Haemoproteus columbae is a globally prevalent avian haemosporidian parasite that infects domestic and feral pigeons (Columba livia). The diagnosis of the parasitic infection requires the manual microscopic examination of blood smears by trained professionals, a time-consuming, tedious and subjective task. The main focus of this study is the presentation of a fuzzy logic-based system for the classification of infected cells in pigeon blood smear images and its comparison with a conventional threshold-based algorithm. The fuzzy approach yielded a cell detection F1 score of 0.9816 and an infected cell F1 score of 0.828; the threshold method achieved similar overall detection (red blood cell and infected cell detection F1-scores 0.9569 and 0.9197 respectively) but it has lower interpretability.