# Distribution of nematophagous fungi and soil-transmitted helminths in outdoor built environments across Latin America

## TL;DR

This study explores how nematophagous fungi in soil may reduce the presence of parasitic helminths in Latin America, offering a natural way to control their spread.

## Contribution

The study provides empirical evidence that Arthrobotrys oligospora reduces helminth DNA in soil and is inversely associated with helminth detection in Latin America.

## Key findings

- In vitro testing showed a 40.1% reduction in viable Toxocara cati eggs when exposed to Arthrobotrys oligospora.
- Soil samples from seven Latin American countries showed a significant decrease in helminth abundance where nematophagous fungi were present.
- The presence of Arthrobotrys oligospora in soil was associated with a 62.4% decrease in its own DNA over 14 days, suggesting dynamic interactions.

## Abstract

Soil-transmitted helminths (STHs) are among the most common global parasitic infections, represent a significant worldwide public health burden, and remain a source of considerable morbidity in Latin America. Nematophagous fungi (NF), such as Arthrobotrys oligospora, naturally inhabit many soil types and are known for their ability to trap and kill nematodes using specialized hyphal structures or secreted enzymes and metabolites. As they prey on different developmental stages of helminths in soil, they may represent an ecological factor influencing helminth persistence and transmission dynamics.

Using an in vitro test, Toxocara cati eggs were exposed to A. oligospora. By using a flotation, filtration, and bead-beating disruption technique, parasite and fungal DNA were collected and detected by multi-parallel real-time quantitative PCR (qPCR). Similar methods were used to extract DNA from soil samples outside built environments across seven Latin American countries, including Argentina, Bolivia, Brazil, Ecuador, Mexico, Paraguay, and Peru.

In vitro testing showed a 40.1% reduction in viable eggs in the presence of A. oligospora, as determined by qPCR (P = 0.0212). Comparing the impact of A. oligospora on T. cati over 14 days revealed a decrease in T. cati DNA concentration compared to control groups (P = 0.0039). Using qPCR to detect A. oligospora, there was a 62.4% decrease in the mean A. oligospora DNA at 14 days. The co-occurrence of NF and STH was evaluated in 805 soil samples from seven Latin American countries representing distinct geoclimatic settings. We observed a significant reduction in helminth abundance (P < 0.05), including Ascaris, Strongyloides, Toxocara, and any helminth.

The ubiquitous presence of A. oligospora in soils and inverse association with STH parasite detection suggest a potential role in environmental helminth transmission patterns.

Soil-transmitted helminths (STH) remain a major cause of illness in many regions because their eggs and larvae remain viable in soil, continually driving reinfection. Current human treatment alone cannot interrupt this cycle. We evaluated Arthrobotrys oligospora, a nematophagous fungus naturally present in soil, to better understand its interactions with STH in environmental settings. In vitro, the fungus reduced helminth DNA concentrations, and its presence was detected in soils from seven Latin American countries. The fungus grows toward and penetrates parasites, including Ascaris, Strongyloides, and Toxocara. Its natural presence in soils in outdoor built environments was associated with decreased STH detection. These findings suggest that soil-dwelling nematophagous fungi may represent an ecological factor influencing environmental helminth persistence and transmission dynamics.