Detection of Brugia malayi by Polymerase Chain Reaction

Lymphatic filariasis is a chronic disease cause by Wuchereria bancrofti, Brugia malayi and Brugia timori. Microscopical diagnosis by finding microfilariae in the blood smear is not sensitive enough to detect low infection cases, chronic infection and occult filariasis. However, diagnosis by immunoassay shows cross reactivity among nematodes antigen and can't distinguish past from current infection. Recently, with the advance in molecular biological techniques, it is possible to detect parasite DNA in the host. One of the methods used is Polymerase Chain Reaction (PCR), an in vitro technique for amplification of DNA template by DNA polymerase enzyme. The B. malayi DNA specific sequence from Hha 1 family is 322 bp length. The PCR product is visualized through agarose gel electrophoresis stained with ethidium bromide, will show bands of 322 bp, 644 bp (dimers) or 966 bp (trimers). This method is very sensitive as it can detect either 1 pico gram B. malayi DNA or 1 microfilariae in 50 ul blood or 1 infective larvae in mosquito. It can also detect any larvae stage in mosquitoes. Specificity study with B. malayi DNA probe, showed PCR amplification product was highly specific for Brugia, because only Brugia DNA was amplified, not human or mosquitoes DNA or other DNA from related filarial species such as W. bancrofti, Onchocerca volvulus and Loa loa. In conclusion, the amplification of Hha 1 DNA sequence by PCR could be used either as an alternative in diagnosis of brugian filariasis of detection of Brugia parasite in mosquitoes for epidemiological and surveillance studies