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

Abstract

SUMMARYThe purpose of this study was to evaluate the influence of variables in a flotation technique for the recovery of Toxocara canis eggs from soil. The trials were done under standardized conditions on one gram of previously sterilized soil samples contaminated with 200 eggs of T. canis. The following variables were evaluated in serial steps: sieving; type of wash; time of stirring; resuspension of sediment; solution flotation. Centrifuge-flotation in sodium nitrate (d = 1.20 g/cm 3 ) was adopted as an initial technique, using Tween 80 (0.2%) and decinormal sodium hydroxide as solutions for washing the samples. Ten tests were done to compare the variables, using counting in triplicate. The sieving of the material reduced significantly the recovery of eggs (p < 0.001) and the number of eggs recovered was higher when the sediment was resuspended (p < 0.05). After standardization, flotation solutions sodium chloride, zinc sulfate, sodium dichromate, magnesium sulfate, and sodium nitrate (d = 1.20g/cm 3 ) were compared. The best results were obtained by using zinc sulfate solution. In conclusion, the chances of recovering T. canis eggs from samples using flotation solutions can be increased by washing of soil twice using distilled water, and resuspension of sediment. On the other hand, the sieving procedure can drastically reduce the number of eggs.

Soil Contamination with Soil Transmitted Helminthes in Schools and Play Areas of Kermanshah City, West of Iran

“…According to the results of the present study, soil contamination with geohelminth eggs (2.6%) is low in Kermanshah compared to the other studied areas in Iran and other countries. Environmental factors such as soil type, preprocessing sieving, suspension of sediment, washing and flotation and specific gravity of flotation solution seem to influence the recovery of geohelminth eggs in the soil (14,15). Furhtermore, some factors like climate, herbage and presence of animals could affect soil contamination (16).…”

Contamination of public parks in Presidente Prudente (São Paulo, Brazil) by Toxocara spp. eggs

“…Human infection is most commonly caused by accidental ingestion of larvated Toxocara spp. eggs that are present in contaminated environments, particularly soil in public areas such as parks and gardens that are frequented by dogs, cats and humans (SANTARÉM et al, 2011).…”

“…To recover Toxocara spp. eggs, a technique described elsewhere was used (SANTARÉM et al, 2009). The Kruskal-Wallis test was used to compare the number of eggs in different areas, months and seasons, while Spearman's correlation was used to evaluate the influence of temperature (°C) and rainfall (mm) on the number of eggs.…”

“…It has been stated that environmental and technical factors, such as the type of soil and the technique used for egg recovery, presumably influence the recovery of ascarid eggs from environmental samples (NUNES et al, 1994;SANTARÉM et al, 2009). Consequently, these factors can influence the process of egg recovery, which creates difficulties in comparing the results from different investigations.…”

Contaminação do solo por ovos de Toxocara spp. em assentamento rural de Mirante do Paranapanema, São Paulo, Brasil

“…Somado a esses problemas, o número de animais de estimação dessas populações é alto, especialmente o de cães, que são criados em condições precárias de higiene e nutrição, o que possibilita a transmissão de zoonoses, como o complexo larva migrans (MATOS et al, 2002 A recuperação de ovos de Toxocara spp. a partir de amostras de solo e a sua viabilidade pode ser influenciada por fatores ligados à técnica de diagnóstico e por fatores ambientais, como temperatura, umidade e tipo de solo (MURADIAN et al, 2005;MAGOTI;SICHIERI, 2009). No presente estudo, a técnica utilizada para recuperação dos ovos foi semelhante à descrita em outros estudos em assentamentos rurais (PRESTES-CARNEIRO et al, 2008;SANTARÉM et al, 2008).…”