FILARIASIS : TREATMENT, PREVENTION AND CONTROL

It is a disease caused by a digenetic nematode parasite Wuchereria bancrofti which is transmitted to human by mosquitoes like like Culex, Aedes or Anopheles. The diseases causes lymphoedema (lymphatic obstruction of lymphatic vessels and glands) lymphadenitis (infection of lymph nodes), lymphangitis (infection of lymph vessels), elephantiasis (enormous enlargement of scrotum, feet, hands, legs, etc.)

The life cycle is completed in two hosts is human and the secondary or intermediate host is a female mosquito (usually Culex pipiens). There is a distinct sexual dimorphism in the parasite. The male worm measure 80-100 in lenth and 0.1 mm diameter. The female is viviparous and gives birth to as many 50,000 microfilariea per day. The microfilariae find their way into the blood stream where they live up to 70 days without any developmental changes. Due to their nocturnal periodically they are shucked up by the secondary host, which is prevalent in night hours. The life cycle completes in 10 to 14 days through the following stages.

•  Ex sheathing  : The micro-filariea comes out of the sheath within 1-2 hours of ingestion in the stomach of the mosquito.
• First stage larva : After exsheathment, the larve penetrates the stomach wall of the mosquito in 6-12 hours and migrates into the thoracic muscles where it grows and develops into a sausage-shaped form.
• Second stage larva : The larva grows in size and develops in the alimentary canal but remains inactive.
• Third stage larva : In this stage, the larva becomes active and ineffective. It migrate to the proboscis of the mosquito and is ready to be transmitted to a new host. In the human host, the ineffective stage larvae grow into the adult males and females.

Treatment : 

Detection and treatment of human carrier : The present strategy is to detect and treat the human carriers by the use of drugs like diethyl carbamazine (DEC) in 12 doses at the rate of 6 mg per kg body-weight daily to be completed in two weeks.

Prevention and control :

Anti-mosquito Measures :  The main objective of this method is the elimination of breeding places of the vector controlling method are ;

• Recurrent anti larval measures in endemic urban areas.
• Use of larvicides like pyrosene oil.
• Removal of aquatic plants like pistia.
• Destruction of derelict water bodies and swamps.
• Anti-adult vector measure like spraying pyrethrins.
• Avoidance of mosquito bite by using mosquito net.
• Using larvivorous fishes like Gambusia.

The national filarial  control programme was initiated in 1955-1956, but since 1978 the programme has been merged with malaria control programme.