Scarce and inconclusive information on general biological impact of Toxocara invasion on paratenic hosts, and people in particular, has led us to undertake a comprehensive study of the problem. The study has been conducted in a rural environment, which is considered a toxocarosis risk factor. In total 200 soil samples have been screened for Toxocara eggs by flotation, of which 14.5% were positive. Backyards close to households were most heavily contaminated with infectious eggs--21.7% of positive samples. ELISA serological tests performed on 242 lower-secondary students found 14.5% of the studied population to be definitely positive--16.5% of boys and 12.8% of girls, respectively. The odds of being infected with Toxocara were 2 times (CI: 1.15-3.85) more likely for individuals who owned a cat than those who did not own a cat. Strong significant correlation between seropositivity and the presence of a dog in a household was found with boys. The level of developmental age was significantly higher in seropositive than in seronegative students. No significant correlation has been observed between the motor abilities and seropositivity of students. Seropositive boys had significantly lower end-of-year grades than their seronegative counterparts.

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This chapter focuses on soil contamination of Toxocara eggs with particular reference to their survival on the soil surface. In addition, this chapter discusses type of soil and egg prevalence, Toxocara canis and T. cati egg discrimination, exposure and countermeasures. The conclusions are summarized as follows: (1) soil contamination with the eggs of Toxocara spp. occurs worldwide, irrespective of socioeconomic and developmental status; (2) there is a clear connection between the degree of soil contamination with Toxocara spp. eggs and the prevalence of toxocariasis among people; (3) the method of recovery of Toxocara spp. eggs in soil should be standardized; (4) species recognition of Toxocara eggs isolated from soil during the environmental studies will allow better prevention; (5) destroying the eggs of Toxocara spp. is difficult because of their resistance to adverse conditions, easy spreading and longevity; (6) effective control of toxocariasis should include - prevention of contamination of public places with pet faeces, systematic disinfestations of definitive hosts and development of educational programmes aimed at increasing public awareness of potential zoonotic threats.

A polymerase chain reaction (PCR) technique has been used for the differentiation of T. canis and T. cati eggs isolated from soil and previously identified from microscopical observations. The method, using specific primers for the identification of the two Toxocara species, was assessed in both the field and laboratory. Successful results were obtained when only a single or large numbers of eggs were recovered from 40 g soil samples. The method is sensitive, allows analysis of material independent of the stage of egg development and can be adapted for the recovery of other species of parasites from soil.

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