Ascariasis epidemiology and demographics


 * Associate Editor-In-Chief: Imtiaz Ahmed Wani, M.B.B.S

Overview
Roughly 1.5 billion individuals are infected with this worm, primarily in Africa and Asia. Ascariasis is endemic in the United States including Gulf Coast; in Nigeria and in Southeast Asia. One study indicated that the prevalence of ascariasis in the United States at about 4 million (2%) [8]. In a survey of a rural Nova Scotia community, 28.1% of 431 individuals tested were positive for Ascaris, all of them being under age 20, while all 276 tested in metropolitan Halifax were negative. Ascariasis occurs in people of all ages, though children are affected more severely than adults.

Deposition of ova (eggs) in sewage hints at the degree of ascariasis incidence. A 1978 study showed about 75% of all sewage sludge samples sampled in United States urban catchments contained Ascaris ova, with rates as high as 5 to 100 eggs per litre. In Frankfort, Indiana, 87.5% of the sludge samples were positive with Ascaris, Toxocara, Trichuris, and hookworm. In Macon, Georgia, one of the 13 soil samples tested positive for Ascaris. 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.

Ascariasis can often be measured by examining food for ova. 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.