FILARIASIS: AN OVERVIEW OF PAST HISTORY IN MALAYSIA

Background

The first reference to Filariasis in Malaysia was by Daniels (1908) who found three (2 Indian and 1 Chinese) microfilarial carriers among 100 patients at the Kuala Lumpur Hospital. Of the total 17,804 admissions for the preceding 4 years, only four cases of elephantiasis were seen. Filariasis was then thought to be rare in the country and Fraser (1912) reported only 11 admissions to the Kuala Lumpur Hospital. Another blood survey in the hospital showed 16 out of 700 (2.3%) patients to be positive for microfilaremia. There was no further mentioned of filariasis in Malaysia until 1934.

​

Filariasis was initially only due to W. bancrofti until in 1927, S.L. Brug described a new species of filarial worm which he name Filaria Malayi. In 1960, Buckley proposed to divide the old genus Wuchereria, into two genera, Wuchereria and introduced a new Brugia after the original discoverer. Then Wuchereria contains only W. bancrofti, which so far has been found to infect only humans, and the genus Brugia contains B. malayi, which infects humans and animals, as well as other zoonotic species Edeson and Wilson (1964). Of the three species of human lymphatic filarial parasites found in South East Asia, only B. malayi and W. bancrofti are present in Malaysia.

W. bancrofti was thought to be found in immigrant and B. malayi proved to be present in Malaysia (J. W. Mak, 1983). The Culex quinquefasciatus is the vector for the less common W. brancofti in urban areas while the common rural B. malayi along the coastal and riverine areas were Ma. uniformis, Ma. bonneae, Ma. annulata, Ma. annulifera, Ma. indiana, Ma. barbirostris and Ma. hyrcanus (W. H. Cheong, 1983).

Ecological features associated with the periodic and subperiodic forms vary. Periodic B. malayi is classically seen in coastal rice field and permanent established agricultural lands like coconut estate. Subperiodic B. malayi is typically associated with swam forest habitats, near low-lying, swampy river banks and in rubber estates near these areas (J. W. Mak, 1983).

The clinical features of periodic B. Malayi usually preceeded by elephantiasis which continuously complicated by episodic adenolymphangitis. The elephantiasis was limited primarily to the lower extremeties. There was no urogenital involvement (Dondero and Mullin, 1972)

​In 1960s, the control measures for Filariasis were directed towards three main areas; reduction of the reservoir of infection, vector control and reduction of human-vector contact. Mass chemotherapy with diethylcarbamazine (DEC) remains the most effective method for control of lymphatic filariasis. Vector control has been effective in periodic B. malayi and rural W. brancofti as part of the spin-off benefit of the Malaria Control Program six monthly cycle of spraying of houses with residual insecticide (Mak et al, 1977). In these areas, the principle Anopheles spp. vectors have been effectively reduced by the residual DDT applications.​

Malaysia initiated Lymphatic Filariasis Elimination Programme (LFEP) in 2001 following the Global Programme to Eliminate Lymphatic Filariasis (GPELF) which was launched by the World Health Organisation (WHO) in 2000. There are 127 endemic Implementation Units (IUs) involving 8 states (Kedah, Perak, Johor, Pahang, Terengganu, Kelantan, Sabah and Sarawak). All endemic IUs have completed 5 rounds of mass drug administration (MDA) in the year 2004-2008 with coverage more than 85% of eligible population.

Figure 4: Malaysia LF Endemicity Mapping, 2021

By the year 2022, there were 122 endemic IUs (96%) passed TAS-3 with the remaining 4 endemic IUs (Tangkasrason, Bangkalalak, Lawas and Sundar) due for TAS-3 in the year 2024 and IU Debak in Sarawak due for TAS-3 by the year 2025.