Reconstruction of the evolutionary history of Haemosporida (Apicomplexa) based on the cyt b gene with characterization of Haemocystidium in geckos (Squamata: Gekkota) from Oman

Unresolved haemosporidia of the Australian skink, Egernia stokesii

The Australian skink Egernia stokesii had been recognised as a host of two species of Plasmodium, Plasmodium mackerrasae and P. circularis; nevertheless, molecular data are available for only a single haemosporidian species of this host. Its sequences are labelled as "Plasmodium sp." or "Plasmodium mackerrasae", but morphological characteristics of this isolate are unavailable. Phylogenetic analyses of these sequences placed them into the clade of the genus Haemocystidium. In this study, blood samples of six E. stokesii were analysed by both, molecular and microscopic methods to clarify the haemosporidia of this lizard. Application of these approaches offered discordant results. Whereas sequence analysis clustered our isolates with lizard species of Haemocystidium, morphology of blood stages is more akin to Plasmodium than Haemocystidium. However, limited sampling, indistinguishable nuclei/merozoites and risk of possible hidden presence of mixed infection prevent reliable species identification of detected parasites or their description as new species of Haemocystidium.

Origin and diversity of malaria parasites and other Haemosporida

Symbionts, including parasites, are ubiquitous in all world ecosystems. Understanding the diversity of symbiont species addresses diverse questions, from the origin of infectious diseases to inferring processes shaping regional biotas. Here, we review the current approaches to studying Haemosporida's species diversity and evolutionary history. Despite the solid knowledge of species linked to diseases, such as the agents of human malaria, studies on haemosporidian phylogeny, diversity, ecology, and evolution are still limited. The available data, however, indicate that Haemosporida is an extraordinarily diverse and cosmopolitan clade of symbionts. Furthermore, this clade seems to have originated with their vertebrate hosts, particularly birds, as part of complex community level processes that we are still characterizing.

Molecular characterization of haemosporidian and haemogregarine diversity in southwestern Iberian amphibians and reptiles

The knowledge of the diversity and geographic distribution of parasite species is the first step towards understanding processes of global epidemiology and species conservation. Despite recent increases in research on haemosporidian and haemogregarine parasites of reptiles and amphibians, we still know little about their diversity and parasite-host interactions, especially in the Iberian Peninsula, where a few studies have been conducted. In this study, the haemosporidian and haemogregarine diversity and phylogenetic relationships of the parasites in southwestern Iberian amphibians and reptiles were assessed using PCR approaches on blood samples of 145 individuals from five amphibian and 13 reptile species. The amphibians did not present any of both groups of parasites studied. Regarding reptiles, five Hepatozoon, one Haemogregarina, and one Haemocystidum haplotypes were found infecting four different species, revealing new host records for these parasites. Among them, we found one new Haemocystidium haplotype and three new and a previously reported Hepatozoon haplotype from a north African snake. The latter finding suggests that some Hepatozoon parasites may not be host-specific and have large geographic ranges even crossing geographical barriers. These results increased the knowledge about the geographic distribution and the number of known host species of some reptile apicomplexan parasites, highlighting the great unexplored diversity of them in this region.

The genetic and morphological diversity of Haemogregarina infecting turtles in Colombia: Are mitochondrial markers useful as barcodes for these parasites?

Adeleorinid parasites commonly infect turtles and tortoises in nature. Currently, our knowledge about such parasites is extremely poor. Their characterization is based on morphological and molecular approaches using the 18S rDNA molecular marker. However, there is a limitation with the 18S rDNA due to its slow rate of evolution. For that reason, the goals of this study were to 1) design primers for new molecular mitochondrial markers to improve the phylogenetic reconstructions of adeleorinid parasites and 2) to determine the morphological and genetic diversity of Haemogregarina infecting turtles and tortoises in Colombia. Turtles from 16 species representing six families were examined for the presence of haemoparasites. We analyzed 457 samples using PCR, and 203 of them were also analyzed by microscopy. Using a mitochondrial genome of Haemogregarina sequenced in this study, we designed primers to amplify fragments of the cytochrome oxidase I (coxI), cytochrome oxidase III (coxIII), and cytochrome b (cytb) mitochondrial markers in adeleorinid parasites. Lineages obtained from nuclear and mitochondrial molecular markers clustered according to the turtle lineages from which they were isolated. It is noteworthy that we found different evolutionary lineages within the same morphotype, which may indicate heteroplasmy and/or cryptic diversity in Haemogregarina. Due to this situation, we could not make a species delimitation, even when integrating the different lines of evidence we had in this study. However, the primers presented here are useful for diagnosis and, moreover, according to the available information, all three genes retain phylogenetic signals; thereby fragments amplified can be used in reconstructing evolutionary relationships. This effort contributes to the knowledge of the diversity of these parasites infecting continental turtles from Colombia.

A phylogenetic study of Haemocystidium parasites and other Haemosporida using complete mitochondrial genome sequences

Haemosporida are diverse vector-borne parasites associated with terrestrial vertebrates. Driven by the interest in species causing malaria (genus Plasmodium), the diversity of avian and mammalian haemosporidian species has been extensively studied, relying mostly on mitochondrial genes, particularly cytochrome b. However, parasites from reptiles have been neglected in biodiversity surveys. Reptilian haemosporidian parasites include Haemocystidium, a genus that shares morphological features with Plasmodium and Haemoproteus. Here, the first complete Haemocystidium mitochondrial DNA (mtDNA) genomes are studied. In particular, three mtDNA genomes from Haemocystidium spp. sampled in Africa, Oceania, and South America, are described. The Haemocystidium mtDNA genomes showed a high A + T content and a gene organization, including an extreme fragmentation of the rRNAs, found in other Haemosporida. These Haemocystidium mtDNA genomes were incorporated in phylogenetic and molecular clock analyses together with a representative sample of haemosporidian parasites from birds, mammals, and reptiles. The recovered phylogeny supported Haemocystidium as a monophyletic group apart from Plasmodium and other Haemosporida. Both the phylogenetic and molecular clock analyses yielded results consistent with a scenario in which haemosporidian parasites radiated with modern birds. Haemocystidium, like mammalian parasite clades, seems to originate from host switches by avian Haemosporida that allowed for the colonization of new vertebrate hosts. This hypothesis can be tested by investigating additional parasite species from all vertebrate hosts, particularly from reptiles. The mtDNA genomes reported here provide baseline data that can be used to scale up studies in haemosporidian parasites of reptiles using barcode approaches.

Further characterisation of Haemocystidium chelodinae-like Haemoproteidae isolated from the Bellinger River snapping turtle (Myuchelys georgesi)

The Bellinger River snapping turtle (Myuchelys georgesi) is endemic to Australia and is confined to a highly restricted distribution in the Bellinger River in New South Wales. Routine veterinary health examinations of 17 healthy turtles were undertaken, along with the collection and analysis of blood samples, during conservation efforts to save the species following a catastrophic population decline. Microscopy analysis of blood films detected Haemoproteidae parasites that morphologically resembled Haemocystidium chelodinae inside turtle erythrocytes. Of the 17 turtles examined, 16 were positive for infection with H. chelodinae by both light microscopy and PCR. DNA sequencing of a partial fragment of the mitochondrial cytochrome b (cytb) gene and phylogenetic analysis identified two different H. chelodinae-like genotypes. The phylogenetic relationship of H. chelodinae-like to other Haemoproteidae species based on cytb sequences grouped H. chelodinae-like into the reptile clade, but revealed the Haemocystidium genus to be paraphyletic as the clade also contained Haemoproteus, thus supporting a re-naming of Haemoproteus species from reptiles to Haemocystidium species. This study reports for the first time the genetic characterisation of H. chelodinae-like organisms isolated from a new Testudine host species, the Bellinger River snapping turtle. As evidence grows, further research will be necessary to understand the mode of transmission and to investigate whether these parasites are pathogenic to their hosts.

Haemocystidium spp., a species complex infecting ancient aquatic turtles of the family Podocnemididae: First report of these parasites in Podocnemis vogli from the Orinoquia

The genus Haemocystidium was described in 1904 by Castellani and Willey. However, several studies considered it a synonym of the genera Plasmodium or Haemoproteus. Recently, molecular evidence has shown the existence of a monophyletic group that corresponds to the genus Haemocystidium. Here, we further explore the clade Haemocystidium spp. by studying parasites from Testudines. A total of 193 individuals belonging to six families of Testudines were analyzed. The samples were collected in five localities in Colombia: Casanare, Vichada, Arauca, Antioquia, and Córdoba. From each individual, a blood sample was taken for molecular analysis, and peripheral blood smears were made, which were fixed and subsequently stained with Giemsa. The prevalence of Haemocystidium spp. was 1.55% (n = 3/193); all infected individuals belonged to Podocnemis vogli (Savanna Side-necked turtle) from the department of Vichada. This is the first report of Haemocystidium spp. in Colombia and in this turtle species. The phylogenetic analysis of a mitochondrial cytb fragment revealed Haemocystidium spp. as a monophyletic group and as a sister taxon of Haemoproteus catharti and the genus Plasmodium. Haemocystidium spp. are difficult to identify by morphology only. As a result, it is possible that some of the taxa, such as Haemocystidium (Simondia) pacayae, represent a species complex. The parasite found in our study is morphologically indistinguishable from Haemocystidium (Simondia) pacayae reported in Peru. However, the new lineage found in P. vogli shows a genetic distance of 0.02 with Hae. pacayae and 0.04 with Hae. peltocephali. It is proposed that this divergent lineage might be a new species. Nevertheless, additional molecular markers and ecological features could support this hypothesis in the future.

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Haemocystidium spp. now reported in Podocnemis vogli in Colombia.

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Haemocystidium spp. are cryptic species in Podocnemididae.

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Our data support that Haemocystidium is a monophyletic group that shares a recent common ancestor with the genus Plasmodium.

The success of sequence capture in relation to phylogenetic distance from a reference genome: a case study of avian haemosporidian parasites

Genomic sequencing of avian haemosporidian parasites (Haemosporida) has been challenging due to excessive contamination from host DNA. In this study, we developed a cost-effective protocol to obtain parasite sequences from naturally infected birds, based on targeted sequence capture and next generation sequencing. With the genomic data of Haemoproteus tartakovskyi as a reference, we successfully sequenced up to 1000 genes from each of the 15 selected samples belonging to nine different cytochrome b lineages, eight of which belong to Haemoproteus and one to Plasmodium. The targeted sequences were enriched to ∼10⁴-fold, and mixed infections were identified as well as the proportions of each mixed lineage. We found that the total number of reads and the proportions of exons sequenced decreased when the parasite lineage became more divergent from the reference genome. For each of the samples, the recovery of sequences from different exons varied with the function and GC content of the exon. From the obtained sequences, we detected within-lineage variation in both mitochondrial and nuclear genes, which may be a result of local adaptation to different host species and environmental conditions. This targeted sequence capture protocol can be applied to a broader range of species and will open a new door for further studies on disease diagnostics and comparative analysis of haemosporidians evolution.

The polyphyly of Plasmodium: comprehensive phylogenetic analyses of the malaria parasites (order Haemosporida) reveal widespread taxonomic conflict

The evolutionary relationships among the apicomplexan blood pathogens known as the malaria parasites (order Haemosporida), some of which infect nearly 200 million humans each year, has remained a vexing phylogenetic problem due to limitations in taxon sampling, character sampling and the extreme nucleotide base composition biases that are characteristic of this clade. Previous phylogenetic work on the malaria parasites has often lacked sufficient representation of the broad taxonomic diversity within the Haemosporida or the multi-locus sequence data needed to resolve deep evolutionary relationships, rendering our understanding of haemosporidian life-history evolution and the origin of the human malaria parasites incomplete. Here we present the most comprehensive phylogenetic analysis of the malaria parasites conducted to date, using samples from a broad diversity of vertebrate hosts that includes numerous enigmatic and poorly known haemosporidian lineages in addition to genome-wide multi-locus sequence data. We find that if base composition differences were corrected for during phylogenetic analysis, we recovered a well-supported topology indicating that the evolutionary history of the malaria parasites was characterized by a complex series of transitions in life-history strategies and host usage. Notably we find that Plasmodium, the malaria parasite genus that includes the species of human medical concern, is polyphyletic with the life-history traits characteristic of this genus having evolved in a dynamic manner across the phylogeny. We find support for multiple instances of gain and loss of asexual proliferation in host blood cells and production of haemozoin pigment, two traits that have been used for taxonomic classification as well as considered to be important factors for parasite virulence and used as drug targets. Lastly, our analysis illustrates the need for a widespread reassessment of malaria parasite taxonomy.

Wildlife parasitology in Australia: past, present and future

Wildlife parasitology is a highly diverse area of research encompassing many fields including taxonomy, ecology, pathology and epidemiology, and with participants from extremely disparate scientific fields. In addition, the organisms studied are highly dissimilar, ranging from platyhelminths, nematodes and acanthocephalans to insects, arachnids, crustaceans and protists. This review of the parasites of wildlife in Australia highlights the advances made to date, focussing on the work, interests and major findings of researchers over the years and identifies current significant gaps that exist in our understanding. The review is divided into three sections covering protist, helminth and arthropod parasites. The challenge to document the diversity of parasites in Australia continues at a traditional level but the advent of molecular methods has heightened the significance of this issue. Modern methods are providing an avenue for major advances in documenting and restructuring the phylogeny of protistan parasites in particular, while facilitating the recognition of species complexes in helminth taxa previously defined by traditional morphological methods. The life cycles, ecology and general biology of most parasites of wildlife in Australia are extremely poorly understood. While the phylogenetic origins of the Australian vertebrate fauna are complex, so too are the likely origins of their parasites, which do not necessarily mirror those of their hosts. This aspect of parasite evolution is a continuing area for research in the case of helminths, but remains to be addressed for many other parasitic groups.

Prevalence and genetic diversity of blood parasite mixed infections in Spanish terrapins, Mauremys leprosa

Blood parasites such as haemogregarines and haemosporidians have been identified in almost all groups of vertebrates and may cause serious damages to their hosts. However, very little is known about biodiversity of these parasites and their effects on some groups of reptiles such as terrapins. Moreover, the information on virulence from blood parasites mixed infection is largely unknown in reptiles. With this aim, we investigated for the first time the prevalence and genetic diversity of blood parasites from one genus of haemoparasitic aplicomplexan (Hepatozoon) in two populations of Spanish terrapins (Mauremys leprosa), a semi-aquatic turtle from southwestern Europe with a vulnerable conservation status. We also examined the association between mixed blood parasite infection and indicators of health of terrapins (body condition, haematocrit values and immune response). Blood parasite infection with Hepatozoon spp was detected in 46·4% of 140 examined terrapins. The prevalence of blood parasites infection differed between populations. We found two different lineages of blood parasite, which have not been found in previous studies. Of the turtles with infection, 5·7% harboured mixed infection by the two lineages. There was no difference in body condition between uninfected, single-infected and mixed-infected turtles, but mixed-infected individuals had the lowest values of haematocrit, thus revealing the negative effects of blood parasite mixed infections. Immune response varied among terrapins with different infection status, where mixed infected individuals had higher immune response than uninfected or single-infected terrapins.