Possible Role of Fish and Frogs as Paratenic Hosts ofDracunculus medinensis, Chad

Abstract

Tadpoles fed infected copepods can harbor infective D. medinensis larvae and thus serve as potential paratenic hosts.

Guinea Worm (Dracunculus medinensis) Infection in a Wild-Caught Frog, Chad

“…Tadpoles and frogs have long been known to experimentally support infective larvae of D. insignis ( 5 – 7 ), and just recently, they have been shown to experimentally support infective larvae of D. medinensis ( 2 ); however, natural infection with Dracunculus species has not previously been documented in any wild-caught amphibian. The finding of a wild-caught frog harboring a natural infection with a D. medinensis larva validates the findings of these experimental infections and demonstrates that such a paratenic host is likely involved in the transmission of D. medinensis larvae in Chad.…”

“…To confirm the species identity of the frog, we extracted DNA from ethanol-fixed tissue and amplified the 16S ribosomal RNA gene ( 2 ). The sequence (450 bp) indicated that the frog was a ranid species in the genus Phrynobatrachus , most likely P. francisci because it shared 99% similarity with P. francisci sequences in GenBank (accession nos.…”

“…Recent experiments demonstrated that D. medinensis worms, like the closely related parasite D. insignis , could utilize green frog ( Lithobates clamitans ) tadpoles as a paratenic host ( 2 ). During June and July 2016, a survey of potential D. medinensis worm paratenic hosts was conducted in Chad.…”

Possible Role of Fish as Transport Hosts for Dracunculus spp. Larvae

“…Previous work on Dracunculus and related spirurids indicates that paratenic hosts might be used to facilitate transmission ( 7 , 8 ). Recently, an experimental study showed D. medinensis worms could use tadpoles as paratenic hosts, and a naturally infected frog was detected in Chad ( 9 , 10 ).…”

Guinea worm eradication: Progress and challenges— should we beware of the dog?

“…Experimental evidence has since shown that amphibians can also harbour viable D . medinensis larvae [10] but recently an infected frog has been found in Chad supporting the hypothesis that paratenic hosts contribute to Dracunculus epidemiology in that setting [11]. A suggested approach to control transmission was to educate the population as to how to dispose of fish entrails (to prevent dogs acquiring infection as they forage) and to ensure the fish were dried and cooked effectively to kill infective D .…”