Dracunculus spp

Cleveland, Christopher A., Garrett, Kayla B., Cozad, Rebecca A., Williams, Brianna M., Murray, Maureen H. & Yabsley, Michael J., 2018, The wild world of Guinea Worms: A review of the genus Dracunculus in wildlife, International Journal for Parasitology: Parasites and Wildlife 7 (3), pp. 289-300 : 294

2.1.3. Dracunculus spp . from Eurasia

The highest diversity of squamate Dracunculus spp . have been reported from Eurasia, including D. oesophageus ( Desportes, 1938) , from Europe and D. coluberensis , D. alii ( Deshmukh, 1969) , and D. houdemeri ( Hsü, 1933) from Asia ( Table 1). Many of these remain poorly described and studied, with the latter three having only been described based on individuals of one sex. Furthermore, from the checkered keelback snake ( Xenochrophis (= Natrix ) piscator), D. alii was described from only male nematodes in India and D. houdemeri was described from only subcutaneous female nematodes in Vietnam ( Hsü, 1933; Deshmukh, 1969). No other life history traits are known, and additional morphological and molecular work is needed to better define the validity of these two species from keelback snakes.

The best studied of this group is D. oesophageus which was described from colubrid snakes ( Moravec, 2006). A male specimen of D. oesophageus originally described as Filaria oesophagea , was detected in the esophagus of a viperine snake Natrix maura (= N. viperina ), thus the specific epithet. Based on morphologic analysis of parasites detected in the grass snake ( Natrix natrix persa ) the parasite was transferred to the genus Dracunculus and renamed D. oesophageus ( Desportes, 1938; Deshmukh, 1970). Parasites from N. natrix described as Pesteria inglisi by Tadros (1966) are presumed to be D. oesophageus . The copepod C. fuscus is a confirmed experimental intermediate host ( Desportes, 1938). The tails of the L3 have the typical tricuspid tail similar to D. medinensis . This species is also the only squamate Dracunculus spp . for which there is any genetic data available; phylogenetic analysis of ∼1,600bp of the 18S rRNA gene from two specimens from the mesenteries of N. natrix from Slovakia indicated that this parasite was related to D. medinensis and the fish parasite Philometra obturans which is in the same order as Dracunculus (Wijová et al., 2005) .

An unidentified female Dracunculus species was reported emerging from the head of a cobra ( Naja tripudians ) that was held in captivity.

Recovered larvae were used to infect copepods and underwent growth (from 300 μm to 600 μm). Subsequent inoculation of snakes with the unidentified Dracunculus species failed, possibly due to the use of copepods that had only been infected for six days and larvae that had not yet molted to the infectious L3 stage (Turkhud, 1920).

The only report of Dracunculus in a lizard species was by Mirza and Basir (1937), but this report is suspect. In that study, 60% of monitor lizards ( Varanus sp. ) in India were infected in the body cavity and in subcutaneous tissues with up to 15 worms. However, identification was based only on one damaged female worm measuring 68 cm long. Although originally identified as D. medinensis , no additional morphologic or molecular work was conducted so it is possible that this parasite is one of the commonly reported filarial worms (e.g., Oswaldofilaria , Hastospiculum ) in Varanus spp. ( Bolette, 1998; Rataj et al., 2011). For example, in 2017 several large subcutaneous nematodes were collected from V. niloticus in Chad, Africa and were identified as filarial worms ( Onchocercidae ) based on molecular analysis of the cytochrome c oxidase I (COI) (Cleveland and Yabsley, unpublished data).