Cystic Echinococcosis of Camels: 12S rRNA Gene Variation Revealed Changing Pattern of Genetic Diversity Within Echinococcus granulosus sensu lato in the Middle East and North/Sub-Saharan Africa.

Mansoureh Dehghani,Sima Rostami,Mohammad Ali Mohammadi,Majid Fasihi Harandi,Saeid Nasibi,Sahel Hemmati

doi:10.3389/fvets.2020.00618

Abstract

Cystic echinococcosis (CE) is one of the most widespread zoonotic diseases, with considerable public health and economic importance. Camels play a significant role in transmission cycle of Echinococcus granulosus especially, in the Middle East and North Africa (MENA). The present study aimed to identify the genetic variation and haplotype distribution of camel isolates of E. granulosus sensu lato using all existing E. granulosus mitochondrial DNA data from camels in different parts of the world. Sequence data from 1,144 camel isolates of E. granulosus s.l. available in the NCBI GenBank including 57 camel hydatid cysts collected in central Iran were used to analyze the nature of genetic variation within the camel isolates of E. granulosus s.l. in MENA region. Fifty-seven camel isolates were also PCR-sequenced on mitochondrial 12S rRNA gene. Haplotype network analysis revealed seven different haplotypes clustered into four major groups. E. intermedius G6 was identified as the most commonly represented genotype in camels followed by G1. Mitochondrial 12S rRNA gene sequence analysis on 57 camel isolates identified three different genotypes, including E. intermedius/G6 (35/57, 61.4%), E. granulosus sensu stricto/G1-G3 (21/57, 36.8%) as well as one isolate identified as E. ortleppi/G5 (1/57, 1.8%). The number of base substitutions per site over 420 positions of partial 12S rRNA gene sequences were shown as 0.000 and 0.004 for E. intermedius (G6) corresponding to the Middle East and sub-Saharan isolates, respectively. Camel isolates of E. granulosus in the MENA region present moderate genetic diversity (Hd = 0.5540–0.6050). The Middle East isolates demonstrated a more diverse population than the North/sub-Saharan isolates, where six out of seven 12S rRNA haplotypes were identified in the former region. E. intermedius (G6 genotype) was shown to be the most common species in the world camel population. In conclusion, camels showed to be an important intermediate host species in the MENA region with different patterns of genetic variation between the Middle East and Africa.

Highlights

Tapeworms of the genus Echinococcus, causing a spectrum of infections known as echinococcosis, are members of the family Taeniidae
Based on the biological and molecular genetic analyses using nuclear and mitochondrial DNA sequences 10 distinct genotypes with different host preferences have been identified for E. granulosus sensu lato and new nomenclature has been adopted for several genotypes [6] i.e., E. granulosus sensu stricto (G1–G3) with a wide range of intermediate hosts sheep, goat and buffaloes, E. equinus (G4) of horses, E. ortleppi (G5) of cattle, E. intermedius (G6–G7) of camels and pigs, E. canadensis (G8 and G10) of Fennoscandian and subarctic cervids and E. felidis of African wild felid population [2]
Of 1,144 camel isolates of E. granulosus s.l. sequences retrieved from NCBI GenBank, 68 records for 12S rRNA gene were identified (Table 1)

Summary

Introduction

Tapeworms of the genus Echinococcus, causing a spectrum of infections known as echinococcosis, are members of the family Taeniidae. Cystic echinococcosis (CE) caused by the larval stages of Echinococcus granulosus sensu lato represents serious zoonotic infections in human and animals with a cosmopolitan distribution [1, 2]. The life cycle involves dogs and other canids as definitive and domestic and wild ungulates as the intermediate hosts [3]. E. granulosus genotype variation, may affect parasite life cycle and transmission patterns, host range and pathogenicity to humans [4, 5]. Based on the biological and molecular genetic analyses using nuclear and mitochondrial DNA sequences 10 distinct genotypes with different host preferences have been identified for E. granulosus sensu lato and new nomenclature has been adopted for several genotypes [6] i.e., E. granulosus sensu stricto (G1–G3) with a wide range of intermediate hosts sheep, goat and buffaloes, E. equinus (G4) of horses, E. ortleppi (G5) of cattle, E. intermedius (G6–G7) of camels and pigs, E. canadensis (G8 and G10) of Fennoscandian and subarctic cervids and E. felidis of African wild felid population [2]

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Discussion

Conclusion