Comparison of two methods for recovering migrating Ascaris suum larvae from the liver and lungs of pigs

Nine groups of 5 pigs were inoculated with Ascaris suum eggs on day 0. Groups 1, 2, and 3 were inoculated with 100 eggs, groups 4, 5, and 6 with 1,000 eggs, and groups 7, 8, and 9 with 10,000 eggs. On day 3, groups 1, 4, and 7 were slaughtered, on day 7 groups 2, 5, and 8, and on day 10 groups 3, 6, and 9. The liver (days 3 and 7) and lungs (days 3, 7, and 10) were removed and 2, 25% samples of both organs were collected. Larvae were recovered from 1 sample by the Baermann method and from the other by an agar-gel method. Overall there were no significant differences in the liver larval recovery between the 2 methods. The use of the agar-gel method resulted in a very clean suspension of larvae and thereby reduced the sample counting time by a factor of 5-10 compared to the Baermann method. With both methods larval recovery from the lungs resulted in a clean larval suspension that was easy to count, and there were overall no significant differences between the 2 methods, although there was a tendency toward the Baermann method recovering more larvae from the lungs than the agar-gel method. The tissue sample dry weight did not significantly influence larval recovery by the agar-gel method, and the time interval from slaughtering to start of incubation on day 3 (interval 51-92 min), day 7 (interval 37-114 min), and day 10 (interval 50129 min) had no significant effect on recovery by either method.