: Wash the celery root clean, boil it with water for several boils, add sugar, and drink it twice a day, once in the morning and once in the evening.
　　Indications: Used for adjuvant treatment of filariasis.
　　Pay attention to diet, try to be light, do not eat too much fish and meat.

　　1. Treatment

　　1. Pathogen treatment

　　(1) Diethylcarbamazine: It has a killing effect on both adult worms and microfilariae of filariae, and its efficacy is better for malayi filariasis than for bancrofti filariasis, but the adverse reactions of the former are more severe than those of the latter. After oral administration, it is rapidly absorbed in the intestines, metabolized in the body, and almost all excreted by urine. After taking one dose, it is difficult to find the trace of diethylcarbamazine in the blood 48 days later. Its long-term efficacy is better than its short-term efficacy. Dosage and method:

　　① Used for the treatment of Brugia malayi carriers: Adults take 1.5g at bedtime; or 0.75g, once a day, for 2 consecutive days; or 0.5g, once a day, for 3 consecutive days.

　　② Used for the treatment of Wuchereria bancrofti carriers: Adults take 1.0 to 1.5g in the afternoon every day for 2 to 3 days, with a total dose of 3.0g or 0.2g per time, 3 times a day, for 7 consecutive days. The latter is more reliable for killing adult worms.

　　③ Intermittent therapy: For the treatment of Wuchereria bancrofti infection, 0.5g is taken once a week for 7 consecutive weeks. For the treatment of Brugia malayi infection, 0.3g is taken once a week for 6 consecutive weeks.

　　Whether or not the microfilaria in the blood turns negative after the treatment of diethylcarbamazine, a continuous treatment of 3 courses is required, with an interval of 1 to 2 months between each course. For those who have not turned negative, the treatment should continue.

　　The adverse reactions of diethylcarbamazine itself are mild, and occasionally nausea, vomiting, dizziness, and insomnia may occur at high doses. During treatment, due to the large-scale killing of adult filariae and microfilariae, allergic reactions such as chills, high fever, headache, muscle pain throughout the body, rash, and even laryngeal edema may occur. Occasionally, liver and spleen enlargement, pain, hematuria, and proteinuria may also occur. Allergic reactions usually appear 6-8 hours after taking the medicine, and antihistamines, aspirin, corticosteroids, and other drugs can treat or alleviate the reactions.

　　(2) Levamisole: Effective in the short term for both Wuchereria bancrofti and Brugia malayi filariasis, but the long-term efficacy is poor. The dose is 200-250mg per day, taken twice a day, for 5 consecutive days. If the dose is 400mg per day, it should be taken for 3 consecutive days. The rate of negative microfilaria conversion after treatment is over 90%, but the rate of negative microfilaria conversion decreases significantly after 4 months. It can enhance the efficacy when used in combination with diethylcarbamazine. The adverse reactions are more serious than those of diethylcarbamazine, mainly fever, headache, muscle pain in the limbs, fatigue, etc. The fever is usually below 39℃, lasting for 2-3 days and disappearing after stopping the medication.

　　(3) Furamidine: Synthesized in China in 1979, it has a significant killing effect on both Wuchereria bancrofti adults and microfilariae. The dose is 20mg/kg per day, taken 2-3 times a day, with a 7-day course of treatment. The adverse reactions are similar to those of diethylcarbamazine.

　　(4) Single dose diethylcarbamazine or single dose diethylcarbamazine plus single dose ivermectin (ivermectin, IVM) treatment: The Indian Ministry of Health uses a single dose of diethylcarbamazine 6mg/kg, plus a single dose of diethylcarbamazine plus a single dose of ivermectin 400?g/kg for collective treatment once a year, resulting in a 1/3 reduction in the rate of microfilaria positivity, and the microfilaria density decreased by 90% and 99% respectively. Jelinek et al. also reported similar cases in 1996, indicating that both drugs are effective in treating filariasis, but combined use is more effective.

　　2. Symptomatic treatment

　　Early allergic reactions such as fever, cough, and asthma can be treated with antihistamines such as chlorphenamine (Piriton), loratadine, or cetirizine (Cetirizine) and adrenocorticosteroids. If chest effusion causes chest tightness and shortness of breath, chest puncture and fluid aspiration should be performed.

　　II. Prognosis

　　Lung filariasis generally does not threaten life. Early diagnosis and treatment can recover quickly. In the late stage, life-threatening conditions often arise due to secondary infections.