Comparative recruitment, morphology and reproduction of a generalist trematode,Dicrocoelium dendriticum, in three species of host

Abstract

SUMMARYEpidemiological rate parameters of host generalist parasites are difficult to estimate, especially in cases where variation in parasite performance can be attributed to host species. Such cases are likely common for generalist parasites of sympatric grazing mammals. In this study, we combined data from experimental exposures in cattle and sheep and natural infections in elk to compare the recruitment, morphology and reproduction of adult Dicrocoelium dendriticum, a generalist trematode that has emerged in sympatric grazing hosts in Cypress Hills Provincial Park, Alberta. Overall, there were no significant differences in the recruitment of metacercariae and in the pre-patency period of adults in experimentally exposed cattle and sheep. All flukes reached reproductive maturity and the degree of reproductive inequality between individual flukes within each infrapopulation was moderate and approximately equal among the three host species. Neither fluke size nor per capita fecundity was constrained by density dependence. Thus, fitness parameters associated with growth and reproduction were approximately equivalent among at least three species of definitive host, two of which are sympatric on pastures in this Park. The generalist life-history strategy of this trematode, which is known to extend to other stages of its life cycle, has likely contributed to its invasion history outside its native range in Europe.

Life-history trade-offs in a generalist digenean from cetaceans: the role of host specificity and environmental factors

“…Also, individuals of P. gastrophilus were able to mature and reproduce in both dolphin hosts, but worms were significantly larger in striped dolphins and also harboured larger eggs. These differences were consistent regardless of substantial variability associated to host individual, and did not appear to be confounded by differential density-dependence [ 5 ]. In fact, bottlenose dolphins provided a larger microhabitat (stomach area: 520 cm 2 vs. 297 cm 2 in striped dolphins, F.J. Aznar, unpub.…”

“…A fundamental question regarding host specificity is the extent to which a putative generalist parasite performs equally well in all exploited host species, namely, whether these hosts are all equally compatible for the parasite [ 4 ]. This question has important implications, not only for understanding the evolution of specificity, but also for population dynamics and epidemiology of generalist parasites [ 5 ]. In some cases, there is little evidence that sympatric hosts impact differently the performance of a putative generalist parasite, e.g.…”

“…In some cases, there is little evidence that sympatric hosts impact differently the performance of a putative generalist parasite, e.g. [ 5 ]. Other studies, however, have reported on significant host species effects on fitness-related traits of the parasite such as dwarfism and impaired reproduction in presumably suboptimal hosts, e.g.…”

“…To our knowledge, few studies have analysed how the combined effect of host species constraints, and local selective pressures on the life-cycle, could shape life history traits of a generalist parasite, e.g. [ 5 ].…”

Comparison of Fecal Egg Counts and ELISA for the Diagnosis of Dicrocoelium Dendriticum Infection

“…dendriticum is one of the most prevalent liver trematodes in animals. This fluke lives inside the binary ducts of liver of cow, sheep, goat, pig and rarely in human (Rack et al 2004, Jeandron et al 2011, Beck et al 2015, Ofori et al 2015. Anemia, Icterus, progressive liver cirrhosis, and weight loss are among the symptoms of being infected by this parasite (Sargison et al 2012, Godara et al 2014.…”