First experimental observation on biology of the avian malaria parasite Plasmodium (Novyella) homonucleophilum (lineage pSW2), with remarks on virulence and distribution

An Overview of the Neglected Modes of Existence in Avian Haemosporidian Parasites

Haemosporidian parasites (Apicomplexa, Haemosporida) are diverse obligatory heteroxenous protists, which infect all major groups of terrestrial vertebrates and use dipterous blood-sucking insects as vectors. These pathogens are responsible for various diseases, including malaria, which remains an important human and animal illness. In the wild, haemosporidians are particularly diverse in reptiles and birds in tropical countries, where they are flourishing. Avian haemosporidians have been particularly extensively investigated, especially due to their high prevalence and global distribution, including the countries with cold climates. The general scheme of the life cycle of haemosporidians is known, but the details of development remain insufficiently investigated or even unknown in most of the described parasite species, suggesting the existence of knowledge gaps. This attracts attention to some recent observations, which remain fragmentary but suggest the existence of formerly neglected or underestimated modes of the haemosporidians' survival in vertebrates. Such findings are worth discussion as they indicate the novel directions in wildlife haemosporidian research. This article overviews some recent findings, which call for broadening of the orthodox views on modes of existence of haemosporidian parasites in avian hosts. Among them are the role of blood merogony in the long-lasting persistence of malaria parasites in birds, the role of gametocytes in the long-lasting survival of Haemoproteus species in vertebrates, the possible reasons of undetectable avian Haemoproteus infections due to peculiarities of exo-erythrocytic development, and the plausible factors driving the narrow vertebrate host specificity of Haemoproteus species.

The Prevalence and Genetic Diversity of Avian Malaria in Wild Birds in the Republic of Korea

With avian malaria threatening populations of wild birds, this study was conducted to determine its prevalence among wild birds rescued in Jeonbuk state in the Republic of Korea. A total of 1043 wild birds were included in this study from 2017 to 2022. Both quantitative polymerase chain reaction and conventional polymerase chain reaction were used. Plasmodium spp. were detected in 75 of the 1043 (7.19%) wild birds. Plasmodium spp. were detected every year, and their prevalence was significantly higher in winter and winter migratory birds (p < 0.05). The Plasmodium spp. detected in wild birds were confirmed to have 30 different lineages. The most frequently detected species was Plasmodium circumflexum (cytochrome b lineage SW5 and TURDUS1), which is known to prefer cold. In this study, the Plasmodium spp. detected in the Republic of Korea were found to contain a high proportion of species preferring colder climates. This suggested that the monitoring of Plasmodium spp. in the Republic of Korea should be conducted year round, with a focus on monitoring migratory birds coming from colder climates. Ongoing monitoring and research are needed to understand the impact of Plasmodium spp. on wild bird populations.