Deforestation increases the abundance of rodents and their ectoparasites in the Lacandon forest, Southern Mexico

Abstract

Introduction: An important ecosystem service tropical forests provide is disease control. However, few studies have focused on analyzing how species more suitable to be zoonotic vectors are affected by deforestation. Objective: We evaluated how deforestation affects the abundance and species richness of rodents and their associated ectoparasites in Marques de Comillas, Chiapas, Southern Mexico. Methods: We captured rodents in 6 landscape units (LU), 1 km² each, with different percentages of tree cover (0.7, 5, 40, 46, 78, and 95 %). In each LU we set 90 Sherman traps that remained active 24 hours for 7 days during two sampling seasons in October 2019, and September 2020. All the captured rodents were checked for ectoparasites in their fur, which were collected to be identified at the lab. Results: We captured 70 rodents of five species: Sigmodon toltecus, Heteromys desmarestianus, Ototylomys phyllotis, Peromyscus mexicanus, and Oryzomys couesi. Rodent abundance increased with forest loss (R² = 0.706, P = 0.022). The greatest richness of rodent species occurred in sites with intermediate forest cover (40 % and 78 %). The most abundant species were S. toltecus (N = 45) followed by O. couesi (N = 9), these species dominated in sites with less forest cover. We recorded a total of 23 different ectoparasites, from these we identified 15 at the species level and eight at the genus level. We detected three species of ectoparasites (Amblyomma sp., Ornithonyssus bacoti, and Androlaelaps fahrenholzi) known to be vectors of zoonotic diseases. Conclusions: We found that the ongoing loss of forests promotes the proliferation of zoonotic disease vectors, which can potentially increase the frequency of affectation among the local population.

Effects of Season, Habitat, and Host Characteristics on Ectoparasites of Wild Rodents in a Mosaic Rural Landscape

“…In terms of vegetation characteristics, we considered only the presence of woody vegetation, whose effect, when significant, was positive on arachnid prevalence (Table 1) and abundance (Table 2) in M. arvalis and overall. Thus, concerning the effect of woody vegetation, we did not confirm the patterns usually reported in studies such as those in neotropical landscapes, where the reduction in forest cover through deforestation leads to increased rates of parasitism [14,61], probably involving the parasite dilution effect given the higher rodent diversity in natural forests compared with the impoverished rodent communities in habitats affected by deforestation. However, in our landscape, forests were rather species-poor, most often with only one captured species per habitat, while the greatest richness was found in fallows and field margins [18], both being habitats without woody vegetation.…”

“…Disentangling the effect of various intrinsic and extrinsic factors on the parasite prevalence and abundance could offer a deeper insight into the mechanisms governing the parasite-rodent host relationship. This may also have epidemiological implications in predicting the transmission risk of rodent-borne diseases [13,14,17,38].…”

“…Although the mechanisms governing the rodent host-ectoparasite relationship are intricate and result from the interaction of numerous host-and environment-related factors, there are some prevailing patterns largely-but not universally-reported in the literature: (i) males are more parasitised than females [7][8][9][10]; (ii) older and heavier animals are more parasitised compared with younger, lighter individuals [11,12]; (iii) parasite prevalence and mean abundance show seasonality [13]; (iv) animals living in habitats with woody vegetation have fewer parasites [14,15]; (v) animals in less intensively used habitats have fewer parasites [13]; and (vi) parasite prevalence and abundance vary among host species [16,17].…”