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Background: The diagnosis of filariasis traditionally relies on the detection of circulating microfilariae (mf) using Giemsa-stained thick blood smears. This approach has several limitations. We developed a semi-automated microfluidic device to improve and simplify the detection of filarial nematodes., Methods: The efficiency and repeatability of the microfluidic device was evaluated. Human EDTA blood samples were 'spiked' with B. malayi mf at high, moderate, and low levels, and subsequently tested 10 times. The device was also used for a field survey of feline filariasis in 383 domesticated cats in an area of Narathiwat Province, Thailand, the endemic area of Brugia malayi infection., Results: In the control blood arbitrarily spiked with mf, the high level, moderate level and low level mf-positive controls yielded coefficient variation (CV) values of 4.44, 4.16 and 4.66%, respectively, at the optimized flow rate of 6 µl/min. During the field survey of feline filariasis in Narathiwat Province, the device detected mf in the blood of 34 of 383 cats (8.9%) whereas mf were detected in 28 (7.3%) cats using the blood smear test. Genomic DNA was extracted from mf trapped in the device after which high-resolution melting (HRM) real-time PCR assay was carried out, which enabled the simultaneous diagnosis of filarial species. Among the 34 mf-positive samples, 12 were identified as B. malayi, 15 as Dirofilaria immitis and 7 as| D. repens., Conclusions: We developed a semi-automated microfluidic device to detect mf of filarial parasites that could be used to diagnose lymphatic filariasis in human populations. This novel device facilitates rapid, higher-throughput detection and identification of infection with filariae in blood samples.

Lymphatic filariasis (LF) is one of the neglected tropical diseases which causes permanent and long term disability worldwide. LF is caused by filarial nematode parasites, i.e. Wuchereria bancrofti, Brugia malayi, and B. timori. All available antifilarial drugs currently being used have shown a limited adulticidal activity. Discoveries of endosymbiont rickettsia-like bacterium, Wolbachia in filarial nematodes provided a novel approach for antibiotic use in eradication of filarial diseases. The earlier studies revealed the macrofilaricidal efficacy of doxycycline against filarial nematodes. Chemotherapeutic efficiency of doxycycline has been studied against many filarial parasites, but there are still no therapeutic trials of the drug regimens for B. malayi treatment in naturally infected cats. Thus, this study would be the first attempt to study the efficiency of doxycycline (DOXY) alone or in combination with ivermectin (IVM) for treatment of B. malayi in naturally infected cats. A total of 26 B. malayi-infected cats in the endemic areas were recruited and divided into 3 groups, receiving different treatment regimens; a single dose of ivermectin only (IVM), doxycycline only (DOXY) and a combination of ivermectin and doxycycline (DOXY-IVM). The efficacy of each therapatic regimen was evaluated by detecting the presence of microfilaria using parasitological and molecular techniques monthly up to 2 years after starting the treatment. The IVM treated group had a significant rapid reduction of microfilariae in the first month; however, recurrence of microfilaraemia was observed in some cats. By contrast, the DOXY and DOXY-IVM groups showed a better result with a gradual decrease in microfilariae with no recurrence. These 2 groups were not only virtually deprived of infection but also sustained the sterility of infection through the course of study. These results revealed the advantages of using in B. malayi treatment in cats. Doxycycline showed to have both microfilaricidal and adulticidal effects on lymphatic filariae which maintained the long-term response to control of B. malayi infection in cats., (Copyright © 2017 Elsevier B.V. All rights reserved.)