Molecular Determination of Toxocara spp. Eggs Isolated from Public Parks and Playgrounds in Zahedan, Southeast Iran

Abstract

Background: Human toxocariasis (HT) is a zoonotic disease with a global expansion. Contaminated soil with Toxocara spp. eggs is the main source of human infection, which may lead to severe complications depending on the organs invaded by migrating larvae.

Aim: This study is aimed at eliciting the prevalence of Toxocara spp. eggs in public parks in Zahedan, southeast Iran, and providing new insight into the soil contamination rate in this area using microscopic and molecular methods.

Methods: Based on five municipal districts, 240 soil samples were collected from public parks and playgrounds in Zahedan. The modified Sheather's flotation technique was employed to isolate Toxocara spp. eggs from the soil, followed by microscopic assessment and molecular evaluation of internal transcribed spacer 1 and 2 ribosomal deoxyribonucleic acid (ITS1 and 2 rDNA) using nested polymerase chain reaction (nested PCR) to identify the presence of Toxocara spp. eggs. The Sanger sequence was used to differentiate the Toxocara species. Subsequently, all the sequenced data were blasted and compared with other sequences available in the GenBank.

Results: Out of 240 soil samples collected, 7 (2.9%) samples were identified to contain Toxocara spp. eggs using Sheather's flotation and microscopic techniques. Meanwhile, 19 (7.9%) samples were positive using nested PCR. According to the Sanger sequencing analysis findings, all positive samples were contaminated with Toxocara cati.

Conclusion: As evidenced by the obtained results, only T. cati species were detected in public parks and playgrounds in Zahedan; therefore, control and prevention programs against this species should be considered in human and animal communities.

Figure 1

The map of the studied parks from five municipal districts of Zahedan for soil sampling.

Figure 2

Toxocara spp. egg was isolated from soil using Sheather's flotation technique.

Figure 3

Agarose gel electrophoresis of the second step of nested PCR products. M: 100 bp DNA marker; N: negative control; lane 1: positive control; lanes 2–9: Toxocara spp. infected soil samples (yielded amplicons of approximately 700 bp).

Figure 4

Alignment of sequences of the ITS1 and ITS2 genes of T. cati (OR591276, OR591277, OR591278, OR591279, OR591280, OR616610, OR616611, and OR616612) isolated from soil samples at the Zahedan, Iran, with T. cati isolated (MF592401) from Shiraz, Iran.