Use of a polyurethane carrier for assessing the survival of helminth eggs in liquid biological sludges.

Soft expanded polyurethane (plastic foam) was used as an egg carrier. A carrier of helminth eggs and a method for their isolation were tested. They proved applicable to evaluation of the survival of helminth eggs in liquid biological substrates (sludges, liquid excrements). The inside of the carrier was inoculated with 1,000 +/- 50 Ascaris suum eggs. After 21 days of incubation in an aerated medium at room temperature, 660.7 (66.1%) eggs were isolated on the average (n = 10, Tab. I). The carriers incubated in the medium at 4 degrees C yielded 716.2 eggs (71.6%) on the average (Tab. II). The intactness of the carriers in helminth eggs was proved during 21 days of incubation in aerated medium when the detected mean percentage of embryonated eggs was 80.5% (Fab. I). From the carriers kept at 4 degrees C for 21 days and subsequently incubated 76.6% of embryonated eggs were recovered on the average (Tab. II). Control showed 80.95% of embryonated eggs on the average, which is a statistically insignificant difference (P < 0.05). With the use of the carrier more than a 13-fold increase in the viable eggs was recorded, compared with a 5% yield obtained at a direct inoculation into liquid substrates. This method is rewarding for its optimization of experimental results and for reducing the number of eggs used in the experiments.