Long-term trends in helminth infections of wood mice (Apodemus sylvaticus) from the vicinity of Malham Tarn in North Yorkshire, England

Abstract

Helminth infections in wood mice (n = 483), trapped over a period of 26 years in the woods surrounding Malham Tarn in North Yorkshire, were analysed. Although 10 species of helminths were identified, the overall mean species richness was 1.01 species/mouse indicating that the helminth community was relatively depauperate in this wood mouse population. The dominant species was Heligmosomoides polygyrus, the prevalence (64.6%) and abundance (10.4 worms/mouse) of which declined significantly over the study period. Because of the dominance of this species, analyses of higher taxa (combined helminths and combined nematodes) also revealed significantly declining values for prevalence, although not abundance. Helminth species richness (HSR) and Brillouin's index of diversity (BID) did not show covariance with year, neither did those remaining species whose overall prevalence exceeded 5% (Syphacia stroma, Aonchotheca murissylvatici and Plagiorchis muris). Significant age effects were detected for the prevalence and abundance of all higher taxa, H. polygyrus and P. muris, and for HSR and BID, reflecting the accumulation of helminths with increasing host age. Only two cases of sex bias were found; male bias in abundance of P. muris and combined Digenea. We discuss the significance of these results and hypothesize about the underlying causes.

Ecological Analysis of the Helminth Community of the Wood Mouse, Apodemus sylvaticus, along an 18-Year Post-Fire Regeneration Period in a Mediterranean Ecosystem

“…The values obtained in the burned area are very similar to those reported in other studies on the wood mouse in the Iberian Peninsula [39,42], being slightly higher than those reported in the burned area of previous periods analysed [14,17]. However, the values in the burned area are higher than those obtained in other wood mouse studies such as a long-term study carried out during 26 years in England, which reported an overall mean species richness of only 1.01 [26].…”

“…Among the influences exercised by the climate on the species richness, the positive correlation of mean temperature and rainy days in the burned area only stands out. The logical and predictable influence of the host age on the species richness has also been reported in other peninsular enclaves, such as the Erro river valley [42] and Sierra Espuña [39], and in England [26], as well as in the burned area, but also in the control area in previous periods analysed in Serra Calderona NP, i.e., in the 2nd-10th PFY period [17].…”

“…The relation of the wood mouse age with the Brillouin index values could be linked to the different diet and territorial behaviour of each subpopulation. Other studies carried out in the UK, Spain and Portugal reported a higher helminth diversity and species richness in the adult subpopulation [23,26,39,41]. This effect of the host age can be related to two facts: first, the increase in the host age goes together with the exposure to helminth infestations; second, the parasite burden accumulates along time [14,17,23,24,26,107,108].…”

“…However, other studies have analysed the ecological aspects that influence the helminth/host relationship in depth. These studies were mainly carried out in central and eastern Europe, Finland and the British Isles [20][21][22][23][24][25][26][27][28][29][30][31], as well as several Mediterranean insular enclaves [32][33][34]. In the Iberian Peninsula, relevant studies were carried out in: Albufera of València [35], Serra da Malcata, Portugal [36], Doñana National Park [37], Serra Calderona Natural Park (NP), Castelló-València [38], Sierra de Espuña, Murcia [39], Sierra de Gredos, Ávila [40], Dunas de Mira, Portugal [41], and the Erro river valley, Navarre [42].…”

Ecological Analysis of the Helminth Community of Microtus lusitanicus (Gerbe, 1879) (Rodentia) in Asturias (NW Spain)

“…Moreover, older animals are more likely to be infected given their age and having covered more territory to come into contact with infective forms [ 53 ]. Prevalence and intensity of helminth parasites increase with host age in other studies with wild rodents [ 19 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ]. In C. minutus , the results were those to be expected.…”