All Tests

Lymphatic filariasis (LF) is a parasitic disease caused by nematodes (Wuchereria bancrofti, Brugia malayi and Brugia timori) whose preferred habitats are the lymphatic vessels and lymph nodes which induce the development of disfiguring and debilitating clinical symptoms. The infection, which is transmitted by various genera of mosquitoes (Sasa 1976), is considered to be one of the health problems of greatest social and economic impact in endemic areas (Ottesen et al. 1997).

Until the 1980s, the only direct way to confirm a diagnosis of infection by W. bancrofti was via the identification of microfilariae (MF) in peripheral blood using camera counting, polycarbonate membrane filtration, the thick smear method or Knott's technique (Knott 1939, Denham et al. 1971, Dennis & Kaen 1971, Eberhard & Lammie 1991). Apart from the low sensitivities of these methods arising from the fact that they only identify filarial infection by way of microfilaremia, they are also inconvenient in terms of the time of day the blood must be collected, namely when the MF are at a peak in peripheral blood, a parameter that varies from one endemic area to another. In Brazil, the peak for microfilaremia occurs between 11 pm-1 am (Dreyer et al. 1996).

In the 1990s, significant advances were made in the diagnosis of LF with the emergence of new diagnostic tools: (i) use of recombinant antigens to detect specific antibodies (Chandrasherkar et al. 1994); (ii) a PCR for the detection of filarial DNA (Zhong et al. 1996, Rocha et al. 2002); (iii) the visualisation of live adult worms (AW) using ultrasound (US) and (iv) circulating filarial antigen (CFA) detection (More & Copeman 1990, Weil et al. 1997). At present, the standard diagnostic tools are US (Amaral et al. 1994) and CFA detection, with the latter using the monoclonal antibodies (McAbs) Og4C3 and AD12. The CFA detection techniques are commercially available in the form of kits and have the advantage of allowing for diagnosis to be carried out using blood samples collected at any time of day (More & Copeman 1990, Amaral et al. 1994, Weil et al. 1997, Rocha 2002, 2004)