Which parasite presents with a Maltese cross on blood smear and hemolytic anemia, transmitted by Ixodes ticks in the northeastern United States?

Which parasite presents with a Maltese cross on blood smear and hemolytic anemia, transmitted by Ixodes ticks in the northeastern United States?

• A. Babesia
• B. Plasmodium falciparum
• C. Giardia lamblia
• D. Entamoeba histolytica

Answer: (D)

Maltese cross formations in red blood cells on a blood smear point to an intraerythrocytic parasite that is transmitted by Ixodes ticks, and it commonly causes hemolytic anemia in the northeastern United States. That pattern is classic for Babesia, most often Babesia microti in the Northeast, which can be transmitted by Ixodes scapularis ticks that also carry Borrelia (Lyme disease) or Anaplasma. The hemolysis comes from parasite replication inside RBCs, leading to destruction of infected cells and anemia. Giardia lamblia and Entamoeba histolytica are intestinal parasites and do not produce intraerythrocytic parasites or Maltese cross formations. Plasmodium falciparum, while also a parasite that infects red blood cells, is transmitted by Anopheles mosquitoes and does not produce the Maltese cross appearance on smear. Diagnosis is supported by seeing the characteristic tetrads (the Maltese cross) on Giemsa-stained blood smears; PCR and serology can help as well. Treatment typically involves a combination such as atovaquone with azithromycin, with more aggressive therapy (like clindamycin plus quinine) for severe cases, and supportive care for hemolytic anemia.

Maltese cross formations in red blood cells on a blood smear point to an intraerythrocytic parasite that is transmitted by Ixodes ticks, and it commonly causes hemolytic anemia in the northeastern United States. That pattern is classic for Babesia, most often Babesia microti in the Northeast, which can be transmitted by Ixodes scapularis ticks that also carry Borrelia (Lyme disease) or Anaplasma. The hemolysis comes from parasite replication inside RBCs, leading to destruction of infected cells and anemia.

Giardia lamblia and Entamoeba histolytica are intestinal parasites and do not produce intraerythrocytic parasites or Maltese cross formations. Plasmodium falciparum, while also a parasite that infects red blood cells, is transmitted by Anopheles mosquitoes and does not produce the Maltese cross appearance on smear.

Diagnosis is supported by seeing the characteristic tetrads (the Maltese cross) on Giemsa-stained blood smears; PCR and serology can help as well. Treatment typically involves a combination such as atovaquone with azithromycin, with more aggressive therapy (like clindamycin plus quinine) for severe cases, and supportive care for hemolytic anemia.