Infection of fishes, including threatened and endangered species by the trematode parasite Haplorchis pumilio (Looss, 1896) (Trematoda: Heterophyidae)

Daniel Huston,David Huffman,Mclean Worsham,Kenneth Ostrand

doi:10.3391/bir.2014.3.3.09

Abstract

Haplorchis pumilio (Trematoda: Heterophyidae) has become widely established around the world because of multiple introductions of its snail hosts, and because of its flexible host requirements at the second-intermediate and definitive levels. Although exotic thiarid snails introduced into North American waters have been previously reported to harbor H. pumilio, metacercariae of H. pumilio have not been reported from native fishes in the continental USA. In this study artificially exposed cyprinids to H. pumilio cercariae from infected snails became infected with the trematode, sometimes lethally, when exposed for only 15 minutes to high cercarial densities. Subsequent collection and examination of fountain darters Etheostoma fonticola, a U.S. federally endangered fish species, and the examination of archived specimens of largemouth bass Micropterus salmoides; the IUCN endangered Dionda diaboli, Gambusia nobilis, Cyprinodon elegans; and IUCN vulnerable Etheostoma grahami from West Texas springs resulted in new host and locality records for H. pumilio metacercarial infections in all species except C. elegans. Metacercariae were found encysted in the connective tissue of the head and at fin insertions. Conversely no integumental or visceral infections were observed, regardless of the fish species or collection locality. It is surmised that Haplorchis pumilio is probably present in many aquatic systems where Melanoides tuberculata and Tarebia granifera have become established, but that the metacercariae have been missed by previous investigators because of their small size and unusual anatomical location. Results from this study suggest that subsequent investigators be on the watch for these metacercariae, and that the anatomical sites typical of the worm (fin insertions, and especially the caudal peduncle) be included in routine necropsy procedures for fishes from such habitats.

Highlights

Haplorchis pumilio (Looss, 1896) was first described from birds in Egypt
Haplorchis pumilio infection was low in the Devils River, where one E. grahami and one D. diaboli had a single H. pumilio metacercaria each
At Phantom Lake, Gambusia nobilis had low metacercarial intensities (0–16, 6), and no H. pumilio metacercariae were found in Cyprinodon elegans from this site, while no H. pumilio metacercariae were found in C. elegans collected from San Solomon Springs

Summary

Introduction

Adults of Haplorchis pumilio have been recovered from the digestive tracts of mammals, birds, and reptiles (Sommerville 1982a; Umadevi and Madhavi 2006; Díaz et al 2008). First intermediate hosts reported for H. pumilio are the thiarid snails Melanoides tuberculata (Müller, 1774) and Tarebia granifera (Lamark, 1822) (Umadevi and Madhavi 2006; Tolley-Jordan and Owen 2008). Haplorchis pumilio metacercariae parasitize a broad range of second intermediate fish hosts, where they are found encysted in the soft tissue of the fin insertions, and the cartilage of the head (Sommerville 1982b; Lo and Lee 1996b). Hemorrhaging in the skeletal muscles has been reported in association with both the penetration and migration of cercariae (Sommerville 1982b; Umadevi and Madhavi 2006), and simultaneous penetration by a large number of cercariae can be lethal to fry and adults of multiple fish species (Sommerville 1982b; Umadevi and Madhavi 2006)

Methods

Results

Conclusion