Prevalence and Molecular Characteristics of Avian Haemosporidian Infection Among Domestic Chickens in Hunan and Guangxi Provinces, China

Avian haemosporidian parasites, especially Plasmodium juxtanucleare, Leucocytozoon caulleryi, and Leucocytozoon sabrazesi, represent major threats to poultry health and production. However, there is limited epidemiological information about these pathogens in domestic chickens in Southern China, which hinders effective disease prevention and control. The objective of this study was to conduct a cross-sectional survey to investigate the epidemiological characteristics of these three parasites in Guangxi and Hunan Provinces between June 2024 and December 2025. A total of 941 blood samples were collected from domestic chickens and analyzed using both nested PCR targeting the cytb gene and species-specific PCR assays targeting the coxI gene. The overall detection rate of haemosporidian infection was 25.40% (239/941). P. juxtanucleare was the most commonly detected species, with a detection rate of 23.59% (222/941), followed by L. caulleryi at 1.81% (17/941), while no L. sabrazesi infections were identified. Analysis of risk factors showed that chickens older than 90 days had significantly higher detection rates for both P. juxtanucleare and L. caulleryi compared to younger birds. Additionally, breed-specific differences were noted, with black-bone and partridge chickens showing higher susceptibility to P. juxtanucleare than three-yellow chickens. Genetic analysis of coxI sequences demonstrated high conservation among P. juxtanucleare isolates (99.7–100% similarity) and complete identity among L. caulleryi strains. Phylogenetic analysis confirmed that all sequences clustered with the corresponding reference strains from GenBank. This study presents an epidemiological evaluation of these three haemosporidian parasites in domestic chickens from Guangxi and Hunan Provinces, identifying P. juxtanucleare as a widespread pathogen and highlighting age and breed as important risk factors. These results emphasize the importance of ongoing monitoring and targeted control measures in the area.