Parasites: Babesia Microti and Leishmania Overview

Babesia Microti

• Babesia microti is a tick-borne parasite that infects red blood cells.
• The parasite can cause babesiosis, a disease that can be asymptomatic or cause hemolytic anemia.
• Symptoms of babesiosis include fever, chills, headache, fatigue, and muscle aches.
• Babesiosis is more severe in people who have a weakened immune system or are splenectomized.
• Some patients may harbor the parasite for months and show serologic evidence of infection with no history of clinical disease.
• The FDA has approved tests for the detection of Babesia microti in whole blood and plasma.

Leishmania

• Leishmania is a genus of protozoan parasites that cause leishmaniasis, a disease that affects the skin, mucous membranes, and internal organs.
• Leishmania parasites are transmitted to humans through the bite of infected sandflies.
• Leishmania species include L. mexicana, L. amazonensis, L. aethiopica, L. peruviana, and L. guyanensis.
• L. mexicana often causes Chiclero ulcers, which are self-limiting lesions that involve the earlobe.
• L. mexicana and L. amazonensis can produce diffuse cutaneous lesions, which are similar to those produced by L. aethiopica.
• L. peruviana causes uta, a benign cutaneous lesion that occurs predominantly in children.
• Leishmania spp have a kinetoplast and do not stain with Gomori methenamine silver (GMS) or periodic acid–Schiff (PAS), while Histoplasma lack the kinetoplast and stain with PAS and GMS.

Intestinal and Urogenital Protozoa

• Protozoa inhabiting the human intestinal tract include amebae, flagellates, ciliates, and coccidia.
• Intestinal protozoa may be nonpathogenic.
• Microsporidia also inhabit the human intestinal tract.
• The morphology of amebae can vary, with different species having different sizes, shapes, and motility.
• The presence of amebae in stool samples can indicate infection.

Entamoeba Histolytica/Dispar

• Entamoeba histolytica and Entamoeba dispar are amebae that infect the intestines of humans.
• They are differentiated from other amebae by their size, shape, and motility.
• Entamoeba histolytica is considered pathogenic and can cause amebic dysentery.
• Entamoeba dispar, in contrast, is generally considered nonpathogenic.

Dientamoeba Fragilis

• Dientamoeba fragilis is an ameboid-appearing protozoan that infects the colon, and has been associated with diarrheal disease, especially in young children.
• It is morphologically similar to amebae but is a flagellate with two nuclei.
• Dientamoeba fragilis is often associated with diarrhea, abdominal pain, and bloating.

Amebic Cysts

• Amebic cysts are a stage in the life cycle of amebae.
• Cysts are resistant to environmental conditions and can survive outside of the host for long periods.
• The morphology of amebic cysts can vary depending on the species.
• Entamoeba Histolytica/Dispar cysts are spherical and range in size between 10 and 20 µm. They contain four nuclei and are usually found in the stool of infected individuals.
• Entamoeba Coli cysts are generally spherical and range in size from 10 to 25 µm. They have a more granular appearance than E. histolytica cysts.
• Endolimax Nana cysts are typically spherical and measure 8–12 µm in diameter. They contain a single nucleus and a large central karyosome.
• Iodamoeba Buetschlii cysts have a characteristic appearance with a single large nucleus containing a prominent karyosome and irregular chromatin. They are typically 8–20 µm in size.
• Dientamoeba Fragilis does not have a cystic stage.

Treatment

• Metronidazole is the drug of choice for treatment of Entamoeba histolytica infection.
• Tinidazole and iodoquinol are alternative drugs for treatment.
• Treatment for other intestinal protozoal infections depends on the specific species involved.