Field-deployable open-source workflow for Cryptosporidium parvum detection in invasive beavers from southern Tierra del Fuego

Since their introduction to Tierra del Fuego in 1946, North American beavers (Castor canadensis) have expanded across the sub-Antarctic regions of Chile and Argentina, where dam building has extensively modified peatlands, mature sub-Antarctic forests, and watercourses. Such environmental modifications may alter the transmission of waterborne and gastrointestinal parasites, including Cryptosporidium spp., raising concerns about wildlife, livestock, and human health within the One Health framework. However, pathogen surveillance infrastructure for beavers in this region has historically been limited. Following our initial report of zoonotic Cryptosporidium parvum in invasive beavers from southern Patagonia based on 105 samples collected between 2017 and 2019 (Larrauri-Aguilar et al., bioRxiv 2025), we implemented a field-deployable surveillance workflow beginning in 2023. During 2024–2025, we applied this integrated approach, combining digital microscopy screening using a 3D-printed open-source microscope (OpenFlexure) with 18S rRNA nested PCR using portable, low-cost, and open-source equipment, validated for deployment in both laboratory and field conditions. Sequencing analysis confirmed C. parvum in all positive samples. Beyond identifying zoonotic pathogens, these findings demonstrate the feasibility of open-source instrumentation for field-deployable pathogen screening in remote sub-Antarctic settings. Sustained surveillance at the wildlife–livestock–human interface is necessary given the continued northward expansion of beavers into Patagonia and ongoing exposure of vulnerable hosts to waterborne pathogens.