The relationships between Ixodes ricinus and small mammal species at the woodland–pasture interface

Abstract

Ixodes ricinus, as vector, and small mammals, as reservoirs, are implicated in pathogen transmission between wild fauna, domestic animals and humans at the woodland-pasture interface. The ecological relationship between ticks and small mammals was monitored in 2005 on four bocage (enclosed pastureland) sites in central France, where questing ticks were collected by dragging and small mammals were trapped. Questing I. ricinus tick and small mammal locations in the environment were assessed through correspondence analysis. I. ricinus larval burden on small mammals was modeled using a negative binomial law. The correspondence analyses underlined three landscape features: grassland, hedgerow, and woodland. Seven small mammal species were trapped, while questing ticks were all I. ricinus, with the highest abundance in woodland and the lowest in pasture. The small mammals were overall more abundant in hedgerow, less present in woodland and sparse in grassland. They carried mainly I. ricinus, and secondarily I. acuminatus and I. trianguliceps. The most likely profile for a tick-infested small mammal corresponded to a male wood mouse (Apodemus sylvaticus) in woodland or hedgerow during a dry day. A. sylvaticus, which was the only species captured in grassland, but was also present in hedgerow and woodland, may be a primary means of transfer of I. ricinus larvae from woodland to pasture.

Ecological Factors Characterizing the Prevalence of Bacterial Tick-Borne Pathogens in Ixodes ricinus Ticks in Pastures and Woodlands

“…The B. burgdorferi sensu lato infection prevalence was higher on pastures that had a high percentage of shrubs on the perimeter. This result is consistent with the fact that B. burgdorferi sensu lato reservoir hosts, i.e., rodents and birds, are particularly concentrated in the shrubby vegetation around pastures (11,65). The B. burgdorferi sensu lato infection prevalence also increased in pastures surrounded by forests with low perimeter length/surface area ratios.…”

“…A larger amount of edge increases the abundance of small vertebrate hosts-rodents, which are the reservoir for both pathogens, and birds, which are a reservoir only for B. burgdorferi sensu lato-because the vegetation complexity is greater at the edge or because several landscape elements are (9,70). Indeed, we found that in a bocage landscape, small mammals were more abundant in the forest-pasture ecotone than inside forests or pastures (11). Similar results were found in the United States, where patch size was found to be predictive of the B. burgdorferi sensu lato infection prevalence of I. scapularis because of the increased abundance of the reservoir host for B. burgdorferi sensu lato (1,12).…”

Ecological implications on the aggregation of Amblyomma fuscum (Acari: Ixodidae) on Thrichomys laurentius (Rodentia: Echimyidae), in northeastern Brazil

“…In overall, larvae were significantly more abundant in the wet season (v 2 = 16.2, df = 1, p \ 0.001), whereas the nymphs were proportionally more abundant in the dry season (v 2 = 6.5, df = 1, p \ 0.01). In the tropics, where there are no large variations in environmental conditions such as average temperatures and photoperiod, all tick stages are active during the year in As vegetation structure is crucial for tick survival and development (Estrada-Peña 2001), habitat quality for ticks might indirectly be estimated by infested host capture (Boyard et al 2008;Guerra et al 2002). Despite the lack of information on life history traits for A. fuscum we found that habitat preferences of T. laurentius are biologically relevant for this tick's biology.…”

“…Finding in Tapacurá fragment a large T. laurentius population suggests that this species locally display a large ecological range. Because fields frequently used by cattle and horses surround this area, T. laurentius might act as an epidemiological bridge (Boyard et al 2008, Paziewska et al 2010) between forested environments and open ones.…”

Susceptibility of selected murine and microtine species to infection by a wild strain of Francisella tularensis subsp. holoarctica

“…In our opinion, the probability of obtaining a live specimen of this species from the wild positive for tularemia by culture of the spleen is very low, because there remain only three active days from infection to capture in this rodent. On the other hand, the probability of yellow-necked mice harbouring F. tularensis is increased by their reported higher degree of infestation by ticks as compared to other rodents (Talleklint and Jaenson, 1997;Rosa et al, 2007;Boyard et al, 2008). Unfortunately, owing to problems in producing sufficient numbers of yellow-necked mice for experiments under laboratory conditions, we were not able to obtain statistically significant data on tissue bacterial burden, minimum infectious dose, and LD 50 .…”