Prevalence of avian haematozoa in wild birds in a high-altitude forest in Japan

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.

Insights into the Biology of Leucocytozoon Species (Haemosporida, Leucocytozoidae): Why Is There Slow Research Progress on Agents of Leucocytozoonosis?

Blood parasites of the genus Leucocytozoon (Leucocytozoidae) only inhabit birds and represent a readily distinct evolutionary branch of the haemosporidians (Haemosporida, Apicomplexa). Some species cause pathology and even severe leucocytozoonosis in avian hosts, including poultry. The diversity of Leucocytozoon pathogens is remarkable, with over 1400 genetic lineages detected, most of which, however, have not been identified to the species level. At most, approximately 45 morphologically distinct species of Leucocytozoon have been described, but only a few have associated molecular data. This is unfortunate because basic information about named and morphologically recognized Leucocytozoon species is essential for a better understanding of phylogenetically closely related leucocytozoids that are known only by DNA sequence. Despite much research on haemosporidian parasites during the past 30 years, there has not been much progress in taxonomy, vectors, patterns of transmission, pathogenicity, and other aspects of the biology of these cosmopolitan bird pathogens. This study reviewed the available basic information on avian Leucocytozoon species, with particular attention to some obstacles that prevent progress to better understanding the biology of leucocytozoids. Major gaps in current Leucocytozoon species research are discussed, and possible approaches are suggested to resolve some issues that have limited practical parasitological studies of these pathogens.

New PCR primers targeting the cytochrome b gene reveal diversity of Leucocytozoon lineages in an individual host

Avian haemosporidian parasites have received considerable attention in ecology and evolution as a result of their wide distribution and ease of detection. However, conventional PCR-based detection methods may sometimes underestimate haemosporidian mixed infections, which are frequent in natural populations. This underestimation is due to differences in PCR sensitivity for detection of lineages within the mixed infections. Therefore, we designed new primers to amplify sequences that were not detected by the conventional primers and examined if our primers were useful for accurate detection of mixed infections. Blood samples were collected from 32 wild birds captured in Hokkaido, and 16 of these were positive for Leucocytozoon using the conventional primers, while 15 were positive using our primers. All positively amplified samples were sequenced, and we found that the conventional primers detected 16% (5/32) of multiple infections and none of them was a novel lineage, whereas our primers detected 44% (14/32) of multiple infections and ten of them were novel lineages. A phylogenetic analysis showed that the new primers can detect a wide range of Leucocytozoon lineages compared with that detected by the conventional primers. The results indicate that our primers are particularly suitable for revealing unique strains from multiple infections. Highly variable multiple infections in the same population of birds at the same location were found for the first time. We revealed a higher diversity of Leucocytozoon lineages in nature than expected, which would provide more information to better understand parasite diversity and host-vector interactions in wildlife.

A long-term field study on mosquito vectors of avian malaria parasites in Japan

Avian malaria is a mosquito-borne disease of birds caused by avian Plasmodium spp. in worldwide scale. Some naïve birds show serious symptoms which can result in death. Surveillance of vectors and parasites are important to understand and control this disease. Although avian malaria has been found in Japan, detailed prevalence and dynamics remained understudied. We aimed to observe annual changes in the abundance of mosquitoes and the prevalence of avian Plasmodium parasites in Japan. Mosquitoes were collected using dry ice traps over a 10-year period, at a fixed research area located in Kanagawa prefecture. Collected mosquitoes were investigated for the species composition, population size and prevalence of avian Plasmodium by PCR. Mosquitoes belonging to 13 species in 7 genera were collected (n=8,965). The dominant species were Aedes (Ae.) albopictus and Culex (Cx.) pipiens group (gr.). Seven avian Plasmodium lineages, all of which were previously known, were detected from Cx. pipiens gr., Ae. albopictus, and Tripteroides bambusa. Three genetic lineages were dominant and were probably transmitted by Cx. pipiens gr. whose could be the primary vector of these parasites. Annual variations in the seasonal prevalence of mosquitoes and avian Plasmodium were revealed for the first time during recent 10 years in Japan. Namely, avian Plasmodium occurrence in the vector population peaked often in June to July and September to October when the density of the vector population was presumably high enough for the transmission of avian Plasmodium upon appearance of infected birds.

First report of haemosporidia and associated risk factors in red junglefowl (Gallus gallus) in China

Background

Avian haemosporidia infect both domestic and wild birds, causing anemia, acute tissue degeneration, and depopulation in wild birds. Poultry and wild birds have been reported as common reservoirs of haemosporidia, but limited information is available for red junglefowl (Gallus gallus) in China. The present study investigated the prevalence and molecular characterization of haemosporidia in red junglefowl.

Methods

Blood samples were collected from 234 red junglefowl from Jinghong City of Yunnan Province, and genomic DNA was extracted from these samples. The prevalence of haemosporidia was determined by nested PCR targeting the mitochondrial cytochrome b (cytb) gene. Molecular characterization was investigated based on phylogenetic analysis of cytb sequences, and associated risk factors were analyzed using the Chi-square (χ²) test.

Results

The overall prevalence of haemosporidia was 74.8% (175/234), and three species were identified, namely Haemoproteus enucleator, Leucocytozoon californicus, and Plasmodium juxtanucleare. The prevalence of haemosporidia in adult fowl (81.1%, 107/132) was significantly higher (χ² = 6.32, df = 1, P = 0.012) than that in juveniles (66.7%, 68/102). Three novel haemosporidian lineages were revealed.

Conclusions

This study examined the prevalence and identified species of avian haemosporidians in red junglefowl, providing new information on the molecular epidemiology and geographical distribution of haemosporidian parasites. Our results indicated high prevalence and diverse species distribution of these haemosporidians in red junglefowl. To the best of our knowledge, this is the first record of haemosporidian infection in red junglefowl in China.

Graphical Abstract

A widespread survey of avian haemosporidia in deceased wild birds of Japan: the hidden value of personally collected samples

Widespread surveys of avian haemosporidia (Plasmodium, Haemoproteus, and Leucocytozoon) in wild birds have substantially advanced information on the haemosporidian fauna of Japan. However, many areas and bird species remain insufficiently investigated. Bird carcasses collected for personal specimen collection seldom reach academic audience particularly in the veterinary field. The presence of avian haemosporidia was investigated in these personally collected bird carcasses, in order to better understand the avian haemosporidian fauna in Japan. Bird carcasses were donated through personal contact upon approval of the study. Tissue samples were collected from the birds and examined for haemosporidian parasites using nested-PCR targeting the cytochrome b gene. One hundred and forty-three birds of 85 species were donated, including 34 species and two subspecies that were molecularly or collectively investigated for the first time in Japan. Avian haemosporidian DNA was detected from 37 of the 134 tested birds (27.61%). In 8 bird species, avian haemosporidia was detected for the first time. Twenty-nine lineages were detected, including 8 novel and 9 known lineages detected in Japan for the first time. Furthermore, 16 lineages were detected from novel host species. While information that could be drawn was limited and risk management of zoonotic diseases needs re-consideration, these findings expanded information on the host range and distribution of several lineages. Collectively, this method of investigation using personally collected bird samples can provide important additions to more fully understand the avian haemosporidian fauna of Japan, as well as other areas with limited investigations.

Fatal toxoplasmosis in Little Penguins (Eudyptula minor) from Penguin Island, Western Australia

Routine post mortems of deceased penguins from Penguin Island, Western Australia, found that a temporal cluster of cases presented with characteristic gross and microscopic changes, namely birds in good body condition with hepatomegaly and splenomegaly, multifocal hepatic and splenic necrosis and numerous, 1–2 μm diameter protozoan parasites within the necrotic foci.

Electron microscopy identified the protozoa as belonging to the phylum Apicomplexa. Molecular investigations by PCR gave inconsistent results. PCR performed by an external laboratory identified a novel Haemoproteus spp. organism in samples from 4 of 10 cases from this group, while PCR at Murdoch University identified Toxoplasma gondii in 12 of 13 cases (including 9 of the 10 assayed at the external laboratory). Immunohistochemistry of formalin fixed tissues also identified Toxoplasma in the hepatic and splenic lesions.

The distinctive mortalities which were observed in this group of penguins are attributed to a fulminant toxoplasmosis, with a concurrent Haemoproteus infection in some cases. Though the clinical signs of infection are unknown, the gross and microscopic appearance at post mortem is sufficiently characteristic to allow a diagnosis to be made on these features. Definitive confirmation of Toxoplasma infection can be made by immunohistochemistry or PCR.

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Deaths in Little Penguins were associated with necrosis in the liver and spleen.

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The necrotic lesions contained protozoa, free and in cysts.

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The protozoa were identified as Toxoplasma by PCR and immunohistochemistry.

First records of prevalence and diversity of avian haemosporidia in snipe species (genus Gallinago) of Japan

Migratory birds are important carriers of pathogens such as viruses, bacteria and protozoa. Avian haemosporidia have been detected from many wild birds of Japan, but the infection status of migratory birds and transmission area are still largely unknown. Gallinago snipes are long-distance migratory shorebirds, and five species migrate to or through Japan, including Latham's snipe which is near threatened. Haemosporidian parasites in four snipe species were investigated to understand the role of migratory birds in the transmission of avian haemosporidia. Namely, this study aimed: i) to investigate differences in parasite prevalence and related factors explaining infection likelihood among these migratory species, ii) to explore the diversity in haemosporidian lineages and possible transmission areas, and iii) to assess the possibility of morphological effects of infection. Blood samples were collected from snipes caught in central and southwest Japan during migration. Parasites cytb gene DNA were detected via PCR-based testing, and detected lineages were phylogenetically analyzed. Additionally, factors related to prevalence and morphological effects of infection were statistically tested. 383 birds from four Gallinago snipe species were caught, showing higher overall prevalence of avian haemosporidia (17.8 %) than reported in other wader species in previous studies. This high infection rate is presumably due to increased contact with vector insects, resultant of environmental preferences. The prevalence of Plasmodium spp. Was higher in Swinhoe's snipes, while Haemoproteus spp. Was higher in Latham's snipes. These differences are thought to be related to ecological factors including habitat use, distribution and migratory route. Six lineages detected from juveniles indicate transmission between the breeding and sampling area. Contrary to expectations, a direct link between morphological features and haemosporidian parasite infection were not detected. These findings provide valuable information for conservation of this endangered migratory bird group. Further studies linking biological and parasitological research are anticipated to contribute to conservational actions.

Description of Haemoproteus asymmetricus n. sp. (Haemoproteidae), with remarks on predictability of the DNA haplotype networks in haemosporidian parasite taxonomy research

Haemoproteus species (Haemosporida, Haemoproteidae) are cosmopolitan blood parasites, which have been neglected for over 100-years, but attracted attention recently due to reports of severe and even lethal haemoproteosis in birds and vectors. Approximately 150 species of avian Haemoproteus have been described and named, but molecular data suggest that hundreds of independently evolving molecular lineages might occur, indicating the existence of a remarkable undescribed species diversity. It is timely to develop a methodology, which allow the application of available genetic data in taxonomy of haemosporidians on species levels. This study aimed to test a hypothesis suggesting that DNA haplotype networks might aid in targeting genetically distinct, but still undescribed parasites, and might be used to direct taxonomic studies on haemosporidian species levels. Mainly, we tested a prediction that the lineage hTUPHI01, a common Haemoproteus parasite of Turdus philomelos, might be a new species, which is morphologically similar and genetically closely related to the parasites of Haemoproteus minutus group. Blood samples of T. philomelos naturally infected with this parasite lineage were collected and studied using microscopic examination of blood films and PCR-based methods. Haemoproteus asymmetricus n. sp. was found in this bird, described and characterised molecularly using partial cytochrome b (cytb) sequences. The new species shared some features with parasites of the H. minutus group, as was predicted by the DNA haplotype network. Due to the visualisation of closely related lineages as well as the evaluation of their host and geographic distributions, DNA haplotype networks can be recommended as the helpful methodology, able to direct and speed practical work on parasite species taxonomy and pathogen biodiversity. The combined molecular phylogenetic and morphological approaches showed that the well-supported clades in Bayesian phylogenetic trees based on the partial cytb gene sequences contain morphologically remarkably different Haemoproteus parasite species, which however, share some basic biological features. Phylogenetic analysis can be used for prediction of these basic features in still undescribed parasites. This study calls for further fusion of advanced molecular and microscopy approaches for better understanding haemosporidian parasite biology.

Prevalence and Diversity of Avian Haemosporidians May Vary with Anthropogenic Disturbance in Tropical Habitats in Myanmar

Avian malaria and related haemosporidians (genera Haemoproteus, Plasmodium and Leucocytozoon) infect most clades of bird. Although these parasites are present in almost all continents, they have been irregularly studied across different geographical regions. Despite the high bird diversity in Asia, the diversity of avian haemosporidians in this region is largely unknown. Moreover, anthropogenic changes to habitats in tropical regions may have a profound impact on the overall composition of haemosporidian communities. Here we analyzed the diversity and host association of bird haemosporidians from areas with different degrees of anthropogenic disturbance in Myanmar, revealing an unexplored diversity of these parasites (27% of newly-discovered haemosporidian lineages, and 64% of new records of host–parasite assemblages) in these tropical environments. This newly discovered diversity will be valuable for detecting host range and transmission areas of haemosporidian parasites. We also found slightly higher haemosporidian prevalence and diversity in birds from paddy fields than in individuals from urban areas and hills, thus implying that human alteration of natural environments may affect the dynamics of vector-borne diseases. These outcomes provide valuable insights for biodiversity conservation management in threatened tropical ecosystems.

Haemosporidian prevalence, parasitaemia and aggregation in relation to avian assemblage life history traits at different elevations

The transmission of vector-borne protozoa such as parasites of the Order Haemosporida is dependent on both biotic and abiotic factors such as host life history traits and environmental conditions. This study aimed to identify the variables that determine haemosporidian prevalence, parasitaemia and aggregation within the context of elevation and avian life history traits in Central Veracruz, Mexico. We sampled 607 birds from 88 species; we used microscopy and the mtDNA cytochrome b gene to detect parasites. We found an overall prevalence of 32.3%. Haemosporidian prevalence was 21.6% in tropical sub-deciduous forest (at sea level), 38% in tropical deciduous forest (265 m above sea level (asl)), 19.4% in montane cloud forest (1630 m asl), and 51.7% in pine-oak forest (2790 m asl). The prevalence of each parasite genus was strongly influenced by elevation (a proxy of habitat type). Plasmodium showed the highest prevalence at low elevation. Haemoproteus increased in prevalence with elevation. Leucocytozoon displayed the highest prevalence at the highest elevation (pine-oak forest). Haemoproteus spp. and Leucocytozoon spp. prevalences were higher in open cup than in closed nests. Haemoproteus prevalence and haemosporidian parasitaemia were lower in solitary birds than birds with pairing and gregarious behavior. Haemosporidian aggregation decreased with elevation, yielding the significantly lowest values at the pine-oak forest. Elevation distribution patterns of prevalence for each genus were similar to those previously reported in other geographical areas (e.g., South America, Europe).

A fatal case of a captive snowy owl (Bubo scandiacus) with Haemoproteus infection in Japan

Parasites of the genus Haemoproteus are vector-borne avian haemosporidia commonly found in bird species of the world. Haemoproteus infections are typically considered relatively benign in birds. However, some Haemoproteus species cause severe disease and mortality, especially for captive birds removed from their original habitat. In September 2018, a captive 15-year-old snowy owl (Bubo scandiacus), kept in a zoological garden of Japan, died subacutely after presenting leg dysfunction. This case showed significantly low PCV and elevated AST, ALT, CK, and LDH values. Many megalomeronts with prominent morphological characteristics of Haemoproteus were observed in the left leg muscles. Those megalomeronts exhibited multilocular structures and were internally filled with merozoites. A new lineage of Haemoproteus was detected by subsequent PCR for the cytochrome b (cytb) gene of avian haemosporidia from DNA extracted from several organ tissues. The detected lineage was classified in the subgenus Parahaemoproteus and was similar to those from the wild birds inhabiting the region including the study area, suggesting that this snowy owl likely acquired its infection from wild birds. This is the first report of a fatal case of a captive bird with a locally transmitted Haemoproteus infection in Japan. We considered the pathogenicity of this infection in conjunction with the clinical course and hematology results. We surmise that snowy owls may be particularly susceptible to infection with Haemoproteus parasites, and warming northern temperatures may exacerbate the overall health of these and other high latitude birds. Further research into the prevalence of Haemoproteus in wild birds near zoological gardens and potential biting midge vectors is necessary for the ex situ conservation of introduced birds.

Contaminations contaminate common databases

The polymerase chain reaction (PCR) is a very powerful method to detect and identify pathogens. The high sensitivity of the method, however, comes with a cost; any of the millions of artificial DNA copies generated by PCR can serve as a template in a following experiment. If not identified as contaminations, these may result in erroneous conclusions on the occurrence of the pathogen, thereby inflating estimates of host range and geographic distribution. In the present paper, we evaluate whether several published records of avian haemosporidian parasites, in either unusual host species or geographical regions, might stem from PCR contaminations rather than novel biological findings. The detailed descriptions of these cases are shedding light upon the steps in the work process that might lead to PCR contaminations. By increasing the awareness of this problem, it will aid in developing procedures that keep these to a minimum. The examples in the present paper are from haemosporidians of birds, however the problem of contaminations and suggested actions should apply generally to all kinds of PCR‐based identifications, not just of parasites and pathogens.

Prevalence and genetic diversity of avian haemosporidian parasites at an intersection point of bird migration routes: Sultan Marshes National Park, Turkey

Avian haemosporidians (Haemosporida) represent a globally distributed, species-rich multiparasite-multihost host-parasite system. Each year, many of these parasite lineages are carried between temperate and tropical regions by migratory birds. While several factors can limit the transmission of avian haemosporidians to new areas, recent studies have shown that some abundant parasites can sometimes disperse and be transmitted in new areas to become emerging infectious diseases. In this study, we investigated the prevalence and diversity of avian haemosporidian parasites in Sultan Marshes National Park (SMNP), a major stopover site in the eastern Mediterranean flyway, and we evaluated the potential for avian haemosporidians in SMNP to be transmitted to areas outside of their known distributions. We sampled a total of 565 migratory and resident birds belonging to 39 species and 23 families. We applied both molecular and microscopic methods to detect and identify avian haemosporidian infections and also quantified the frequency of potential abortive infections. We identified a total of 52 different mitochondrial cytochrome b (cyt b) parasite lineages belonging to the genera Plasmodium (N = 12), Haemoproteus (N = 31), and Leucocytozoon (N = 9) in 193 (34.2%) infected birds. Ten of the lineages were reported for the first time. Our findings show that numerous parasite lineages are actively transmitted among resident bird species of SMNP. Our findings also revealed new parasite-host interactions while considering the role of possible abortive infections. The relatively high frequency of presumed abortive infections suggests that analyses of datasets generated only by PCR-based methods should be interpreted with caution. We also compared the prevalence and distribution of avian haemosporidian infections in both resident and migratory bird species and showed that haemosporidian prevalence was related to bird migratory behavior. The results of this study contribute to a better understanding of the ecological and genetic adaptations associated with changes in transmission areas of avian haemosporidian parasites.

Mosquito identification and haemosporidian parasites detection in the enclosure of the African penguins (Spheniscus demersus) at the SANBI zoological garden

The National Zoological Gardens (NZG) is a facility of the South African National Biodiversity Institute (SANBI) and the largest zoo in southern Africa. Among the 9000 captive animals kept by the NZG, is the endangered African penguin (Spheniscus demersus). There have been several post-mortem reports on deaths of penguins in the NZG due to haemosporidian infections, however, the haemosporidian lineages involved and possible insect vector are unknown. Haemosporidians are apicomplexan parasites that infect vertebrates through blood-sucking dipteran insects. Therefore, the current study aimed to identify mosquitoes that are potential vectors found within the African penguin enclosure as well as to detect the haemosporidian parasites from these insects using nested-PCR and real-time PCR (qPCR) analyses. Mosquito samples were collected using an overnight UV-light trap setup for 3 months. From the 65 pooled samples representing 325 mosquitoes, morphological and molecular analysis showed that Culex pipiens (52.31%) was the dominant species followed by Cx. t heileri (30.77%) and Cx. quinquefasciatus (16.92%). Nested-PCR detected parasite DNA of Leucocytozoon sp. and Plasmodium sp. The Cx. pipiens had the highest minimum infection rate (MIR) of 5.88% by nested-PCR and 9.41% by qPCR whilst Cx. quinquefasciatus had MIR of 3.64% in both assays and no haemosporidian parasites were detected from Cx. t heileri. One Cx. pipiens sample had a co-infection of both Plasmodium sp. and Leucocytozoon sp. detected by nested-PCR. These findings suggest that effective control measures for blood-sucking dipteran insects is required at the NZG and more studies should be conducted to determine the actual prevalence of these haemosporidian parasites among other bird species within NZG.

Adaptive landscape genetics and malaria across divergent island bird populations

Environmental conditions play a major role in shaping the spatial distributions of pathogens, which in turn can drive local adaptation and divergence in host genetic diversity. Haemosporidians, such as Plasmodium (malaria), are a strong selective force, impacting survival and fitness of hosts, with geographic distributions largely determined by habitat suitability for their insect vectors. Here, we have tested whether patterns of fine-scale local adaptation to malaria are replicated across discrete, ecologically differing island populations of Berthelot's pipits Anthus berthelotii. We sequenced TLR4, an innate immunity gene that is potentially under positive selection in Berthelot's pipits, and two SNPs previously identified as being associated with malaria infection in a genome-wide association study (GWAS) in Berthelot's pipits in the Canary Islands. We determined the environmental predictors of malaria infection, using these to estimate variation in malaria risk on Porto Santo, and found some congruence with previously identified environmental risk factors on Tenerife. We also found a negative association between malaria infection and a TLR4 variant in Tenerife. In contrast, one of the GWAS SNPs showed an association with malaria risk in Porto Santo, but in the opposite direction to that found in the Canary Islands GWAS. Together, these findings suggest that disease-driven local adaptation may be an important factor in shaping variation among island populations.

Spatial distribution, prevalence and diversity of haemosporidians in the rufous-collared sparrow, Zonotrichia capensis

BACKGROUND

Parasite prevalence and diversity are determined by the distribution of hosts and vectors and by the interplay among a suite of environmental factors. Distributions of parasite lineages vary based on host susceptibility and geographical barriers. Hemoparasites of the genera Haemoproteus and Plasmodium have wide distributions, and high prevalence and genetic diversity within perching birds (Order Passeriformes). The rufous-collared sparrow (Zonotrichia capensis) is widely distributed in Central and South America across an immense diversity of environments from sea level to more than 4000 meters above sea level. It therefore provides an excellent model to investigate whether altitudinal and latitudinal gradients influence the distribution, prevalence and diversity of haemosporidian parasites, their population structure and the biogeographical boundaries of distinct parasite lineages.

RESULTS

We assembled samples from 1317 rufous-collared sparrows spanning 75 locales from across Central and South America (between 9.5°N and 54°S; 10-4655 meters above sea level). We used DNA sequence data from a fragment of the mitochondrial cytochrome b gene (cytb) of Haemoproteus and Plasmodium from 325 positive samples and found prevalences of 22 and 3%, respectively. Haemoproteus exhibited a higher prevalence than Plasmodium but with comparatively lower genetic diversity. We detected a relationship of Plasmodium and Haemoproteus prevalence with altitude and latitude; however, altitude and latitude did not influence parasite diversity.

CONCLUSIONS

Parasite lineages showed a phylogeographical boundary coincident with the Andes Mountains, although we also observed a north-south disjunction in Peru for Haemoproteus. Haemosporidian distribution was not homogeneous but differed based on latitude and altitude. This is most probably due to environmental factors that have influenced both vector distribution and abundance, as well as parasite development. Our study provides key insights on the distribution of haemoparasite lineages and parasite dynamics within hosts.

Prevalence and diversity of haemosporidian parasites in the yellow-rumped warbler hybrid zone

Parasites can play a role in speciation, by exerting different selection pressures on different host lineages, leading to reproductive barriers in regions of possible interbreeding. Hybrid zones therefore offer an ideal system to study the effect of parasites on speciation. Here, we study a hybrid zone in the foothills of the Rocky Mountains where two yellow-rumped warbler subspecies, Setophaga coronata coronata and S. c. auduboni, interbreed. There is partial reproductive isolation between them, but no evidence of strong assortative mating within the hybrid zone, suggesting the existence of a postzygotic selection against hybrids. Here, we test whether haemosporidian parasites might play a role in selecting against hybrids between S. c. coronata and S. c. auduboni. We screened birds from five transects across the hybrid zone for three phylogenetic groupings of avian haemosporidians Plasmodium, Haemoproteus and Leucocytozoon parasites and quantified intensity of infection. Contrary to our prediction, hybrids did not have higher haemosporidian parasite prevalence. Variation in Haemoproteus prevalence was best explained by an interaction between a birds' hybrid index and elevation, while the probability of infection with Leucocytozoon parasites was only influenced by elevation. We also found no significant difference in the diversity of haemosporidian lineages between the warbler subspecies and their hybrids. Finally, intensity of infection by Haemoproteus increased significantly with elevation, but was not significantly linked to birds' hybrid index. In conclusion, our data suggest that haemosporidian parasites do not seem to play a major role in selecting against hybrids in this system.

Malaria parasites and related haemosporidians cause mortality in cranes: a study on the parasites diversity, prevalence and distribution in Beijing Zoo

Background

Malaria parasites and related haemosporidian parasites are widespread and may cause severe diseases in birds. These pathogens should be considered in projects aiming breeding of birds for purposes of sustained ex situ conservation. Cranes are the ‘flagship species’ for health assessment of wetland ecosystems, and the majority of species are endangered. Malaria parasites and other haemosporidians have been reported in cranes, but the host-parasite relationships remain insufficiently understood. Morbidity of cranes due to malaria has been reported in Beijing Zoo. This study report prevalence, diversity and distribution of malaria parasites and related haemosporidians in cranes in Beijing Zoo and suggest simple measures to protect vulnerable individuals.

Methods

In all, 123 cranes (62 adults and 61 juveniles) belonging to 10 species were examined using PCR-based testing and microscopic examination of blood samples collected in 2007–2014. All birds were maintained in open-air aviaries, except for 19 chicks that were raised in a greenhouse with the aim to protect them from bites of blood-sucking insects. Bayesian phylogenetic analysis was used to identify the closely related avian haemosporidian parasites.

Results

Species of Plasmodium (5 lineages), Haemoproteus (1) and Leucocytozoon (2) were reported. Malaria parasites predominated (83% of all reported infections). The overall prevalence of haemosporidians in juveniles was approximately seven-fold higher than in adults, indicating high susceptibility of chicks and local transmission. Juvenile and adult birds hosted different lineages of Plasmodium, indicating that chicks got infection from non-parent birds. Plasmodium relictum (pSGS1) was the most prevalent malaria parasite. Mortality was not reported in adults, but 53% of infected chicks died, with reports of co-infection with Plasmodium and Leucocytozoon species. All chicks maintained in the greenhouse were non-infected and survived. Species of Leucocytozoon were undetectable by commonly used PCR protocol, but readily visible in blood films.

Conclusion

Crane chicks often die due to malaria and Leucocytozoon infections, which they likely gain from wild free-living birds in Beijing Zoo. Molecular diagnostics of crane Leucocytozoon parasites needs improvement. Because the reported infections are mainly chick diseases, the authors recommend maintaining of juvenile birds in vector-free facilities until the age of approximately 6 months before they are placed in open-air aviaries.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2385-3) contains supplementary material, which is available to authorized users.

Prevalence of avian haemosporidia among injured wild birds in Tokyo and environs, Japan

Avian haemosporidia have been reported in various birds of Japan, which is part of the East Asian-Australian flyway and is an important stopover site for migratory birds potentially carrying new pathogens from other areas. We investigated the prevalence of avian malaria in injured wild birds, rescued in Tokyo and surrounding areas. We also evaluated the effects of migration by examining the prevalence of avian malaria for each migratory status. 475 birds of 80 species were sampled from four facilities. All samples were examined for haemosporidian infection via nested polymerase chain reaction (PCR) of the cytochrome b (cytb) gene. 100 birds (21.1%) of 43 species were PCR positive for avian haemosporidia. Prevalence in wintering birds, migratory breeders, and resident birds was 46.0%, 19.3%, 17.3% respectively. There was a bias in wintering birds due to Eurasian coot (Fulica atra) and Anseriformes. In wintering birds, lineages which are likely to be transmitted by Culiseta sp. in Northern Japan and lineages from resident species of Northern Japan or continental Asia were found, suggesting that wintering birds are mainly infected at their breeding sites. Meanwhile, there were numerous lineages found from resident and migratory breeders, suggesting that they are transmitted in Japan, some possibly unique to Japan. Although there are limits in studying rescued birds, rehabilitation facilities make sampling of difficult-to-catch migratory species possible and also allow for long-term monitoring within areas.

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Prevalence of avian malaria in rescued wild birds in Japan has been demonstrated.

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Many new lineages have been identified, including possibly unique to Japan.

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Rehabilitation facilities allow sampling and monitoring of wild birds possible.

Monitoring the Prevalence of Leucocytozoon sabrazesi in Southern China and Testing Tricyclic Compounds against Gametocytes

Leucocytozoon parasites infect many species of avian hosts, including domestic chicken, and can inflict heavy economic loss on the poultry industry. Two major species of Leucocytozoon parasites have been reported in China, L. sabrazesi and L. caulleryi, although L. sabrazesi appears to be more widespread than L. caulleryi in southern China. The traditional method for detecting Leucocytozoon infection is microscopic examination of blood smears for the presence of mature gametocytes in circulation, which may miss infections with low parasitemia (gametocytemia) or immature gametocytes. Here we developed a PCR-based method to monitor L. sabrazesi infections at seven sites in four provinces of China after testing two PCR primer pairs based on parasite mitochondrial cytochrome b (cytb) and cytochrome c oxidase III (coxIII) genes. We compared the results of PCR detection with those of microscopic observation. As expected, the PCR assays were more sensitive than microscope examination in detecting L. sabrazesi infection and were able to detect parasite DNA after gametocytes disappeared in the blood stream. Using these methods, we investigated monthly dynamics of L. sabrazesi in chickens from a free-range farm in Xiamen, Fujian province of China, over one year. Our results showed that chickens were infected with L. sabrazesi year-round in southern China. Finally, we tested several compounds for potential treatment of Leucocytozoon infections, including primaquine, ketotifen, clomipramine hydrochloride, desipramine hydrochloride, sulfaquinoxaline, and pyrimethamine. Only primaquine had activity against L. sabrazesi gametocytes. Our results provide important information for controlling parasite transmission in southern China and disease management.

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.

Manifold habitat effects on the prevalence and diversity of avian blood parasites

Habitats are rapidly changing across the planet and the consequences will have major and long-lasting effects on wildlife and their parasites. Birds harbor many types of blood parasites, but because of their relatively high prevalence and ease of diagnosis, it is the haemosporidians – Plasmodium, Haemoproteus, and Leucocytozoon – that are the best studied in terms of ecology and evolution. For parasite transmission to occur, environmental conditions must be permissive, and given the many constraints on the competency of parasites, vectors and hosts, it is rather remarkable that these parasites are so prevalent and successful. Over the last decade, a rapidly growing body of literature has begun to clarify how environmental factors affect birds and the insects that vector their hematozoan parasites. Moreover, several studies have modeled how anthropogenic effects such as global climate change, deforestation and urbanization will impact the dynamics of parasite transmission. This review highlights recent research that impacts our understanding of how habitat and environmental changes can affect the distribution, diversity, prevalence and parasitemia of these avian blood parasites. Given the importance of environmental factors on transmission, it remains essential that researchers studying avian hematozoa document abiotic factors such as temperature, moisture and landscape elements. Ultimately, this continued research has the potential to inform conservation policies and help avert the loss of bird species and threatened habitats.

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Review of recent literature studying habitat effects on avian blood parasites.

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Habitat affects the prevalence, parasitemia, distribution and diversity of avian hematozoa.

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Environmental conditions must be permissive for parasite transmission to occur.

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Anthropogenic environmental changes will affect host–vector–parasite interactions.

The Gametocytes of Leucocytozoon sabrazesi Infect Chicken Thrombocytes, Not Other Blood Cells

Leucocytozoon parasites infect a large number of avian hosts, including domestic chicken, and cause significant economical loss to the poultry industry. Although the transmission stages of the parasites were observed in avian blood cells more than a century ago, the specific host cell type(s) that the gametocytes infect remain uncertain. Because all the avian blood cells, including red blood cells (RBCs), are nucleated, and the developing parasites dramatically change the morphology of the infected host cells, it has been difficult to identify Leucocytozoon infected host cell(s). Here we use cell-type specific antibodies to investigate the identities of the host cells infected by Leucocytozoon sabrazesi gametocytes. Anti-RBC antibodies stained RBCs membrane strongly, but not the parasite-infected cells, ruling out the possibility of RBCs being the infected host cells. Antibodies recognizing various leukocytes including heterophils, monocytes, lymphocytes, and macrophages did not stain the infected cells either. Antisera raised against a peptide of the parasite cytochrome B (CYTB) stained parasite-infected cells and some leukocytes, particularly cells with a single round nucleus as well as clear/pale cytoplasm suggestive of thrombocytes. Finally, a monoclonal antibody known to specifically bind chicken thrombocytes also stained the infected cells, confirming that L. sabrazesi gametocytes develop within chicken thrombocytes. The identification of L. sabrazesi infected host cell solves a long unresolved puzzle and provides important information for studying parasite invasion of host cells and for developing reagents to interrupt parasite transmission.

Molecular characterization of five widespread avian haemosporidian parasites (Haemosporida), with perspectives on the PCR-based detection of haemosporidians in wildlife

Haemosporidians (Haemosporida) are cosmopolitan in birds. Over 250 species of these blood parasites have been described and named; however, molecular markers remain unidentified for the great majority of them. This is unfortunate because linkage between DNA sequences and identifications based on morphological species can provide important information about patterns of transmission, virulence, and evolutionary biology of these organisms. There is an urgent need to remedy this because few experts possess the knowledge to identify haemosporidian species and few laboratories are involved in training these taxonomic skills. Here, we describe new mitochondrial cytochrome b markers for the polymerase chain reaction (PCR)-based detection of four widespread species of avian Haemoproteus (Haemoproteus hirundinis, Haemoproteus parabelopolskyi, Haemoproteus pastoris, Haemoproteus syrnii) and 1 species of Plasmodium (Plasmodium circumflexum). Illustrations of blood stages of the reported species are given, and morphological and phylogenetic analyses identify the DNA lineages that are associated with these parasites. This study indicates that morphological characters, which have been traditionally used in taxonomy of avian haemosporidian parasites, have a phylogenetic value. Perspectives on haemosporidian diagnostics using microscopic and PCR-based methods are discussed, particularly the difficulties in detection of light parasitemia, coinfections, and abortive parasite development. We emphasize that sensitive PCR amplifies more infections than can be transmitted; it should be used carefully in epidemiology studies, particularly in wildlife parasitology research. Because molecular studies are describing remarkably more parasite diversity than previously expected, the need for traditional taxonomy and traditional biological knowledge is becoming all the more crucial. The linkage of molecular and morphological approaches is worth more of the attention of researchers because this approach provides new knowledge for better understanding insufficiently investigated lethal diseases caused by haemosporidian infections, particularly on the exoerythrocytic (tissue) and vector stages. That requires close collaboration between researchers from different fields with a common interest.

Multi-strain infections and 'relapse' of Leucocytozoon sabrazesi gametocytes in domestic chickens in southern China

Leucocytozoon parasites infect many species of avian hosts, including domestic chicken, and can inflict heavy economic loss to the poultry industry. Although the prevalence and distribution of two Leucocytozoon species (L. sabrazesi and L. caulleryi) have been reported in China previously, there are many questions related to the parasite infection that remain unanswered, including population diversity and transmission dynamics in domestic chickens. Here we surveyed chicken blood samples from seven sites in four provinces of China to identify Leucocytozoon infection, characterized parasite diversity within individual infected hosts and between sampling sites, and investigated the dynamics of gametocytemia in chickens over time. We found high infection rates in three of the seven sites. Clustering parasite sequences of the mitochondrial cytochrome oxidase III (coxIII) and cytochrome b (cytb) genes showed lack of grouping according to geographic origins and individual hosts carrying large numbers of L. sabrazesi strains. Monitoring gametocytemia in blood samples from infected chickens over time showed ‘relapse’ or persistence of low-level gametocytemia for 4–5 months, which could be explored as an in vivo model for testing drugs against liver stages of Apicomplexan parasites. This study provides important information on population diversity and transmission dynamics of L. sabrazesi and for disease control.

Phylogenetic comparison of avian haemosporidian parasites from resident and migratory birds in northern Japan

We analyzed blood samples of resident and migratory Japanese birds to evaluate the prevalence and genetic background of avian blood parasites in northern Japan. We used PCR targeting the mitochondrial cytochrome b gene to examine infections of Leucocytozoon, Haemoproteus, and Plasmodium parasites in blood samples from 243 birds of 14 species in three orders (Passeriformes, Columbiformes, and Anseriformes). Sequences were subjected to phylogenetic analysis. The infection rate was 21% in pigeons (Columbiformes) and 17% in Anseriformes. A high infection rate of 93.8% was found in crow species (Passeriformes). Haemoproteus and Plasmodium parasites were detected in only two species. Infected blood samples obtained from seven bird species involved two major clades of Leucocytozoon, which were divided between resident and migratory birds. The parasites, which are genetically distinct from parasites in Japanese resident birds, may have been introduced to Japan by migratory bird species.

First report of birds infection by intestinal parasites in Khorramabad, west Iran

Parasitic infections in birds are omnipresent, even when they occur in low amounts, may result in subclinical diseases. There aren't any studies, based on Iranian data, investigating the prevalence of intestinal parasitic infections in some birds' species. We conducted a cross-sectional study between December 2011 and December 2012. The fecal samples were taken from 451 birds including hen, turkey, sparrow, pigeon and decorative birds. The samples screened for intestinal parasitic infections using direct smear, formalin-ether concentration technique, modified Ziehl-Neelsen staining, Culture in RPMI 1640 medium, sporulation with potassium dichromate and Trichrome and Giemsa staining. Out of 451 birds' species, 157 (34.8 %), were infected with one or more type of intestinal parasites. We identified two nematode, two cestoda species and five protozoan parasites species. No trematodes were found in the samples studied. The parasites identified among birds involved Raillietina spp. (4.2 %) and Eimeria spp. (7.1 %) were the most common helminthes and protozoa respectively. From total of birds study, 12 (2.7 %) and 6 (1.3 %) have two and three mixed infections respectively. Intestinal parasitic infections are common in birds in west Iran. The future studies are needed in order to determine to which extent the infections influence mortality and performance of the birds.

Altitudinal variation in haemosporidian parasite distribution in great tit populations

BACKGROUND

One of the major issues concerning disease ecology and conservation is knowledge of the factors that influence the distribution of parasites and consequently disease outbreaks. This study aimed to investigate avian haemosporidian composition and the distribution of these parasites in three altitudinally separated great tit (Parus major) populations in western Switzerland over a three-year period. The objectives were to determine the lineage diversity of parasites occuring across the study populations and to investigate whether altitudinal gradients govern the distribution of haemosporidian parasites by lineage.

METHODS

In this study molecular approaches (PCR and sequencing) were used to detect avian blood parasites (Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp.) in populations of adult great tits caught on their nests during three consecutive breeding seasons.

RESULTS

High levels of parasite prevalence (88-96%) were found across all of the study populations with no significant altitude effect. Altitude did, however, govern the distribution of parasites belonging to different genera, with Plasmodium parasites being more prevalent at lower altitudes, Leucocytozoon parasites more at high altitude and Haemoproteus parasite prevalence increasing with altitude. A total of 27 haemosporidian parasite lineages were recorded across all study sites, with diversity showing a positive correlation to altitude. Parasites belonging to lineage SGS1 (P. relictum) and PARUS4 and PARUS19 (Leucocytozoon sp.) dominated lower altitudes. SW2 (P. polare) was the second most prevalent lineage of parasite detected overall and these parasites were responsible for 68% of infections at intermediate altitude, but were only documented at this one study site.

CONCLUSIONS

Avian haemosporidian parasites are not homogeneously distributed across host populations, but differ by altitude. This difference is most probably brought about by environmental factors influencing vector prevalence and distribution. The high occurrence of co-infection by different genera of parasites might have pronounced effects on host fitness and should consequently be investigated more rigorously.

Booster responses by oral vaccination with transgenic plants against chicken leucocytozoonosis

We developed a transgenic potato (TrP/R7) expressing the recombinant R7 (rR7) antigen for use as an oral vaccine to protect against a chicken protozoan disease, chicken leucocytozoonosis. The TrP/R7 potato was produced by Agrobacterium tumefaciens-mediated transformation and regeneration, and the R7 gene insertion into potato chromosomes was confirmed by genomic polymerase chain reaction and Southern hybridization. rR7 antigen expression in TrP/R7 potato was also confirmed by sandwich enzyme-linked immunosorbent assay and western blotting using an antibody against the second-generation schizont of Leucocytozoon caulleryi. A transgenic potato clone with the highest rR7 antigen expression (3 µg rR7 antigen per gram of fresh-weight potato leaves) was selected, cultivated, and used in oral administration experiments to examine its ability to boost immunity. Chickens were immunized with chicken leucocytozoonosis vaccine "Hokken" by injection, and chickens that developed moderate levels of antibody titres were fed with TrP/R7 leaves. Chickens fed with TrP/R7 leaves showed increased antibody responses. In contrast, chickens fed with non-transgenic potato leaves showed a continuous decrease in antibody titres. Furthermore, chickens fed with TrP/R7 potato leaves showed strong resistance against experimental challenge with L. caulleryi infection. This study demonstrates the use of a plant-based oral vaccine to boost immunity against a protozoan disease.