Larval gryporhynchid tapeworms (Cestoda: Cyclophyllidea) of British freshwater fish, with a description of the pathology caused byParadilepis scolecina

Abstract

Larvae of the cyclophyllidean tapeworms Paradilepis scolecina (Rudolphi, 1819), Neogryporhynchus cheilancristrotus (Wedl, 1855) and Valipora campylancristrota (Wedl, 1855), are described from British freshwater fish. The morphometrics of the rostellar hooks, infection characteristics and host ranges of these parasites from fisheries in England and Wales are presented. Difficulties in the detection, handling and identification of these tapeworms are highlighted, and may in part explain the paucity of records from Britain. Tissue digestion was shown to be a useful technique for the examination of these parasites, providing clear and consistent preparations of the rostellar hooks for measurement. The pathological changes caused by P. scolecina to the liver of wild tench, Tinca tinca, are detailed for the first time. Tapeworms located in the hepatic parenchyma and pancreatic tissues caused little pathological damage and invoked only mild inflammatory responses. The small size of these tapeworms and their encapsulation within host tissues appear to limit the severity of pathology, compared with parasites that insert their rostellum during attachment.

A Study on the Pathological Effects of Trypanorhyncha Cestodes in Dusky Groupers Epinephelus marginatus from the Canary Islands

“…However, mobilization and proliferation of MA [55] may also be features of a chronic inflammatory response [55,56]. It has been shown that these pigmentladen aggregates may be found surrounding and within the encapsulating response of parasites [47,55,57], as observed in our study. Thus, MA are likely to act as collections of scavenging cells stimulated by excessive degenerating tissue [58].…”

“…Extensive proliferation of connective tissue with encapsulation of the plerocerci appears to be a common response in long-standing infections with cestodes [44][45][46][47][48]. Containment in this way serves to separate the parasite from the tissues to prevent further damage to the host [45,46].…”

Genetic Variants and Increased Expression of Parascaris equorum P-glycoprotein-11 in Populations with Decreased Ivermectin Susceptibility

“…Comparison of non-feeding, relatively resistant third larvae of H. contortus showed similar results, i.e. no significant differences were found in expression of nine Pgp mRNAs between a resistant and susceptible strain [16]. These authors suggested, among noting that only constitutive mRNA levels were under investigation, expression may change throughout the life cycle.…”

“…More recently, an overexpression of five Pgps was demonstrated in an ivermectin (IVM) resistant C. elegans strain [14]. Furthermore, eight Pgps were reported in Brugia malayi [15], nine full or partial sequences in Haemonchus contortus [10], [16], [17], [18], at least two Pgp cDNAs in cyathostomins [19], eleven partial sequences in Teladorsagia circumcincta [20] and two full-length Pgp-encoding sequences in Onchocerca volvulus [17], [21]. However, there are currently no database entries for Parascaris equorum Pgps although there are several P. equorum populations known to show reduced susceptibility or even resistance against IVM as reported from various countries in Europe and the Americas [22].…”