This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Which of the following organ is most severely affected in Kala azar? \nSelect and explain. \nA. Spleen, B. Liver, C. Kidney, D. Bone Marrow', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A disease caused by infection with leishmania parasites.\nVisceral leishmaniasis / Black fever is spread by sandfly bites.\xa0\nThis type of leishmaniasis affects the internal organs, usually the spleen, liver and bone marrow.\nSome people have no symptoms.\nFor others, symptoms may include fever, weight loss and swelling of the spleen or liver.\nIf left untreated, severe cases are typically fatal, by affecting spleen.', 'role': 'assistant'}]