Trematode Fluke Procerovum varium as Cause of Ocular Inflammation in Children, South India.

Lalan Kumar Arya,Sivakumar R Rathinam,Usha R Kim,Prajna Lalitha,Veena Tandon,Sudeep Ghatani

doi:10.3201/eid2202.150051

Abstract

Trematodes are recognized as a group of emerging parasites in tropical countries. We identified a trematode as a cause of ocular granulomas that developed in children who bathed in ponds or rivers in South India. DNA was isolated from patients' surgically excised granulomas and from the trematode cercariae (larvae) released by the snail Melanoides tuberculata in water in which the children bathed. Real-time and conventional PCRs were performed that targeted ribosomal DNA regions spanning the internal transcribed spacer 2 and 28S sequences of this trematode. The PCR-amplified products were subjected to bidirectional sequencing. Analysis of sequences for the granuloma samples and the trematode cercariae showed maximum sequence similarity with Procerovum varium (family Heterophyidae). Our results confirmed the etiology of the ocular infection, implicating snail vectors as environmental risk factors for ocular parasitosis.

Highlights

IntroductionWe identified a trematode as a cause of ocular granulomas that developed in children who bathed in ponds or rivers in South India
Trematodes are recognized as a group of emerging parasites in tropical countries
In South India, infection with the trematode P. varium was reported in the pond heron Ardeola grayii, and heavy infections with metacercariae were found in the fish Oryzias melastigma [21]

Summary

Introduction

We identified a trematode as a cause of ocular granulomas that developed in children who bathed in ponds or rivers in South India. Analysis of sequences for the granuloma samples and the trematode cercariae showed maximum sequence similarity with Procerovum varium (family Heterophyidae). We later reported molecular evidence that established the trematode Procerovum varium as the source of the ocular granuloma in a single patient from the same region as that of the children in the previous study [19]. Ocular parasitosis caused by Procerovum spp. was first reported in fish in the Philippines [22]. Recent development of molecular methodologies like real-time PCR, sequencing, and BLAST analysis (http:// blast.ncbi.nlm.nih.gov/Blast.cgi) offer opportunities for identifying the parasite at the species level [25,26,27,28]

Methods

Results

Conclusion