Recovery threshold of Toxocara canis eggs from soil

The purpose of this study was to evaluate the threshold of Toxocara canis eggs form soil samples through utilisation of a centrifuge-flotation technique (CFT). Aliquots of soil (1 g each) were artificially contaminated with known numbers of T. canis eggs (1, 10, 25, 50, 100, and 200 eggs). The threshold was evaluated based on a CFT using zinc sulphate (Zn2SO4) and sodium nitrate (Na2NO3) solutions at a specific gravity of 1.20. The number of eggs recovered was directly proportional to the number of eggs employed to seed the soil. Both solutions enabled full recovery of samples containing merely three eggs; only Zn2SO4 demonstrated efficiency in soil contaminated with a single egg. A recovery rate of 100% was obtained for all tests with samples containing 10 and 25 eggs for Zn2SO4 and Na2NO3, respectively. There was no difference in the mean number of recovered eggs regarding either the efficacy of the solutions or the repetition of evaluations in the same trial (p > 0.05). Therefore, the CFT is efficient for the detection of Toxocara eggs, even in samples containing low egg numbers. (C) 2009 Elsevier B.V. All rights reserved.