The Gut-Wrenching Effects of Cryptosporidiosis and Giardiasis in Children

Abstract

Cryptosporidium species and Giardia duodenalis are infectious intestinal protozoan pathogens that cause alarming rates of morbidity and mortality worldwide. Children are more likely to have clinical symptoms due to their less developed immune systems and factors such as undernutrition, especially in low- and middle-income countries. The severity of the symptoms and clinical manifestations in children may vary from asymptomatic to life-threatening depending on the Cryptosporidium species/G. duodenalis strains and the resulting complex stepwise interactions between the parasite, the host nutritional and immunologic status, and the gut microbiome profile. Structural damages inflicted by both parasites to epithelial cells in the large and small intestines could severely impair children's gut health, including the ability to absorb nutrients, resulting in stunted growth, diminished neurocognitive development, and other long-term effects. Clinically approved cryptosporidiosis and giardiasis drugs have broad antimicrobial effects that have incomprehensible impacts on growing children's gut health.

Keywords: children’s gut health; cryptosporidiosis and giardiasis; gut microbiota; immunocompromised; undernutrition.

Figure 1

This is a simplified figure showing similarities in the life-cycle stages that initiate human infection and outbreaks of Cryptosporidium and G. duodenalis. The figure also shows the differences in their impacts on epithelial cells as a result of infection. Adapted from “Cryptosporidium Infection Cycle” by Biorender.com (28 August 2023).

Figure 2

Blender software version 3.5.1-generated image showing a host infected with Cryptosporidium (left) and Giardia (right). Cryptosporidium and/or G. duodenalis infection could alter the gut microbiota ecological balance (colored particles) through dysbiosis in the mucosal layers of epithelial cells. Giardia duodenalis cysteine proteases, beta-N-acetylglucosaminidase, and beta-N-acetylgalactosaminidase can efficiently break down mucins, which are the molecular framework of the epithelial mucosal layers on the intestine. Histological evidence of the marked depletion of intracellular mucin and gastrointestinal mucosal injury have been reported in HIV-positive individuals with cryptosporidiosis [74].