Rapid adaptation to a novel pathogen through disease tolerance in a wild songbird.

Animal hosts can adapt to emerging infectious disease through both disease resistance, which decreases pathogen numbers, and disease tolerance, which limits damage during infection without limiting pathogen replication. Both resistance and tolerance mechanisms can drive pathogen transmission dynamics. However, it is not well understood how quickly host tolerance evolves in response to novel pathogens or what physiological mechanisms underlie this defense. Using natural populations of house finches (Haemorhous mexicanus) across the temporal invasion gradient of a recently emerged bacterial pathogen (Mycoplasma gallisepticum), we find rapid evolution of tolerance (<25 years). In particular, populations with a longer history of MG endemism have less pathology but similar pathogen loads compared with populations with a shorter history of MG endemism. Further, gene expression data reveal that more-targeted immune responses early in infection are associated with tolerance. These results suggest an important role for tolerance in host adaptation to emerging infectious diseases, a phenomenon with broad implications for pathogen spread and evolution.

Wildlife susceptibility to infectious diseases at global scales.

Disease transmission prediction across wildlife is crucial for risk assessment of emerging infectious diseases. Susceptibility of host species to pathogens is influenced by the geographic, environmental, and phylogenetic context of the specific system under study. We used machine learning to analyze how such variables influence pathogen incidence for multihost pathogen assemblages, including one of direct transmission (coronaviruses and bats) and two vector-borne systems (West Nile Virus [WNV] and birds, and malaria and birds). Here we show that this methodology is able to provide reliable global spatial susceptibility predictions for the studied host-pathogen systems, even when using a small amount of incidence information (i.e., [Formula: see text] of information in a database). We found that avian malaria was mostly affected by environmental factors and by an interaction between phylogeny and geography, and WNV susceptibility was mostly influenced by phylogeny and by the interaction between geographic and environmental distances, whereas coronavirus susceptibility was mostly affected by geography. This approach will help to direct surveillance and field efforts providing cost-effective decisions on where to invest limited resources.

Investigating pigeon circovirus infection in a pigeon farm: molecular detection, phylogenetic analysis and complete genome analysis.

BACKGROUND: Pigeon circovirus infections in pigeons (Columba livia domestica) have been reported worldwide. Pigeons should be PiCV-free when utilized as qualified experimental animals. However, pigeons can be freely purchased as experimental animals without any clear guidelines to follow. Herein, we investigated the status quo of PiCV infections on a pigeon farm in Beijing, China, which provides pigeons for experimental use. RESULTS: PiCV infection was verified in at least three types of tissues in all forty pigeons tested. A total of 29 full-length genomes were obtained and deposited in GenBank. The whole genome sequence comparison among the 29 identified PiCV strains revealed nucleotide homologies of 85.8-100%, and these sequences exhibited nucleotide homologies of 82.7-98.9% as compared with those of the reference sequences. The cap gene displayed genetic diversity, with a wide range of amino acid homologies ranging from 64.5% to 100%. Phylogenetic analysis of the 29 full-genome sequences revealed that the PiCV strains in this study could be further divided into four clades: A (17.2%), B (10.4%), C (37.9%) and D (34.5%). Thirteen recombination events were also detected in 18 out of the 29 PiCV genomes obtained in this study. Phylogenetic research using the rep and cap genes verified the recombination events, which occurred between clades A/F, A/B, C/D, and B/D among the 18 PiCV strains studied. CONCLUSIONS: In conclusion, PiCV infection, which is highly genetically varied, is extremely widespread on pigeon farms in Beijing. These findings indicate that if pigeons are to be used as experimental animals, it is necessary to evaluate the impact of PiCV infection on the results.

Reverse genetics of parrot bornavirus 4 reveals a unique splicing of the glycoprotein gene that affects viral propagation.

Viruses can utilize host splicing machinery to enable the expression of multiple genes from a limited-sized genome. Orthobornaviruses use alternative splicing to regulate the expression level of viral proteins and achieve efficient viral replication in the nucleus. Although more than 20 orthobornaviruses have been identified belonging to eight different viral species, virus-specific splicing has not been demonstrated. Here, we demonstrate that the glycoprotein (G) transcript of parrot bornavirus 4 (PaBV-4; species Orthobornavirus alphapsittaciforme), a highly virulent virus in psittacines, undergoes mRNA splicing and expresses a soluble isoform termed sGP. Interestingly, the splicing donor for sGP is not conserved in other orthobornaviruses, including those belonging to the same orthobornavirus species, suggesting that this splicing has evolved as a PaBV-4-specific event. We have also shown that exogenous expression of sGP does not affect PaBV-4 replication or de novo virion infectivity. In this study, to investigate the role of sGP in viral replication, we established a reverse genetics system for PaBV-4 by using avian cell lines and generated a recombinant virus lacking the spliced mRNA for sGP. Using the recombinant viruses, we show that the replication of the sGP-deficient virus is significantly slower than that of the wild-type virus and that the exogenous expression of sGP cannot restore its propagation efficiency. These results suggest that autologous or controlled expression of sGP by splicing may be important for PaBV-4 propagation. The reverse genetics system for avian bornaviruses developed here will be a powerful tool for understanding the replication strategies and pathogenesis of avian orthobornaviruses. IMPORTANCE Parrot bornavirus 4 (PaBV-4) is the dominant cause of proventricular dilatation disease, a severe gastrointestinal and central nervous system disease among avian bornaviruses. In this study, we discovered that PaBV-4 expresses a soluble isoform of glycoprotein (G), called sGP, through alternative splicing of the G mRNA, which is unique to this virus. To understand the role of sGP in viral replication, we generated recombinant PaBV-4 lacking the newly identified splicing donor site for sGP using a reverse genetics system and found that its propagation was significantly slower than that of the wild-type virus, suggesting that sGP plays an essential role in PaBV-4 infection. Our results provide important insights not only into the replication strategy but also into the pathogenesis of PaBV-4, which is the most prevalent bornavirus in captive psittacines worldwide.

Co-phylogeny of a hyper-symbiotic system: Endosymbiotic bacteria (Gammaproteobacteria), chewing lice (Insecta: Phthiraptera) and birds (Passeriformes).

Chewing lice are hosts to endosymbiotic bacteria as well as themselves being permanent parasites. This offers a unique opportunity to examine the cophylogenetic relationships between three ecologically interconnected organismal groups: birds, chewing lice, and bacteria. Here, we examine the cophylogenetic relationships between lice in the genus Guimaraesiella Eichler, 1949, their endosymbiotic Sodalis-allied bacteria, and a range of bird species from across South China. Both event and distance-based cophylogenetic analyses were explored to compare phylogenies of the three organismal groups. Pair-wise comparisons between lice-endosymbionts and bird-endosymbionts indicated that their evolutionary histories are not independent. However, comparisons between lice and birds, showed mixed results; the distance-based method of ParaFit indicated that their evolutionary histories are not independent, while the event-based method of Jane indicated that their phylogenies were no more congruent than expected by chance. Notably, louse host-switching does not seem to have affected bacterial strains, as conspecific lice sampled from distantly related hosts share bacteria belonging to the same clade.

Empirically tuned theory reveals why symbiont abundance 'mite' vary across hosts.

Research Highlight: del Mar Labrador, M., Serrano, D., Doña, J., Aguilera, E., Arroyo, J. L., Atiénzar, F., Barba, E., Bermejo, A., Blanco, G., Borràs, A., Calleja, J. A., Cantó, J. L., Cortés, V., de la Puente, J., de Palacio, D., Fernández-González, S., Figuerola, J., Frías, Ó., Fuertes-Marcos, B. Garamszegi, L. Z., Gordo, Ó., Gurpegui, M., Kovács, I., Martínez, J. L., Meléndez, L., Mestre, A., Møller, A. P., Monrós, J. S., Moreno-Opo, R., Navarro, C., Pap, P. L., Pérez-Tris, J., Piculo, R., Ponce, C., Proctor, H., Rodríguez, R., Sallent, Á., Senar, J., Tella, J. L., Vágási, C. I., Vögeli, M., & Jovani, R. (2023). Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.14032. Symbionts represent crucial links between species in ecosystems. Consequently, understanding their patterns of abundance is a major goal in the study of symbioses. However, multiple biotic and abiotic factors may regulate symbionts, and disentangling the mechanisms that drive variation in their abundance across host species is challenging. One promising strategy to approach this challenge is to incorporate biologically relevant data into theoretical models. In a recent study, Labrador et al. (2023) used this strategy to investigate the poorly understood symbiosis between feather mites and their avian hosts. They integrate a remarkable amount of empirical data with models based on the metabolic theory of ecology to determine what factors limit feather mite abundance across European passerines. Their quantitative analyses indicate that the number of feather barbs limits mite abundance across host species, suggesting that mite populations are spatially, but not energetically, constrained. These findings not only reveal mechanisms that may drive the variation in feather mite abundances across hosts, but also advance our understanding of the ecology of interspecific interactions more generally.

Male pathology regardless of behaviour drives transmission in an avian host-pathogen system.

Host sex is an important source of heterogeneity in the severity of epidemics. Pinpointing the mechanisms causing this heterogeneity can be difficult because differences in behaviour among sexes (e.g. greater territorial aggression in males) can bias exposure risk, obfuscating the role of immune function, which can lead to differences in pathology, in driving differential susceptibility between sexes. Thus, sex-biased transmission driven by differences in immune function independent of behaviour is poorly understood, especially in non-mammalian systems. Here we examine the previously unexplored potential for male-biased pathology to affect transmission using an avian host-pathogen system. We employ a sex-dependent multistate transmission model parameterized with isolated, individual-based experimental exposures of domestic canaries and experimental transmission data of house finches. The experiment revealed that male birds have shorter incubation periods, longer recovery periods, higher pathogen burdens and greater disease pathology than females. Our model revealed that male-biased pathology led to epidemic size rapidly increasing with the proportion of male birds, with a nearly 10-fold increase in total epidemic size from an all-female to an all-male simulation. Our results demonstrate that female-biased resistance, independent of male behaviour, can drive sex-dependent transmission in wildlife, indicating that sex-based differences in immune function, not just differences in exposure risk, can shape epidemic dynamics.

Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species.

Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constrains symbiont populations. We parameterized metabolic theory equations to investigate how bird species' body size and the body size of their feather mites relate to mite abundance according to four potential energy (uropygial gland size) and space constraints (wing area, total length of barbs and number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance across 106 passerine bird species (26,604 individual birds sampled), using phylogenetic modelling and quantile regression. Feather mite abundance was strongly constrained by host space (number of feather barbs) but not by energy. Moreover, feather mite species' body size was unrelated to the body size of their host species. We discuss the implications of our results for our understanding of the bird-feather mite system and for symbiont abundance in general.

Genome analysis of gyroviruses identified in waterfowl in Arizona (USA).

Gyroviruses are small single-stranded DNA (ssDNA) viruses that are largely associated with birds. Chicken anemia virus is the most extensively studied gyrovirus due to its disease impact on the poultry industry. However, we know much less about gyroviruses infecting other avian species. To investigate gyroviruses infecting waterfowl, we determined six complete genome sequences that fall into three gyrovirus groups, referred to as waterfowl gyrovirus 1 (n = 3), 2 (n = 2), and 3 (n = 1), in organs from hunter-harvested waterfowl from Arizona (USA). The waterfowl gyrovirus 1 variants were identified in multiple organs of a single American wigeon and represent a tentative new species. The waterfowl gyrovirus 2 variants were identified in the livers of two American wigeons and share >70% VP1 nucleotide sequence identity with gyrovirus 9, previously identified in the spleen of a Brazilian Pekin duck (MT318123) and a human fecal sample (KP742975). Waterfowl gyrovirus 3 was identified in a northern pintail spleen sample, and it shares >73% VP1 nucleotide sequence identity with two gyrovirus 13 sequences previously identified in Brazilian Pekin duck spleens (MT318125 and MT318127). These gyroviruses are the first to be identified in waterfowl in North America, as well as in American wigeons and northern pintails.

Prevalence, genotypes, and infection risk factors of psittacine beak and feather disease virus and budgerigar fledgling disease virus in captive birds in Hong Kong.

Psittacine beak and feather disease virus (PBFDV) and budgerigar fledgling disease virus (BFDV) are significant avian pathogens that threaten both captive and wild birds, particularly parrots, which are common hosts. This study involved sampling and testing of 516 captive birds from households, pet shops, and an animal clinic in Hong Kong for PBFDV and BFDV. The results showed that PBFDV and BFDV were present in 7.17% and 0.58% of the samples, respectively. These rates were lower than those reported in most parts of Asia. Notably, the infection rates of PBFDV in pet shops were significantly higher compared to other sources, while no BFDV-positive samples were found in pet shops. Most of the positive samples came from parrots, but PBFDV was also detected in two non-parrot species, including Swinhoe's white-eyes (Zosterops simplex), which had not been reported previously. The ability of PBFDV to infect both psittacine and passerine birds is concerning, especially in densely populated urban areas such as Hong Kong, where captive flocks come into close contact with wildlife. Phylogenetic analysis of the Cap and Rep genes of PBFDV revealed that the strains found in Hong Kong were closely related to those in Europe and other parts of Asia, including mainland China, Thailand, Taiwan, and Saudi Arabia. These findings indicate the presence of both viruses among captive birds in Hong Kong. We recommend implementing regular surveillance for both viruses and adopting measures to prevent contact between captive and wild birds, thereby reducing the transmission of introduced diseases to native species.

Selection of suitable reference genes for normalization of RT-qPCR in three tissues of Northern bobwhite (Colinus virginianus) infected with eyeworm (Oxyspirura petrowi).

BACKGROUND: The Northern bobwhite (Colinus virginianus) is an economically important, and popular game bird in North America. Northern bobwhites have experiencing declines of > 3.5% annually in recent decades due to several factors. The eyeworm Oxyspirura petrowi is a nematode parasite frequently found in the eyes of bobwhites. Although reported frequently in wild bobwhites, there is no research to understand the host-parasite mechanism. Hence, it is important to investigate mechanisms of eyeworm invasion and immune modulation in bobwhite. Cytokine gene expression using RT-PCR is widely used to identify the innate immune response of a host to an infection. METHODOLOGY: In this study, we evaluated ten reference genes (HMBS, RPL19, RPL32, RPS7, RPS8, TATA, SDHA, YWHAZ, GAPDH, and ACTB) for their stability across three tissues (liver, spleen, and caecal tonsils) of control and O. petrowi infected Northern bobwhites. Primer efficiency and reference genes stability were assessed using GeNorm, NormFinder, and BestKeeper. RESULTS: Expression of these reference genes with respect to O. petrowi infection in bobwhites showed RPL32 and HMBS were the most stable genes in the liver, HMBS and SDHA were the most stable genes in the spleen, and HMBS and YWHAZ were equally stable reference genes in the caecal tonsils. CONCLUSION: Based on the geometric mean of all three analyses, our results indicate that the combination of RPL32 and HMBS for the liver, HMBS and SDHA for the spleen, and YWHAZ and HMBS for caecal tonsils might be used as reference genes for normalization in gene expression investigations on Northern bobwhites.

The association between haemosporidian infection and non-breeding moult location in great reed warblers revisited by combining feather stable isotope profiles and geolocator data.

Stable isotope analysis provides valuable insights into the ecology of long-distance migratory birds during periods spent away from a specific study site. In a previous study, Swedish great reed warblers (Acrocephalus arundinaceus) infected with haemosporidian parasites differed in feather isotope ratios compared to non-infected birds, suggesting that infected and non-infected birds spent the non-breeding season in different locations or habitats. Here, we use a novel dataset comprising geolocator data, isotopes, and haemosporidian infection status of 92 individuals from four Eurasian populations to investigate whether parasite transmission varies with geography or habitats. We found that the probability of harbouring Plasmodium and Leucocytozoon parasites was higher in birds moulting in the eastern region of the non-breeding grounds. However, no geographic pattern occurred for Haemoproteus infections or overall infection status. In contrast to the previous study, we did not find any relationship between feather isotope ratios and overall haemosporidian infection for the entire current dataset. Plasmodium-infected birds had lower feather δ15N values indicating that they occupied more mesic habitats. Leucocytozoon-infected birds had higher feather δ34S values suggesting more coastal sites or wetlands with anoxic sulphate reduction. As the composition and prevalence of haemosporidian parasites differed between the old and the current dataset, we suggest that the differences might be a consequence of temporal dynamics of haemosporidian parasites. Our results emphasize the importance of replicating studies conducted on a single population over a restricted time period, as the patterns can become more complex for data from wider geographical areas and different time periods.

Large-scale spatial drivers of avian schistosomes in Northern Michigan inland lakes.

Avian schistosomes are snail-borne trematode parasites (Trichobilharzia spp.) that can cause a nasty skin rash in humans when their cercariae mistake us for their normal bird hosts. We sought to investigate drivers of the spatial distribution of Trichobilharzia cercaria abundance throughout Northern Michigan lakes. For 38 sites on 16 lakes, we assessed several dozen potential environmental predictors that we hypothesized might have direct or indirect effects on overall cercaria abundance, based on known relationships between abiotic and biotic factors in wetland ecosystems. We included variables quantifying local densities of intermediate hosts, temperature, periphyton growth rates, human land use and hydrology. We also measured daily abundance of schistosome cercariae in the water over a 5-week period, supported by community scientists who collected and preserved filtered water samples for qPCR. The strongest predictor of cercaria abundance was Lymnaea host snail density. Lymnaea density was higher in deeper lakes and at sites with more deciduous tree cover, consistent with their association with cool temperature habitats. Contrary to past studies of human schistosomes, we also found a significant negative relationship between cercaria abundance and submerged aquatic vegetation, possibly due to vegetation blocking cercaria movement from offshore snail beds. If future work shows that these effects are indeed causal, then these results suggest possible new approaches to managing swimmer's itch risk in northern MI lakes, such as modifying tree cover and shallow-water vegetation at local sites.

Assessing global drivers of parasite diversity: host diversity and body mass boost avian haemosporidian diversity.

Biodiversity varies worldwide and is influenced by multiple factors, such as environmental stability and past historical events (e.g. Panama Isthmus). At the same time, organisms with unique life histories (e.g. parasites) are subject to unique selective pressures that structure their diversity patterns. Parasites represent one of the most successful life strategies, impacting, directly and indirectly, ecosystems by cascading effects on host fitness and survival. Here, I focused on a highly diverse, prevalent and cosmopolitan group of parasites (avian haemosporidians) to investigate the main drivers (e.g. host and environmental features) of regional parasite diversity on a global scale. To do so, I compiled data from 4 global datasets on (i) avian haemosporidian (malaria and malaria-like) parasites, (ii) bird species diversity, (iii) avian functional traits and (iv) climate data. Then, using generalized least square models, I evaluated the effect of host and environmental features on haemosporidian diversity. I found that haemosporidian diversity mirrors host regional diversity and that higher host body mass increases haemosporidian diversity. On the other hand, climatic conditions had no effect on haemosporidian diversity in any model. When evaluating Leucocytozoon parasites separately, I found parasite diversity was boosted by a higher proportion of migratory hosts. In conclusion, I demonstrated that haemosporidian parasite diversity is intrinsically associated with their hosts' diversity and body mass.

Lost companions: a new quill mite species and its possible coextinction with the Carolina parakeet.

Investigations of the parasites associated with extinct avian species provide unique insights into the ecology and evolution of both hosts and their parasitic counterparts. In the present paper, a new quill mite species, Peristerophila conuropsis sp. n., belonging to the family Syringophilidae (Prostigmata: Cheyletoidea) is described from the Carolina parakeet Conuropsis carolinensis Linnaeus (Psittaciformes: Psittacidae). This new species was collected from museum dry skin of the Carolina parakeet, the only native representative of the Psittacidae in the United States, which was an abundant resident of the southeastern and midwestern states and has been extinct in the beginning of the 20th century. Comment on the current taxonomic state and host associations of the genus Peristerophila are provided. Based on the host associations and habitats occupied by Peristerophila and related genera on parrots, it is hypothesized with the high probability that P. conuropsis has been extinct along with its host.

Coinfection of slime feather duster worms (Annelida, Myxicola) by different gregarine apicomplexans (Selenidium) and astome ciliates reflects spatial niche partitioning and host specificity.

Individual organisms can host multiple species of parasites (or symbionts), and one species of parasite can infect different host species, creating complex interactions among multiple hosts and parasites. When multiple parasite species coexist in a host, they may compete or use strategies, such as spatial niche partitioning, to reduce competition. Here, we present a host­symbiont system with two species of Selenidium (Apicomplexa, Gregarinida) and one species of astome ciliate co-infecting two different species of slime feather duster worms (Annelida, Sabellidae, Myxicola) living in neighbouring habitats. We examined the morphology of the endosymbionts with light and scanning electron microscopy (SEM) and inferred their phylogenetic interrelationships using small subunit (SSU) rDNA sequences. In the host 'Myxicola sp. Quadra', we found two distinct species of Selenidium; S. cf. mesnili exclusively inhabited the foregut, and S. elongatum n. sp. inhabited the mid to hindgut, reflecting spatial niche partitioning. Selenidium elongatum n. sp. was also present in the host M. aesthetica, which harboured the astome ciliate Pennarella elegantia n. gen. et sp. Selenidium cf. mesnili and P. elegantia n. gen. et sp. were absent in the other host species, indicating host specificity. This system offers an intriguing opportunity to explore diverse aspects of host­endosymbiont interactions and competition among endosymbionts.

Systemic avian poxvirus infections associated with the B1 subclade of canarypox virus.

Avian poxvirus infections typically manifest as 2 forms: cutaneous ("dry") pox, characterized by proliferative nodules on the skin, and diphtheritic ("wet") pox, characterized by plaques of caseous exudate in the oropharynx and upper respiratory and gastrointestinal tracts. Systemic spread of virus to visceral organs beyond the skin and mucous membranes is rarely reported. Out of 151 cases diagnosed with avian poxvirus over a 20-year period at a zoological institution, 22 were characterized as having systemic involvement based on histopathology and molecular findings. Gross lesions in systemic cases included soft white nodules scattered throughout the liver, spleen, and kidneys. Two histopathologic patterns emerged: (1) widespread histiocytic inflammation in visceral organs with intrahistiocytic viral inclusions and (2) severe, localized dry or wet pox lesions with poxvirus-like inclusions within dermal and subepithelial histiocytes. In situ hybridization targeting the core P4b protein gene confirmed the presence of poxvirus DNA within histiocytes in both patterns. Polymerase chain reaction was performed targeting the reticuloendothelial virus long terminal repeat (REV LTR) flanking region and the core P4b protein gene. Sequences of the REV LTR flanking region from all systemic pox cases were identical to a previously described condorpox virus isolated from an Andean condor with systemic pox. Sequences of the core P4b protein gene from all systemic pox cases grouped into cluster 2 of the B1 subclade of canarypox viruses. Systemic involvement of avian poxvirus likely occurs as a result of infection with certain strain variations in combination with various possible host and environmental factors.

Pathological lesions associated with avian schistosomes (Digenea: Schistosomatidae) in the freshwater snail Chilina dombeiana (Gastropoda: Chilinidae) from Southern Chile.

Avian schistosomes inhabit the blood stream of domestic and wild birds with aquatic snails as their intermediate hosts. In the Neotropics there is an emerging effort to describe species from these hosts, including Chile, although the knowledge about their pathological consequences is mostly understudied. This study aimed to describe the pathological changes associated with the parasitism of a native schistosomatid restricted to the Southern Cone of Neotropics. To achieve this, a total of 401 Chilina dombeiana snails (Chilinidae) were collected in two locations from Southern Chile. All of them were disposed to cercarial release procedure for three consecutive days. Furcocercariae released were stained and characterized by microscopic evaluation. Then, all snails were dissected under stereomicroscope and preserved in 10 % buffered formalin until histopathological analysis was performed. Eight out 401 (P = 2 %) snails were found parasitized with avian schistosomes. The released furcocercariae were identified as Schistosomatidae gen. sp. Lineage II which was previously reported in the same host. The main pathological change was an atrophy of ovotestes and an absence or mild infiltration of hemocytes in the surrounding tissues. Besides, a co-infection with echinostomes was found which was associated with a moderate hemocyte infiltration, granuloma-like lesion, and a reduced presence of schistosome' sporocysts. The latter would suggest an antagonistic interaction between these two digeneans, as has been proposed in the Echinostoma spp.-Schistosoma mansoni model. Despite the above, the release of furcocercariae was present but reduced, in contrast with the non-release of echinocercariae. This interaction requires further attention. This study represents the first attempt to characterize the pathological consequences of parasitism by a native, yet undescribed, avian schistosome in an endemic snail. Future studies should consider experimental infections to understand the dynamics of single infections in other Chilina species, including inter- and intra-specific parasitism as previous studies have found, including this study.

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.

Environmental and ecological factors affecting tick infestation in wild birds of the Americas.

The Americas hold the greatest bird diversity worldwide. Likewise, ectoparasite diversity is remarkable, including ticks of the Argasidae and Ixodidae families - commonly associated with birds. Considering that ticks have potential health implications for humans, animals, and ecosystems, we conducted a systematic review to evaluate the effects of bioclimatic, geographic variables, and bird species richness on tick infestation on wild birds across the Americas. We identified 72 articles that met our inclusion criteria and provided data on tick prevalence in wild birds. Using Generalized Additive Models, we assessed the effect of environmental factors, such as habitat type, climatic conditions, bird species richness, and geographic location, on tick infestation. Our findings show that most bird infestation case studies involved immature ticks, such as larvae or nymphs, while adult ticks represented only 13% of case studies. We found birds infested by ticks of the genera Amblyomma (68%), Ixodes (22%), Haemaphysalis (5%), Dermacentor (1%), and Rhipicephalus (0.8%) in twelve countries across the Americas. Our findings revealed that temperature variation and bird species richness were negatively associated with tick infestation, which also varied with geographic location, increasing in mid-latitudes but declining in extreme latitudes. Our results highlight the importance of understanding how environmental and bird community factors influence tick infestation in wild birds across the Americas and the dynamics of tick-borne diseases and their impact on biodiversity.