Microsporidia Spores are oval in shape but are difficult to differentiate from bacteria because they are so small. Identification of spores in feces is actually possible with a modified trichrome stain that stain spores in red. This slide has not been stained and for those practitioners who are not looking for this parasite, they are easy to miss!
What is Microsporidia? Microsporidia are protozoal parasites of animals and insects responsible for common diseases of crustaceans and fish, and have been found in most other animal groups, including humans. Microsporidia are obligate, intracellular, spore-forming protozoa known to infect many animals. They are very ancient. Intestinal infection with Enterocytozoon bieneusi is increasingly recognized in patients with AIDS and chronic diarrhea where the prevalence is about 23-33%. The pathogenic role of E.bieneusi is still controversial. Replication takes place within the host’s cells, usually in the duodenum and gall bladder. The Microspiridium spore is the infective stage. These vary in size from 1-4.5 micrometers, making them some of the smallest parasites ever and so it’s hard to tell the difference between the parasite and a cocci-shaped bacteria.
Microsporidia enter individuals via ingestion or inhalation. Resistant spores are formed within the host and are secreted from the body in feces and urine, and possibly through mucous secretion although this has not been documented. Therefore, microsporidiosis is predisposed to spread via fecal-oral, urine-oral, and waterborne transmission. Microsporidia spores have been shown to survive prolonged periods of time in water (up to 4 months) and have been detected in surface water. The levels of Microsporidia spores found in raw sewage are comparable to that of Cryptosporidium and Giardia.
Microsporidiosis is more common in people with weakened immune systems (i.e., immunocompromised), but cases do occur among those with normal immune systems. Microsporidia have the potential to be waterborne because they are released in feces and urine. The most frequent cause of human Microsporidium infection is Enterocytozoon bieneusi. Other Microsporidum that we know about include: Encephalitozoon hellem, Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Nosema corneum.
Common Sources of Microsporidia Infection—Contaminated water
Symptoms of Microsporidia infection include being asymptomatic (no symptoms) to having diarrhea, bronchitis, pneumonia, and sinusitis. Microsporidia can also cause bile duct pain and inflammation (pain in the upper right abdomen).
Diagnosis and Treatment of Microsporidia: Microsporidiosis can be diagnosed through examination of stool, urine, or nasal washings. Special fluorescent antibody studies are often needed to detect Microsporidia. These tests are not usually recommended by doctors. Routine standard stains such Giemsa or Gram are not adequate for detecting spores in presence of bacteria. Giemsa stain is useful in staining duodenal fluid where both spores and developing stages can be observed.
Differentiation between the two intestinal microsporidia is required for an adequate therapy management. E. intestinalis infections are treated with albendazole, while fumagillin has been shown to be effective for eradicating E. bieneusi. Thus, species identification is important for defining the appropriate treatment.
Treatment of Microsporidia: Currently, there is no standard treatment for microsporidiosis but Albendazole, metronidazole, and thalidomide have all been used to treat microsporidiosis with limited success.
Prevention of Microsporidia: Always wash your hands with soap and water any time you might have touched human or animal feces, changed diapers, cleaned up feces, or gardened. Always wash your hands before eating. Avoid sex that may involve contact with feces. Know the source of your water: (a) do not drink or swallow water directly from rivers, lakes, streams, pools, or spas, (b) if you travel outside the United States you may want to avoid drinking water that has not been boiled or filtered for Microsporidia.
If you are immunocompromised you should consider additional protective steps such as boiling your drinking water for one minute, which will kill any Microsporidia in it. You could also use a water filter certified by National Science Foundation (NSF) International to remove cysts.
References for Microsporidia: