Gray wolves as sentinels for the presence of Echinococcus spp. and other gastrointestinal parasites in France.

Over the past 30 years, the gray wolf population has recovered in France, initially to wolves from Italy passing through the Alps. The population is carefully monitored, but little information is available on their helminth fauna, which includes parasites of public health importance: Echinococcus multilocularis and Echinococcus granulosus sensu lato. Capitalizing on the availability of 911 fecal samples collected for the noninvasive genetic monitoring of French wolf populations, along with the intestines from 15 dead wolves, the presence of Echinococcus species among others helminth species was evaluated in French wolves. A copro-PCR approach amplifying a large spectrum of parasites was used for fecal samples while intestines were analyzed using SCT. The fecal occurrences of E. granulosus sensu stricto (2.4%) and E. multilocularis (0.3%), and indeedother parasitic species, are similar to those of other European wolf populations including Taenia hydatigena (7.2%), Taenia krabbei (2.4%), Uncinaria stenocephala (2.4%), Mesocestoides litteratus (1.9%), Taenia ovis (0.3%), Taenia multiceps (0.1%), and Toxascaris leonina (0.1%). The three most abundant species were also found in the intestines. Infections by E. granulosus sensu stricto are in accordance with the overlap of wolf pack areas and sheep breeding pastoral units. However, the wolf does not appear to play a significant role in the lifecycle of E. granulosus sensu stricto. The availability of this opportunistic fecal sampling of wolves in southeastern France means that they can be used as sentinels for the surveillance of E. multilocularis in the context of its southward expansion observed in recent years.

Rodent control programmes can integrate Echinococcus multilocularis surveillance by facilitating parasite genotyping: the case of Arvicola terrestris voles screening in France.

The tapeworm Echinococcus multilocularis is the causative agent of alveolar echinococcosis, the most serious parasitic disease for humans in Europe. In Europe, the E. multilocularis lifecycle is based on a prey-predator relationship between the red fox and small rodents. Over the last three decades, the surveillance of E. multilocularis infection in red foxes has led to the description of a wider distribution pattern across Europe. France constitutes the current European western border, but only the north-eastern half of the country is considered endemic. The red fox is the host mainly targeted in E. multilocularis surveillance programmes, but surveys targeting small rodents may be useful for obtaining molecular data, especially when the time-consuming trapping is already carried out in dedicated pest-control programmes. Here, we screened for parasitic lesions in the livers of 1238 Arvicola terrestris voles originating from the historical, but neglected focal area located in central France (Auvergne region) and from Hautes-Alpes, a recently identified endemic department in south-eastern France. This screening identified six voles infected with E. multilocularis in Hautes-Alpes and none in Puy-de-Dôme (Auvergne region) after molecular confirmation. The absence of infected rodents from Puy-de-Dôme can be mainly explained by the generally low prevalence reported in intermediate hosts. The infected Hautes-Alpes samples come all from the same trapping site situated at around 5 km from one of the three fox faecal samples with E. multilocularis DNA collected 15 years prior, thereby confirming the existence and persistence of the E. multilocularis lifecycle in the area. All the rodent E. multilocularis samples from Hautes-Alpes showed the same EmsB microsatellite marker profile. This profile has previously been described in Europe only in the Jura department (central eastern France), located at least 180 km further north. Successive migrations of infected foxes from the historical focal area, including from Jura, to Hautes-Alpes may explain the detection of the parasite in A. terrestris in Hautes-Alpes. Existing trapping efforts in areas where farmers trap A. terrestris for surveillance and pest control can be an effective complement to sampling foxes or fox faeces to obtain E. multilocularis molecular profiles.

Disappearance of TBEV Circulation among Rodents in a Natural Focus in Alsace, Eastern France.

Tick-borne encephalitis virus (TBEV) depends mainly on a fragile mode of transmission, the co-feeding between infected nymphs and larvae on rodents, and thus persists under a limited set of biotic and abiotic conditions. If these conditions change, natural TBEV foci might be unstable over time. We conducted a longitudinal study over seven years in a mountain forest in Alsace, Eastern France, located at the western border of known TBEV distribution. The objectives were (i) to monitor the persistence of TBEV circulation between small mammals and ticks and (ii) to discuss the presence of TBEV circulation in relation to the synchronous activity of larvae and nymphs, to the densities of questing nymphs and small mammals, and to potential changes in meteorological conditions and deer densities. Small mammals were trapped five times per year from 2012 to 2018 to collect blood samples and record the presence of feeding ticks, and were then released. Questing nymphs were collected twice a year. Overall, 1344 different small mammals (Myodes glareolus and Apodemus flavicollis) were captured and 2031 serum samples were tested for the presence of antibodies against TBEV using an in-house ELISA. Seropositive rodents (2.1%) were only found from 2012 to 2015, suggesting that the virus disappeared afterwards. In parallel, we observed unusual variations in inter-annual nymph abundance and intra-annual larval activity that could be related to exceptional meteorological conditions. Changes in the densities of questing nymphs and deer associated with the natural stochastic variations in the frequency of contacts between rodents and infected ticks may have contributed to the endemic fadeout of TBEV on the study site. Further studies are needed to assess whether such events occur relatively frequently in the area, which could explain the low human incidence of TBE in Alsace and even in other areas of France.