Correction: Aquatic invasive alien rodents in Western France: Where do we stand today after decades of control?

[This corrects the article DOI: 10.1371/journal.pone.0249904.].

Aquatic invasive alien rodents in Western France: Where do we stand today after decades of control?

Two aquatic invasive alien rodents, the coypu (Myocastor coypus) and muskrat (Ondatra zibethicus), have taken over a significant amount of wetlands in France. Pays de la Loire is an administrative region of about 32 000 km2 in the Western France with 6.3% of its area in wetlands (excluding the Loire River). Populations of coypus and muskrats are established and a permanent control programme has been set to reduce their impacts. The control plan is based on few professional trappers and many volunteers which makes this programme unique compared to other programme relying on professionals only. The aim of this study is to analyse the temporal and spatial dynamics of coypu and muskrat captures during the last 10 years to evaluate their effectiveness. The number of rodents removed per year increased by 50% in 10 years and reached about 288 000 individuals in 2016 with about 80% of them being coypus. During the same time length, the number of trappers involved in the programme also increased by 50% to reach 3 000 people in 2016. Although the raise of coypus and muskrats trapped can possibly be explained by an increase of the number of trappers, the number of coypus removed per trapper per year increased by 22%. Despite the outstanding number of individuals removed per year, our results suggest that the programme does not limit the population dynamics of coypus. Finally, since 2017, the number of data gathered from municipalities decreased, as did the total number of individuals trapped. Indeed, although rewards are crucial to recruit new volunteers, subsidies from local and regional authorities are declining. Decision makers and financers should be encouraged to fund this programme from the perspectives of the direct or indirect costs related to the presence of aquatic invasive alien rodents in wetlands.

Muskrats are greater carriers of pathogenic Leptospira than coypus in ecosystems with temperate climates.

Knowledge on the possible sources of human leptospirosis, other than rats, is currently lacking. To assess the distribution pattern of exposure and infection by Leptospira serogroups in the two main semi-aquatic rodents of Western France, coypus (Myocastor coypus) and muskrats (Ondatra zibethicus), results of micro-agglutination testing and renal tissue PCR were used. In coypus, the apparent prevalence was 11% (n = 524, CI95% = [9% - 14%]), seroprevalence was 42% (n = 590, CI95% = [38% - 46%]), and the predominant serogroup was Australis (84%). In muskrats, the apparent prevalence was 33% (n = 274, CI95% = [27% - 39%]), seroprevalence was 57% (n = 305, CI95% = [52% - 63%]), and the predominant serogroup was Grippotyphosa (47%). Muskrats should therefore be considered an important source of Grippotyphosa infection in humans and domestic animals exposed in this part of France.

Nutrias and muskrats as bioindicators for the presence of Echinococcus multilocularis in new endemic areas.

Nutrias (Myocastor coypus) and muskrats (Ondatra zibethicus) are large invasive semi-aquatic or aquatic rodents, naturalized throughout Europe. They are regarded as pests, and can be infected with several pathogens and parasites transmissible to wildlife, livestock, pets and humans. As a rule, in Europe the life cycle of the cestode Echinococcus multilocularis involves red foxes (Vulpes vulpes) as main definitive hosts and common voles as intermediate hosts. The suitability of nutrias and muskrats as intermediate hosts has already been described. Here, we investigate the occurrence of E. multilocularis in the context of a wide-scale health study on nutrias and muskrats in 12 "départements" in the western part of France. During the sampling period, a total of 817 aquatic rodents were trapped in five rivers or ponds in each "départements". During post-mortem examinations, lesions were observed on the livers of 21 nutrias and 104 muskrats, and analyzed by PCR and sequencing of the mitochondrial cox1 gene for specific identification. Several non-zoonotic parasites were identified: Taenia taeniaformis, Taenia mustelae, Taenia polyacantha and Taenia martis. Four livers from 2 nutrias and 2 muskrats exhibited E. multilocularis infection. One of the muskrats was infected with fertile E. multilocularis lesions. The 4 animals came from 3 French "départements" where foxes have recently been found to be infected by E. multilocularis. These results lead us to consider nutrias and muskrats as relevant bioindicators for the presence of E. multilocularis in this environment. Our results also suggest that, when listed as pests and targeted by large trapping campaigns, nutrias and muskrats could be used to detect the presence of E. multilocularis in areas considered free of this parasite.