Date Published: December 23, 2015
Publisher: Public Library of Science
Author(s): Mónica J. Pajuelo, María Eguiluz, Eric Dahlstrom, David Requena, Frank Guzmán, Manuel Ramirez, Patricia Sheen, Michael Frace, Scott Sammons, Vitaliano Cama, Sarah Anzick, Dan Bruno, Siddhartha Mahanty, Patricia Wilkins, Theodore Nash, Armando Gonzalez, Héctor H. García, Robert H. Gilman, Steve Porcella, Mirko Zimic, Klaus Brehm. http://doi.org/10.1371/journal.pntd.0004316
Abstract: BackgroundInfections with Taenia solium are the most common cause of adult acquired seizures worldwide, and are the leading cause of epilepsy in developing countries. A better understanding of the genetic diversity of T. solium will improve parasite diagnostics and transmission pathways in endemic areas thereby facilitating the design of future control measures and interventions. Microsatellite markers are useful genome features, which enable strain typing and identification in complex pathogen genomes. Here we describe microsatellite identification and characterization in T. solium, providing information that will assist in global efforts to control this important pathogen.MethodsFor genome sequencing, T. solium cysts and proglottids were collected from Huancayo and Puno in Peru, respectively. Using next generation sequencing (NGS) and de novo assembly, we assembled two draft genomes and one hybrid genome. Microsatellite sequences were identified and 36 of them were selected for further analysis. Twenty T. solium isolates were collected from Tumbes in the northern region, and twenty from Puno in the southern region of Peru. The size-polymorphism of the selected microsatellites was determined with multi-capillary electrophoresis. We analyzed the association between microsatellite polymorphism and the geographic origin of the samples.ResultsThe predicted size of the hybrid (proglottid genome combined with cyst genome) T. solium genome was 111 MB with a GC content of 42.54%. A total of 7,979 contigs (>1,000 nt) were obtained. We identified 9,129 microsatellites in the Puno-proglottid genome and 9,936 in the Huancayo-cyst genome, with 5 or more repeats, ranging from mono- to hexa-nucleotide. Seven microsatellites were polymorphic and 29 were monomorphic within the analyzed isolates. T. solium tapeworms were classified into two genetic groups that correlated with the North/South geographic origin of the parasites.Conclusions/SignificanceThe availability of draft genomes for T. solium represents a significant step towards the understanding the biology of the parasite. We report here a set of T. solium polymorphic microsatellite markers that appear promising for genetic epidemiology studies.
Partial Text: Cysticercosis is an infection caused by the larval stage of the cestode Taenia solium. When the larval stages infect the central nervous system, the infection is known as neurocysticercosis (NCC) and is the most common cause of adult-onset seizures in endemic regions worldwide. Crude estimates of the burden of infection and disease suggest that greater than ten million people have NCC and as many as 2.7–5.6 million suffer from epilepsy . A recent analysis concluded that in Latin America, vast parts of Asia, the Indian subcontinent and Southern China, Sub-Saharan Africa, and Oceania, 29% of all cases of epilepsy are attributable to NCC .
The present study describes the draft genome sequences of two T. solium isolates and the identification and characterization of DNA microsatellites. The T. solium microsatellites reported here were found to be distributed along the entire genome. The length polymorphism of microsatellites was analyzed for its association with the geographic origin of tapeworm isolates. We found novel microsatellites that were able to differentiate tapeworms between the northern and southern regions of Peru.