Studies on the incidence of Toxocara and Toxascaris spp. ova in the environment. 1. A comparison of flotation procedures for recovering Toxocara spp. ova from soil

Abstract

Seven different flotation fluids were assessed for their efficiency in recovering Toxocara canis ova from artificially seeded soil samples. Using the most efficient (a saturated solution of magnesium sulphate plus 5% potassium iodide) 25 g amounts of 234 environmental soil samples were examined for the presence of Toxocara spp. and Toxascaris ova. Twenty-six samples (11.1%) yielded ova of one or other species. There was no discernible pattern of distribution of positives with relation to the source of the samples. The maximum number of ova recovered in any one sample was 19. All the ova recovered from the environment were considered viable and potentially infective.

Effectiveness of coproscopic concentration techniques

“…The implementation of the centrifugation step improves the recovery of strongyle type eggs as it was reported for other flotation techniques with different media (Zajac et al, 2002;Cebra & Stang, 2008). In the present study, a centrifugation step was added to both flotation procedures, so differences in strongyle egg counts among flotation techniques are not solely dependent on specific gravities of solutions as it was proposed by other authors (Quinn et al, 1980;Cringoli et al, 2004), being probably that differences in the solution characteristics, like viscosity and/or osmotic pressure may be influencing eggs floating capacity. Additionally, since strongyle type eggs have thin shells, the addition of drops of hydrochloric acid to the tube before the addition of the zinc chloride solution, in the case of the centrifugation in the zinc chloride flotation, could also destroy or modify egg shells, inhibiting their suspensions.…”

“…For flotation procedures, specific gravity of the flotation solution, viscosity, the volume of flotation solution employed, application of additional centrifugation step, duration and speed of centrifugation and the elapsed time, among others, must be considered (O'Grady & Slocomb, 1980;Cringoli et al, 2004Cringoli et al, , 2010. Additionally important consideration is the selection of those procedures that causes the minimal egg distortion or destruction (O'Grady & Slocomb, 1980;Quinn et al, 1980;Cringoli et al, 2004). Parasitological research on SAC usually utilizes flotation procedures with low specific gravities solutions (δ < 1.3) (Leguía & Casas, 1998;Jarvinen, 1999;Cafrune et al, 2001;Beldoménico et al, 2003;Cebra & Stang, 2008) being probable that some parasites with high density are underscore, as it was suggested for E. macusaniensis or L. chavezi, among others (Jarvinen, 1999;Cafrune et al, 2001Cafrune et al, , 2009Cebra & Stang, 2008).…”

Influence of variables on centrifuge-flotation technique for recovery of Toxocara canis eggs from soil

“…In an attempt to evaluate the best technique to recover Toxocara eggs some authors carried out comparative studies among different techniques 7,19,24,27,28 . They compared the techniques as a whole, disregarding the possible interference of variables in each technique.…”

Division of methods for counting helminths’ eggs and the problem of efficiency of these methods

“…Considering the fact that at present there is no method for the determination of eggs of helminths in sewage sludge, the standardized flotation method by Spindler is used, as modified by Wasilkowa, designed mainly for the examination of soil, and the flotation method by Quinn et al (1980). The number of eggs is converted into 1kg dry mass of the sample [22,23].…”