Contrasting the seasonal and elevational prevalence of generalist avian haemosporidia in co-occurring host species

Leucocytozoon infections in tits (Aves, Paridae): blood and tissue stages investigated using an integrative approach

Leucocytozoon species are cosmopolitan and prevalent avian parasites, with some infections being lethal, mainly due to the exo-erythrocytic development of the parasite in bird tissues. The patterns of exo-erythrocytic development in Leucocytozoon spp. infections in wild birds remain poorly studied. This study investigated the development of Leucocytozoon spp. tissue stages in tits (Paridae). Great tits (Parus major), Blue tits (Cyanistes caeruleus), and Coal tits (Periparus ater) were screened for infections using an integrative approach that consisted of microscopic analysis of thin blood smears, histological techniques, chromogenic in situ hybridization (CISH), PCR-based methods, and phylogenetic analysis. In total, 41 individuals were analyzed (eight naturally infected that were selected and euthanized, and 33 found dead in the wild and opportunistically sampled). Among the naturally infected birds, all individuals that were microscopically positive for Leucocytozoon species were also PCR-positive for these parasites. Co-infections with Plasmodium spp. and Haemoproteus spp. were commonly found, mainly among the opportunistically sampled birds. Two morphotypes were identified, Leucocytozoon majoris (Laveran, 1902) and Leucocytozoon fringillinarum Woodcock, 1910. Tissue stages were present in three birds sampled exclusively during the non-breeding season, two of them with meronts developing in the kidneys and liver, and one individual with a megalomeront in the heart. All the exo-erythrocytic stages were confirmed to be Leucocytozoon spp. by CISH using a Leucocytozoon genus-specific probe. Phylogenetic analysis placed parasite lineages with different morphotypes in separate clades. The developmental patterns of exo-erythrocytic stages of Leucocytozoon spp. in naturally infected passerines are poorly understood, requiring further research.

The Role of Host-Range Expansion and Co-Speciation in Host-Parasite Associations With the Divergence of the Great Tit Species Complex

During the evolution of parasites, co-speciation and host-range expansion are thought to play roles in establishing associations with hosts, while sorting events can lead to dissolution of those associations. To address the roles of these processes, we focus on avian haemosporidian parasites infecting hosts of the intensively studied great tit species complex. We estimated the phylogeography of lineages detected in the species complex, and quantified their transition probabilities among hosts. Lineages detected in different host species presented a strong geographical signal but did not form monophyletic groups. Yet, distributions of lineages are not merely the result of their dispersal limitations, as many lineages that infect only one focal species can be found in birds sympatric with other focal species. Besides, closely related lineages that infect the same host species reach more similar rates of infection than expected by chance. Finally, Haemoproteus and Leucocytozoon lineages infecting P. major, the most recently dispersed species, were more generalized than others, consistent with a pattern of generalist parasites expanding their host ranges by infecting newly encountered host species. Our results suggest that host-parasite associations in this system are mainly the result of sorting events and host-range expansion of parasites, rather than co-speciation.

Seasonal Variation in Detection of Haemosporidia in a Bird Community: A Comparison of Nested PCR and Microscopy

In a 2-yr study on prevalence of Haemosporidia in an avian community in Ithaca, New York, USA, we tested the hypothesis that apparent seasonal variation in prevalence is influenced by the detection protocol. We confirmed a higher detection of Haemosporidia using a molecular diagnosis technique (PCR) than by microscopy; this further increased when the PCR test was triplicated. Microscopic examination and PCR techniques have different specificity and sensitivity and therefore different probabilities of detecting hemoparasites. Birds with chronic infections or sampled during winter often have very low parasitemia, and such infections may be missed by microscopy but detected by PCR. Haemosporidian prevalence was higher during the breeding season than during the nonbreeding season regardless of the method used. Detection of Leucocytozoon spp. infection from blood smears using microscopy was challenging.

Contribution to ecological environmental factors and the occurrence of haemosporidians in birds in Zhongar Alatau National Park, Kazakhstan

In addition to the presence of a suitable host and vector, the prevalence of haemosporidians is influenced by several important factors, including the environmental conditions of the habitat, which depend on broader geographic characteristics. The aim of this study is to perform a preliminarily assessment of the distribution of blood parasites in birds from the mountainous area of Zhongar Alatau NP and to find potential new sites for research on their ecology in Kazakhstan. The results of this research constitute the first report on the occurrence of blood parasites from this area. A total of 58 birds, from the order Passeriformes and one individual from the order Caprimulgiformes, were examined during the study. The overall prevalence of infections caused by haemosporidian parasites (Haemoproteus, Leucocytozoon) was 18.6%. Neither the genus Plasmodium nor the presence of trypanosomes and microfilariae was detected in the birds examined. Three birds (5.1% prevalence) were infected with parasites of the genus Haemoproteus, in all eleven positive birds the analyses showed the presence of parasites of the genus Leucocytozoon (18.6% prevalence). The presence of parasites genus Haemoproteus was detected only in birds that were also infected with Leucocytozoon parasites. More infections with parasites of the genus Leucocytozoon are predicted due to the higher altitude and ecological factors at the capture sites, which are more favourable for the development of vectors of this genus. The species Haemoproteus majoris was detected in the host Emberiza cioides and species Haemoproteus minutus in host Turdus merula. Other species of this genus in the hosts Cyanistes cyanus and Turdus atrogularis were not determined. The species Leucocytozoon fringilinarum was detected in the hosts Cyanistes cyanus and Parus major, Leucocytozoon dubreuili was detected in Turdus atrogularis and Turdus merula. In the other host species Aegithalos caudatus, Emberiza cioides and Periparus aterus, it was not possible to dermine the species of the genus Leucocytozoon.

Very low prevalence of haemosporidian parasites in two species of marsh terns

Vector-transmitted haemosporidians are among the most common parasites in birds, but our knowledge of the inter-specific patterns of infection rates and the parasite community composition is far from complete because of the unequal distribution of the screening effort across bird families and genera. To assess infection rates and the diversity of haemosporidians from the genera Plasmodium, Haemoproteus, and Leucocytozoon in marsh terns, which represent poorly explored in this regard genus of the family gulls, terns, and skimmers (Laridae), we screened two species: the Whiskered Tern (Chlidonias hybrida) and the Black Tern (Chlidonias niger). We sampled these long-distance migratory birds on breeding grounds: the Whiskered Tern in south-central Poland and north-central Ukraine, and the Black Tern-in north-central Ukraine. We found that birds from both species were infected only sporadically, with prevalence at the population level not exceeding 3.4%. Only parasites from the genera Plasmodium and Leucocytozoon were detected. There was neither an inter-specific difference nor a difference between populations of the Whiskered Tern in infection rates. In total, we registered three lineages-one Plasmodium and two Leucocytozoon-that were previously recorded in other bird species, and two unidentified Plasmodium infections. One of the lineages (Leucocytozoon LARCAC02) represents a specialist parasite with the host range restricted to larids and geographic range restricted to Poland, and two others (Plasmodium SGS1 and Leucocytozoon CIAE02) represent generalist parasites with very broad host and geographic ranges. This study reinforces the existing evidence that terns host parasites from genera Haemoproteus, Plasmodium, and Leucocytozoon only sporadically.

Parasite detection and quantification in avian blood is dependent on storage medium and duration

Studies of parasites in wild animal populations often rely on molecular methods to both detect and quantify infections. However, method accuracy is likely to be influenced by the sampling approach taken prior to nucleic acid extraction. Avian Haemosporidia are studied primarily through the screening of host blood, and a range of storage mediums are available for the short- to long-term preservation of samples. Previous research has suggested that storage medium choice may impact the accuracy of PCR-based parasite detection, however, this relationship has never been explicitly tested and may be exacerbated by the duration of sample storage. These considerations could also be especially critical for sensitive molecular methods used to quantify infection (qPCR). To test the effect of storage medium and duration on Plasmodium detection and quantification, we split blood samples collected from wild birds across three medium types (filter paper, Queen's lysis buffer, and 96% ethanol) and carried out DNA extractions at five time points (1, 6, 12, 24, and 36 months post-sampling). First, we found variation in DNA yield obtained from blood samples dependent on their storage medium which had subsequent negative impacts on both detection and estimates of Plasmodium copy number. Second, we found that detection accuracy (incidence of true positives) was highest for filter-paper-stored samples (97%), while accuracy for ethanol and Queen's lysis buffer-stored samples was influenced by either storage duration or extraction yield, respectively. Lastly, longer storage durations were associated with decreased copy number estimates across all storage mediums; equating to a 58% reduction between the first- and third-year post-sampling for lysis-stored samples. These results raise questions regarding the utility of standardizing samples by dilution, while also illustrating the critical importance of considering storage approaches in studies of Haemosporidia comparing samples subjected to different storage regimes and/or stored for varying lengths of time.

Determinants of haemosporidian single- and co-infection risks in western palearctic birds

Understanding the drivers of infection risk helps us to detect the most at-risk species in a community and identify species whose intrinsic characteristics could act as potential reservoirs of pathogens. This knowledge is crucial if we are to predict the emergence and evolution of infectious diseases. To date, most studies have only focused on infections caused by a single parasite, leaving out co-infections. Yet, co-infections are of paramount importance in understanding the ecology and evolution of host-parasite interactions due to the wide range of effects they can have on host fitness and on the evolutionary trajectories of parasites. Here, we used a multinomial Bayesian phylogenetic modelling framework to explore the extent to which bird ecology and phylogeny impact the probability of being infected by one genus (hereafter single infection) or by multiple genera (hereafter co-infection) of haemosporidian parasites. We show that while nesting and migration behaviors influenced both the probability of being single- and co-infected, species position along the slow-fast life-history continuum and geographic range size were only pertinent in explaining variation in co-infection risk. We also found evidence for a phylogenetic conservatism regarding both single- and co-infections, indicating that phylogenetically related bird species tend to have similar infection patterns. This phylogenetic signal was four times stronger for co-infections than for single infections, suggesting that co-infections may act as a stronger selective pressure than single infections. Overall, our study underscores the combined influence of hosts' evolutionary history and attributes in determining infection risk in avian host communities. These results also suggest that co-infection risk might be under stronger deterministic control than single infection risk, potentially paving the way toward a better understanding of the emergence and evolution of infectious diseases.

Phylogeographic Patterns of Haemoproteid Assemblages of Selected Avian Hosts: Ecological and Evolutionary Implications

BACKGROUND

While the dynamics of disease emergence is driven by host-parasite interactions, the structure and dynamics of these interactions are still poorly understood. Here we study the phylogenetic and morphological clustering of haemosporidian parasite lineages in a local avian host community. Subsequently, we examine geographical patterns of parasite assemblages in selected avian hosts breeding in Europe.

METHODS

We conduct phylogenetic and haplotype network analyses of Haemoproteus (Parahaemoproteus) lineages based on a short and an extended cytochrome b barcode region. Ordination analyses are used to examine changes in parasite assemblages with respect to climate type and geography.

RESULTS

We reveal relatively low phylogenetic clustering of haemoproteid lineages in a local avian host community and identify a potentially new Haemoproteus morphospecies. Further, we find that climate is effectively capturing geographical changes in parasite assemblages in selected widespread avian hosts. Moreover, parasite assemblages are found to vary distinctly across the host's breeding range, even within a single avian host.

CONCLUSIONS

This study suggests that a few keystone hosts can be important for the local phylogenetic and morphological clustering of haemoproteid parasites. Host spatio-temporal dynamics, both for partially and long-distance migratory birds, appear to explain geographical variation in haemoproteid parasite assemblages. This study also gives support to the idea that climate variation in terms of rainfall seasonality can be linked to the propensity for host switching in haemosporidians.

A citizen science-based survey of avian mortality focusing on haemosporidian infections in wild passerine birds

BACKGROUND

Haemosporidioses are common in birds and their manifestations range from subclinical infections to severe disease, depending on the involved parasite and bird species. Clinical haemosporidioses are often observed in non-adapted zoo or aviary birds, whereas in wild birds, particularly passerines, haemosporidian infections frequently seem to be asymptomatic. However, a recent study from Austria showed pathogenic haemosporidian infections in common blackbirds due to high parasite burdens of Plasmodium matutinum LINN1, a common parasite in this bird species, suggesting that virulent infections also occur in natural hosts. Based on these findings, the present study aimed to explore whether and to what extent other native bird species are possibly affected by pathogenic haemosporidian lineages, contributing to avian morbidity.

METHODS

Carcasses of passerine birds and woodpeckers were collected during a citizen science-based survey for avian mortality in Austria, from June to October 2020. Tissue samples were taken and examined for haemosporidian parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon by nested PCR and sequencing the mitochondrial cytb barcode region, histology, and chromogenic in situ hybridization applying genus-specific probes.

RESULTS

From over 160 dead bird reportings, 83 carcasses of 25 avian species were submitted for investigation. Overall haemosporidian infection rate was 31%, with finches and tits prevailing species counts and infections. Sequence analyses revealed 17 different haplotypes (4 Plasmodium, 4 Haemoproteus, 9 Leucocytozoon), including 4 novel Leucocytozoon lineages. Most infected birds presented low parasite burdens in the peripheral blood and tissues, ruling out a significant contribution of haemosporidian infections to morbidity or death of the examined birds. However, two great tits showed signs of avian malaria, suggesting pathogenic effects of the detected species Plasmodium relictum SGS1 and Plasmodium elongatum GRW06. Further, exo-erythrocytic tissue stages of several haemosporidian lineages are reported.

CONCLUSIONS

While suggesting generally little contribution of haemosporidian infections to mortality of the investigated bird species, the findings indicate a possible role of certain haemosporidian lineages in overall clinical manifestation, either as main causes or as concurrent disease agents. Further, the study presents new data on exo-erythrocytic stages of previously reported lineages and shows how citizen science can be used in the field of haemosporidian research.

Seasonal Dynamics and Diversity of Haemosporidians in a Natural Woodland Bird Community in Slovakia

Despite the ubiquity of disease seasonality, mechanisms behind the fluctuations in seasonal diseases are still poorly understood. Avian hemosporidiosis is increasingly used as a model for ecological and evolutionary studies on disease dynamics, but the results are complex, depending on the focus (hosts, parasites, vectors) and scale (individuals, community, populations) of the study. Here, we examine the local diversity of haemosporidian parasites and the seasonal patterns of infections, parasite richness, and diversity in a natural woodland bird community in Slovakia. In 35 avian species, we detected 111, including 19 novel, haemosporidian cytochrome b lineages. The highest numbers of lineages were detected during spring and autumn, corresponding with higher avian species richness and infection prevalence in the avian community during these periods of time. Nevertheless, the haemosporidian community in the local breeders in summer was relatively stable, Haemoproteus lineages dominated in the local avian haemosporidian community, and only few parasite lineages were abundant within each genus. While prevailing Leucocytozoon infections in spring suggest that the majority of sampled birds wintered in the Mediterranean region, Plasmodium infections in spring can be due to relapses in reproductively active short-distance migrants. Multiple haemosporidian infections, both intra- and inter-generic ones, were common in the local avian community. Infection intensity peaked during summer and tended to be higher in older birds, pointing to the role of supressed immunity in reproductively active birds.