Brugia Malayi - Laboratory Diagnosis

Laboratory Diagnosis

Tender or enlarged inguinal lymph nodes or swelling in the extremities can alert physicians or public health officials to infection.

With appropriate laboratory equipment, microscopic examination of differential morphological features of microfilariae in stained blood films can aid diagnosis—in particular the examination of the tail portion, the presence of a sheath, and the size of the cephalic space. Giemsa staining will uniquely stain B. malayi sheath pink. However, blood films can prove difficult given the nocturnal periodicity of some forms of B. malayi.

PCR based assays are highly sensitive and can be used to monitor infections both in the human and the mosquito vector. However, PCR assays are time-consuming, labor intensive and require laboratory equipment. Lymphatic filariasis mainly affects the poor, who live in areas without such resources.

The ICT antigen card test is widely used in the diagnosis of W. bancrofti, but commercial antigens of B. malayi have not been historically widely available. However, new research developments have identified a recombinant antigen (BmR1) that is both specific and sensitive in the detection of IgG4 antibodies against B. malayi and B. timori in ELISA and immunochromatographic rapid dipstick (Brugia Rapid) test. However, it appears that immunoreactivity to this antigen is variable in individuals infected with other filarial nematodes. This research has led to the development of two new rapid immunochromatographic IgG4 cassette tests—WB rapid and panLF rapid—which detect bancroftian filariasis and all three species of lymphatic filariasis, respectively, with high sensitivity and selectivity.