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Exo-erythrocytic stages of Haemoproteus sp. in common buzzard (Buteo buteo): A histopathological and molecular study.

ABSTRACT: Haemosporidian parasites are responsible for anemia, acute tissue degeneration, and depopulation in wild birds. This study aimed to investigate the prevalence of haemosporidians and also morphologic and molecular evaluation of tissue stages of Haemoproteus sp. in common buzzards (Buteo buteo). Eleven free-living common buzzards were referred to the Avian Clinic of Veterinary School of Lorestan University with lethargy, weight loss, and ataxia. Gametocytes of Leucocytozoon buteonis were found in blood smears of six (54.5 %) birds, while one had simultaneous infection with blood stages of Haemoproteus and Leucocytozoon. During histopathological examinations, exo-erythrocytic stages of the genus Haemoproteus were seen in the lung and kidney of a dead bird. This study is the first report of exo-erythrocytic infection of Haemoproteus in common buzzards. Molecular assays confirmed the infection of Haemoproteus sp. (lineage BUTBUT15) in tissue samples. Phylogenetic analysis using cytochrome b gene suggested that BUTBUT15 was more closely related to the lineages isolated from the family Falconidae in contrast to the Accipitridae.

SUBMITTER: Shokrani H

PROVIDER: S-EPMC8379368 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:The complex life cycle of malaria parasites requires well-orchestrated stage specific gene expression. In the vertebrate host the parasites grow and multiply by schizogony in two different environments: within erythrocytes and within hepatocytes. Whereas erythrocytic parasites are well-studied in this respect, relatively little is known about the exo-erythrocytic stages. METHODS:In an attempt to fill this gap, genome wide RNA-seq analyses of various exo-erythrocytic stages of Plasmodium berghei including sporozoites, samples from a time-course of liver stage development and detached cells were performed. These latter contain infectious merozoites and represent the final step in exo-erythrocytic development. RESULTS:The analysis represents the complete transcriptome of the entire life cycle of P. berghei parasites with temporal detailed analysis of the liver stage allowing comparison of gene expression across the progression of the life cycle. These RNA-seq data from different developmental stages were used to cluster genes with similar expression profiles, in order to infer their functions. A comparison with published data from other parasite stages confirmed stage-specific gene expression and revealed numerous genes that are expressed differentially in blood and exo-erythrocytic stages. One of the most exo-erythrocytic stage-specific genes was PBANKA_1003900, which has previously been annotated as a "gametocyte specific protein". The promoter of this gene drove high GFP expression in exo-erythrocytic stages, confirming its expression profile seen by RNA-seq. CONCLUSIONS:The comparative analysis of the genome wide mRNA expression profiles of erythrocytic and different exo-erythrocytic stages could be used to improve the understanding of gene regulation in Plasmodium parasites and can be used to model exo-erythrocytic stage metabolic networks toward the identification of differences in metabolic processes during schizogony in erythrocytes and hepatocytes.

Project description:BackgroundBirds chronically infected with avian malaria parasites often show relapses of parasitaemia after latent stages marked by absence of parasites in the peripheral circulation. These relapses are assumed to result from the activation of dormant exo-erythrocytic stages produced during secondary (post-erythrocytic) merogony of avian Plasmodium spp. Yet, there is no morphological proof of persistent or dormant tissue stages in the avian host during latent infections. This study investigated persistence of Plasmodium relictum pSGS1 in birds with latent infections during winter, with the goal to detect presumed persisting tissue stages using a highly sensitive RNAscope® in situ hybridization technology.MethodsFourteen domestic canaries were infected with P. relictum pSGS1 by blood-inoculation in spring, and blood films examined during the first 4 months post infection, and during winter and spring of the following year. After parasitaemia was no longer detectable, half of the birds were dissected, and tissue samples investigated for persisting tissue stages using RNAscope ISH and histology. The remaining birds were blood-checked and dissected after re-appearance of parasitaemia, and their tissues equally examined.ResultsSystematic examination of tissues showed no exo-erythrocytic stages in birds exhibiting latent infections by blood-film microscopy, indicating absence of dormant tissue stages in P. relictum pSGS1-infected canaries. Instead, RNAscope ISH revealed rare P. relictum blood stages in capillaries of various tissues and organs, demonstrating persistence of the parasites in the microvasculature. Birds examined after re-appearance of parasitemia showed higher numbers of P. relictum blood stages in both capillaries and larger blood vessels, indicating replication during early spring and re-appearance in the peripheral circulation.ConclusionsThe findings suggest that persistence of P. relictum pSGS1 during latent infection is mediated by continuous low-level erythrocytic merogony and possibly tissue sequestration of infected blood cells. Re-appearance of parasitaemia in spring seems to result from increased erythrocytic merogony, therefore representing recrudescence and not relapse in blood-inoculated canaries. Further, the study highlights strengths and limitations of the RNAscope ISH technology for the detection of rare parasite stages in tissues, providing directions for future research on persistence and tissue sequestration of avian malaria and related haemosporidian parasites.

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Exo-erythrocytic stages of Haemoproteus sp. in common buzzard (Buteo buteo): A histopathological and molecular study.

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