High prevalence of haemosporidian parasites in Eurasian jays.

Avian haemosporidians are vector-borne parasites, infecting a great variety of birds. The order Passeriformes has the highest average infection probability; nevertheless, some common species of Passeriformes have been rather poorly studied. We investigated haemosporidians in one such species, the Eurasian jay Garrulus glandarius (Corvidae), from a forest population in Hesse, Central Germany. All individuals were infected with at least one haemosporidian genus (overall prevalence: 100%). The most common infection pattern was a mixed Haemoproteus and Leucocytozoon infection, whereas no Plasmodium infection was detected. Results on lineage diversity indicate a rather pronounced host-specificity of Haemoproteus and Leucocytozoon lineages infecting birds of the family Corvidae.

Surveillance of avian malaria and related haemoparasites in common terns (Sterna hirundo) on the Atlantic coast of South America.

Haemosporidia (Apicomplexa, Haemosporida) are protozoa that infect vertebrate blood cells and are transmitted by vectors. Among vertebrates, birds possess the greatest diversity of haemosporidia, historically placed in 3 genera: Haemoproteus, Leucocytozoon and Plasmodium, the causative agent of avian malaria. In South America, existing data on haemosporidia are spatially and temporally dispersed, so increased surveillance is needed to improve the determination and diagnosis of these parasites. During the non-breeding season in 2020 and 2021, 60 common terns (Sterna hirundo) were captured and bled as part of ongoing research on the population health of migratory birds on the Argentinian Atlantic coast. Blood samples and blood smears were obtained. Fifty-eight samples were screened for Plasmodium, Haemoproteus and Leucocytozoon, as well as for Babesia parasites by nested polymerase chain reaction and by microscopic examination of smears. Two positive samples for Plasmodium were found. The cytochrome b lineages detected in the present study are found for the first time, and are close to Plasmodium lineages found in other bird orders. The low prevalence (3.6%) of haemoparasites found in this research was similar to those reported for previous studies on seabirds, including Charadriiformes. Our findings provide new information about the distribution and prevalence of haemosporidian parasites from charadriiforms in the southernmost part of South America, which remains understudied.

First evidence for development of Plasmodium relictum (Grassi and Feletti, 1891) sporozoites in the salivary glands of Culex modestus Ficalbi, 1889.

The competence of insect vectors to transmit diseases plays a key role in host-parasite interactions and in the dynamics of avian malaria and other haemosporidian infections (Apicomplexa, Haemosporida). However, the presence of parasite DNA in the body of blood-sucking insects does not always constitute evidence for their competence as vectors. In this study, we investigate the susceptibility of wild-caught mosquitoes (Culex spp.) to complete sporogony of Plasmodium relictum (cyt b lineage SGS1) isolated from great tits (Parus major L., 1758). Adult female mosquitoes were collected with a CO2 bait trap overnight. A set of 50 mosquitoes was allowed to feed for 3 h at night on a single great tit infected with P. relictum. This trial was repeated on 6 different birds. The bloodfed mosquitoes that survived (n = 68) were dissected within 1-2 days (for ookinetes, n = 10) and 10-33 days post infection (for oocysts and sporozoites, n = 58) in order to confirm the respective parasite stages in their organs. The experiment confirmed the successful development of P. relictum (cyt b lineage SGS1) to the stage of sporozoites in Culex pipiens L., 1758 (n = 27) and in Culex modestus (n = 2). Our study provides the first evidence that C. modestus is a competent vector of P. relictum isolated from great tits, suggesting that this mosquito species could also play a role in the natural transmission of avian malaria.

Molecular investigation on infection by haemosporidians in three Western Palearctic species of swift (Apodidae) and their ectoparasitic louse flies.

Swifts (Apodidae) are an unusual group of birds that spend most of their lives in flight, landing only when breeding. Although this aerial lifestyle greatly reduces their likelihood of being bitten by vectors and infected by vector-born parasites, swifts can still be heavily infested during breeding by nest-based vectors such as louse flies (Hippoboscidae). Here, we investigated host, vector, and vector-borne parasite relationships in the three most widespread swift species in the Western Palearctic (WP): common swifts (Apus apus), pallid swifts (A. pallidus), and alpine swifts (Tachymarptis melba), their nest-based louse flies (Crataerina pallida and C. melbae) and avian haemosporidians (genera Haemoproteus, Plasmodium, and Leucocytozoon). Studies of haemosporidian infections in Apodidae remain limited, with clear evidence of infection found to date in just four Neotropical and one Australasian species. The possible role of louse flies in transmitting haemosporidian infections has never been tested in swifts. We assessed the occurrence of haemosporidian infection by PCR screenings of DNA from blood samples from 34 common swifts and 44 pallid swifts from Italy, and 45 alpine swifts from Switzerland. We also screened 20 ectoparasitic louse flies present on 20 birds and identified them by both morphological features and cytochrome oxidase subunit 1 (COI) barcodes. Our results provide no evidence of haemosporidian infection in the 123 swifts tested or in the two louse fly species we identified. Our findings are consistent with available knowledge showing no haemosporidian occurrence in WP swift species and that the most likely infection route for these highly aerial species (via louse fly ectoparasites during nesting) is unlikely.

Double trouble: untangling mixed sequence signals in bird samples with avian haemosporidian co-infections.

Blood parasites comprise some of the most prevalent pathogens in nature, and their detection and identification are major objectives in varied fields such as ecology and biomedicine. Two approaches were compared, one based on Sanger sequencing and the other next-generation sequencing (NGS) based, in terms of their performance in detecting avian blood parasites across tropical Southeast Asian birds. Across a panel of 528 bird individuals, 43 birds were ascertained to be infected with avian haemosporidians using a polymerase chain reaction-based detection method. Among these samples, NGS-based barcoding confirmed co-infections by multiple blood parasites in all eight cases where Sanger sequencing produced double peaks. Importantly however, the NGS-based method produced another five diagnoses of co-infections (62.5%) in which Sanger-based barcoding remained equivocal. In contrast to Sanger sequencing, the NGS-based method was able to identify co-infecting haemosporidian lineages via their barcodes. The accuracy of avian haemosporidian lineage identification was not compromised by the shorter length of NGS sequences, with ~94% of NGS barcodes producing matches identical to those of the Sanger barcodes. The application of NGS-based barcoding methods promises to enhance parasite identification and reduce erroneous inferences based on artefacts.

Parasitemia and elevation as predictors of hemoglobin concentration and antioxidant capacity in two sympatric lizards.

Studies which quantify the influence of abiotic factors on physiological variation are paramount to comprehend organismal responses to diverse environments. We studied three physiological aspects of metabolism in two sympatric and ecologically similar European lizard species, Podarcis muralis and Iberolacerta horvathi, across an 830-m elevational gradient. We collected blood samples and tail tips from adult lizards, which were analyzed for parasitemia, hemoglobin concentration, potential metabolic activity and catalase activity. Hemoglobin concentration was higher in males than females and it increased across elevation in one of the studied species - P. muralis. Parasitemia was not an important predictor of the variation in hemoglobin concentration, which suggests that blood parasites do not constraint the aerobic capacity of the lizards. On the other hand, catalase activity reflected increased antioxidant activity in the presence of higher parasitemia, possibly acting as an adaptive mechanism to reduce oxidative stress during immune activation. Potential metabolic activity, as a proxy for maximum respiratory enzymatic capacity, did not differ between species or sexes nor was it affected by elevation or levels of parasitemia. The results provide insight into the relationships between physiological, biotic, and environmental traits in sympatric lizards.

Haemosporidia of grey crowned cranes in Rwanda.

Grey crowned cranes (Balearica regulorum) have been facing significant and long-term population declines in East Africa. Studies of Haemosporidian infections are essential to gain insight into pathogenic threats and help infer vector-host relationships, resolve parasite relationships, and support conservation efforts. As part of a program to reintroduce captive cranes in Rwanda back to their natural habitats, through health checks and initial microscopic examination, 120 grey crowned cranes were selected under suspicion of harboring Haemosporidian infections following initial peripheral blood smear examinations. Of these, 104 were infected with Haemoproteus and 3 were coinfected with Leucocytozoon as detected by PCR and microscopy. Sequencing allowed us to identify 2 distinct unreported lineages of Haemoproteus antigonis and one lineage of Leucocytozoon in the subspecies of Grey Crowned Cranes endemic to East Africa, B. r. gibbericeps. Molecularly, our two lineages of Haemoproteus antigonis differ by 32 base pairs and matched with about 95 percent identity to previously reported sequences of H. antigonis found in other species of cranes. No visible morphologic differences were found when compared to images of H. antigonis from previous studies. Our work demonstrates not only a need for increased testing within the family Gruidae, but also to investigate the possibility of cryptic speciation within the morphospecies Haemoproteus antigonis.

Molecular and morphological description of the first Hepatozoon (Apicomplexa: Hepatozoidae) species infecting a neotropical turtle, with an approach to its phylogenetic relationships.

Haemogregarines (Adeleorina) have a high prevalence in turtles. Nevertheless, there is only one Hepatozoon species described that infects Testudines so far; it is Hepatozoon fitzsimonsi which infects the African tortoise Kinixys belliana. Colombia harbours a great diversity of chelonians; however, most of them are threatened. It is important to identify and characterize chelonian haemoparasite infections to improve the clinical assessments, treatments and the conservation and reintroduction programs of these animals. To evaluate such infections for the Colombian wood turtle Rhinoclemmys melanosterna, we analysed blood from 70 individuals. By using the morphological characteristics of blood stages as well as molecular information (18S rRNA sequences), here we report a new Hepatozoon species that represents the first report of a hepatozoid species infecting a semi-aquatic continental turtle in the world. Although the isolated lineage clusters within the phylogenetic clades that have morphological species of parasites already determined, their low nodal support makes their position within each group inconclusive. It is important to identify new molecular markers to improve parasite species identification. In-depth research on blood parasites infecting turtles is essential for increasing knowledge that could assess this potential unknown threat, to inform the conservation of turtles and for increasing the state of knowledge on parasites.

Blood parasites (Babesia, Hepatozoon and Trypanosoma) of rodents, Lithuania: part I. Molecular and traditional microscopy approach.

Wild rodents, as natural reservoir hosts carrying various species of pathogens, play an important role in the evolution and emergence of zoonotic diseases. In this study, protist parasites, namely Babesia sp., Trypanosoma sp. and Hepatozoon sp. were studied in rodent populations in Lithuania. Two hundred forty rodent specimens of seven species were analysed by a combined approach using polymerase chain reaction (PCR)-based techniques and traditional microscopic examination. The total prevalence of blood parasites reached 35% in rodent communities. The prevalence of Hepatozoon sp. reached the highest value (32%), followed by Trypanosoma sp. (5%) and Babesia sp. (3%). Myodes glareolus and Microtus agrestis were the most heavily infected rodent species. Comparison of microscopy and PCR-based methods showed that the two approaches might give different results and thus can lead to an underestimation of the actual prevalence and abundance of parasites. In our study, PCR-based assays were more sensitive and robust than traditional microscopy. However, precise molecular results for the estimation of the prevalence of Babesia sp. and Hepatozoon sp. were achieved only by using several sets of primers. To avoid inaccurate results, the improvement and detailed description of molecular and microscopy protocols are required.

Correlates of blood parasitism in a threatened marshland passerine: infection by kinetoplastids of the genus Trypanosoma is related to landscape metrics of habitat edge.

In birds, vector-borne parasites invading the bloodstream are important agents of disease, affect fitness and shape population viability, thus being of conservation interest. Here, we molecularly identified protozoan blood parasites in two populations of the threatened Aquatic Warbler Acrocephalus paludicola, a migratory passerine nesting in open marsh. We explored whether prevalence and lineage diversity of the parasites vary by population and whether infection status is explained by landscape metrics of habitat edge and individual traits (body mass, fat score, wing length and sex). Aquatic Warblers were infected by genera Plasmodium, Leucocytozoon and Trypanosoma, with seven, one and four lineages, and 29.9, 0.7 and 12.5% prevalence, respectively. No Haemoproteus infections were detected. Prevalence did not vary between the populations, but lineage diversity was higher in Polesie than in Biebrza for all the lineages pooled and for Plasmodium. Infection by Trypanosoma decreased with patch core area and increased with density of habitat edge. Infection status was not predicted by the individual traits. Our study is the first to show an association between edge-related landscape features and blood parasitism in an open habitat bird. This finding will support informed conservation measures for avian species of the globally shrinking marshland and other treeless habitats.

Detection and prevalence of Haemoproteus archilochus (Haemosporida, Haemoproteidae) in two species of California hummingbirds.

Haemosporidian blood parasites are transmitted to a wide range of avian hosts via blood-sucking dipteran vectors. Microscopy has revealed an impressive diversity of avian haemosporidia with more than 250 species described. Moreover, PCR and subsequent sequence analyses have suggested a much greater diversity of haemosporidia than morphological analyses alone. Given the importance of these parasites, very few studies have focused on the charismatic hummingbirds. To date, three Haemoproteus species (Haemoproteus archilochus, Haemoproteus trochili, and Haemoproteus witti) and one Leucocytozoon species (Leucocytozoon quynzae) have been described in blood samples taken from hummingbirds (Trochilidae). Unconfirmed Plasmodium lineages have also been detected in hummingbirds. Here, we report the detection of H. archilochus in two hummingbird species (Calypte anna and Archilochus alexandri) sampled in Northern California and perform a phylogenetic analysis of mitochondrial cytochrome b (cyt b) gene lineages. A total of 261 hummingbirds (157 C. anna, 104 A. alexandri) were sampled and screened for blood parasites using PCR and microscopy techniques. Combining both methods, 4 (2.55%) haemosporidian infections were detected in C. anna and 18 (17.31%) haemosporidian infections were detected in A. alexandri. Molecular analyses revealed four distinct H. archilocus cyt b lineages, which clustered as a monophyletic clade. No species of Plasmodium or Leucocytozoon were detected in this study, raising the possibility of specific vector associations with hummingbirds. These results provide resources for future studies of haemosporidian prevalence, diversity, and pathogenicity in California hummingbird populations.

Blood parasites in northern goshawk (Accipiter gentilis) with an emphasis to Leucocytozoon toddi.

Haemosporidians and trypanosomes of the northern goshawk (Accipiter gentilis) population in the Czech Republic were studied by morphological and molecular methods. Despite the wide distribution of these medium-large birds of prey, virtually nothing is known about their blood parasites. During a 5-year period, altogether 88 nestlings and 15 adults were screened for haemosporidians and trypanosomes by microscopic examination of blood smears and by nested PCR. Both methods revealed consistently higher prevalence of blood protists in adults, Leucocytozoon (80.0 % in adults vs. 13.6 % in nestlings), Haemoproteus (60.0 vs. 2.3 %), Plasmodium (6.7 vs. 0 %), and Trypanosoma (60.0 vs. 2.3 %). Altogether, five haemosporidian lineages were detected by cytochrome b sequencing. Two broadly distributed and host nonspecific lineages, Plasmodium (TURDUS1) and Leucocytozoon (BT2), were detected only sporadically, while three newly described northern goshawk host-specific Leucocytozoon lineages (ACGE01-03) represent the absolute majority of the haemosporidians identified by molecular methods. Our findings support evidences that in falconiform birds the Leucocytozoon toddi group is formed by several host-specific clusters, with Leucocytozoon buteonis in buzzards and Leucocytozoon mathisi in hawks. Between-year comparisons revealed that the infection status of adults remained predominantly unchanged and individuals stayed uninfected or possessed the same parasite lineages; however, two gains and one loss of blood parasite taxa were also recorded.

Haemosporidian infections in the Tengmalm's Owl (Aegolius funereus) and potential insect vectors of their transmission.

Sedentary bird species are suitable model hosts for identifying potential vectors of avian blood parasites. We studied haemosporidian infections in the Tengmalm's Owl (Aegolius funereus) in the Ore Mountains of the Czech Republic using molecular detection methods. Sex of owl nestlings was scored using molecular sexing based on fragment analysis of PCR-amplified CHD1 introns. Observed infection prevalences in nestlings and adult owls were 51 and 86 %, respectively. Five parasite lineages were detected. Most of the infections comprised the Leucocytozoon AEFUN02 and STOCC06 lineages that probably refer to distinct Leucocytozoon species. Other lineages were detected only sporadically. Mixed infections were found in 49 % of samples. The main factor affecting the probability of infection was host age. No effect of individual sex on infection probability was evidenced. The youngest infected nestling was 12 days old. High parasite prevalence in the Tengmalm's Owl nestlings suggests that insect vectors must enter nest boxes to transmit parasites before fledging. Hence, we placed sticky insect traps into modified nest boxes, collected potential insect vectors, and examined them for the presence of haemosporidian parasites using molecular detection. We trapped 201 insects which were determined as biting midges from the Culicoides genus and two black fly species, Simulium (Nevermannia) vernum and Simulium (Eusimulium) angustipes. Six haemosporidian lineages were detected in the potential insect vectors, among which the Leucocytozoon lineage BT2 was common to the Tengmalm's Owl and the trapped insects. However, we have not detected the most frequently encountered Tengmalm's Owl Leucocytozoon lineages AEFUN02 and STOCC06 in insects.

Investigation of avian haemosporidian parasites from raptor birds in Turkey, with molecular characterisation and microscopic confirmation.

Avian haemosporidians are common vector-borne blood parasites that have been reported in birds all over the world. Investigations of avian haemosporidian parasites are conducted mainly on passerine birds. However, studies that focus on non-passerine avian hosts are important for our understanding of the true diversity, host specificity and genetic variability among these widespread parasites. In the present study, blood samples from a total of 22 raptor birds belonging to two orders, two families and six species from the Central Anatolia Region of Turkey were investigated for three genera of avian haemosporidians (Plasmodium Marchiafava et Celli, 1885, Haemoproteus Kruse, 1890 and Leucocytozoon Sambon, 1908) using a combination of microscopic examination of blood films and nested PCR targeting the parasite mitochondrial cytochrome b gene (cyt-b). In total, six individual raptor birds identified positive for species of Plasmodium or Leucocytozoon and one individual was found co-infected with all three haemosporidian genera. We identified five parasite cyt-b haplotypes, three of which were reported for the first time. Among these, one Plasmodium haplotype is linked to a corresponding morphospecies (P-TURDUS1, Plasmodium circumflexum Kikuth, 1931). All haplotypes were clearly distinguishable in phylogenetic analyses. As one of the first studies to investigate blood parasites from non-passerine birds in the Central Anatolia Region of Turkey, this study provides important new information on the phylogenetic relationships and genetic diversity of avian haemosporidian parasites from raptor birds. We discuss these findings in the context of avian haemosporidian host-parasite relationships and we draw attention to the need for microscopy to detect parasite sexual development stages in surveys of avian haemosporidians.

Apparent vector-mediated parent-to-offspring transmission in an avian malaria-like parasite.

Parasite transmission strategies strongly impact host-parasite co-evolution and virulence. However, studies of vector-borne parasites such as avian malaria have neglected the potential effects of host relatedness on the exchange of parasites. To test whether extended parental care in the presence of vectors increases the probability of transmission from parents to offspring, we used high-throughput sequencing to develop microsatellites for malaria-like Leucocytozoon parasites of a wild raptor population. We show that host siblings carry genetically more similar parasites than unrelated chicks both within and across years. Moreover, chicks of mothers of the same plumage morph carried more similar parasites than nestlings whose mothers were of different morphs, consistent with matrilineal transmission of morph-specific parasite strains. Ours is the first evidence of an association between host relatedness and parasite genetic similarity, consistent with vector-mediated parent-to-offspring transmission. The conditions for such 'quasi-vertical' transmission may be common and could suppress the evolution of pathogen virulence.

Ageing and reproduction: antioxidant supplementation alleviates telomere loss in wild birds.

Reproduction is inherently costly. Environmental stressors, such as infection and limited food resources, can compromise investment at each breeding attempt. For example, recent data on captive birds showed that increased reproductive effort accelerates ageing. However, the effects of nutritional status and infection on ageing remain unknown. Telomeres function as protective caps at the ends of eukaryotic chromosomes, and changes in telomere length is a commonly used proxy for ageing. To partially address the mechanisms of ageing following reproduction, we supplemented, medicated or administered a combined treatment to wild blue tits (Cyanistes caeruleus) breeding in central Spain during 2012. The nutritional supplement consisted of two different antioxidants, whereas the medication was an antimalarial treatment against blood parasites. We evaluated the effect of these manipulations on reproductive success and parasite loads in the first breeding season, and on changes in telomere length between two consecutive breeding seasons. Supplemented birds showed no reduction in blood parasite infections in 2012, although they exhibited higher body mass and fledging success. The antimalarial drugs reduced infections by several parasite species, but this had no effect on fitness parameters. In the following season, telomeres from supplemented birds had shortened less. Altogether, we found that supplementation with antioxidants provided fitness benefits in the short term and reduced telomere loss a year following treatment. Our results provide indirect empirical support for accelerated telomere loss as a cost of reproduction.

Genetic diversity, temporal dynamics, and host specificity in blood parasites of passerines in north China.

Avian blood parasites have been preliminarily studied in East Asia, but no data are available from long-term monitoring. The aim of this study was to evaluate the prevalence, genetic diversity, and temporal dynamics of Plasmodium, Haemoproteus, and Leucocytozoon in two passerine communities (one forest and one urban) in north China from 2008 to 2013, as well as the association between infected lineages and host specificities. Out of 633 birds from 40 species, 157 individuals (24.8 %) were infected; overall prevalence was 26.7 % and 16.8 % in two sites, respectively. The dominant avian blood parasite genus in the forest park changed yearly between Plasmodium and Haemoproteus, while the Leucocytozoon maintained a low infection level. Forty-four haplotypes were identified by sequencing a 432-bp fragment of the cytochrome b (cyt b) gene; more than 70 % were novel (six Plasmodium lineages, 16 Haemoproteus lineages, and nine Leucocytozoon lineages). Based on our data gathered over consecutive years, we found that the highly observed lineages of Haemoproteus showed higher host diversities than those of Plasmodium, and the most infected lineage EMEL01 (100 % identity with SGS1) take on the highest host diversity but low temporal diversity of the two genera, implying that this lineage infected a great diversity of species in certain years, but maintained a lower infection level or even disappeared in other years. The results suggest that genetic diversity of avian blood parasites in East Asia is high and provides scope for further research. In addition, compared with overall analysis, yearly prevalence monitoring is important in uncovering the temporal dynamic and host specificity variations over time.

Does the niche breadth or trade-off hypothesis explain the abundance-occupancy relationship in avian Haemosporidia?

Two hypotheses have been proposed to explain the abundance-occupancy relationship (AOR) in parasites. The niche breadth hypothesis suggests that host generalists are more abundant and efficient at colonizing different host communities than specialists. The trade-off hypothesis argues that host specialists achieve high density across their hosts' ranges, whereas generalists incur the high cost of adaptation to diverse immuno-defence systems. We tested these hypotheses using 386 haemosporidian cytochrome-b lineages (1894 sequences) recovered from 2318 birds of 103 species sampled in NW Africa, NW Iberia, W Greater Caucasus and Transcaucasia. The number of regions occupied by lineages was associated with their frequency suggesting the presence of AOR in avian Haemosporidia. However, neither hypothesis provided a better explanation for the AOR. Although the host generalist Plasmodium SGS1 was over three times more abundant than other widespread lineages, both host specialists and generalists were successful in colonizing all study regions and achieved high overall prevalence.

Finding a needle in a haystack: DNA Haemoproteus columbae enrichment using percoll density gradient and flow cytometry.

Isolation of genomic DNA of blood parasites in birds, reptiles, amphibians, and fishes is a challenging task, given that their red blood cells are nucleated; for that reason, parasite genomic DNA is only a fraction of the total extracted DNA, and it is challenging to obtain concentrated high-quality genetic material. Percoll Density Gradient (PDG) and flow cytometry are tools for separating and analyzing cell populations or even a single cell, and both represent potent approaches for isolating avian haemosporidians parasites. Our experimental design included several steps seeking to concentrate the parasite´s DNA. We used blood samples from a Rock pigeon infected with Haemoproteus columbae. After inducing parasite exflagellation and gametogenesis in vitro, we subjected the samples to a Percoll Density Gradient to separate the parasites from the rest of the blood cells. Following centrifugation, the layer containing extracellular parasites underwent a flow cytometry and cell sorting process, during which we selected two different subpopulations of cells for analysis. Based on qPCR analyses, we demonstrate parasite DNA enrichment in Percoll Density Gradient and flow cytometry samples; simultaneously, these samples showed the lowest concentration of Columba livia DNA. However, the concentration of parasite DNA was higher in the PDG than in the cell sorting sample. This study reports the concentration of the Haemoproteus parasite by flow cytometry without DNA-intercalating dyes, and this methodology can serve as a technique for DNA enrichment of blood parasites infecting nucleated red blood cells to improve techniques that allow obtaining complete genomes.

Impact of ultrastructural and molecular identified Babesiosoma spp. in both Egyptian freshwater fishes (common carp and African catfish): Hematological, biochemical, and histopathological findings.

Background: Babesiosomes are apicomplexan parasites of both marine and freshwater fish species. Aim: In this study, we recorded the prevalence of Babesiosoma spp in two Egyptian freshwater fish species; the common carp and the African catfish with full pathological evaluation of the diseased condition, hematological and biochemical analysis of some parameters with exact recognition of the parasite with different methods. Methods: Two hundred and forty fish blood samples from Al-Sharqiya and Al-Ismailia governorates from August 2022 to January 2023 followed by blood film examinations, performing electron microscopy and molecular detection of the parasite via polymerase chain reaction. Results: The total infection prevalence was 63.75% with a higher prevalence observed among African catfish (42.5%) than Common carp (21.25%). Regarding hematologic parameters, the obtained results showed a significant decrease in the hematocrit values and a significant increase in the total leukocyte and lymphocyte values in both infected fish species. The serum ferritin, superoxide dismutase, and glutathione peroxidase were also significantly increased. However, the total iron binding capacity was significantly decreased. There was also a significant increase in the total serum bilirubin in the examined fish, all at (p < 0.001). Histopathologically, the lesions were more intense in the African catfish than the common carp but generally, the infected fish showed many changes with the gills being severely affected with pronounced hyperplasia of secondary lamellae with fusion and telangiectasis. The spleen, heart, and kidney are also affected. Conclusion: Serious adverse effects on the health status of previously examined fishes infected with Babesia spp. were observed and detected by several diagnostic and descriptive tools. Histopathological, hematological, and biochemical studies give an idea of the extent of these changes which are largely fatal affecting the economic system depending on the fish industry.