First Report on Molecular Characterization of Taenia multiceps Isolates From Sheep and Goats in Faisalabad, Pakistan

Abstract

Coenurus cerebralis is the larval stage of Taenia multiceps commonly found in the brain (cerebral form), intramuscular and subcutaneous tissues (non-cerebral form) of ungulates. Globally, few reports exist on the molecular characterization and genetic diversity of C. cerebralis with none available for Pakistan. The current study molecularly characterized 12 C. cerebralis isolates surgically recovered from sheep (n = 4) and goats (n = 8) from a total of 3,040 small ruminants using a portion of the cytochrome c oxidase subunit 1 (cox1) mitochondrial (mt) gene. NCBI BLAST search confirmed the identity of each isolate. A high haplotype and a low nucleotide diversity with three haplotypes from the 12 isolates were observed. The findings suggest the existence of unique haplotypes of C. cerebralis in Pakistan. The negative value of Tajima's D and the positive value of Fu's Fs were inconsistent with population expansion, however, the sample size was small. Bayesian phylogeny revealed that all Pakistani isolates alongside the Chinese sequences (obtained from GenBank) constituted a cluster while sequences from other regions constituted another cluster. This is the first molecular study to determine the genetic diversity of C. cerebralis in Pakistan and serves as a foundation for prospective studies on the prevalence and population structure of C. cerebralis in the country. Furthermore, in this study, we amplified only a partial segment of the cox1 gene from a limited sample size. This could have implications on the interpretation of the actual population structure in reality. Thus, we recommend future studies to consider a larger sample size in a massive epidemiological survey for further insights.

Keywords: Coenurus cerebralis; Pakistan; Taenia multiceps; cox1; genetic diversity; phylogeny.

Figure 1

(a) A goat presented to the CMS Department of University of Agriculture, Faisalabad, Pakistan with a swollen mass around the neck region. (b) Surgically isolated Coenurus cerebralis cyst from the neck region of a goat. Scolices are attached to the internal layer of the cyst (white clusters). (c) Ultrasound scan of T. multiceps cyst in goat. Lengthwise and widthwise boundaries of the cyst are demarcated with dotted lines and plus (+) signs. The yellow arrow indicates the host's muscular layer, blue arrow indicates hypoechoic cyst wall, white arrow indicates anechoic cystic fluid, and red arrow indicates protoscolices.

Figure 2

(A) Median-joining network of Coenurus cerebralis isolates from Pakistani sheep and goats based on cox1 gene (639 bp) sequences. Circle sizes are proportional to the haplotype frequencies. Hatch marks represent the number of mutations. Small black spheres are median vectors i.e., unsampled or hypothetical haplotypes. (B) Median-joining network of Taenia multiceps isolates from different hosts and geographical locations based on the mitochondrial cox1 gene (339 bp) sequences. Circle sizes are proportional to the haplotype frequencies. Hatch marks represent the number of mutations. Small black circles are median vectors (i.e., hypothetical haplotypes).

Figure 3

Bayesian phylogeny of Pakistani Coenurus cerebralis isolates inferred from the cox1 gene. Echinococcus granulosus is used as an outgroup. Red = Coenurus cerebralis haplotypes representing isolates from this study. Posterior probability values are depicted at the nodes.