Human dirofilariasis due to Dirofilaria (Nochtiella) repens is a common zoonotic infection in Sri Lanka. Todate 70 cases are on record, and they include 3 expatriates from Russia, England and Korea, who were undoubtedly infected in Sri Lanka. Around 30-60% of dogs are infected with D. repens in various parts of the country and the mosquito vectors are Aedes aegypti, Armigeres subalbatus, Mansonia uniformis and M. annulifera. Unlike in other countries of the old world infection is most common in children under the age of 9 years, the youngest being 4 months old and the scrotum, penis and perianal regions of male children appear to be frequent sites for the worms. Dirofilaria (Dirofilaria) immitis is not present in Sri Lanka though it is present in neighbouring countries like India, and Malaysia.
In the global effort to eliminate lymphatic filariasis (LF), rapid field-applicable tests are useful tools that will allow on-site testing to be performed in remote places and the results to be obtained rapidly. Exclusive reliance on the few existing tests may jeopardize the progress of the LF elimination program, thus the introduction of other rapid tests would be useful to address this issue. Two new rapid immunochromatographic IgG4 cassette tests have been produced, namely WB rapid and panLF rapid, for detection of bancroftian filariasis and all three species of lymphatic filaria respectively. WB rapid was developed using BmSXP recombinant antigen, while PanLF rapid was developed using BmR1 and BmSXP recombinant antigens. A total of 165 WB rapid and 276 panLF rapid tests respectively were evaluated at USM and the rest were couriered to another university in Malaysia (98 WB rapid, 129 panLF rapid) and to universities in Indonesia (56 WB rapid, 62 panLF rapid), Japan (152 of each test) and India (18 of each test) where each of the tests underwent independent evaluations in a blinded manner. The average sensitivities of WB rapid and panLF rapid were found to be 97.6% (94%-100%) and 96.5% (94%-100%) respectively; while their average specificities were both 99.6% (99%-100%). Thus this study demonstrated that both the IgG4 rapid tests were highly sensitive and specific, and would be useful additional tests to facilitate the global drive to eliminate this disease.