Poverty associated with the environmental contamination of gastrointestinal parasites in the Southern United States
Authors: Blackburn Christine Crudo , Yan Sally Mingshuang , McCormick David , Herrera Lauren Nicholas , Iordanov Roumen Borilov , Bailey Mark Daniel , Bottazzi Maria Elena , Hotez Peter J. , Mejia Rojelio 
Published: January 2023

Background

Gastrointestinal parasites are generally associated with lower-income countries in tropical and subtropical areas, but they are also prevalent in low-income and extreme low-income communities in the Southern United States. To date, studies characterizing the epidemiology of gastrointestinal parasites in the United States are limited, resulting in little comprehensive understanding of the challenge. This study investigates the environmental contamination of gastrointestinal parasites in the Southern United States by determining the contamination rate and burden of each parasite in five low-income communities.

Methods

A total of 499 soil samples of approximately 50g were collected from public parks and private residences in Alabama, Louisiana, Mississippi, South Carolina, and Texas. A novel technique utilizing parasite floatation, filtration, and bead-beating was applied to concentrate and extract parasite DNA from samples and detected via multi-parallel qPCR.

Findings

qPCR detectedBlastocystisspp (19.0%),Toxocara cati(6.01%),Toxocara canis(3.61%),Strongyloides stercoralis(2.00%),Trichuris trichiura(1.80%),Ancylostoma duodenale(1.42%),Giardia intestinalis(1.40%),Cryptosporidiumspp (1.00%),Entamoeba histolytica(0.201%),and Necator americanus(0.200%). Overall parasite contamination rates varied significantly between communities: Western Mississippi (46.88%); Southwestern Alabama (39.62%); Northeastern Louisiana (28.24%); Southwestern South Carolina (27.03%); and South Texas (6.93%) (p < 0.0001).Toxocara catiDNA burdens were greater in communities with higher poverty rates, including Northeastern Louisiana (50.57%) and Western Mississippi (49.60%) compared to Southwestern Alabama (30.05%) (p = 0.0011).

Interpretation

This study demonstrates the environmental contamination of parasites and their relationship with high poverty rates in communities in the Southern United States.

Funding

This work was supported by the Maternal and Infant Environmental Health Riskscape (MIEHR) Center of Excellence on Environmental Health Disparities Research, NIMHD grant #P50 MD015496

Research in context

Evidence before this study

Several research articles on parasites in the Southern USA were used to determine the extent of parasitosis in the selected regions (Mckenna et al,Am J Trop Med Hyg2018; Singer et al,Am J Trop Med Hyg2020; Bradbury et al,Emerg Infect Dis2021). Criteria used included terms hookworm, soil-transmitted helminths, protozoa, and parasites in the United States. The most recent parasite prevalence studies indicate areas with 62.9%Blastocystis, 34.5% hookworm (Necator americanus), 16.5%Strongyloides stercoralis, 5.2%Toxocara, 2.9%Cryptosporidium, 2.3%Giardia intestinalis, and 1.8%Entamoeba histolyticafrom human serum or stool samples. These studies focus on human parasite infections, but there are no current published studies on environmental parasite surveys in the Southern US. The parasites in this study all have part of their life-cycle in soil and can directly infect humans living in these areas.

Added value of this study

Our work expands the current understanding of prevalence of parasites in the Southern US soil from built environments. We further correlate the type of parasites and their intensity of soil contamination with higher poverty rates.

Implications of all the available evidence

These parasitic infections represent a major source of contamination in the built environments and their association with poverty. This study will help focus public policy on the potential risks that environmental parasites have on human health. It further describes the high contamination rates in the USA, a high-income country.