Prevalence, morphological and molecular characterization of <i>Leucocytozoon macleani</i> (Apicomplexa: Haemosporida) from chickens in Thailand

Leucocytozoon species are common in countries with warm climates but are an often neglected blood parasite in poultry. Although Leucocytozoon macleani is less virulent than Leucocytozoon caulleryi, it can still negatively impact production performance. In Thailand, the available reports indicate a high prevalence of Leucocytozoon spp., but detailed morphological characteristics of the parasites remain insufficiently known. In this study, Giemsa-stained blood smears and extracted genomic (g) DNA were obtained from 60 domestic chickens (Gallus gallus domesticus). Blood smears were examined for the presence of Leucocytozoon species and their morphological characteristics were examined. A total of 60 gDNA samples were used for nested-PCR amplification of the cytochrome b gene of Leucocytozoon species, followed by sequencing and phylogenetic analysis. The microscopic and molecular examinations revealed prevalence of leucocytozoonosis in chickens of 85% and 90%, respectively. Sequence analysis indicated that several infected chickens harboured multiple Leucocytozoon lineages. Leucocytozoon macleani was morphologically identified in nine samples and could be linked to the lineages GALLUS17, GALLUS34, and the new lineages GALLUS63. The found gametocytes of L. macleani morphologically resembled those reported previously, but exhibited some distinct characteristics. Phylogenetically, the lineages of L. macleani isolated in this study grouped separately from some other L. macleani lineages deposited in GenBank. In conclusion, the prevalence of Leucocytozoon infection in chickens from Northeastern Thailand was high, with frequent co-infections by multiple lineages. Leucocytozoon macleani may exhibit cryptic specification. This study is the first report of L. macleani lineages described using MalAvi database nomenclature, alongside their morphological characteristics.