Filariasis

Filariasis is a mosquito borne. The disease prevalent in the urban areas. Man is primarily responsible for the high prevalence of the disease because the mosquito transmitting the infection, Cuiex quinquefasciatus is associated with man and living in his domestic environment breeding in exclusively man made habitats such as cesspits, blocked drains etc with domestic washings. Rapid uncontrolled urbanization without concurrent improvement in sanitation and waste disposal is a contribution factor.The causative organism is a thread-like worm called Wuchereria bancrotti. The adult worms live in tiny channels in the body, called lymph vessels. The female produces larvae referred to as microfilariae, which circulate in the blood stream and usually appear is surface blood vessels at night. When Cuiex quinquefasciatus mosquito sucks blood from a patient at night it ingests a number of larvae (microfilariae) with the blood. These larvae grow inside the body of the mosquito to become mature larvae. Later when the infected mosquito sucks blood the mature larvae make their way into the body of that person. They travel to the lymph vessels and grow into adult worms. 

Many people who get infected may not show any symptoms. Some may develop fever with chills or recurrent swelling, usually in the limbs or scrotum. This condition is called lymphangitis. In fair skinned persons red streaks may be visible in the affected area. These episodes disappear after sometime even without treatment. In the later stages of the illness,the patient may get swelling of the arms and legs, which usually persist Very rarely in poorly treated or untreated patients, the legs may become so swollen that they are almost elephant leg size. This stage of leg is called elephantiasis. When the larvae travel into the lungs, they cause Eosinophilia or Eosinophilic Bronchitis, as the eosinophils (a type of white blood cells) are very much increased in this condition. 

Filariasis disease is confirmed by the microscopic examination of a fixed quantity, a drop of finger prick blood spread evenly on a glass slide taken around 10 o’ clock at night. A measured quantity gives a more accurate count The side is examined under the microscope for microfilariae. The National Anti-Filariasis Campaigns of endemic countries routinely conducts these investigations in the endemic areas. The members of the public can obtain this service either at the campaign or in clinics conducted by the Medical Officers of Health in different areas. Some of the other sophisticated methods of diagnosis of the disease include examination for microfilariae in 1ml of venous blood filtered through a Nuclepore membrane and stained and immunodiagnosis using serum from filter paper soaked whole blood for circulating antigens.

Treatment and Prevention

Diethylcarbamazine (DEC) (brand names: Hetrazan, Banocide) is the drug of choice for the treatment of the disease. An individual is treated with 12 daily doses of DEC each dose consisting of 6mg per Kg body weight (roughly 300mg per adult and 150mg per child). The daily dose may be taken is three divided doses after meals to avoid or minimize any side effects. The common side effects may be headache, body ache, fever and nausea, sometimes vomiting which do not last long. These reactions are associated with the presence and intensity of microfilariae. 

The improvement of methods of diagnosis of the disease and treatment the World Health Assembly adopted a resolution calling for the elimination of lymphatic filariasis globally. Supporting this action a Health Care Pharmaceutical Company is presently collaborating in this effort by donating the drug albendazole to governments for as long as necessary to ensure the elimination program. Under this program the entire community in the world where the disease is endemic is to be treated with a single dose of drug combination, DEC (6mg/Kg body weight) and albendazole (400mg), once a year for five consecutive years. It is therefore important that every citizen participates in the program to make it a success. The value of albendazole is that in addition to enhancing the effect of DEC in the elimination of microfilaria larvae it has the bonus of controlling the intestinal worms. Drug treatment has no effect on advanced lymphangitis and elephantiasis. Secondary bacterial fungal infections aggravate these conditions. The other activity in addition to mass drug administration in PELF is Morbidity Control. There is much relief by simple washing and drying and application of antibiotic and antifungal preparations.

Prevention

A programme for vector control is must for any country with endemics. This involves keeping the drains clean and polluted water collections eliminated. Built tanks with permanent breeding are treated with polystyrene beads to cover the water surface and prevent the larvae developing into adults. insecticides are used in several instances of heavy breeding.The use of insecticide impregnated bed nets and door and window curtains in bedrooms offer protection from adult mosquito bites.