Flies are insects of the order Diptera, the name has meaning in two wings or they have only single pair of wings to fly and the hindwings having evolved know as halteres (small size). They have three bodies regions including head, thorax and abdomen along with three pairs of legs. In suborders Nematocera, it have special characteristics as elongated segments antennae which consist of mosquito, sand fly, black fly and biting midges. Black fly or Simulium spp. They have a small size (1-5 mm. in long) black color, short leg, sucking mouthparts, humped-back appearance, horn like antennae without hair and complete metamorphosis. They are the vector for Onchocerciasis (River blindness) cause by Onchocerca volvulus.The mechanism of transmission starts with the infected black flies take a blood meal on human, its will release L3 larvae. The larvae migrate to subcutaneous tissue and grow into adult. The adult parasites will produce microfilariae (diagnostic stages). The microfilariae normally have found in skin and lymphatics tissue but can found in peripheral blood. After this the new black flies will come to human to take a blood meal, that also get the microfilia from the infected host and develop in black flies. When black flies took a blood meal on new human who became infected host.
Thawatchai Ketboonlue
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