Effects of antibiotics on filarial transmission

Abstract

INTRODUCTION: The symbiosis of filarial nematodes and intracellular Wolbachia bacteria has recently been exploited as a target for therapy of filariasis. OBJECTIVE: To study the effects of antibiotics on filarial transmission in-vitro. METHODS: Two groups of microfilariae (mf) of Brugia pahangi (cat filarial species) were maintained in culture and exposed to 10 µm) solutions of tetracycline and doxycycline respectively, for 48 hours. A control group of Mf was maintained for 48 hours with no added antibiotics except for those routinely included in the culture medium. Mf counts in cultures were determined at the onset of experiment (8000 mf/culture flask). Three groups of Aedes aegypti mosquitoes were artificially infected with the treated and untreated mf by membrane feeding technique (mf concentration; 2000 mf/ml of blood). Mosquito dissections were performed 2 hours and 15 days post-infection to assess mf intake and development in vector hosts. RESULTS: Mf intake was similar in the treated and the control groups {8,5 and 9 mf recovered in 4,3 and 3 mosquitoes from tetracycline(n=6), doxycycline(n=6) and control(n=6) groups respectively}. Mosquitoes fed on tetracycline treated B.pahangi (n=70) were completely free of L3 (infective larvae while in the doxycycline (n=71) and control groups (n=71) the percentage of infection was 1.4% (01 infective larva in 01 mosquito) and 24% (17 infective larvae in 13 mosquitoes) respectively. The infectivity of mosquitoes fed on antibiotic treated Mf was significantly reduced (P value < 0.001). CONCLUSIONS: Exposure of Mf of B.pahangi to physiological concentrations of anti-wolbachia antibiotics even for a brief duration significantly affects their transmission potential.