Macroscopic and microscopic lesions in passerine birds caused by plasmodium spp., leucocytozoon spp. and haemoproteus spp
Degree Final Project defended by Gonzalo Anibarro García-Baquero
September 30th, 2024
The order Passeriformes, known as `passerines`, is a large and diverse order of birds that groups some 6,500 species, which are of great importance at an ecological and public health level. It currently faces numerous threats, both natural and human, that endanger the survival of its populations. Among these threats, parasites of the order Haemosporida occupy a relevant place. This work focuses on knowing the incidence of Haemosporida parasites in the population of passerine birds and describing the macroscopic and histological lesions they cause in order to understand and deepen in their pathogenesis, besides using these findings as a complementary and/or alternative diagnostic method to PCR and the study of blood samples.
The autopsy of 34 passerine birds from the Community of Madrid was carried out. The study focused on the description of macroscopic and histopathological lesions, as well as on the diagnosis by PCR (14 animals +) and genomic sequencing (9 animals +) of hematic parasites, after which a statistical analysis was performed. A prevalence of 26.5% in Haemosporida parasites was detected, with 8.8% Plasmodium spp., 11.8% Leucocytozoon spp. and 8.8% Haemoproteus spp. Macroscopic lesions were significantly (p<0.05) higher in parasitized animals and were mostly present in the liver (77.8%), lungs (66.7%), kidneys (55.6%) and spleen (44.4%). However, there were no significant differences (p>0.05) in histological lesions identified in the parasitized group with respect to the non-parasitized group. In the birds with hemoparasites, they were detected mainly in liver and lungs (88.9%), kidneys (77.8%), digestive tract (66.7%) and spleen (44.4%). The results may be a consequence of both the error in the diagnostic technique and the presence of lesions caused by other pathologies different from the identified hematic parasites. The macroscopic and histopathological study of wild birds of the order Passeriformes is not sufficient by itself to identify Plasmodium spp., Leucocytozoon spp. or Haemoproteus spp. as the cause of death. Although the histological visualization of compatible parasitic formations confirms the diagnosis of hematic parasites, additional confirmatory immunohistochemical studies with specific antibodies would be necessary to identify the different predominant genera.
Keywords: Passeriformes, Plasmodium, Leucocytozoon, Haemoproteus, macroscopic lesions, histopathology.