Development of Mansonella perstans in the surrogate vector Aedes aegypti

The biology of the human filaria Mansonella perstans has been poorly studied due in part to the lack of experimental animal models in which its life-cycle could be produced. In nature Culicodes spp. (and probably simuliids) are the vectors involved in disease transmission. In the present work Aedes aegypti black-eyed strain was experimentally infected with M. perstans microfilariae by intrathoracic inoculation of 8 to 15 parasites contained in 0.4-0.6 μl of RPMI 1640. Concentration of microfilariae was achieved by means of a ficoll separation technique. A. aegypti were maintained at 26°C and 80% relative humidity with a sugar-water diet, except on day 4 post-infection on which they received an uninfected blood meal. Larval development was slow, taking no less than 4 days to reach the sausage stage, which measured 95-100 μm in length. Molt to the second stage took place on the 6th day; the differentiation into a long muscular and glandular esophagus, and short intestine measuring approximately one fourth of the total larval length were the most significant changes. At the end of this period 4 small but well demarcated tail papillae were observed. The first third-stage larvae appeared at the 8th day post-infection, measuring 650 to 680 μm in length. Beyond the 10th day larvae with an average length of 750 μm were found in the thorax, head, and mouthparts. Four conspicuous tail papillae characteristic of the genus Mansonella were seen in all third-stage larvae. Although the black-eyed strain of A. aegypti is an inefficient experimental vector of M. perstans, its tolerance to intrathoracic inoculations and facility to be reared in the laboratory make it a suitable alternative for obtaining larvae of this filaria.