Microsporidiosis - Causes, Symptoms, Diagnosis, and Treatment

What Is Microsporidiosis?

Microsporidiosis is a condition brought on by an infection with microorganisms known as microsporidia. Eukaryotic parasites called microsporidia require the presence of other host cells to produce contagious spores.

Although it is uncommon, these spores can also inflict disease on people with a healthy immune system. These spores are the primary cause of microsporidiosis, a condition primarily seen in people with HIV (human immunodeficiency virus). The parasite Microsporidia is widespread worldwide and can live on vertebrates and invertebrates.

The intestine, lungs, kidney, brain, sinuses, muscles, and eyes are among the organs that microsporidiosis can infect. There are more than 1,400 different species of microsporidia, but only 15 are harmful to people.

What Causes Microsporidiosis?

The microsporidia are a class of unicellular intracellular parasites closely related to fungi, though it is unclear. They were historically categorized as protozoa and are frequently under the control of diagnostic parasitology laboratories, despite repeated debate and revisions regarding their taxonomic position. The production of resistant spores with a range in size (typically one to four micrometers for species with medical importance) distinguishes microsporidia from other microorganisms. Furthermore, their ultrastructure reveals that they have a special organelle called the polar tubule or polar filament, which is coil-like inside the spore. In addition to having mitosomes and degenerated mitochondria, microsporidia do not have a typical golgi apparatus.

More than 1400 species from more than 200 genera have been identified as parasites that infect various vertebrate and invertebrate hosts. At least 15 species of microsporidian have been identified as human pathogens, with Enterocytozoon bieneusi being the primary culprit in the vast majority of cases, followed by a few Encephalitozoon species (E. cuniculi, E. hellem, and E. intestinalis (Septata intestinalis)).

Other less frequently reported pathogens include those belonging to the genera:

• Anncaliia (Brachiola) (A. algerae, A. connori, A. vesicularum).

• Microsporidium (M. ceylonensis, M. africanum).

• Trachipleistophora (T. hominis, T. anthropophthera).

• Nosema ocularum.

• Pleistophora ronneafiei.

• Vittaforma corneae.

What Are the Risk Factors for Microsporidiosis?

Immunodeficiency is the main risk factor for contracting microsporidiosis. Most microsporidiosis cases involve people with weakened immune systems, primarily those with immunosuppression brought on by HIV/AIDS (acquired immunodeficiency syndrome).

Additionally, it may affect those immunocompromised, such as organ transplant recipients, people with diabetes, cancer patients, and people who take steroids for a long term. Rarely healthy individuals with a normal immune system can contract microsporidiosis.

How Do Microsporidia Spread?

Animals with the infection release microsporidia spores in their urine, respiratory secretions, and stool. Microsporidia can be found in various animals, including insects, birds, and mammals.

Though the exact mechanism is not fully understood, it is believed that humans ingest or inhale these spores, through which the infection is transmitted. Additionally, studies have raised the possibility of water-borne and food-borne transmission. The microsporidia grow and multiply once inside a cell, creating more spores. The cell then swells and bursts, releasing the infectious spores.

What Are the Signs and Symptoms of Microsporidiosis?

Despite the possibility, microsporidiosis is extremely rare in people with healthy immune systems. Instead, microsporidiosis symptoms are most common in immunocompromised individuals, such as HIV-positive people and organ transplant recipients. Microsporidiosis can result in illness of the intestines, kidneys, lungs, brain, sinuses, muscles, or eyes.

1. Intestinal or Biliary Microsporidiosis Symptoms:

• Chronic diarrhea (loose, watery, non-bloody).

• Weight loss.

• Abdominal pain.

• Nausea.

• Vomiting.

• Gallbladder diseases.

Chronic diarrhea in AIDS patients carries high mortality (death) risk and can be highly debilitating. Enterocytozoon bieneusi is the main cause of intestinal microsporidiosis in AIDS patients.

2. Disseminated Microsporidiosis Symptoms:

• Renal failure, respiratory infections, and cholecystitis (inflammation of the gall bladder) symptoms.

• Patients with respiratory tract involvement may exhibit dyspnea (difficulty in breathing), wheezing, and a persistent cough.

• Involvement of the sinuses may be indicated by headache, nasal discharge or congestion, ocular pain, and taste loss.

• Patients who have urinary tract involvement usually do not exhibit any symptoms.

Additionally, microsporidia can disseminate throughout the body and inflame the muscle, pancreas, and brain.

3. Ocular Microsporidiosis Symptoms:

Microsporidia eye infection can result in corneal and conjunctival inflammation (keratoconjunctivitis).

• Foreign body sensation in the eye.

• Eye pain.

• Light sensitivity.

• Ocular redness.

• Excessive tearing.

• Blurred or decreased vision.

4. Musculoskeletal Microsporidiosis: Patients with severe cellular immunodeficiency and myositis frequently experience myalgia, generalized muscle weakness, and fever.

5. Dermatologic Microsporidiosis: In patients with HIV infection, microsporidia have been linked to a nodular cutaneous lesion.

6. Microsporidiosis of the CNS (Central Nervous System): Patients with brain microsporidiosis may experience headaches and seizures.

How Is Microsporidiosis Diagnosed?

The diagnosis of microsporidia infection can be made using several tests. Although it may not always be possible to identify the precise species of microsporidia, rapid diagnosis is made possible by examination of stained samples of body fluids, primarily fecal samples. When the kidney or bladder is involved, spores can also be found in urine samples.

Microsporidia infection can also be detected in the research laboratory using additional techniques like immunofluorescence assays and polymerase chain reaction (PCR) testing. In addition, imaging studies and blood tests can also help detect microsporidiosis.

How Is Microsporidiosis Treated?

Medications and supportive care are typically used to treat microsporidiosis. Various medications are available depending on the microsporidia species involved and the infection site.

• Albendazole (Albenza) and Fumagillin are the two drugs for microsporidiosis used most frequently.

• Electrolyte replacement and intravenous fluid administration may be required for patients with diarrhea and dehydration. Nutritional and dietary plans can also help with chronic diarrhea.

• Finally, antiretroviral therapy for HIV-infected patients may help the immune system function better, resulting in symptom improvement.

Can Microsporidiosis Be Prevented?

Microsporidiosis can be avoided in HIV-positive patients by keeping their immune systems strong and taking antiretroviral drugs. It is also advised to frequently wash hands and avoid exposure to sources of infection. Safe sexual practices are a crucial preventive measure due to the possibility of sexual transmission. A vaccine to stop microsporidiosis is not yet available.

Conclusion

Microsporidiosis is an intestinal infection caused by microsporidia species and brings about symptoms like diarrhea. In general, healthy people with a normal immune system have a good prognosis for microsporidiosis. The prognosis is more uncertain for immunocompromised people who contract microsporidiosis; the location, severity, and timing of seeking prompt medical attention all play a role in the outcome. Microsporidiosis can be prevented in HIV-positive patients by maintaining immunity and taking antiretroviral drugs.