Microsporidiosis

Microsporidia are intracellular pathogens transmitted by food and water. These ubiquitous pathogens parasitize a wide range of invertebrate and vertebrate hosts. There are about 200 genera and more than 1500 species of microsporidia. They are important parasites in both immune-deficient and immune-competent hosts; for instance, infection is seen in the setting of organ transplantation, human immunodeficiency infection, travel, children, and the elderly. This infection is an increasing problem in patients with transplants, where clusters of infection due to latent infection in transplanted organs have been demonstrated. Although the prevalence rate has fallen in the United States, due to the widespread use of combination antiretroviral therapy, infection with these pathogens remains a major problem in the majority of the world, with reported prevalence rates of 20% to 40%. Microsporidia also cause infection in insects, fish, mammals, and birds, leading to significant economic damage. These pathogens are classified based on ultrastructural features, developmental cycle, host-parasite relationship and molecular analysis. Phylogenetic analysis suggests that the Microsporidia are related to the Fungi, being either a basal branch or sister group.