First Report of Haemoproteus (Haemosporida, Haemoproteidae) Megalomeronts in the Brain of an Avian Host, with Description of Megalomerogony of Haemoproteus Pastoris, the Blood Parasite of the Common Starling

Abstract

Species of Haemoproteus (Haemoproteidae, Haemosporida) are common bird pathogens. Recent molecular studies combined with histopathology research have reported development of megalomeronts of these parasites in various organs, sometimes resulting in the death of the avian host. Five Common starlings (Sturnus vulgaris) were found naturally infected with Haemoproteus pastoris lineage hLAMPUR01. The parasite was identified using microscopic examination of blood films and DNA sequences. Infected bird organs were investigated histologically for (i) the presence of exo-erythrocytic stages and (ii) the patterns of development (morphology and localization) in different host individuals. For the first time, megalomeronts of Haemoproteus parasites were seen developing in the brain, while numerous others at different stages of maturation were found in the intestine, pancreas, kidneys, lungs, esophagus, spleen, gizzard, and trachea. Megalomeronts were predominantly roundish or oval, up to 800 μm, they were surrounded by a capsular-like wall and developed asynchronously in the same bird individual. After megalomeront maturation and rupture, a massive infiltration of blood cells occurred, indicating the hemorrhagic processes. Review of available data showed that different Haemoproteus species produce markedly different megalomeronts, morphology of which can probably be predicted using phylogenetic analysis based on partial sequences of cytochrome b gene.

Exo-erythrocytic development of Plasmodium matutinum (lineage pLINN1) in a naturally infected roadkill fieldfare Turdus pilaris

“…This indicates possible involvement of avian haemoproteosis in road mortalities. This is not unexpected due to recent findings of megalomeronts of Haemoproteus parasites in brain of naturally infected birds [ 3 ]. This limited available information suggests that avian haemosporidian infections are worth more attention as agents of avian diseases.…”

“…However, information on an important part of the life cycle of malaria parasites and related haemosporidians (Haemosporida)–the exo-erythrocytic development–still remains at an early stage. This is particularly true for wild birds due to the difficulties in accessing these stages for research, which requires animal dissection, direct investigation of organs and application of histologic techniques [ 3 , 4 ].…”

Keys to the avian Haemoproteus parasites (Haemosporida, Haemoproteidae)

“…The recent discoveries of severe damage caused by tissue stages (meronts and megalomeronts) of Haemoproteus parasites in various organs, including the brain, heart, lungs, kidneys and skeletal muscles of naturally infected birds call for research aimed at better understanding the diversity and patterns of development of these pathogens [ 2 , 24 , 25 , 27 , 28 , 170 , 186 ]. This work requires parasite species identification and molecular data analysis.…”

Exo-Erythrocytic Development of Avian Haemosporidian Parasites in European Owls

“…The exo-erythrocytic development and its effect have been studied quite well in several Leucocytozoon species using experimental infections [ 12 ]. By contrast, in the case of Haemoproteus parasites, only the application of methods such as polymerase chain reaction (PCR), chromogenic in situ hybridization (CISH), and single-cell laser microdissection allowed to show that these parasites can also have severe negative effects on their avian hosts [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ], raising doubts about the previously supposed benignity of these organisms. Further studies using the aforementioned and likely other modern techniques (for example RNAScope technology) are needed to gain a more complete understanding of the haemosporidian exo-erythrocytic development in the avian host and determine its patterns and relation to bird health.…”