Flotation and adherence characteristics of Toxocara canis and T. cati and a reliable method for recovering Toxocara eggs from soil

Abstract

Toxocara canis and T. cati are worldwide distributed intestinal nematodes of canids and felids and pose a threat to public health due to possible clinical manifestations in humans. Different methods for detection of Toxocara eggs in soil have been described, but conducted studies deal with egg recovery rates of T. canis or "Toxocara spp." only whereas T. cati egg recovery has not been taken into consideration. Thus, flotation properties in sodium chloride solution and adherence characteristics to different substrates possibly coming into contact with Toxocara eggs before or during purification from soil were evaluated for both, T. canis and T. cati eggs. No significant difference was observed in flotation characteristics, but comparison of adherence properties revealed significantly less adherence of T. cati eggs on almost all evaluated substrates ("sand", side sealed bags, glass beaker, centrifuge tube) and different washing solutions (tap water, Tween(®) 80, Triton™ X-100). Mean adhesion rates of T. cati eggs ranged from 15.9% to 68.9%, those of T. canis eggs from 28.3% to 83.9%. While adherence of T. cati eggs on any substrate was significantly reduced when rinsing with Tween(®) 80 solution, no effect on T. canis eggs could be observed. Generally, Toxocara eggs adhere better on plastic than on glass. Evaluation of a method including only non-hazardous substances for purification of Toxocara eggs from soil resulted in a statistically significant higher recovery rate of T. canis (42.6% recovered eggs) compared to T. cati eggs (30.9% recovered eggs). As these percentages are above average for described methods to recover Toxocara eggs from soil, the presented method is considered reliable for prevalence studies.

Keywords: Adherence; Egg recovery; Flotation; Roundworms; Sand; Soil; Toxocara canis; Toxocara cati.