Identifying Intra-Specific Variability in the Virulence of Eimeria tenella Using SCAR Markers
Abstract
Background and Objective: Coccidia are major parasitic pathogens of poultry, with infection characterized by intestinal lesions, blood loss, body weight loss, a poor feed conversion ratio, increased susceptibility to other microorganisms and mortality. The present study was undertaken to identify intra-specific variability in the virulence of Eimeria tenella strains using conventional polymerase chain reaction (PCR) and sequence characterized amplified region (SCAR) markers. Materials and Methods: A single PCR-based assay was performed to detect and identify E. tenella using SCAR markers for four strains that represent four Egyptian governorates (Alexandria, Beheira, Gharbia and Kafr El-Sheikh). The Coccivac B<*sup>® vaccine was used as a source of E. tenella (wild type). Results: Sequencing and a phylogenetic tree of all E. tenella strains showed 100% identity, except for the Gharbia governorate strain, which exhibited 97.86% identity with the other governorate strains. However, these results did not correlate with an evaluation of strain virulence using 25×10<*sup>3 oocysts per chick, as the Alexandria strain was found to be the most virulent (60% mortality and a significant reduction in weight gain). The Beheira strain was the second most virulent strain (33.33% mortality), followed by the Gharbia and Kafr El-Sheikh strains (no mortality). Conclusion: These results indicate that the nucleotide variations identified between the Gharbia strain and other strains may occur infrequently or that the portion of the genome under study is not involved in the pathogenicity of E. tenella. Furthermore, the SCAR markers used in this study may be species specific (E. tenella) and may not reveal intra-specific variations.
Keywords:
<i>Eimeria tenella</i>, Coccidia, Egypt, pathogenicity, poultry, SCAR markersArticle Metrics
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