File:Ascaris Larva.The larva of Ascaris lumbricoides developing in the egg File:Ascaris lumbricoides.Ascaris lumbricoides adult worms (with measuring tape for scale) File:Ascaris lumbricoides adult worms.Ascaris lumbricoides adult worms File:Ascaris egg, incubation process.Ascaris egg, incubation process: The Ascaris egg incubation process consists of placing the egg in a controlled environment, at 26 °C during 28 days, in acidic conditions. This process allows for the evaluation of an egg to determine if it is viable or not. Ascaris life cycle: Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with feces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4), the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation and/or lymphatics to the lungs. The larvae mature further in the lungs (6) (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years. Transmission The source of infection is from objects which have been contaminated with fecal matter containing eggs. Ingestion of infective eggs from soil contaminated with human feces or contaminated vegetables and water is the primary route of infection. Infectious eggs may occur on other objects such as hands, money and furniture. Transmission from human to human by direct contact is impossible. Transmission comes through municipal recycling of wastewater into crop fields. This is quite common in emerging industrial economies and poses serious risks for local crop sales and exports of contaminated vegetables. A 1986 outbreak of<unk>  in Italy was traced to irresponsible wastewater recycling used to grow Balkan vegetable exports. The number of ova (eggs) in sewage or in crops that were irrigated with raw or partially treated sewage, is a measure of the degree of<unk>  incidence. For example: * In a study published in 1992, municipal wastewater in Riyadh, Saudi Arabia detected over 100 eggs per litre of wastewater and in Czechoslovakia was as high as 240–1050 eggs per litre. * In one field study in Marrakech, Morocco, where raw sewage is used to fertilize crop fields, Ascaris eggs were detected at the rate of 0.18 eggs/kg in potatoes, 0.27 eggs/kg in turnip, 4.63 eggs/kg in mint, 0.7 eggs/kg in carrots, and 1.64 eggs/kg in radish. A similar study in the same area showed that 73% of children working on these farms were infected with helminths, particularly Ascaris, probably as a result of exposure to the raw sewage. Lifecycle The first appearance of eggs in stools is 60–70 days. In larval<unk> , symptoms occur 4–16 days after infection. The final symptoms are gastrointestinal discomfort, colic and vomiting, fever, and observation of live worms in stools. Some patients may have pulmonary symptoms or neurological disorders during migration of the larvae. There are generally few or no symptoms. A bolus of worms may obstruct the intestine; migrating larvae may cause pneumonitis and eosinophilia. Adult worms have a lifespan of 1–2 years which means that individuals may be infected all their lives as worms die and new worms are acquired. Eggs can survive potentially for 15 years and a single worm may produce 200,000 eggs a day. They maintain their position by swimming against the intestinal flow.
Ascariasis
Toxocariasis
Acariasis
Schistosomiasis
Strongyloidiasis
Myiasis
Monorchism
Intestinal capillariasis