Hematological and phylogenetic studies of Leucocytozoon spp. in backyard chickens and fighting cocks around Kamphaeng Saen, Thailand

Abstract

Leucocytozoon infections are found in birds and chicken in Southeast Asia including Thailand. Although chicken Leucocytozoon infections are common in Thailand, the associated hematological and molecular studies are scarce. Blood samples were collected from 52 backyard birds (22 chickens, 16 fighting cocks (FCs), 13 ducks and 1 goose) from four provinces (Ayutthaya, Nakhon Pathom, Pathum Thani and Kanchanaburi) in Thailand and processed for complete blood cell counts. Polymerase chain reaction (PCR) was performed for a partial cytochrome b gene from Leucocytozoon. Microscopic examinations revealed that 8 chickens and 13 ducks (21/52, 40%) were negative for blood parasites but 9 chickens and 15 FCs (24/52, 46%) were positive for Leucocytozoon spp. Three chickens and 7 FCs had mixed infections with microfilaria, Plasmodium/Haemoproteus spp. and Trypanosoma spp. There were no significant differences in the extensive hematological values among low rate (< 0.01% Leucocytozoon parasites), high rate (> 0.01% Leucocytozoon parasites) and mixed infections, except for the packed cell volume, hemoglobin concentration and fibrinogen concentration that were lower and for punctate reticulocytes that were higher in the high rate infections (p < 0.05). The information based on gametocytes and their host cells identified L. sabrasezi. In total, 24 PCR positive samples (both chickens and FCs) were divided into five groups based on four positions of 462 base pair amplicons without primer regions. Phylogenetic analysis showed that groups I–III were 99.1–99.8% similar and also closely related (98.0% similarity) to leucocytozoids isolated from chicken in Malaysia. Microscopy and molecular studies revealed similar morphology and phylogenetic groups of Leucocytozoon in both chickens and FCs.