Prevalence of poultry red mite (Dermanyssus gallinae) in Korean layer farms and the presence of avian pathogens in the mite

The poultry red mite, Dermanyssus gallinae, is a blood-feeding parasite of layer hens and a potential vector of several avian infectious agents. High infestation with D. gallinae in layer farm buildings could result in economic losses, and the mites may act as a reservoir of avian pathogens within farms. This study aimed to assess the prevalence of D. gallinae in layer farm buildings in Korea and to investigate avian pathogens in the collected mites. The mite samples were collected from 36 Korean layer farm buildings on 21 farms nationwide. Information obtained from each farm building included the flock size, flock age, methods for controlling D. gallinae, and cleaning status. Association between these variables and the population density of D. gallinae was analyzed. Additionally, the presence of 10 avian pathogens was assessed using DNA samples from mites collected in 16 farm buildings. The prevalence of D. gallinae was 75% at the farm building level (90.5% at the farm level). Repetitive cleaning procedures for each building were significantly related with the mite infestation level, and the most influential factor for determining the mite population in the layer farm buildings. In the 16 DNA samples, we detected avian pathogenic Escherichia coli (n = 6), wild-type fowlpox virus (n = 3), wild-type Marek’s disease virus (n = 2), chicken anemia virus (n = 1), and fowl adenovirus (n = 1). These findings suggest that repetitive cleaning procedures for the layer farm buildings could decrease the numbers of D. gallinae which may transmit avian pathogens within the farm.