Development of human and pig ascaris in the pig and rabbit

Pigs on balanced rations were given single inocula of 100, 500 or 5,000 infective eggs of pig ascaris (A. suum) or human ascaris (A. lumbricoides) and examined 9 to 91 days later. Rabbits were similarly inoculated. At 9, 11, and 22 days of infection in rabbits more larvae of A. lumbricoides than of A. suum were recovered, while in pigs more larvae of A. suum usually were recovered. A. suum had a more rapid rate of tracheal migration in both pigs and rabbits and, with few exceptions, a shorter prepatent period in pigs (40 to 53 days) than did A. lumbricoides (54 to 61 days). At 45 to 91 days of infection, 20 of 21 pigs inoculated with A. suum harbored 3 to 669 worms, and 8 of 11 pigs inoculated with A. lumbricoides harbored 1 to 23 worms; among 15 uninoculated controls, two harbored 1 and 4 worms, respectively. The observations indicate that in the pig A. lumbricoides is capable of producing patent infection, though it differs markedly from A. suum in the rate and frequency of development to sexual maturity.