Influence of habitat alteration on the structure of helminth communities in small mammals: a systematic review and critical appraisal of theory and current evidence

Despite the extensive information on the effects of habitat alteration on the structure of helminth communities in small mammals, the evidence is still inconclusive. A systematic review was carried out using the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guideline to compile and synthesize available literature on the influence of habitat alteration on the structure of helminth communities in small mammals. The aim of this review was to describe the variation in infection rates of helminth species associated with habitat alteration and to discuss the theoretical framework that may explain such changes in relation to parasite, host, and environmental features. Twenty-three scientific articles published between 2005 and 2022 were reviewed, 22 of which investigated parasite prevalence, 10 parasite burden, and 14 parasite richness in both altered and natural habitats. Information in assessed articles suggests that the structure of helminth communities in small mammals can be impacted by anthropogenic habitat alteration in various ways. Infection rates of monoxenous and heteroxenous helminths may increase or decrease in small mammals depending on whether their hosts (definitive and intermediate) are available, and environmental and host conditions modify the survival and transmission of parasitic forms. Also, given that habitat alteration may favor inter-species contacts, transmission rates of low host-specific helminths could be increased due to exposure to new reservoir hosts. In a continually changing world, it is essential to assess the spatio-temporal variations of helminth communities in wildlife inhabiting altered and natural habitats to determine potential impacts on wildlife conservation and public health.