Genetic structure and phylogeography of Echinococcus granulosus sensu stricto genotypes G1 and G3 in Pakistan and other regions of the world based on nad5 gene

Pakistan is a neglected endemic focus for Echinococcus granulosus sensu lato, a zoonotic parasite species complex with the ability to infect wide spectrum of hosts. Wide gaps exist in literature for etiological agents of cystic echinococcosis (CE) in Pakistan due to a very low number of studies on identifying the exact genotypes involved in epidemiological manifestation of this disease. Focusing on transmission patterns and epidemiological dynamics, this study aimed at investigating infective genotypes among the cattle population of south Punjab, Pakistan, employing a mitochondrial marker nad5 (680 bp). Nucleotide sequences retrieved from 28 hydatid cyst isolates displayed considerable intraspecific variation revealing the existence of G3 and G1 strains of Echinococcus granulosus sensu stricto. The G3 genotype emerged as the predominant cause (78.57%) of hydatidosis in cattle. Apart from this, to understand phylogeographical relations, homologous nucleotide sequences of the partial nad5 gene from six major regions of the world were employed in the population genetics analysis to have an insight into genetic variability and demographics of G3 genotype in particular. Diversification of G3 and its haplotypes in Pakistan (n = 11) and other regions of the world (India, Iran, Turkey, Italy and France) was demonstrated. It was further demonstrated that the South Asian population (Pakistan and India) was highly differentiated from the other regions. It could, therefore, be speculated that G3 is diverging and expanding its population with South Asia as the main focal point.

Echinococcus granulosus sensu stricto G1 is the predominant genotype in human and livestock isolates from Turkey and Iran, based on mitochondrial nad5 gene differentiation

Background

Different genotypes of Echinococcus granulosus sensu stricto (s.s.) isolated from livestock and humans have been identified based on cox1 and nad1 genomic fragments. The present study was performed to differentiate the G1/G3 genotypes of Echinococcus granulosus (s.s.) isolated from humans and livestock (sheep and cattle) from Azerbaijan in northwestern Iran, Fars Province in southern Iran, and Van province in Eastern Turkey, using the nad5 gene fragment as a suitable marker to distinguish these two genotypes.

Methods

A total of 60 pathologically confirmed human hydatid cysts and 90 hydatid cyst samples from livestock were collected from Turkey and Iran. PCR was performed on all of the samples, targeting the nad5 gene. Based on PCR product quality, host type, and the geographical area where the samples were obtained, 36 of the samples were sequenced and were used in the phylogenetic analysis.

Results

Out of 36 evaluated samples, 26 (72.2%) samples belonged to G1, and 10 (27.8%) samples belonged to the G3 genotype. Out of 21 samples from Turkey, 16 (76.2%) were G1 and 5 (23.8%) were G3, while out of 15 samples from Iran, 10 (66.7%) were G1 and 5 (33.3%) were the G3 genotype. None of the samples isolated from humans in Iran or from sheep in Turkey were G3. Overall, between the two countries, 18.18% of E. granulosus isolates in cattle, 41.66% of isolates in sheep, and 23.07% of human samples were identified as G3, and the others as the G1 genotype. The G3 genotype was not detected in human samples from Iran or sheep samples from Turkey.

Conclusion

The findings of the study revealed that the G1 genotype of E. granulosus s.s. is the predominant genotype in humans and livestock, both in Turkey and Iran. The ratio of the E. granulosus s.s. G1 to G3 genotype was 3.2 in Turkey and 2 in Iran. The study also further confirmed that the nad5 gene properly differentiated the G1/G3 isolates of E. granulosus from both humans and livestock.

Graphical Abstract

Genetic diversity and transmission patterns of Echinococcus granulosus sensu stricto among domestic ungulates of Sardinia, Italy

Cystic echinococcosis (CE), a parasitic zoonosis of public health and economic concern, is highly endemic in Sardinia, Italy. The study involved examining the intraspecific variability and demographic structure of Echinococcus granulosussensu stricto (s.s.) in common hosts of this parasite. Molecular surveillance included the fragment amplification of a partial mitochondrial gene, cox1 (750 bp), for a total of 69 isolates derived from sheep (n = 52), cattle (n = 11), pigs (n = 4), and goats (n = 2). It was ascertained that E. granulosus s.s. was the primary agent of infection among these ungulates and G1 genotype was highly prevalent (79.71%). Considerable intraspecific variation was found, revealing the existence of 22 haplotypes with relatively high haplotype (0.8555 ± 0.033) and low nucleotide diversities (0.00281 ± 0.00030). Population demographics indicated an expanding parasitic population signifying negative deviation from neutrality indices. Little genetic differentiation was found between the subpopulations of E. granulosus s.s. in the island. Moreover, the geographic dispersal of genotypes G1 and G3 also indicated similarity between Sardinian and mainland Echinococcus granulosus s.s. populations reaffirming the sympatric occurrence and efficient transmission of G1 and G3 genotypes. Molecular survey of CE has the potential to yield baseline information on the infective genotypes among the intermediate hosts and helps in devising suitable control strategies for curtailing the disease.

Taeniid cestodes in a wolf pack living in a highly anthropic hilly agro-ecosystem

The Italian wolf population in human-modified landscapes has increased greatly in the last few decades. Anthropisation increases the risk of transmission of many zoonotic infections and in this context, control of taeniid cestode species needs to be addressed from a One Health perspective. Predator-prey interactions are at the root of taeniid cestode transmission, and the wolf plays a key role in the maintenance and transmission of taeniids. To date, all available data on the taeniids of wolves in Italy refer to populations living in a wild habitat. Between 2018 and 2019, we investigated taeniids in a wolf pack living in a highly anthropic hilly agro-ecosystem. Thirty-eight faecal samples were collected and analysed, 4 of which were also genetically characterised for individual wolves and belonged to three different animals. Samples collected were analysed microscopically and by molecular analysis in order to identify the taeniid species. Taeniid eggs were detected in 34.2% (13/38) of samples. Within samples positive to taeniid eggs only Echinococcus granulosus s.s. and Taenia hydatigena were identified in 26.3% and 10.5% of the samples, respectively. On microscopic examination, Capillaria spp., Ancylostomatidae and Toxocara canis eggs, Crenosoma vulpis larvae, and coccidian oocysts were also found. The combination of low biodiversity of taeniid species with a high occurrence of E. granulosus s.s. recorded in this study could be the consequence of a deeper link occurring between wolves and livestock in human-modified landscapes than in wild settings.

Comprehensive study based on mtDNA signature (nad1) providing insights on Echinococcus granulosus s.s. genotypes from Pakistan and potential role of buffalo-dog cycle

Pakistan has long been considered neglected endemic region for Echinococcus granulosus. Limited surveillance studies have failed to epidemiologically draw complete picture on geographical presence and etiological agents of cystic echinococcosis. Amidst such lacunae, current study explored main transmission routes of this disease through molecular characterization of hydatid cyst isolates obtained from sheep (n = 35), goats (n = 26), cattle (n = 30) and buffalo (n = 30) from the four provinces of Pakistan. Two strains of E. granulosus sensu stricto, G1/G3, and their haplotypes were observed to be cycling in sympatry in the domestic ungulate populations. G3 genotype had higher prevalence (66.94%) in the hosts compared to G1 genotype (33.06%) which was not surprising, considering the large buffalo population in Pakistan. Haplotypic analysis revealed presence of 9 different haplotypes configured in a double clustered network with two centrally positioned haplotypes referred to as G3 (PKH1) and G1 (PKH6). Population demographics and genetic variability indices suggested expanding parasitic population in multiple host spectrum. Elucidating local transmission patterns of E. granulosus sensu stricto, buffalo-dog cycle emerged as one of the dominant causes of G3 dispersal in contrary to other global studies. Adaptability of G3 to environmental conditions of Pakistan and high affinity for buffaloes emphasize on heterogeneous nature of this strain in contrast to G1. However, more studies involving larger datasets and mitochondrial sequences could confirm this hypothetically formulated inference.

Two haplotype clusters of Echinococcus granulosus sensu stricto in northern Iraq (Kurdistan region) support the hypothesis of a parasite cradle in the Middle East

Human cystic echinococcosis (CE) caused by Echinococcus granulosus s.s. is a major public health problem in Iraqi Kurdistan with a reported surgical incidence of 6.3 per 100,000 Arbil inhabitants. A total of 125 Echinococcus isolates retrieved from sheep, goats and cattle were used in this study. Our aim was to determine species/genotypes infecting livestock in Iraqi Kurdistan and examine intraspecific variation and population structure of Echinococcus granulosus s.s. in this region and relate it to that of other regions worldwide. Using nucleotide sequences of the mitochondrial cytochrome c oxidase subunit 1 (cox 1) we identified E. granulosus s.s. as the cause of hydatidosis in all examined animals. The haplotype network displayed a double-clustered topology with two main E. granulosus s.s. haplotypes, (KU05) and (KU33). The 'founder' haplotype (KU05) confirmed the presence of a common lineage of non-genetically differentiated populations as inferred by the low non-significant fixation index values. Overall diversity and neutrality indices indicated demographic expansion. We used E. granulosus s.s. nucleotide sequences from GenBank to draw haplotype networks for the Middle East (Iran, Jordan and Turkey), Europe (Albania, Greece, Italy, Romania and Spain), China, Mongolia, Russia, South America (Argentina, Brazil, Chile and Mexico) and Tunisia. Networks with two haplotype clusters like that reported here for Iraqi Kurdistan were seen for the Middle East, Europe, Mongolia, Russia and Tunisia using both 827bp and 1609bp cox1 nucleotide sequences, whereas a star-like network was observed for China and South America. We hypothesize that the double clustering seen at what is generally assumed to be the cradle of domestication may have emerged independently and dispersed from the Middle East to other regions and that haplotype (KU33) may be the main haplotype within a second cluster in the Middle East from where it has spread into Europe, Mongolia, Russia and North Africa. Further studies using metacestodes of human origin are required to investigate the biological importance of E. granulosus s.s. haplotypes/clusters and their association, if any with clinical manifestations of CE infection.