Parasite contamination of soil in different Peruvian locations and outside built environments.

Background: Soil is a reservoir for many parasites that can affect human and animal health, especially in tropical regions where soil-transmitted helminths and protozoa thrive. Understanding how environmental factors influence parasite distribution will provide a basis for relating how climate changes may intensify their impacts, altering parasite habitats and increasing transmission risks. We surveyed soil parasite prevalence, burden, and diversity in several different Peruvian environmental ecologies to catalog current parasite presence and provide a baseline for future surveys.

Methods: A total of 198 soil samples from 43 locations across three Peruvian regions-Tingo María (TM) (Amazon rainforest), Andabamba/Marabamba (A/M) (Andean highlands), and Huánuco city parks-were analyzed using multi-parallel quantitative real-time polymerase chain reaction (qPCR) to detect soil-transmitted helminths (STH) and protozoan DNA from entry, patio, and latrine sites.

Results: Parasites were detected in 93% of locations, with 84% showing polyparasitism. TM houses had a higher odds ratio of contamination with Ascaris lumbricoides and Trichuris trichiura than those in A/M. TM also showed significantly higher odds of helminth contamination in patios than entries. TM had significantly more parasite species, with helminth species significantly higher in the patio versus entry. A/M had higher protozoan prevalence with Blastocystis species, with a greater odd ratios to TM. A/M had an increase of Acanthamoeba species in patios versus entries, indicating a niche favoring protozoans in these arid conditions.

Conclusions: The observed variability in soil parasite prevalence between tropical rainforest and highland regions highlights the influence of environmental niches on parasite distribution, which may shift further due to climate change. This study demonstrates a sensitive approach to monitoring environmental contamination with parasites by leveraging qPCR. The findings underscore the importance of ecological surveillance for assessing parasitic transmission risks, which is crucial for guiding public health interventions, especially as environmental changes accelerate.