Abstract
Leucocytozoon sabrazesi is the intracellular protozoa of leucocytozoonosis, which is transmitted by the insect vectors and affects chickens in most subtropical and tropical regions of the globe, except South America, and causing enormous economic losses due to decreasing meat yield and egg production. In this study, L. sabrazesi gametocytes have been observed in the blood smears, and molecular methods have been used to analyse the occurrence and genetic diversity of L. sabrazesi in blood samples from 313 chickens raised in northern, western and southern parts of Thailand. The nested polymerase chain reaction (nested PCR) assay based on the cytb gene revealed that 80.51% (252/313) chickens were positive of L. sabrazesi. The phylogenetic analysis indicated that L. sabrazesi cytb gene is conserved in Thailand, showed 2 clades and 2 subclades with similarity ranged from 89.5 to 100%. The diversity analysis showed 13 and 18 haplotypes of the sequences from Thailand and from other countries, respectively. The entropy analyses of nucleic acid sequences showed 26 high entropy peaks with values ranging from 0.24493 to 1.21056, while those of amino acid sequences exhibited 5 high entropy peaks with values ranging from 0.39267 to 0.97012. The results; therefore, indicate a high molecular occurrence of L. sabrazesi in chicken blood samples with the associated factors that is statistically significant (p < 0.05). Hence, our results could be used to improve the immunodiagnostic methods and to find appropriate preventive control strategies or vaccination programs against leucocytozoonosis in order to mitigate or eliminate the harmful impact of this infection on chicken industry.
Highlights
Leucocytozoon sabrazesi is the intracellular protozoa of leucocytozoonosis, which is transmitted by the insect vectors and affects chickens in most subtropical and tropical regions of the globe, except South America, and causing enormous economic losses due to decreasing meat yield and egg production
Detection of parasites DNA or RNA using polymerase chain reaction (PCR) method utilizing primers derived from parasites mitochondrial cytochrome b gene could be more common reliable and widely used in diagnosing the infections particular in laboratory for high sensitivity and specificity even when blood smears are negative in case of low parasitemia or early stage of infection in animals[9,12,20,21,22]
Of the 313 chicken blood samples were examined under light microscope to observe the intra-erythrocytic L. sabrazesi gametocytes in blood smears (Fig. 1)
Summary
Leucocytozoon sabrazesi is the intracellular protozoa of leucocytozoonosis, which is transmitted by the insect vectors and affects chickens in most subtropical and tropical regions of the globe, except South America, and causing enormous economic losses due to decreasing meat yield and egg production. L. sabrazesi gametocytes have been observed in the blood smears, and molecular methods have been used to analyse the occurrence and genetic diversity of L. sabrazesi in blood samples from 313 chickens raised in northern, western and southern parts of Thailand. Leucocytozoon is a haemosporidian protozoan that belongs to the phylum of Apicomplexa causing leucocytozoonosis in birds, including chickens. This parasite is found in blood cells of avian hosts, and transmitted by simuliid blackflies (Diptera: Simuliidae) or Culicoides midges (Diptera: Ceratopogonidae)[1,2,3]. The aim of this study was to further investigate the occurrence and genetic diversity of this parasite in chickens from three regions (northern, western and southern) of Thailand. Results could provide the information on the genetic diversity structure of this parasite’s population for further development of the immunodiagnostic methods and vaccine strategies
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