Host manipulation by Ligula intestinalis: a cause or consequence of parasite aggregation?

Area of Science:

• Ecology
• Parasitology
• Behavioral Ecology

Background:

• The cestode Ligula intestinalis causes behavioral and morphological changes in its intermediate fish host, roach (Rutilus rutilus).
• These changes are hypothesized to promote parasite transmission to definitive avian hosts.
• The distribution patterns of parasite infections within fish populations are not fully understood.

Purpose of the Study:

• To investigate whether parasite-induced behavioral changes in roach influence the distribution of Ligula intestinalis infections.
• To explore the role of host manipulation in the aggregation of parasites within the fish host population.

Main Methods:

• Analysis of field data on parasite burdens in roach populations.
• Experimental infections of roach with Ligula intestinalis.
• Comparison of empirical data with contagious distribution and compound Poisson models.

Main Results:

• Field data revealed a scarcity of single parasite infections, resulting in a bimodal distribution of worm counts (0 and >1).
• Experimental infections showed no evidence of multiple parasite establishment even with high parasite loads in intermediate hosts.
• Parasite-induced host manipulation was identified as a significant factor contributing to parasite aggregation.

Conclusions:

• Parasite-induced host manipulation in the Ligula intestinalis-roach system acts as both a cause and consequence of parasite aggregation.
• The interplay between host manipulation and parasite aggregation shapes parasite distribution and transmission dynamics.
• This mutual interaction highlights complex ecological dynamics often overlooked in isolated studies.