Crowding effect on adult growth, pre-patent period and egg shedding of Fasciola hepatica

Abstract

Fascioliasis pathogenesis depends on fluke burden. In human hyperendemic zones, individual infection intensities reach very high levels and the majority of infected subjects should be in the advanced chronic phase. The rat model offers a useful approach for pathological research in the advanced chronic period. The influence of infection intensity per rat on fluke development, pre-patent period and egg shedding (eggs/g faeces/worm) was analysed in 3 groups (I: 1-3 worms/rat; II: 4-6; III: 7-9). Ontogenetic trajectories of fluke body measures followed a logistic model. Results showed that when the burden increases, the maximum values of fluke measures decrease. The crowding effect is manifest when fluke measures approximate their maximums in the advanced chronic stage. The pre-patent period and egg production decrease when the burden increases. This means that measurements of eggs per gramme of faeces tend to underestimate the fluke burden. The present study demonstrates how to quantify the fascioliasis experimental rat model crowding effect on adult growth, pre-patent period and egg production. This quantification may be of great interest in epidemiological studies and in experimental research on the in vivo actions of different anthelminthic drugs and vaccines, pathology, immunology and resistance studies.

In Vivo and In Vitro Sensitivity of Fasciola hepatica to Triclabendazole Combined with Artesunate, Artemether, or OZ78

“…Fasciola hepatica eggs were detected in all 132 fecal samples examined prior to drug treatment, and posttreatment egg counts correlated significantly with surviving worms. It appears that the treatment reduced the worm burden and therefore minimized the influence of the crowding effect (a decreased egg output as a function of higher worm burden), which was previously documented in F. hepatica-infected rats (36).…”

Liver fluke (Fasciola hepatica) naturally infecting introduced European brown hare (Lepus europaeus) in northern Patagonia: phenotype, prevalence and potential risk

“…This implies that the morphometric development of the fasciolid adult is not limited but 'damped' and does not exceed certain characteristic maximum (Valero et al 1998(Valero et al , 2006b. Since the morphometric maximum values are characteristic for each population, they are considered the comparative base of this study (Table I).…”

Within-host competition and diversification of macro-parasites

“…within a parasite 'infrapopulation', lead to parasite diversification inside a population of conspecifics and sympatric host individuals. Several lines of evidence point at the potential significance of such adaptive speciation in macro-parasites: within-host intraspecific competition has an impact on parasite life history [19], infra-populations are often genetically diverse [20], several congeneric species can live on the same host individual [21] and within-host competition influences the patterns of associations between such species [10]. Hypothetically, within-host competition could also contribute to micro-parasite diversity because infra-populations also are genetically diverse [7,22], and competition between strains is an important force driving parasite life-history evolution [23].…”