Pneumocystis jiroveci (carinii). Pneumocystis jiroveci – previously  known as Pneumocystis carinii (classified as a protozoon at that time) is a fungus causing pneumacystosis. However, if you are very worried about catching this fungus, consult a doctor, and before that, order an essay and read more to understand the symptoms and risks. It affects people with a weaker immunity like: children and the elderly but these are rather occasional cases. Most cases of  Pneumocystis jiroveci infections constitute  as AIDS infection symptoms. The fungus occurs in the digestive system of most pets and domestic animals (dog, cats, cattle and horses) however they very rarely infect healthy organisms.  Generally, this germ infects persons suffering from AIDS, large bowel cancer or people having thier immune systems handicapped in some sort of way. Pneumacytosis is detected by colouring the sputum with silver.