HISTORY OF FILARIASIS

Bahr (1914), Sweet and Dirckze (1925), Catre (1932), and Dassanayake (1936) spotlighted the presence of the disease in certain parts of the country. The incidence and distribution of filariasis in the country were not known until a large-scale survey was conducted by Dassanayake in 1939. The disease was found to be prevalent in certain pockets in the Southern, North Western, Eastern, Western, and North Central Provinces. The predominant species responsible for the disease was Brugia malayi. The Bancroftian type was found mainly in Galle and Matara.

About a year or two after the termination of the second world war, many cases of lymphangitis were brought to the notice of the Department of Health and as a result, established the Anti Filariasis Campaign (AFC) on 24th October 1947(3). Surveys carried out by the AFC revealed foci of infection in the South-Western coastal belt of Ceylon, especially in Negombo, Dehiwala, Kotte, Kolonnawa, Peliyagoda, Moratuwa, Beruwala, Induruwa, Weragoda, Galle, Weligama and Matara. In the urban areas, the type of infection was by W.bancrofti and in the rural areas it was principally confined to B.malayi.

Sri Lanka was declared eliminating Filariasis as a public health problem in 2016 by the WHO, due to the reduction of microfilaria rate (mf rate) to less than 1%. This success story is a result of disease surveillance through parasitological, and entomological techniques and treatment as a result of the dedication and hard work of our former Directors, Consultant Community Physicians, Medical Officers, Entomologist, Regional Medical officers, Public Health Inspectors, Public Health field Officers, Public Health Laboratory Technicians, Health Entomological Officers, and other staff.

Currently, Filariasis is endemic in 8 districts (Colombo, Kalutara, Gampaha, Galle, Matara, Hambantota, Puttalam, and Kurunegala) in 3 provinces (Western, Southern & North Western) (Western, Southern & North Western) and eight Regional Medical Officers are supervising the anti-filariasis activities in the endemic districts.

Research into the history of filarial diseases of Sri Lanka or earlier called Ceylon points to far as B. malayi is concerned, to an invasion by a Malayan army under the King Kalinga kings during the days of close relations between Ceylon and Southeast Asia during the 12th and 13th centuries, as far as B. malayi is concerned. Where Wuchereria bancrofti is concerned, a Chinese army, invading the southern coast in the early 15th century, is responsible (1). This information also partly answers the puzzling question of why only the southern and Western coastal regions were affected by filariasis in Sri Lanka though there were focal infections in Peradeniya (2) and Eastern Province several decades ago. Confinement of the disease to the Southern and Western Coastal Belt despite the large volume of internal migration is attributed to the climatic conditions conducive to the breeding of vectors and the dense vulnerable population along the breeding sites in these areas.

The first survey was conducted in 1912/1913 concentrating on urban areas, followed by a second survey in the 1930s with emphasis on the rural parts. The results displayed a remarkable distribution pattern: Wuchereria bancrofti, the so-called “urban type”, concentrated in Galle and Matara towns, whereas Brugia malayi, the “rural type”, widespread along the southwest coast from Matara to Negombo, plus isolated pockets in the northwest, central north, east and south. The survey of the 1930s led to the supposition that the occurrence of B. malayi should be associated with the distribution of certain water plants, a suspicion later on confirmed in that Pistia stratiotes in particular–but other water plants as well–are essential for the survival of the vector (Taeniorhynchus (Mansonoides) uniformis) during its early (submersed) stages of development (1).