Improved method for recovering ascarid and other helminth eggs from soil associated with epizootics and during survey...

Two noncentrifugal and 5 centrifugal flotation methods for the recovery of infective Baylisascaris procyonis eggs from contaminated soil were evaluated after an epizootic of fatal cerebrospinal nematodiasis in bobwhites. All involved the use of inexpensive, readily available materials and routine procedures. In all but 1 of the methods, sizes of the soil samples were 30 g; in 1 centrifugal method, the sample size was 1 g. The centrifugal methods included various combinations of (i) anionic detergent (Tween) pretreatment of the soil, (ii) 3 X washing of the sediment, (iii) NaNO3 or ZnSO4 flotation solution, and (iv) resuspension and reexamination of the sediment. By the 30-g sample centrifugal methods, significantly more eggs (av 251 to 448) were recovered than by the noncentrifugal methods (av 7 and 12) or the 1-g sample method (av 44). In the most efficacious method, the combination of Tween pretreatment, washed sediment, NaNO3 flotation solution, and resuspension/reexamination of the sediment was used. This method was tested against the 1-g sample method on soil from a naturally occurring infection of Toxocara cati visceral larva migrans in a child. On initial examination of 5 areas, 3 to 10 eggs were recovered by the 30-g sample method vs 0 eggs by the 1-g sample method. Using sandbox soil and 10 replicates each, recoveries by the 30-g sample method averaged 9.2 eggs/replicate (range 5 to 12) and those by the 1-g sample method, 0.1 eggs (range 0 to 1).