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Digital archive of theses discussed at the University of Pisa

 

Thesis etd-05182021-165650


Thesis type
Tesi di dottorato di ricerca
Author
MARTINI, MATILDE
URN
etd-05182021-165650
Thesis title
EFFECT OF INFECTION BY TROPHICALLY-TRANSMITTED MACROPARASITES ON ANTI-PREDATORY BEHAVIOUR OF THEIR INTERMEDIATE HOSTS
Academic discipline
BIO/05
Course of study
BIOLOGIA
Supervisors
tutor Prof. Massolo, Alessandro
correlatore Dott.ssa Gagliardo, Anna
correlatore Dott. Romig, Thomas
Keywords
  • behavioural alteration
  • Echinococcus multilocularis
  • epidemiology
  • Microtus arvalis
  • muskrat
  • predator-prey relationship
  • reproduction
  • trophically-transmitted parasites
Graduation session start date
21/05/2021
Availability
Full
Summary
The cestode Echinococcus multilocularis is a trophically-transmitted parasite that is normally maintained in a sylvatic life-cycle involving wild canid definitive hosts and small mammal intermediate hosts. As etiological agent of Alveolar Echinococcosis in humans, this cestode is currently considered the third most impacting food-borne parasite globally. Understanding E. multilocularis transmission strategies, combined with data of parasite infection in wild intermediate hosts, is crucial for disease prevention and risk management.
Manipulation of host behaviour by parasites to enhance transmission to the next host is a fascinating phenomenon that interested scientist since the ’70s. It has been proposed that infection with the cestode Echinococcus multilocularis in common voles (Microtus arvalis) produces an impairment of the anti-predator behaviour in the rodent intermediate host, which facilitates transmission of the tapeworm to the canid final host. In this study we observed the behaviour of infected common voles at 8 and 12 weeks post-infection, when protoscoleces production and maturation normally occurs, in order to assess the occurrence of behavioural changes compared to uninfected controls, that might ease predation in the wild. Infected and uninfected voles were monitored 24-hour at each experimental stage in order to observe their spontaneous activity. In addition, on the next day both infected and uninfected voles were subjected to four different behavioural tests: open field test, barrier test, platform test and air-puff test in a running wheel. No significant difference between uninfected and infected voles emerged during the behavioural tests. However, the observation of the spontaneous activity revealed that infected voles increased their feeding frequency and spent significantly longer time above bedding even when not eating, compared to the uninfected controls. The latter behavioural changes in the wild increase the exposure to environmental factors and might increase the probability to be predated. These findings are the first direct evidence consistent to a behavioural manipulation by E. multilocularis on common voles.
In Europe, E. multilocularis mainly circulates between the red fox (Vulpes Vulpes) as definitive host, and several arvicolid species. Also, invasive species like muskrat (Ondatra zibethicus) can enter into its life-cycle. This semi-aquatic rodent species, native to North America, can be used as a model to investigate the risk factors for E. multilocularis in new aquatic habitat as well as to assess the larval development in the infected liver. Collecting data about E. multilocularis liver lesions in muskrats, trapped along two main rivers of Luxemburg, allowed to estimate an overall parasite prevalence of 14.6 % (true prevalence of 15.4 %), and to identify different risk factors, such as capture period, animal age and co-infection with another cestode species, that can affect the infection and the presence of E. multilocularis in a specific habitat. Moreover, a preference for the right medial liver lobe was found, making my evidence as a start point for the assessment of a lobe preference during the settlement and establishment of the metacestode in other IHs.
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