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After molting twice and growing considerably in size while in the lung alveoli, the larvae travel up the bronchi and trachea to the epiglottis and are swallowed. The worms mature within the lumen of the small intestine, especially the jejunum, and reach a size of 15-35 cm in about 2 months. The adult female ascarid is somewhat larger than the male, measuring 22-35 cm in length and 3-6 mm in width, whereas the male ranges from 15-31 cm in length and 2-4 mm in width. The adult worms are fusiform and cylindrical in shape and white or creamy-pink. The anterior end of the ascarid is blunt, whereas the posterior end is pointed and, in the male, coiled (Fig. 10.4). Copulation occurs in the small intestine and a new generation of ova appears in the feces 2 to 3 months after ingesting infective eggs. The fertile female has a life span of 6 months to 1 year and, during this time, produces up to 25 million eggs, depositing up to 250,000 ova per day.

Fig. 10.4 Adult Ascaris male and female worms. Note the coiled or recurved posterior end of the male Ascaris.

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