Cases of mortality in little penguins (Eudyptula minor) in New Zealand associated with avian malaria

New insight into avian malaria vectors in New Zealand

BACKGROUND

Mosquitoes (Culicidae) are vectors for most malaria parasites of the Plasmodium species and are required for Plasmodium spp. to complete their life cycle. Despite having 16 species of mosquitoes and the detection of many Plasmodium species in birds, little is known about the role of different mosquito species in the avian malaria life cycle in New Zealand.

METHODS

In this study, we used nested polymerase chain reaction (PCR) and real-time PCR to determine Plasmodium spp. prevalence and diversity of mitochondrial cytochrome b gene sequences in wild-caught mosquitoes sampled across ten sites on the North Island of New Zealand during 2012-2014. The mosquitoes were pooled by species and location collected, and the thorax and abdomens were examined separately for Plasmodium spp. DNA. Akaike information criterion (AIC) modeling was used to test whether location, year of sampling, and mosquito species were significant predictors of minimum infection rates (MIR).

RESULTS

We collected 788 unengorged mosquitoes of six species, both native and introduced. The most frequently caught mosquito species were the introduced Aedes notoscriptus and the native Culex pervigilans. Plasmodium sp DNA was detected in 37% of matched thorax and abdomen pools. When considered separately, 33% of abdomen and 23% of thorax pools tested positive by nested PCR. The MIR of the positive thorax pools from introduced mosquito species was 1.79% for Ae. notoscriptus and 0% for Cx. quinquefasciatus, while the MIR for the positive thorax pools of native mosquito species was 4.9% for Cx. pervigilans and 0% for Opifex fuscus. For the overall MIR, site and mosquito species were significant predictors of Plasmodium overall MIR. Aedes notoscriptus and Cx. pervigilans were positive for malaria DNA in the thorax samples, indicating that they may play a role as avian malaria vectors. Four different Plasmodium lineages (SYAT05, LINN1, GRW6, and a new lineage of P (Haemamoeba) sp. AENOT11) were identified in the pooled samples.

CONCLUSIONS

This is the first detection of avian Plasmodium DNA extracted from thoraxes of native Culex and introduced Aedes mosquito species in New Zealand and therefore the first study providing an indication of potential vectors in this country.

Pharmacokinetics in Penguins Compared to Other Avian Species: A Review of Enrofloxacin and Voriconazole

Australasia is home to unique and endangered avian species. Drug administration to this group of animal patients for prophylaxis and treatment is challenging from a number of different perspectives. A key limitation for optimal drug dosing in birds is the lack of published pharmacokinetic studies to guide dose requirements. The aim of this review was to systematically investigate published literature on pharmacokinetics in penguin species and compare that with the pharmacokinetics of other avian species with a focus on two drugs: enrofloxacin and voriconazole. The review was conducted following PRISMA guidelines. A systematic literature search was performed in Pubmed, Embase, Scopus, and Web of Science databases. A key finding is that penguin pharmacokinetics differs from other avian species, with weight-adjusted AUC and Cmax values higher than most other avian species (e.g., for enrofloxacin, the AUC in the African penguin is 85.7 μg h/mL, which is more than double the other bird species). Doses for some avian species may be successfully extrapolated from other avian species; however, it appears important to consider factors other than just body weight (e.g., clearance mechanism and drug physicochemical characteristics). Consequently, there is an important need for robust pharmacokinetic data in wildlife species to ensure optimal therapy for this special group of patients. As part of this review, we identify key aspects that should be considered when estimating dose in species for which there is limited pharmacokinetic information available.

Epidemiology of protozoan and helminthic parasites in wild passerine birds of Britain and Ireland

Avian endoparasites play important roles in conservation, biodiversity and host evolution. Currently, little is known about the epidemiology of intestinal helminths and protozoans infecting wild birds of Britain and Ireland. This study aimed to determine the rates of parasite prevalence, abundance and infection intensity in wild passerines. Fecal samples (n = 755) from 18 bird families were collected from 13 sites across England, Wales and Ireland from March 2020 to June 2021. A conventional sodium nitrate flotation method allowed morphological identification and abundance estimation of eggs/oocysts. Associations with host family and age were examined alongside spatiotemporal and ecological factors using Bayesian phylogenetically controlled models. Parasites were detected in 20.0% of samples, with corvids and finches having the highest prevalences and intensities, respectively. Syngamus (33%) and Isospora (32%) were the most prevalent genera observed. Parasite prevalence and abundance differed amongst avian families and seasons, while infection intensity varied between families and regions. Prevalence was affected by diet diversity, while abundance differed by host age and habitat diversity. Infection intensity was higher in birds using a wider range of habitats, and doubled in areas with feeders present. The elucidation of these patterns will increase the understanding of parasite fauna in British and Irish birds.

Avian haemosporidian parasites in captive and free-ranging, wild birds from zoological institutions in Switzerland: Molecular characterization and clinical importance

Avian haemosporidian parasites are widespread and infect birds from a broad variety of avian families with diverse consequences ranging from subclinical infections to severe and fatal disease. This study aimed to determine the occurrence and diversity of avian haemosporidia including associated clinical signs and pathomorphological lesions in captive and free-ranging, wild birds from two zoos and the near environment in Switzerland. Blood samples from 475 birds, including 230 captive and 245 free-ranging, wild individuals belonging to 42 different avian species from 15 orders were examined for the presence of avian haemosporidian DNA by a one-step multiplex PCR designed to simultaneously detect and discriminate the genera Plasmodium, Haemoproteus and Leucocytozoon by targeting mitochondrial genome sequences. Positive samples were additionally tested using a nested PCR targeting the cytochrome b gene of Plasmodium and Haemoproteus. The obtained amplicons were bidirectionally sequenced. This study revealed haemosporidian DNA in 42 samples, belonging to ten host species. The most commonly detected lineage was Plasmodium relictum SGS1, which was identified in 29 birds (Phoenicopterus roseus: n = 24, Alectoris graeca: n = 1, Lamprotornis superbus: n = 1, Somateria mollissima: n = 1, Spheniscus demersus: n = 1, Tetrao urogallus crassirostris: n = 1), followed by Haemoproteus sp. STRURA03 in six avian hosts (Bubo bubo: n = 5, Bubo scandiacus = 1), Plasmodium relictum GRW11 in four individuals (Phoenicopterus roseus: n = 3, Spheniscus demersus: n = 1) and Plasmodium elongatum GRW06 in one Alectura lathami lathami. A Phalacrocorax carbo was infected with Plasmodium relictum, but the exact lineage could not be determined. One mixed infection with P. relictum and Haemoproteus sp. was detected in a Bubo scandiacus. Only five individuals (Spheniscus demersus: n = 2, Somateria mollissima: n = 1, Bubo scandiacus: n = 1, Alectoris graeca: n = 1) showed clinical and pathomorphological evidence of a haemosporidian infection.

The Pathology of Fatal Avian Malaria Due to Plasmodium elongatum (GRW6) and Plasmodium matutinum (LINN1) Infection in New Zealand Kiwi (Apteryx spp.)

Avian malaria caused by Plasmodium species is a known cause of mortality in avifauna worldwide, however reports within New Zealand kiwi (Apteryx spp.) are scant. Postmortem reports from kiwi were obtained from the Massey University/Te Kunenga ki Pūrehuroa School of Veterinary Science Pathology Register from August 2010-August 2020. Gross lesions were described from postmortem reports, and archived H.E.-stained slides used for histological assessment. Nested PCR testing was performed on formalin-fixed paraffin-embedded tissue samples to assess the presence of Plasmodium spp. and Toxoplasma gondii DNA and cases with a PCR-positive result were sequenced to determine the lineage involved. Of 1005 postmortem reports, 23 cases of confirmed or suspected avian malaria were included in this study. The most consistent gross lesions included splenomegaly, hepatomegaly, and interstitial pneumonia with oedema. Histological lesions were characterised by severe interstitial pneumonia, pulmonary oedema, interstitial myocarditis, hepatic sinusoidal congestion and hypercellularity, and splenic macrophage hyperplasia and hyperaemia/congestion with numerous haemosiderophages. Cytoplasmic meronts were consistently found within endothelial cells of a variety of tissues, and within tissue macrophages of the liver, lung and spleen. A diagnosis of avian malaria was confirmed via PCR testing in 13 cases, with sequencing revealing P. matutinum (LINN1) and P. elongatum (GRW6) as the species involved. This is the largest case series describing the pathology of avian malaria as a cause of mortality in endemic New Zealand avifauna.

Molecular and epidemiological surveillance of Plasmodium spp. during a mortality event affecting Humboldt penguins (Spheniscus humboldti) at a zoo in the UK

In 2017, a mortality event affected Humboldt penguins at Chester Zoo (UK), which coincided with the diagnosis of avian malaria (AM) in some birds. AM is found worldwide wherever a competent mosquito vector is present, but the disease is particularly severe in penguins and other species that originate from non-endemic regions. To better understand the role of AM and manage its threat to penguin collections, Plasmodium was surveyed through PCR at Chester Zoo in mosquitoes, penguins, and dead free-living wild birds during and around the mortality event. Additional sequences were obtained from penguin fatalities from four other UK zoological collections. All sequences were integrated into phylogenetic analyses to determine parasite species and lineages. In total, 753/6459 positive mosquitoes were recorded (11.7% prevalence), reaching a weekly peak of 30% prevalence in mid-summer. Among penguin fatalities at Chester Zoo, several penguins presented signs and lesions compatible with AM; nevertheless, exoerythrocytic meronts were identified in only one case and Plasmodium spp. was identified in 5/22 birds. Phylogenetic analysis revealed at least five parasite cytb lineages of three Plasmodium species (P. matutinum, P. relictum and P. vaughani) circulating in mosquitoes at Chester Zoo; however, infections in free-living wild birds and penguins were only from P. matutinum. Plasmodium matutinum was confirmed as the cause of death of one penguin and was highly suspected to be the cause of death of another three. The lineage LINN1 was associated with 4/5 penguin infections. AM had a key role in the penguin multicausal mortality event. Understanding the risk of AM to penguin collections at Chester Zoo and elsewhere requires long-term surveillance to examine the association between Plasmodium infection and penguin mortality and the variability in parasite virulence. Surveillance of Plasmodium spp. in mosquitoes and local birds provides information about the parasite's transmission cycle locally, and could warn about infection risks to species of interest, which is essential for efficient disease control and prevention.

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Plasmodium infection in penguins, mosquito and wild birds is described.

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Humboldt penguin mortality due to P. matutinum was recorded for the first time.

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One of three Plasmodium spp. found in mosquitoes infected penguins and wild birds.

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Detecting Plasmodium infections is challenging despite pathological evidence.

Parasite-associated mortality in birds: the roles of specialist parasites and host evolutionary distance

The factors that influence whether a parasite is likely to cause death in a given host species are not well known. Generalist parasites with high local abundances, broad distributions and the ability to infect a wide phylogenetic diversity of hosts are often considered especially dangerous for host populations, though comparatively little research has been done on the potential for specialist parasites to cause host mortality. Here, using a novel database of avian mortality records, we tested whether phylogenetic host specialist or host generalist haemosporidian blood parasites were associated with avian host deaths based on infection records from over 81 000 examined hosts. In support of the hypothesis that host specialist parasites can be highly virulent in novel hosts, we found that the parasites that were associated with avian host mortality predominantly infected more closely related host species than expected under a null model. Hosts that died tended to be distantly related to the host species that a parasite lineage typically infects, illustrating that specialist parasites can cause death outside of their limited host range. Overall, this study highlights the overlooked potential for host specialist parasites to cause host mortality despite their constrained ecological niches.

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.

Plasmodium matutinum Causing Avian Malaria in Lovebirds (Agapornis roseicollis) Hosted in an Italian Zoo

Avian malaria is a worldwide distributed, vector-born disease of birds caused by parasites of the order Haemosporida. There is a lack of knowledge about the presence and pathogenetic role of Haemosporida in Psittacidae. Here we report a case of avian malaria infection in lovebirds (Agapornis roseicollis), with the genetic characterization of the Plasmodium species involved. The birds were hosted in a zoo located in Italy, where avian malaria cases in African penguins (Spheniscus demersus) were already reported. Animals (n = 11) were submitted for necropsy after sudden death and were subjected to further analyses including histopathology, bacteriology, and PCR for the research of haemosporidians. Clinical history, gross lesions and histopathological observation of schizonts, together with positive PCR results for Plasmodium spp., demonstrated that avian malaria was the cause of death for one animal and the possible cause of death for the other nine. The sequences obtained were compared using BLAST and analyzed for similarity to sequences available at the MalAvi database. Genetic analyses demonstrated a 100% nucleotide identity to Plasmodium matutinum LINN1 for all the obtained sequences. To our knowledge, this is the first report describing avian malaria in lovebirds.

Plasmodium matutinum Transmitted by Culex pipiens as a Cause of Avian Malaria in Captive African Penguins (Spheniscus demersus) in Italy

Avian malaria is a parasitic disease of birds caused by protozoa belonging to the genus Plasmodium, within the order Haemosporida. Penguins are considered particularly susceptible, and outbreaks in captive populations can lead to high mortality. We used a multidisciplinary approach to investigate the death due to avian malaria, occurred between 2015 and 2019, in eight African penguins (Spheniscus demersus) kept in two Italian zoos located in central Italy, and situated about 30 km apart. We also provided information about the presence and circulation of Plasmodium spp. in mosquitoes in central Italy by sampling mosquitoes in both zoos where penguin mortalities occurred. In the eight dead penguins, gross and histopathological lesions were consistent with those previously observed by other authors in avian malaria outbreaks. Organs from dead penguins and mosquitoes collected in both zoos were tested for avian malaria parasites by using a PCR assay targeting the partial mitochondrial conserved region of the cytochrome b gene. Identification at species level was performed by sequencing analysis. Plasmodium matutinum was detected in both dead penguins and in mosquitoes (Culex pipiens), while Plasmodium vaughani in Culex pipiens only. Parasites were not found in any of the PCR tested Aedes albopictus samples. Based on our phylogenetic analysis, we detected three previously characterized lineages: Plasmodium matutinum LINN1 and AFTRU5, P. vaughani SYAT05. In Culex pipiens we also identified two novel lineages, CXPIP32 (inferred morphospecies Plasmodium matutinum) and CXPIP33 (inferred morphospecies P. vaughani). Significantly, LINN1 and AFTRU5 were found to be associated to penguin deaths, although only LINN1 was detected both in penguins (along the years of the study) and in Culex pipiens, while AFTRU5 was detected in a single penguin dead in 2017. In conclusion, in our study Plasmodium matutinum was found to cause avian malaria in captive penguins kept in Europe, with Culex pipiens being its most probable vector. Our results are in agreement with previous studies suggesting that Culex pipiens is one of the main vectors of Plasmodium spp. in Europe and the Northern Hemisphere. Zoos maintaining captive penguins in temperate areas where Culex pipiens is abundant should be well aware of the risks of avian malaria, and should put every effort to prevent outbreaks, in particular during the periods when the number of vectors is higher.

Mosquitoes in an Urban Zoo: Identification of Blood Meals, Flight Distances of Engorged Females, and Avian Malaria Infections

Zoological gardens are home to a large number of vertebrate species and as such are suitable sites for both mosquito breeding and maintenance. They are excellent places for entomological studies of mosquito phenology, diversity, and blood-feeding patterns, as well as for xenomonitoring. During 2016, we sampled mosquitoes in Barcelona Zoo and used molecular methods to determine their blood-feeding patterns and the prevalence and diversity of avian malaria parasites. We also estimated the flight distance of engorged mosquitoes in the area. Overall, 1,384 adult Culex pipiens s.l., Culiseta longiareolata, and Aedes albopictus were captured. Birds dominated the diet of Cx. pipiens s.l. (n = 87) and Cs. longiareolata (n = 6), while humans were the only blood-meal source of Ae. albopictus (n = 3). Mosquitoes had a mean flight distance of 95.67 m after feeding on blood (range 38.71–168.51 m). Blood parasites were detected in the abdomen of 13 engorged Cx. pipiens s.l., eight of which had fed on magpies. Four Plasmodium lineages and a single lineage of the malaria-like parasite Haemoproteus were identified. These results suggest that Cx. pipiens s.l. is involved in the local transmission of avian Plasmodium, which potentially affects the circulation of parasites between and within wildlife and enclosed animals. Vigilance regarding possible mosquito breeding sites in this zoo is thus recommended.

Presence and diversity of mixed avian Plasmodium spp. infections in introduced birds whose distribution overlapped with threatened New Zealand endemic birds

Aims: To determine the presence of infection and co-infection of Plasmodium lineages in introduced birds at translocation sites for the North Island saddleback (Philesturnus rufusater), to investigate their role as Plasmodium spp. reservoirs.Methods: Blood samples were collected from introduced bird species, with a special focus on blackbirds (Turdus merula) and song thrushes (Turdus philomelos), at six locations in the North Island of New Zealand that were the origin, or translocation sites, for North Island saddleback. Where available, blood smears were examined, and blood samples were tested using nested PCR with subsequent sequence analysis, for the presence of Plasmodium spp.Results: Of the 55 samples tested using PCR analysis, 39 (71%) were positive for Plasmodium spp., and 28/40 (62%) blood smears were positive for Plasmodium spp. Overall, 31 blood samples were from blackbirds with 28/31 (90%) samples positive for Plasmodium spp. Six distinct avian Plasmodium lineages were identified, including three cosmopolitan lineages; Plasmodium vaughani SYAT05 was detected in 16 samples, Plasmodium matutinum Linn1 in 10 samples and Plasmodium elongatum GRW6 in eight samples. Mixed infections with more than one lineage were detected in 12 samples. Samples from two Australian magpies (Gymnorhina tibicen) were positive for Plasmodium. sp. lineage MYNA02, previously not identified in New Zealand.Conclusions and clinical relevance: This is the first report from New Zealand in which specific Plasmodium spp. mixed infections have been found in introduced birds. Co-infections with several cosmopolitan Plasmodium lineages were identified, as well as the first report in New Zealand of an exotic avian Plasmodium sp. lineage, in Australian magpies. Whilst the role of introduced birds in maintaining and spreading pathogenic avian malaria in New Zealand is unclear, there is a potential infection risk to native birds, especially where distributions overlap.

Epidemiology, hematology, and unusual morphological characteristics of Plasmodium during an avian malaria outbreak in penguins in Brazil

Avian malaria is a mosquito-borne disease caused by Plasmodium spp. protozoa, and penguins are considered particularly susceptible to this disease, developing rapid outbreaks with potentially high mortality. We report on an outbreak of avian malaria in Magellanic penguins (Spheniscus magellanicus) at a rehabilitation center in Espírito Santo, southeast Brazil. In August and September 2015, a total of 89 Magellanic penguins (87 juveniles and 2 adults) received care at Institute of Research and Rehabilitation of Marine Animals. Over a period of 2 weeks, Plasmodium infections were identified in eight individuals (9.0%), four of which died (mortality = 4.5%, lethality = 50%). Blood smears and sequencing of the mitochondrial cytochrome b gene revealed the presence of Plasmodium lutzi SPMAG06, Plasmodium elongatum GRW06, Plasmodium sp. PHPAT01, Plasmodium sp. SPMAG10, and Plasmodium cathemerium (sequencing not successful). Two unusual morphological features were observed in individuals infected with lineage SPMAG06: (a) lack of clumping of pigment granules and (b) presence of circulating exoerythrocytic meronts. Hematological results (packed cell volume, plasma total solids, complete blood cell counts) of positive individuals showed differences from those of negative individuals depending on the lineages, but there was no overarching pattern consistently observed for all Plasmodium spp. The epidemiology of the outbreak and the phylogeography of the parasite lineages detected in this study support the notion that malarial infections in penguins undergoing rehabilitation in Brazil are the result of the spillover inoculation by plasmodia that circulate in the local avifauna, especially Passeriformes.

Molecular detection of vector-borne pathogens from mosquitoes collected in two zoological gardens in Germany

In Germany, knowledge of disease agents transmitted by arthropods in zoological gardens is scarce. In the framework of ecological studies, mosquitoes were therefore collected in German zoological gardens and examined for mosquito-borne pathogen DNA and RNA. In total, 3840 mosquitoes were screened for filarial nematodes and three groups of viruses (orthobunyaviruses, flaviviruses, alphaviruses) while 405 mosquitoes were tested for avian malaria parasites. In addition to the filarial nematode species Dirofilaria repens (n = 1) and Setaria tundra (n = 8), Sindbis virus (n = 1) and the haemosporidian genera Haemoproteus (n = 8), Leucocytozoon (n = 10) and Plasmodium (n = 1) were demonstrated. Identified pathogens have the potential to cause disease in zoo and wild animals, but some of them also in humans. Positive mosquitoes were collected most often in July, indicating the highest infection risk during this month. Most of the pathogens were found in mosquito specimens of the Culex pipiens complex, suggesting that its members possibly act as the most important vectors in the surveyed zoos, although the mere demonstration of pathogen DNA/RNA in a homogenised complete mosquito is not finally indicative for a vector role. Outcomes of the study are not only significant for arthropod management in zoological gardens, but also for the general understanding of the occurrence and spread of mosquito-borne disease agents.

Wildlife diseases in New Zealand: recent findings and future challenges

Our knowledge of diseases in New Zealand wildlife has expanded rapidly in the last two decades. Much of this is due to a greater awareness of disease as a cause of mortality in some of our highly threatened species or as a limiting factor to the successful captive rearing of intensely managed species such as hihi (Notiomystis cincta), kiwi (Apteryx spp.) and kakapo (Strigops habroptilus). An important factor contributing to the increase of our knowledge has been the development of new diagnostic techniques in the fields of molecular biology and immunohistochemistry, particularly for the diagnosis and epidemiology of viral and protozoan diseases. Although New Zealand remains free of serious exotic viruses there has been much work on understanding the taxonomy and epidemiology of local strains of avipox virus and circoviruses. Bacterial diseases such as salmonellosis, erysipelas and tuberculosis have also been closely investigated in wildlife and opportunist mycotic infections such as aspergillosis remain a major problem in many species. Nutritional diseases such as hyperplastic goitre due to iodine deficiency and metabolic bone disease due to Ca:P imbalance have made significant impacts on some captive reared birds, while lead poisoning is a problem in some localities. The increasing use of wildlife translocations to avoid the extinction of threatened species has highlighted the need for improved methods to assess the disease risks inherent in these operations and other intensive conservation management strategies such as creching young animals. We have also become more aware of the likelihood of inbreeding suppression as populations of many species decrease or pass through a genetic bottleneck. Climate change and habitat loss, however, remain the greatest threats to biodiversity and wildlife health worldwide. Temperature changes will affect our wildlife habitats, alter the distribution of disease vectors and wildlife predators, or directly harm threatened species in vulnerable localities.

Characterization of Plasmodium relictum, a cosmopolitan agent of avian malaria

Background

Microscopic research has shown that Plasmodium relictum is the most common agent of avian malaria. Recent molecular studies confirmed this conclusion and identified several mtDNA lineages, suggesting the existence of significant intra-species genetic variation or cryptic speciation. Most identified lineages have a broad range of hosts and geographical distribution. Here, a rare new lineage of P. relictum was reported and information about biological characters of different lineages of this pathogen was reviewed, suggesting issues for future research.

Methods

The new lineage pPHCOL01 was detected in Common chiffchaff Phylloscopus collybita, and the parasite was passaged in domestic canaries Serinus canaria. Organs of infected birds were examined using histology and chromogenic in situ hybridization methods. Culex quinquefasciatus mosquitoes, Zebra finch Taeniopygia guttata, Budgerigar Melopsittacus undulatus and European goldfinch Carduelis carduelis were exposed experimentally. Both Bayesian and Maximum Likelihood analyses identified the same phylogenetic relationships among different, closely-related lineages pSGS1, pGRW4, pGRW11, pLZFUS01, pPHCOL01 of P. relictum. Morphology of their blood stages was compared using fixed and stained blood smears, and biological properties of these parasites were reviewed.

Results

Common canary and European goldfinch were susceptible to the parasite pPHCOL01, and had markedly variable individual prepatent periods and light transient parasitaemia. Exo-erythrocytic and sporogonic stages were not seen. The Zebra finch and Budgerigar were resistant. Neither blood stages nor vector stages of all examined P. relictum lineages can be distinguished morphologically.

Conclusion

Within the huge spectrum of vertebrate hosts, mosquito vectors, and ecological conditions, different lineages of P. relictum exhibit indistinguishable, markedly variable morphological forms. Parasites of same lineages often develop differently in different bird species. Even more, the variation of biological properties (parasitaemia dynamics, blood pathology, prepatent period) in different isolates of the same lineage might be greater than the variation in different lineages during development in the same species of birds, indicating negligible taxonomic value of such features. Available lineage information is excellent for parasite diagnostics, but is limited in predictions about relationships in certain host-parasite associations. A combination of experiments, field observations, microscopic and molecular diagnostics is essential for understanding the role of different P. relictum lineages in bird health.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2325-2) contains supplementary material, which is available to authorized users.