The usual habitat of the parasite is lymph nodes. The parasites block the lymph flow, resulting in Elephantiasis characterised by severe swelling of limbs, usually legs and sometimes breast or the scrotum.
Worldwide Problem with Filariasis
Filariasis is a global problem. According to WHO reports, an estimated 751 million people are at “Risk” of infection, and 120 million have actually been infected. The public health problem of lymphatic filariasis is greatest in China, India and Indonesia. These three countries account for about two–thirds of the estimated world total of persons infected.
Filarial Problem in India
Filariasis is a major public health problem in India. There are an estimated six million attacks of acute filarial disease per year, and at least 45 million persons currently have one or more chronic filarial lesions. Heavily infected areas are found in Uttar Pradesh, Bihar, Andhra Pradesh, Orissa, Tamil Nadu, Kerala and Gujarat.
The infection is acquired from a person who has filariasis. The maximum infectivity is when the organisms are circulating in the blood. The largest number appear in the blood at night time, and retreat from the blood stream during day. Their usual habitat is in the lymph nodes. The mosquito feeds on such a person and acquires the filarial parasite. The filarial organism is transmitted when the mosquito bites a person. The parasite is deposited near the site of puncture. It passes through the punctured skin or may penetrate the skin on its own and finally reach the lymphatic system. Filariasis affects all age groups.