The plerocercoid larva (sparganum) of Spirometra tapeworms can parasitize humans and represent an important foodborne parasitic zoonosis . The Spirometra erinaceieuropaei plerocercoid is the main etiological agent of human sparganosis and may result in serious disease, including blindness, paralysis, and even death . Human sparganosis occur worldwide, mostly in eastern and south-eastern Asian countries, such as China, Korea, Japan, and Thailand [3, 4].
As the most common second intermediate hosts in the life cycle of S. erinaceieuropaei, snakes and frogs transmit sparganosis to humans in China [5, 6]. Humans can be infected by consuming raw or undercooked snake/frog meat or using raw snake/frog flesh in traditional poultices . Recently, eating snake and frog meat has become increasingly popular . Such customs may facilitate human infection with spargana in China. The number of reported human cases has exceeded 1300 in China, but the actual number of infections may be far higher because many cases may not be recognized or reported . Therefore, sparganosis may pose a serious threat to human health in China. As a result, knowledge regarding the genetic characteristics of sparganum populations is valuable for preventing and controlling sparganosis in humans.
Extensive genetic studies on spargana isolated from frogs in different regions in China have been performed [8, 9, 10, 11, 12, 13]. However, snakes are a very important source of human sparganosis, and data on the population genetics of Spirometra tapeworms from snakes remain scarce. Therefore, we set out to perform an exhaustive genetic diversity analysis of Spirometra tapeworms isolated from different snakes in different geographical locations. We used mitochondrial cytochrome b (cytb) and cytochrome c oxidase subunit I (cox1) genes that are verified as suitable markers for inferring genetic population differences of Spirometra tapeworms [11, 14].
Moreover, using mitochondrial genes, or even the complete mitochondrial genome, the sparganum isolates collected in different locations in China were classified as S. erinaceieuropaei [6, 8, 11, 15, 16]. This classification suggests that S. erinaceieuropaei might be the only etiologic agent of sparganosis in China. No other species of Spirometra as a source of human infection has been reported in the country. However, two Spirometra species, S. erinaceieuropaei and S. decipiens, have been identified as species that can infect humans in Korea through morphological and genetic methods . In addition, several sparganum isolates collected from snakes (Dinodon rufozonatum and Agkistrodon saxatilis) in China were identified as S. decipiens based on the multiplex polymerase chain reaction (PCR) assay . Therefore, the exact identification of Spirometra species from snakes requires further investigation. More specifically, the aims of this study were as follows: (1) to identify Spirometra isolates from snakes using multiplex PCR; (2) to perform a genetic diversity analysis of collected isolates from different geographical locations.