Pathology and molecular characterization of recent Leucocytozoon caulleryi cases in layer flocks

Abstract

Leucocytozoonosis was found in three layer farms in chickens with suspected fatty liver or fatty liver hemorrhagic syndrome in Korea between 2009 and 2011. These layer chicken flocks showed both mortality and decreased egg production for one or two weeks when they were between 59 and 82 weeks old. At the necropsy, the most prominent gross lesions were found in the liver, which was enlarged, had a fragile texture, exhibited yellowish discolorations, and had various hemorrhagic lesions. Tissue reactions associated with megaloschizonts specific for Leucocytozoon caulleryi were prominent upon microscopic examination of the liver without significant lipidosis. In addition, the ovaries and uterus were the most affected organs for Leucocytozoon caulleryi multiplication, which led to decreased egg productions. Molecular studies with formalin-fixed, paraffin-embedded tissues were performed in search of a partial region of the cytochrome b gene for hemosporidian parasites. Based on these results, the causal agent was determined to be closely related to Leucocytozoon caulleryi reported in Japan and Malaysia. In this study, we describe recently re-occurring leucocytozoonosis in layer chickens, which required histopathology for disease diagnosis. To prevent outbreaks and maintain chicken health and egg production, layer chickens need to be monitored for symptoms of leucocytozoonosis.

Exo-erythrocytic development of avian malaria and related haemosporidian parasites

“…These parasites do not multiply in blood cells, and only tissue merogony occurs, as is the case in Haemoproteus parasites [ 2 , 4 , 166 , 173 ]. The exo-erythrocytic meronts have been found and described in 14 leucocytozoid species (Table 4 ), and merogony was studied particularly well in several species of subgenus Leucocytozoon ( Leucocytozoon danilewskyi, Leucocytozoon fringillinarum, Leucocytozoon dubreuili, Leucocytozoon simondi, Leucocytozoon smithi) and one species of Akiba ( Leucocytozoon caulleryi ) using sporozoite-induced infections [ 162 , 177 , 179 , 195 , 197 , 199 , 202 , 206 , 209 , 211 , 217 , 221 , 226 ]. The exo-erythrocytic development occurs in the parenchymal cells of the liver (hepatocytes), in tubular cells of kidneys, in macrophages and various other reticuloendothelial cells, including endothelial cells of the capillaries.…”

“…Exo-erythrocytic merogony of L. (Akiba) caulleryi differs from the species of subgenus Leucocytozoon in several characters [ 216 , 218 , 221 , 224 , 226 ]. First, the meronts of the first and following generations do not develop in hepatic cells.…”

“…Third, megalomeronts complete their development extracellularly and they do not have the ‘central body’ [ 221 , 223 , 224 , 226 , 228 ]. Extracellular development occurs when the infected cells rupture, and growing megalomeronts containing numerous cytomeres are released from the cells (Fig.…”

“…5 a), and they complete maturation extracellularly, a unique character in described haemosporidian parasites. Large megalomeronts can reach more than 300 μm in diameter [ 221 , 222 ]. The size of megalomeronts depends on their location.…”

Molecular detection and genetic diversity of Leucocytozoon sabrazesi in chickens in Thailand

“…The infected chickens possess mortality rate more than 50% resulting in significant economic losses 9 . Outbreaks of Leucocytozoon infection have been reported in chicken (Asia and Africa), waterfowl (Asia, Europe and North America), turkeys (North America), and free-living and captive avian species throughout the globe 7 , 11 – 16 . In Thailand, the first case of leucocytozoonosis was reported by Campbell 17 known as ‘Bangkok hemorhagic disease’ in chicken.…”