The prevalence of Leucocytozoon spp. in nestlings of three wild raptor species including implications on haematological and blood chemistry values

Abstract

Leucocytozoonosis is a vector-borne infection of birds, caused by members of the haemosporidian genus Leucocytozoon . The clinical presentation may range from asymptomatic to severe disease. Consequences of Leucocytozoon infection on blood profiles remain to be described, especially for different host species in the wild. In the current study, the prevalence of Leucocytozoon infection was determined in wild nestlings of three European raptor species, the common buzzard ( Buteo buteo , n = 464), red kite ( Milvus milvus , n = 46) and northern goshawk ( Accipiter gentilis , n = 18). Among 528 nestlings, 51.9% (n = 274) were infected with Leucocytozoon spp., whereby the highest prevalence was found in common buzzards (54.9%), followed by red kites (32.6%) and northern goshawks (22.2%). For a subset of 87 individuals (50 common buzzards, 29 red kites, 8 northern goshawks), a detailed analysis of differential leukocyte counts and several blood chemistry parameters in response to infection was conducted: AP (alkaline phosphatase), AST (aspartate aminotransferase), GLDH (glutamate dehydrogenase), LDH (lactate dehydrogenase), GGT (gamma glutamyl transferase), CK (creatine kinase), BuChE (butyrylcholinesterase), BA (bile acids), ALB (albumin) and TP (total protein). Even though in the physiological range, infected nestlings displayed significantly increased levels of heterophils, aspartate aminotransferase, lactate dehydrogenase, bile acids and butyrylcholinesterase, but decreased lymphocyte and monocyte values compared to uninfected ones. Furthermore, significant species differences with regard to blood parameters, but no sex differences were found. Overall, obtained results show a high prevalence, but a low pathogenicity of Leucocytozoon spp. in wild raptor chicks, presumably resulting from coevolutionary adaptation, but show signatures of infection in the haematological and blood chemistry profiles.

Early-life factors shaping the gut microbiota of Common buzzard nestlings

“…Severe malaria is caused by Plasmodium blood parasites, while related Leucocytozoon parasites can induce similar conditions in a wide range of avian hosts [ 5 ]. Despite a high prevalence (55%) of Leucocytozoon infection in buzzard nestlings previously found on this study site, research suggests low pathogenicity and minimal impacts on host condition [ 117 ]. Nevertheless, signatures of infection were found in haematological and blood chemistry profiles [ 117 ].…”

A Four-Year Survey of Hemoparasites from Nocturnal Raptors (Strigiformes) Confirms a Relation between Leucocytozoon and Low Hematocrit and Body Condition Scores of Parasitized Birds

“…However, the function of eosinophiles in birds is still little known. Some previous studies had linked Leucocytozoon infections to higher eosinophil counts in raptors [ 55 , 56 ]. Our data did not reveal significant differences on the leukocyte formula between parasitized and non-parasitized birds.…”

“…This result is in accordance with Clark et al (2016) and Wiegmann et al (2021), who found increased H/L rates in Zosterops spp. infected by Microfilariae and raptors infected by hematozoa, respectively [ 56 , 57 ]. In this context, it is important to highlight that the proportion of heterophils and lymphocytes (H/L) is a reliable indicator of immune response to stress or illness in birds, including parasitemia [ 54 ].…”

Tolerability of Atovaquone—Proguanil Application in Common Buzzard Nestlings

“…Compared with human medicine, elevated levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are among the possible adverse side effects of Malarone ® treatment [33], but these are known as reversible and not associated with clinical signs [45]. However, when evaluating changes in blood chemistry, it should also be considered that existing haemosporidian infections may account for additional variation [22,46,47].…”

“…All individuals examined for blood chemistry values were part of a previous study that analysed changes in blood chemistry in response to Leucocytozoon infection [22]. Here, we expanded the dataset by comparing blood chemistry values of Malarone ® -treated individuals before and after resampling.…”