Transmission<unk> <unk>  infective larvae (L3) are transmitted to humans by the deer fly vectors Chrysops silica and C. dimidiata. These carriers are blood-sucking and day-biting, and they are found in rainforest-like environments in western and central Africa. Infective larvae (L3) mature to adults (L5) in the subcutaneous tissues of the human host, after which the adult worms—assuming presence of a male and female worm—mate and produce microfilariae. The cycle of infection continues when a non-infected mango or deer fly takes a blood meal from a microfilaremic human host, and this stage of the transmission is possible because of the combination of the diurnal periodicity of microfilariae and the day-biting tendencies of the Chrysops spp. Reservoir Humans are the primary reservoir for<unk> <unk> . Other minor potential reservoirs have been indicated in various fly-biting habit studies, such as hippopotamus, wild ruminants (e.g. buffalo), rodents and lizards. A simian type of loiasis exists in monkeys and apes but it is transmitted by Chrysops langi. There is no crossover between the human and simian types of the disease. A related fly, Chrysops langi, has been isolated as a vector of simian loiasis, but this variant hunts within the forest and has not as yet been associated with human infection. Vector<unk> <unk>  is transmitted by several species of tabanid flies (Order: Diptera; Family: Tabanidae). Although horseflies of the genus Tabanus are often mentioned as vectors, the two most prominent vectors are from the tabanid genus Chrysops—C. silacea and C. dimidiata. These species exist only in Africa and are popularly known as deer flies and mango, or mangrove, flies. Chrysops spp. are small (5–20 mm long) with a large head and downward-pointing mouthparts. Their wings are clear or speckled brown. They are hematophagous and typically live in forested and muddy habitats like swamps, streams and reservoirs, and in rotting vegetation. Female mango and deer flies require a blood meal for production of a second batch of eggs. This batch is deposited near water, where the eggs hatch in 5–7 days. The larvae mature in water or soil, where they feed on organic material such as decaying animal and vegetable products. Fly larvae are 1–6 cm long and take 1–3 years to mature from egg to adult. When fully mature, C. silacea and C. dimidiata assume the day-biting tendencies of all tabanids. The bite of the mango fly can be very painful, possibly because of the laceration style employed; rather than puncturing the skin as a mosquito does, the mango fly (and deer fly) makes a laceration in the skin and subsequently laps up the blood. Female flies require a fair amount of blood for their aforementioned reproductive purposes and thus may take multiple blood meals from the same host if disturbed during the first one. Although Chrysops silacea and C. dimidiata are attracted to canopied rainforests, they do not do their biting there. Instead, they leave the forest and take most blood meals in open areas. The flies are attracted to smoke from wood fires and they use visual cues and sensation of carbon dioxide plumes to find their preferred host, humans. A study of Chrysops spp. biting habits showed that C. silacea and C. dimidiata take human blood meals approximately 90% of the time, with hippopotamus, wild ruminant, rodent and lizard blood meals making up the other 10%. Morphology Adult<unk>  worms are sexually dimorphic, with males considerably smaller than females at 30–34 mm long and 0.35–0.42 mm wide compared to 40–70 mm long and 0.5 mm wide. Adults live in the subcutaneous tissues of humans, where they mate and produce wormlike eggs called microfilariae. These microfilariae are 250–300 μm long, 6–8 μm wide and can be distinguished morphologically from other filariae, as they are sheathed and contain body nuclei that extend to the tip of the tail. Lifecycle<unk> <unk>  life cycle. Source: CDC The vector for<unk>  originates with flies from two hematophagous species of the genus Chrysops (deer flies), C. silacea and C. dimidiata. During a blood meal, an infected fly (genus Chrysops, day-biting flies) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound. The larvae develop into adults that commonly reside in subcutaneous tissue. The female worms measure 40 to 70 mm in length and 0.5 mm in diameter, while the males measure 30 to 34 mm in length and 0.35 to 0.43 mm in diameter. Adults produce microfilariae measuring 250 to 300 μm by 6 to 8 μm, which are sheathed and have diurnal periodicity. Microfilariae have been recovered from spinal fluids, urine and sputum. During the day, they are found in peripheral blood, but during the noncirculation phase, they are found in the lungs. The fly ingests microfilariae during a blood meal. After ingestion, the microfilariae lose their sheaths and migrate from the fly's midgut through the hemocoel to the thoracic muscles of the arthropod. There the microfilariae develop into first-stage larvae and subsequently into third-stage infective larvae. The third-stage infective larvae migrate to the fly's proboscis and can infect another human when the fly takes a blood meal.
Loa loa filariasis
Onchocerciasis
Isosporiasis
Thelaziasis
Cyclosporiasis
Necatoriasis
Toxocariasis
Paragonimiasis