<prompt> Apart from plasmodium, which of the following can infect RBCs in ring forms?Babesia microtiTyrpanosomasSchistosomiaMicrofilaria  <response>: Ans. a Babesia microti. Ref. Harrisons, Principles of Internal Medicine, 16th ed., pg1232Babesiosis B. microti Babesiosis is a worldwide protozoan disease of animals that is transmitted by ticks; humans are infected incidentally and initially develop a nonspecific febrile illness that can lead to hemolytic anemia. Babesia organisms enter RBCs and resemble malarial parasites morphologically, posing a diagnostic problem. Ixodid hard-bodied ticks, in particular Ixodes scapularis . dammini and I. ricinus, are the vectors of the parasite. Transfusions are another source of babesiosis. The incubation period for B. microti infection is 1 to 4 weeks. Immunosuppressed patients, splenectomized individuals, and the elderly have the most severe illness. The clinical presentation varies widely and resembles malaria or rickettsiosis; symptoms and signs include a gradual onset of irregular fever, chills, sweating, muscle pain, and fatigue. Mild hepatosplenomegaly and mild hemolytic anemia may develop, but a rash is not present. Giemsa-stained thick and thin blood films examined for small intraerythrocytic parasites. b. microti appears as a small ring form resembling P. falciparum. Unlike infection with Plasmodium, however, Babesia does not cause the production of pigment in parasites, nor are schizonts or gametocytes formed. A species-specific polymerase chain reaction test using the RNA gene has been used to show parasite persistence when the blood smear is negative. Treatment of Babesiosis:OrganismAdultsBabesia microtiAtovaquone 750 mg bid PO plus azithromycin 600 mg d PO or clindamycin 1200 mg bid IV.Babesia divergens and other Babesia species, including MO-1,WA-1, and CA-1Quinine 650 mg tid PO plus clindamycin 1200 mg bid IV or 600 mg tid PO plus atovaquone 750 mg bid POo 