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Filariasis is a parasitic infectious disease caused mainly by a filarial worm named Wuchereria bancrofti but can be caused by other types of filarial worms. This disease is capable of causing elephantiasis which is the permanent swelling of the limbs and other parts of the body with associated thickening of skin caused by obstruction of lymph by the adult worms.
Filariasis occurs worldwide (affecting about 200 to 300 million people) but is endemic in the tropical areas of Africa, Asia, and Latin America. The species of mosquito that acts as the vector varies from area to area and some species have been named according to the area. Filariasis is mainly caused by the parasite Wuchereria bancrofti (in 90% of cases), carried by the culex fatigans mosquito and female anopheles mosquito but other causes of filariasis (in 10% of cases) include some species of filarial worms such as Brugia malayi and Brugia timori. Even though Filariasis rarely cause death, it is the second most common cause of long term disability according to the World Health Organization (WHO); the first cause of disability being Leprosy.
Filariasis Mode of Transmission
Filariasis is transmitted through the bite of an infected mosquito, the larvae then enter the lymphatics and are carried to regional lymph nodes where they grow and mature for about 6 to 18 months. The adult worms are responsible for causing lymphangitis with subsequent fibrosis of the lymphatics leading to obstruction and elephantiasis occurs.
Filariasis Symptoms and signs
- It may be asymptomatic (when the filariasis shows no sign or symptoms)
- Acute symptoms of filariasis may include episodic attacks of fever
- There may be pain, tenderness and erythema (redness) along the course of affected lymphatics
- Dry cough when the respiratory tract is affected in the mild forms of filariasis
- There may be lymphadenitis and lymphangitis inflammation of the lymph nodes and ducts respectively
- Elephantiasis the thickening and swelling of the limbs and some
Filariasis Risk factors
- Living in an endemic area
- Living in the Tropics
- Exposing yourself to mosquito
- Poor sanitation allowing stagnant water around houses and not clearing of bushes around houses
Diagnosis of Filariasis is done by making a thick smear of blood (usually taken from the patient at night) and viewing it under the microscope. The presence of the microfilariae shows the patient has Filariasis. Serological tests are done to detect early cases of filariasis because the tests are sensitive. Even after effective treatment, the microfilariae may still be detected in blood until after one year when the tests may be negative. The disadvantage of using serologic tests is that it may cross-react with other nematodes giving false positive tests.
- Medical treatment with drugs such as Diethylcarbamazine (DEC) is very effective in the early phase before swelling of limbs occurs. Ivermectin is also used
- In the early phase of limb swelling, the use of intermittent pneumatic compression helps
- Excision can be done to reduce the hydrocele in scrotal filariasis
- Reconstructive surgery may be needed to remove excess tissue in the limbs the benefit of this is uncertain
- Vector control must be included in treated to prevent re-infection. Control of vector can be seen below under prevention of filariasis
- It may cause pulmonary eosinophilia a condition in which the microfilariae become trapped in the pulmonary capillaries leading to intense local allergic response. The pneumonitis causes cough, fever, weight loss and shifting radiological changes, associated with a high peripheral eosinophil count.
- Scrotal filariasis may develop hydrocele if not promptly treated
- Cosmetics problems and psychology problems which may lead to depression
- Secondary wound infection may occur
- Permanent disability following repeated infections leading to Elephantiasis
- Chyluria and chylous ascites may occur
- Clear all bushes around the house
- Clear all drainages to ensure free flow of water and prevent stagnant water which may serve as a breeding ground for mosquitoes
- Wear clothes that cover most of your body especially in the evening in endemic areas
- Apply mosquito repellent cream to prevent mosquito bites especially in endemic areas
- Always use mosquito nets on windows and for beds
- If you notice any symptom and you suspect Filariasis, present yourself to a medical facility for test to be carried out to diagnose and treat immediately before elephantiasis develops