Microsporidiosis is an opportunistic intestinal infection that causes diarrhea and wasting in immunocompromised individuals (HIV, for example). It results from different species of microsporidia, a group of microbial (unicellular) fungi.In HIV infected individuals, microsporidiosis generally occurs when CD4+ T cell counts fall below 150. Microsporidia have emerged with significant mortality risk in immunocompromised individuals. These are small, single-celled, obligately intracellular parasites linked to water sources as well as wild, and domestic animals. They were once considered protozoans or protists, but are now known to be fungi, or a sister group to fungi. The most common causes of microsporidiosis is Enterocytozoon bieneusi and Encephalitozoon intestinalis. Cause
At least 15 microsporidian species have been recognized as human pathogens, spread across nine genera:

Anncaliia
A. algerae, A. connori, A. vesicularum
Encephalitozoon
E. cuniculi, E. hellem, E. intestinalis
Enterocytozoon
E. bieneusi
Microsporidium
M. ceylonensis, M. africanum
Nosema
N. ocularum
Pleistophora  sp. Trachipleistophora
T. hominis, T. anthropophthera
Vittaforma
V. corneae. Tubulinosema
T. acridophagusThe primary causes are Enterocytozoon bieneusi and Encephalitozoon intestinalis. Life cycle
(Coded to image at right). The infective form of microsporidia is the resistant spore and it can survive for an extended period of time in the environment. The spore extrudes its polar tubule and infects the host cell. The spore injects the infective sporoplasm into the eukaryotic host cell through the polar tubule. Inside the cell, the sporoplasm undergoes extensive multiplication either by merogony (binary fission) or schizogony (multiple fission). This development can occur either in direct contact with the host cell cytoplasm (E. bieneusi) or inside a vacuole called a parasitophorous vacuole (E. intestinalis).
Teduglutide (brand names Gattex in the US and Revestive in Europe) is a 33-membered polypeptide and glucagon-like peptide-2 (GLP-2) analog that is used for the treatment of short bowel syndrome. It works by promoting mucosal growth and possibly restoring gastric emptying and secretion. In Europe it has been granted orphan drug status and is marketed under the brand Revestive by Nycomed. It was approved by the United States under the name Gattex on 21 December 2012, where it was given status as an orphan drug. Medical uses
Up to a certain point, the gut can adapt to partial resections that result in short bowel syndrome. Still, parenteral substitution of water, minerals and vitamins (depending on which part of the gut has been removed) is often necessary. Teduglutide may reduce or shorten the necessity of such infusions by improving the intestinal mucosa and possibly by other mechanisms. Adverse effects
Common adverse effects in clinical studies included abdominal discomfort (49% of patients), respiratory infections (28%), nausea (27%) and vomiting (14%), local reactions at the injection site (21%), and headache (17%). Chemistry and mechanism of action
Teduglutide differs from natural GLP-2 by a single amino acid: an alanine is replaced with a glycine. This blocks breaking down of the molecule by dipeptidyl peptidase and increases its half-life from seven minutes (GLP-2) to about two hours, while retaining its biological actions. These include maintenance of the intestinal mucosa, increasing intestinal blood flow, reducing gastrointestinal motility and secretion of gastric acid. == References ==