Avian haemosporidium is an extremely common problem all over the world, and responsible for anemia, acute tissue degeneration and depopulation in birds, especially for Leucocytozoon and Plasmodium [15, 16]. The diagnosis, prevention and control of avian haemosporidia are critical for poultry breeding, domestic and wild bird protection. For avian haemosporidiosis, it can be diagnosed with clinical observation, combining morphological and molecular biology techniques from the veterinary standpoint. Relevant research reports can be used a mixture of trimethoprim and sulphaquinoxaline (TMP/SQX, ratio 1:3), with a wide spectrum of activity against bacteria and coccidia, and blood-induced Plasmodium gallinaceum malaria .
The traditional detection method of haemosporidium is carry out by observing the blood smears of birds under the microscope, identifying and classify them according to a series of morphological characteristics such as the size, shape, position and pigment arrangement of the parasite gametophyte or schizont (Plasmodium only) in the blood cells [8, 18]. Microscopic examination of blood smears requires experience and high quality of blood smears, and the sensitivity is limited, so false negative results occur frequently. In addition, microscopic examination is difficult to distinguish species with similar morphological characteristics (e.g., Plasmodium which has many hidden species). Microscopic examination often underestimates the diversity of haemosporidia. With the development of science and technology, molecular methods based on PCR (polymerase chain reaction) technology have gradually become popular, greatly improving the detection efficiency, sensitivity and precision .
In this research, the global prevalence of avian haemosporidia in red jungle fowls (Gallus gallus) was 74.8% (175/234), which was much higher than that of fighting cocks (Gallus gallus) from Thailand (20.8%, 52/250) , in domestic chicken (Gallus gallus) form Nan, Prachinburi, and Chachoengsao Provinces of Thailand (79.6%, 125/157) ; but it is lower than that in indigenous chickens form the North Central part of Nigeria (75.0%, 81/108) . The prevalence of avian haemosporidia infection was higher in birds in tropical areas than in other areas, such as Jinghong City, Xishuangbanna belongs to the tropics. The reason for this may be the abundance of vegetation in tropical areas living with species of Culicoides and avian haemosporidia transmitted by biting midges [22, 23]. In addition, the reason for the prevalence variation is complicated, and many factors will affect the detection rate such as sampling time, age group, sampling number and geographic conditions . In addition, similar to previous studies, the proportion of single infection was much higher than that of mixed infections [25, 26], and mixed infections showed multiple combinations [27, 28].
Avian haemosporidians has been detected in juvenile fowls and adult fowls with the infection ratio of 66.7% (68/102) and 81.1% (107/132) (P = 0.012 < 0.05), respectively. In previous studies showed that infection rates were higher in young birds relative to adults, possibly due to the lower immune resistance in young birds [29, 30]. Juvenile and adult bird infected haematosporidia belong to distinct lineages, indicating that chicks got infection from non-parent birds . Larger bare skins of young gulls make them accessible to the pathogen vectors more easily . The weight of black-headed gulls did not appear to contribute significantly to Haemoproteus sp. infection. It is true that many studies have shown that different host-traits and abiotic factors are important determinants in a host-parasite interaction [33, 34]. Factors such as plant richness, vector species, temperature, and humidity in wild bird habitats contribute significantly to the prevalence and diversification of Haemoproteus sp. [35–38].
Avian haemosporidians in birds is genetic diversity [39, 40]. Representative Haemoproteus gene (accession no. OM965002) is closely related to Haemoproteus sp. in avian from India (99–100% similarities) (accession no EF380176.1) [40). The Plasmodium juxtanucleare (accession no. OM965004) in this study is very similar to the strain from Thailand (accession no. KU248845.1). The lineage detected in the present study is new and may be a novel lineage from in red jungle fowls (Gallus gallus). We revealed that the known and novel lineage found in this study have biological invasion in China and can be transmitted to other birds.