Neglected parasite reservoirs in wetlands: Prevalence and diversity of avian haemosporidians in waterbird communities in Northeast China

Global prevalence of Plasmodium infection in wild birds: A systematic review and meta-analysis

Avian malaria is a vector-borne parasitic disease caused by Plasmodium infection transmitted to birds by mosquitoes. The aim of this systematic review was to analyze the global prevalence of malaria and risk factors associated with infection in wild birds. A systematic search of the databases CNKI, WanFang, VIP, PubMed, and ScienceDirect was performed from database inception to 24 February 2023. The search identified 3181 retrieved articles, of which 52 articles met predetermined inclusion criteria. Meta-analysis was performed using the random-effects model. The estimated pooled global prevalence of Plasmodium infection in wild birds was 16%. Sub-group analysis showed that the highest prevalence was associated with adult birds, migrant birds, North America, tropical rainforest climate, birds captured by mist nets, detection of infection by microscopy, medium quality studies, and studies published after 2016. Our study highlights the need for more understanding of Plasmodium prevalence in wild birds and identifying risk factors associated with infection to inform future infection control measures.

Insights into the Biology of Leucocytozoon Species (Haemosporida, Leucocytozoidae): Why Is There Slow Research Progress on Agents of Leucocytozoonosis?

Blood parasites of the genus Leucocytozoon (Leucocytozoidae) only inhabit birds and represent a readily distinct evolutionary branch of the haemosporidians (Haemosporida, Apicomplexa). Some species cause pathology and even severe leucocytozoonosis in avian hosts, including poultry. The diversity of Leucocytozoon pathogens is remarkable, with over 1400 genetic lineages detected, most of which, however, have not been identified to the species level. At most, approximately 45 morphologically distinct species of Leucocytozoon have been described, but only a few have associated molecular data. This is unfortunate because basic information about named and morphologically recognized Leucocytozoon species is essential for a better understanding of phylogenetically closely related leucocytozoids that are known only by DNA sequence. Despite much research on haemosporidian parasites during the past 30 years, there has not been much progress in taxonomy, vectors, patterns of transmission, pathogenicity, and other aspects of the biology of these cosmopolitan bird pathogens. This study reviewed the available basic information on avian Leucocytozoon species, with particular attention to some obstacles that prevent progress to better understanding the biology of leucocytozoids. Major gaps in current Leucocytozoon species research are discussed, and possible approaches are suggested to resolve some issues that have limited practical parasitological studies of these pathogens.

Sex-biased, but not plumage color-based, prevalence of haemosporidian parasites in free-range chickens

Previous studies found a relationship between blood parasite infection and bird gender, with higher prevalence in males. Some studies also found a relationship between host plumage color and parasitic infection, while others did not. Here, we investigated the blood parasite prevalence in correlation with sex and plumage color in free-range chickens (Gallus gallus domesticus) in China. We analyzed a total of 297 blood samples, out of which 234 chickens tested positive for haemosporidian parasites, with 78.5% parasite prevalence. Out of 139 males, 118 tested positive with 84.8% parasite prevalence while 116 of 158 female samples tested positive (73.4%). Leucocytotozoon was the most frequent genus isolated (193 infected individuals /234 birds), followed by Plasmodium (41 infected individuals/234 birds), with no Haemoproteus parasites being detected. There were no significant differences in the body parameters and chicken color plumages with regards to the infection status. Our study indicated that blood parasite infection was significantly different between male and female chickens, with infection prevalent in males.

Prevalence and genetic diversity of Haemoproteus and Plasmodium in raptors from Thailand: Data from rehabilitation center

The diurnal raptors (Family: Accipitridae and Falconidae) are important as ecosystem bioindicators. Unfortunately, the global number of these birds has fallen, and they are close to extinction. This study reports the molecular prevalence and genetic diversity of Haemoproteus and Plasmodium in raptors admitted to the Kasetsart University Raptor Rehabilitation Unit over a period of 6 years. A total of 198 raptors, including 22 species from 30 provinces in Thailand, were admitted. The prevalence of parasites in raptors was low: Haemoproteus was 4.04% (95% CI: 1.29-6.78), and Plasmodium 2.53% (95% CI: 0.34-4.71). Eleven lineages of haemosporidian parasites were identified, and four lineages (ACCBAD02, NISALB01, NISALB02, and AEGMO03) are new globally. Interestingly, six lineages were isolated from birds belonging to the Accipitridae and Falconidae families (TYTAL4, TYTAL6, GLACUC08, MILANS06, OTUSCO02, and ORW1), indicating host shift of these parasites. Furthermore, the low prevalence of Haemoproteus and Plasmodium in raptors compared with that in previous reports suggests a relationship between the activity of avian hosts and vectors. This information is valuable for application in raptor rehabilitation and further research.