Pneumocystosis in humans is caused by Pneumocystis jirovecii, whereas in animals it is caused by Pneumocystis. Pneumocystosis causes opportunistic infections such as pneumonia in patients of acquired immunodeficiency syndrome (AIDS). Treatment can be done by cotrimoxazole, pentamidine, and atovaquone. Kala-azar/Visceral leishmaniasis caused due to Leishmania donovani. Infection transmitted by bite of female sand fly Phlebotomus. Trypanosomiasis is caused by protozoa of genus Trypanosoma. Suramin, pentamidine, melarsoprol, eflornithine, nifurtimox and benznidazole are the drug used for the treatment of Trypanosomiasis.