Sparganosis is a zoonotic parasitic disease caused by the larvae (spargana) of the genus Spirometra, which is widely distributed globally and threatens human health. More than 60 species of Spirometra have already been identified, and over 2000 cases have been reported. This review summarizes the prevalence of humans, frogs, snakes, and other animals with spargana. Furthermore, the infection mode, distribution, and site are summarized and analyzed. We also describe the epidemiology, molecular diagnosis, and other aspects which are of considerable significance to preventing sparganum.

Ascarid nematodes are the most common and harmful nematodes parasites in animals. By analyzing genetic variation, this study explores the genetic and phylogenetic relationship among ascarids from 11 different hosts. This study collected ascarid samples from the feces of nine animal species in Changsha Ecological Zoo of Hunan Province and two animal kinds in the College of Veterinary Medicine of Hunan Agricultural University. The mitochondrial gene (pcox1) and ribosomal ITS sequences were amplified, sequenced, and analyzed by PCR to identify the species of the samples. The phylogenetic tree was constructed based on two genes (cox1 and ITS) by the Neighbor-joining method, and the phylogenetic relationship was analyzed. The sequencing results showed that the sequence lengths of pcox1 and ITS genes in the samples were 441 bp and 838–1,177 bp, respectively. The difference rates were 0.00–1.70% in pcox1 gene and 0.00–7.30% in ITS gene. Phylogenetic analysis showed that ascarid worms from the white lion, Northeast tiger, South China tiger and cheetah were identified as Toxascaris leonina. Ascarids from the zebra were identified as Parascaris equorum, while those from chicken and peacocks were identified as Ascaridia galli. Ascarids of wolf and dog origin were Toxocara canis, the snake ascarids belonged to Ophidascaris filaria, and the bear ascarids belonged to Baylisascaris transfuga. There was a significant gap between different kinds of ascarid worms. We found that these two mitochondrial genes pcox1 and ITS showed a common characteristic that the intraspecific differences were significantly smaller than the interspecific differences, confirming that these two genes could be used as interspecific genetic markers for molecular identification of different ascarids origins. The intraspecific variation rate of the ITS gene was higher than that of pcox1, indicating that ITS can also be used in the genetic research of Ascaris species development. This study revealed the genetic evolution and phylogeny of ascarids in wild animals, and our results will help prevent and control ascarids in wild animals.

Sparganosis is a neglected zoonotic parasitic disease that poses huge threats to humans worldwide. Snakes play an important role in sparganosis transmission because they are the most common second intermediate hosts for Spirometra parasites. However, the population genetics of Spirometra isolates from snakes is currently not well studied in China. The present study was performed to explore the molecular characteristics and phylogenetic analysis of Spirometra tapeworms from different species of snakes in Hunan Province. This study obtained 49 Spirometra isolates from 15 geographical areas in Hunan Province, Central China. Subsequently, the 18S and 28S ribosomal DNA (rDNA) fragments were amplified from the isolated parasites, and their sequences were analyzed to assess their genetic diversity. Phylogenetic analyses were performed using the maximum likelihood algorithm. The results showed that sequence variations among these isolates were 0–2.3% and 0–0.1% for 18S and 28S rDNA, respectively. The phylogenetic analysis showed that all Spirometra isolates from Hunan Province were clustered into the same branch with Spirometra erinaceieuropaei isolated from other areas (China, Vietnam, Australia). Moreover, the phylogenetic trees revealed that Spirometra is closely related to Adenocephalus, Pyramicocephalus, Ligula, Dibothriocephalus, Schistocephalus, and Diphyllobothrium. The Spirometra isolates of different hosts/regions in Hunan Province are not host segregated or geographically isolated, and support for the taxonomic status of Spirometra tapeworms in China has been added. These results provide reference values for future accurate identification and taxonomic status of Spirometra tapeworms in China.

Background: Sparganosis, caused by the larval plerocercoid of Spirometra tapeworms, still poses a potential public health hazard in China. Snakes are an important source of infection for human sparganosis; however, insufficient studies on the population genetics of Spirometra isolates from snakes have occurred to date. This study collected 67 Spirometra isolates from snakes, and several definitive hosts (Panthera tigris, Prionailurus bengalensis, Felis silvestris), in 15 geographical locations in Hunan Province of central China. They were identified using a multiplex polymerase chain reaction assay. Next, these isolates’ population genetic diversity and phylogenetic pattern were explored based on mitochondrial cytb and cox1 genes. Results: All Spirometra isolates collected in the Hunan Province belonged to the genotype of the Korean “Spirometra decipiens” (KJ599679). The genetic diversity analysis based on concatenated sequences revealed no distinct genetic structure among Spirometra populations. Conclusions: The phylogenetic analysis supported the distinction between Polish and Chinese Spirometra isolates. The taxonomy of Spirometra spp. remains ambiguous; more morphological and molecular studies are necessary to clarify the systematics of the genus of Spirometra.

Background: Spirometra erinaceieuropaei, the causative agent of food/water-borne sparganosis, has been widely reported worldwide. However, the taxonomy of the genus Spirometra has always been complicated. The main objectives of this study were to assemble 7 complete mitochondrial genomes of Spirometra erinaceieuropaei, collected from different hosts in the Hunan province of China, and to analyze the phylogenetic relationship and genetic diversity of cestode species.Methods: In this study, seven Spirometra erinaceieuropaei (three spargana and 4 adults) were collected from different hosts in Hunan province, China. The long-PCR was performed to amplify the four large fragments of the Spirometra mitochondria (mt) genome by using specific primers reported in a previous study. Then, the mt genome of each S. erinaceieuropaei was assembled and annotated after overlapping four large fragments. Sliding window analysis was carried out to explore the nucleotide variation of the mt genome between 7 isolates obtained in this study and 8 reported Spirometra. The genetic diversity of cestode species was also investigated by Bayesian analysis based on 12 protein-coding genes.Results: Seven mt genomes of S. erinaceieuropaei obtained in this study were successfully assembled and annotated. The genome features of S. erinaceieuropaei are similar to other reported cestode species, containing 12 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and two ribosomal RNA genes (rRNA), large non-coding regions (NC), and small non-coding regions (NR). Sequencing analysis revealed 97.40%-99.90% sequence similarity among seven mt genomes identified in this study. Sliding window analysis indicated that the Korea isolate (KJ599680) might be the differential specie of genus Spirometra, and nad4L, cox3, and nad6 were the top three genes with the lowest variation rates in mt DNA. Phylogenetic analysis based on 12 PCGs further demonstrated that S. mansoni (AB374543) might be the misnamed S. erinaceieuropaei.Conclusion: The results of the current study supports the previously reported conclusion that multiple genotypes exist within S. erinaceieuropaei, and the Korean isolate (KJ599680) be a novel genotype or even a novel species of the genus Spirometra, and we strongly suggests that S. decipines may be a misnamed of S. erinaceieuropaei like S. mansoni is. nad4L, cox3 and nad6 are more suitable molecular genetic markers than cox1 for S. erinaceieuropaei identification. However, the authentic relationships among S. erinaceieuropaei isolates from different hosts and geographical sites are still unknown. More samples must be collected in different host and geographical positions to help us understand the genus Spirometra.