Ophidascaris sp. is a group of gastrointestinal ascaridoid nematodes parasitic on snakes. Pythons commonly acquire this parasitic infection through ingestion of infected intermediate hosts, such as mice and frogs (Sprent,1988; Lettoof et al., 2019). Even after the intermediate host had died, Ophidascaris sp. larvae survived carcass putrefaction, remained viable in water for a minimum of three weeks, and retained their infectivity to snakes (Sprent, 1970). In pythons, the migration of Ophidascaris larvae resulted in tissue bleeding, inflammation, and secondary infection, while adult parasitism caused severe gastric granulomas and adenocarcinoma, intestinal obstruction, anorexia, malnutrition, and even death (Elbihari and Hussein,1973; Hamir,1986; Baron et al., 2018; Suwanti et al., 2018). Thus, this parasitic nematode can threaten the health of snakes and the economic value of their products. Until now, snake infection with Ophidascaris sp. has been reported in many countries, including China, Iran, Indonesia, Thailand, and Australia (Li et al.,2014; Ganjali et al., 2015; Ngamniyom et al., 2015; Baron et al., 2018; Suwanti et al., 2018; Zhou et al., 2021; Zhao et al., 2021).
Ophidascaris sp. identification has been controversial (Sprent, 1969; Sprent, 1970; Sprent, 1988). Although the classification of Ophidascaris sp. has been documented for a long time, it is limited to host characteristics, geographical distribution, and a few morphological features. Morphologically, Ophidascaris species infecting pythons belong to the ῾filaria’ group of genus Ophidascaris, including eight species, O. filaria, O. baylisi, O. papuanus, O. robertsi, O. infundibulicola, O. amucronata, O. niuginiensis, and O. moreliae (Sprent, 1969). However, all these species are morphologically similar and lack epidemiological data. Moreover, individual morphological differences often exist within the same species (Sprent, 1988). With the development of scanning electron microscope, Li et al. (2016) noted that the number of postcloacal papillae of Ophidascaris sp. could also be used as a classification standard, but this technique is complicated. Thus, further studies are required to explore an alternative accurate and fast method for Ophidascaris species identification.
Molecular markers have proven to be more valuable and efficient than morphological methods for helminth identification. The ribosomal internal transcribed spacer (ITS) has been shown as a helpful population genetic marker to classify and identify helminths (Liu et al., 2015; Shi et al., 2018; Ran et al., 2020). However, Ophidascaris sp. ITS data are lacking. Therefore, PCR amplification and sequence analysis of ITS sequence of Ophidascaris baylisi from Burmese pythons could lay a scientific basis for rapid identification of these roundworms.