Spirurida

Life cycle of Wuchereria bancroftiVarious species of mosquitoes are known vectors of Wuchereria bancrofti filariasis, depending on geographic distribution. Among these are: Culex (C. annulirostris, C. bitaeniorhynchus, C. quinquefasciatus, and C. pipiens); Anopheles (A. arabinensis, A. bancroftii, A. farauti, A. funestus, A. gambiae, A. koliensis, A. melas, A. merus, A. punctulatus and A. wellcomei); Aedes (A. aegypti, A. aquasalis, A. bellator, A. cooki, A. darlingi, A. kochi, A. polynesiensis, A. pseudoscutellaris, A. rotumae, A. scapularis, and A. vigilax); Mansonia (M. pseudotitillans, M. uniformis); and Coquillettidia (C. juxtamansonia). During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound (1). They develop in adults that commonly reside in the lymphatics (2). The female worms measure 80 to 100 mm in length and 0.24 to 0.30 mm in diameter, while the males measure about 40 mm by 0.1 mm. Adults produce microfilariae measuring 244 to 296 μm by 7.5 to 10 μm, which are sheathed and have nocturnal periodicity, except for the South Pacific microfilariae, which lack marked periodicity. The microfilariae migrate into lymph and blood channels moving actively through lymph and blood (3). A mosquito ingests the microfilariae during a blood meal (4). After ingestion, the microfilariae lose their sheaths and some of them work their way through the wall of the proventriculus and cardiac portion of the mosquito's midgut and reach the thoracic muscles (5). There the microfilariae develop into first-stage larvae (6) and subsequently into third-stage infective larvae (7). The third-stage infective larvae migrate through the hemocoel to the mosquito's prosbocis (8) and can infect another human when the mosquito takes a blood meal (1).From Centers for Disease Control Parasites and Health website.

Figure 2.Longior longior Morffe & García sp. n. (female). A Esophageal region B Cephalic end C Tail, ventral view D Vulva E Egg F Genital tract G Entire nematode, lateral view.

Figure 3.Longior longior Morffe & Garcíasp. n. (male). A Entire nematode, lateral view B Esophageal region, lateral view C Cephalic end D Tail, lateral view.

Figure 5. Longior longior Morffe & García sp. n. (female). A Cephalic end B Egg. Longior longior Morffe & García sp. n. (male) C Cephalic end D Tail, lateral view E Pre-cloacal median mammiform papilla, lateral view F Post-cloacal dorso-lateral papilla. Longior similis Morffe, García & Ventosa, 2009 (male) G Cephalic end H Tail, lateral view. Scale bars: A, B, C, D, G, H. 0.05 mm. E, F. 0.020 mm.

Magnified 125X, this photomicrograph revealed the presence of a fertile Ascaris sp. egg that was found in an unstained formalin-preserved stool sample. See PHIL 411 for an example of an unfertilized Ascaris lumbricoides egg.Geographic Distribution:The most common human helminthic infection, Ascaris sp. have a worldwide distribution. Their highest prevalence is in tropical and subtropical regions, and areas with inadequate sanitation. Ascariasis occurs in rural areas of the southeastern United States.Created: 1973

This diagram depicts the various stages in the life cycle of the human pinworm nematode Enterobius vermicularis.Created: 1982

This illustration depicts the life cycle of Baylisascaris procyonis, the causal agent of Baylisascariasis.Created: 2002

This is an illustration of the life cycle of Dracunculus medinensis, the causal agent of Dracunculiasis.Created: 2002

This is an illustration of the life cycle of Mansonella perstans, one of the causal agents of Filariasis.Created: 2002

This illustration depicts the life cycle of A. simplex and P. decipiens, the causal agents of Anisakiasis.Created: 2002

This is an illustration of the life cycle of Mansonella streptocerca, one of the causal agents of Filariasis.Created: 2002

This is an illustration of the life cycle of Toxocara canis and Toxocara cati, the causal agents of Toxocariasis.Created: 2002

This is an illustration of the life cycle of Wuchereria bancrofti, one the causal agents of Filariasis.Created: 2003

This illustration depicts the life cycle of Brugia malayi, the causal agent of Filariasis.Created: 2002

This is an illustration of the life cycle of Loa loa, one of the causal agents of Filariasis.Created: 2003

This diagram depicts the various stages in the life cycle of the intestinal roundworm nematode Ascaris lumbricoides.Created: 1982

Depicted in this 1960 photograph were two Ascaris lumbricoides nematods, i.e., roundworms. The larger of the two was the female of the species, while the normally smaller male was on the right. Adult female worms can grow over 12 inches in length.Created: 1960

This 2007 photograph depicted Center for Disease Control/ NCZVED/DPD laboratory technician, Henry Bishop holding a mass of Ascaris lumbricoides worms, which had been passed by a child in Kenya, Africa. This nematode parasitizes the human small intestine, and is spread from human to human by the fecal-oral route. Children seem to be infected more often than adults, and though the organisms depicted here originated in Africa, the disease can be acquired in the southeastern United States.Created: 2007

This is an illustration of the life cycle of Mansonella ozzardi, one of the causal agents of Filariasis.Created: 2002